Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
  • B32B17/10743—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer containing acrylate (co)polymers or salts thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
  • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
  • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
  • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
  • B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
  • B32B17/10779—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer containing polyester
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/0007—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding involving treatment or provisions in order to avoid deformation or air inclusion, e.g. to improve surface quality
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
  • B32B37/12—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by using adhesives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/12—Bonding of a preformed macromolecular material to the same or other solid material such as metal, glass, leather, e.g. using adhesives
  • C08J5/122—Bonding of a preformed macromolecular material to the same or other solid material such as metal, glass, leather, e.g. using adhesives using low molecular chemically inert solvents, swelling or softening agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/40—Properties of the layers or laminate having particular optical properties
  • B32B2307/412—Transparent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/702—Amorphous
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
  • B32B2309/02—Temperature
  • B32B2309/027—Ambient temperature
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2309/00—Parameters for the laminating or treatment process; Apparatus details
  • B32B2309/04—Time
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2315/00—Other materials containing non-metallic inorganic compounds not provided for in groups B32B2311/00 - B32B2313/04
  • B32B2315/08—Glass

Definitions

• This invention pertains to plasticizer-assisted bond formation useful for defect-free lamination.
• Laminated articles are used in a multitude of applications. As would be expected, numerous lamination methods have been used to prepare laminated articles. While the objective of many lamination methods is solely the joining of two substrates, certain applications have additional requirements to achieve the full utility of the laminate article.
• glass laminates may be used in optical applications where it is necessary or desirable to see through the laminate, preferably with an undistorted view.
• two substrates are bonded together with a material therebetween.
• glass laminates used for safety glass such as that used in automobiles, where a layer of, for example, polyvinyl butyral, can be laminated between two glass sheets.
• a solar control film such as those described in U.S. Patent No. 3,681,179 (Theissen), may be laminated to a glass substrate.
• Films described therein include pressure-sensitive adhesive acrylate copolymers overcoated with a dried coating of a water-soluble overcoat, which overcoat may include up to about 15% water-soluble plasticizers. It is preferred that the water- soluble overcoat is incompatible with pressure sensitive adhesives comprising the film so as to prevent any -gradual plasticization of the pressure sensitive adhesive.
• the solar control films are wet with water to bond them to a substrate.
• polymeric films useful for repairing glass substrates may also be bonded to form laminates, such as described in copending U.S. Patent Application Serial No. 09/181,198, assigned to the assignee of the present application and entitled "Repaired Scratched and/or Abraded Transparent Substrates Having Protective Removable Sheets Thereon and a Method of Making.”
• Preferred films include poly(meth)acrylates, polyolefins, silicones, or rubber-based pressure sensitive adhesives that have a stress relaxation value of about 15 percent or greater. These polymeric films are typically wet with water or solutions of water and detergent and then bonded to the glass substrate.
• the above methods and other conventional methods utilize water to wet surfaces to be bonded in order for a bond to develop between the surfaces.
• water has its drawbacks. For example, as water is volatile at typical bonding temperatures, it evaporates from the laminate assembly during the drying step necessary to complete bond formation. That is, water is essentially not present in the ultimate dried laminate assembly. For the final bond to form, water must, therefore, escape from the laminate assembly.
• bond formation may take several hours or days to complete. While this may be satisfactory for certain applications (e.g., those where repositioning of the surfaces to be bonded needs to occur after activating the bonding mechanism), more timely bonding may be desirable or necessary for certain applications.
• the laminate assembly may appear hazy. For optical applications, the haziness may be problematic, especially if it lasts for several days.
• laminating glass Particularly problematic with laminating glass is the persistent entrapment of air between the layers during lamination. Residual air bubbles remain as "defects" in the final laminate. The defects may impair ones ability to see through the laminate.
• Many conventional methods of laminating glass involve laminating a plastic material between two sheets of glass. For example, see Nichols, R.T. and R.M. Sowers, "Laminated Materials, Glass,” Kirk-Othmer Encyclopedia of Chemical Technology. 4 th Ed., where methods of laminating glass are described. In one conventional lamination method, the glass sheets are assembled with a plastic material sandwiched therebetween, after which the sandwich construction is passed between heated pinch rolls at about 40 psi to exclude air from between the sheets and to obtain an initial bond.
• the glass sheets are then sandwiched against opposite faces of the interlayer, thereby trapping a small quantity of the resin therebetween.
• the resin then either absorbs into the interlayer or polymerizes to a solid state, depending on the materials used, thereby bonding the glass sheets together.
• Suitable polymerizable resins are stated to be epoxides, polyesters, vinyl monomers, and mixtures of the three.
• Exemplified interlayers include paper, cloth fabrics, metal foils, monofilaments, metallic flakes, and particulate materials.
• the interlayer is an organic plastic film.
• the interlayer may be a thermoplastic film, such as plasticized polyvinyl chloride, plasticized polyvinyl butyral (e.g., 15-50 parts plasticizer per hundred parts polyvinyl butyral), or plasticized ethyl cellulose (e.g., 10-100 parts plasticizer per hundred parts ethyl cellulose).
• the interlayer may be a thermosetting film, such as a rubber elastomer or silicone elastomer compounded with crosslinking or vulcanizing materials.
• the bath in which the film is immersed is that of a plasticizer for the film (e.g., triethylene glycol di(2-ethyl butyrate), dibutyl sebacate, or hexadecyl alcohol for polyvinyl butyral or ethyl cellulose plastic films or a silicone prepolymer, such as methyl silicone oil containing a curing agent, such as benzoyl peroxide, for silicone elastomer plastic films).
• a plasticizer for the film e.g., triethylene glycol di(2-ethyl butyrate), dibutyl sebacate, or hexadecyl alcohol for polyvinyl butyral or ethyl cellulose plastic films or a silicone prepolymer, such as methyl silicone oil containing a curing agent, such as benzoyl peroxide, for silicone elastomer plastic films.
• U.S. Patent No. 4,341,576 (Lewis) teaches a method of fabricating laminated safety glass without using an autoclave.
• Excess liquid plasticizer is applied to a sheet of plasticized interlayer material (i.e., polyvinyl butyral) by soaking at room temperature for a sufficient amount of time to "soften" surfaces of the plasticized interlayer material so that the interlayer becomes more amenable to adhesion to glass sheets, but not such a long time that the plasticizer content is normalized throughout the thickness of the plasticized sheet.
• Large glass sheets are then assembled around opposite sides of the plasticized interlayer material. Excess plasticizer is removed by compressing the assembly.
• a method for forming a laminate according to the present invention comprises the steps of: (a) providing a substrate comprising a surface to be bonded; (b) providing an amo ⁇ hous polymeric film comprising a first major surface and a second major surface; (c) coating at least a portion of at least one of the substrate surface to be bonded and the first major surface of the polymeric film with a non-volatile plasticizer, wherein the non-volatile plasticizer is substantially non-reactive with itself; (d) positioning the first major surface of the polymeric film with the substrate surface to be bonded; and (e) forming an adhesive bond between the polymeric film and the substrate due to the absorption of the plasticizer into the polymeric film.
• At least one of the first major surface of the polymeric film and the substrate surface to be bonded is at least partially structured.
• a further embodiment also comprises the steps of: (f) providing a second substrate; (g) coating at least a portion of at least one of the second substrate surface to be bonded and the second major surface of the polymeric film with a non-volatile plasticizer, wherein the non-volatile plasticizer is substantially non-reactive with itself; (h) positioning the second major surface of the polymeric film with the second substrate surface to be bonded; and (i) forming an adhesive bond between the polymeric film and the second substrate at essentially room temperature due to the absorption of the plasticizer into the polymeric film.
• the substrate may be rigid or the substrate may be flexible.
• preferred substrates are transparent (e.g., glass or polymeric materials)
• the plasticizer may be a solid at room temperature.
• the method further comprises the step of thermally activating the plasticizer.
• the plasticizer may be a liquid at room temperature.
• the plasticizer is selected from the group consisting of monoalkyl esters of aliphatic carboxylic acids, monoalkyl esters of aromatic carboxylic acids, polyalkyl esters of aliphatic carboxylic acids, polyalkyl esters of aromatic carboxylic acids, polyalkyl esters of aliphatic alcohols, polyalkyl esters of phosphonic acids, poly(alkoxylated) esters of aliphatic carboxylic acids, poly(alkoxylated) esters of aromatic carboxylic acids, poly(alkoxylated) ethers of aliphatic alcohols, poly(alkoxylatcd) ethers of phenols, and mixtures thereof.
• polymeric films can be used. For ease of handling, it is preferred that the polymeric film has a glass transition temperature of less than about 35°C. It is also preferred that the polymeric film has a glass transition temperature of greater than about -20°C.
• amo ⁇ hous polymeric films include those comprising the following polymers: poly(meth)acrylates and copolymers derived from (meth)acrylate monomers, styrene-butadiene copolymers, polyvinyl esters and copolymers derived from vinyl ester monomers, and combinations thereof. Due to the widespread availability of (meth)acrylates and their ability to provide optical laminates, preferred polymeric films comprise a (meth)acrylate-derived polymer. Preferably, the polymeric film has a thickness of about 25 micrometers to about 500 micrometers.
• the adhesive bond can be formed at essentially room temperature.
• Another advantage is that the adhesive bond can be formed at essentially atmospheric pressure.
• the method may be used for repairing transparent substrates having at least one blemish (e.g., scratch or abrasion) thereon.
• the substrate surface to be bonded is a transparent substrate having at least one blemish thereon.
• a blemish can be made essentially invisible after bond formation.
• Laminate articles can be prepared using the method of the invention.
• a transparent substrate laminate comprises a plasticized polymeric film and a substrate having at least one blemish thereon that is repaired using the method of the invention.
• an essentially defect-free laminate article comprises a substrate and a plasticized amo ⁇ hous polymeric film comprising an amo ⁇ hous polymer and a plasticizer dispersed throughout the amo ⁇ hous polymer.
• the plasticizer is typically dispersed throughout the amo ⁇ hous polymer due to abso ⁇ tion during bond formation.
• the plasticizer is dispersed substantially uniformly throughout the plasticized polymeric film when bonding of the laminate is complete.
• an essentially defect-free optical laminate article comprises a substrate and a plasticized polymeric film comprising: a polymer selected from the group consisting of (meth)acrylate-derived polymers and vinyl ester-derived polymers and a plasticizer.
• the optical laminate may further comprise a second substrate, assembled such that the plasticized polymeric film is positioned between the substrate and the second substrate.
• the substrate and second substrate each individually comprise a material selected from the group consisting of glass and polymeric materials.
• Kits of the invention can be used with the lamination method described herein.
• the kits typically comprise an amo ⁇ hous polymeric film and a sufficient amount of a non- volatile plasticizer for forming a laminate comprising the amo ⁇ hous polymeric film and a substrate.
• the kits can be used for repair of transparent substrates. For example, blemishes on the surface of transparent substrates can be repaired such that the blemish is essentially invisible to the unaided human eye.
• the transparent substrate, upon repair has an appearance similar to that of non-blemished portions of the substrate.
• the amorphous polymeric film comprises a (meth)acrylate-derived polymer.
• the amo ⁇ hous polymeric film comprises a first major surface to be bonded to a first substrate and further comprises a second substrate to be bonded to a second major surface of the polymeric film.
• Laminated articles of the present invention are prepared using at least one substrate to be bonded, a polymeric film, and a plasticizer for coating at least one surface of the substrate or polymeric film to be bonded. Upon absorption of the plasticizer into the polymeric film, a laminate article (also referred to simply as a laminate) is formed.
• Laminated articles that are "essentially defect-free” are preparable using the method of the invention.
• "Defect-free” laminate articles are those that do not contain any entrapped air bubbles that are visible to the unaided human eye.
• Laminate articles of the present invention are "essentially defect-free.” The ability to provide laminate articles with reduced or no defects allows the laminate articles to be used effectively in optical applications. That is, "optical laminate articles" of the present invention are those through which a user can see with an essentially undistorted view.
• Suitable substrates can be of any Young's modulus and may be, for example, rigid (e.g., the substrate may be a 6 millimeter-thick sheet of plate glass) or flexible (e.g., the substrate may be a 37 micrometer-thick polyester film).
• a single substrate is laminated to a polymeric film.
• two substrates are laminated around a polymeric film.
• two rigid substrates can be laminated together using the method of the invention.
• Two flexible substrates can be laminated together using the method of the invention.
• one rigid substrate and one flexible substrate can be laminated together using the method of the invention.
• Further laminates can be prepared based on these embodiments.
• a laminate assembly may comprise a first substrate, a polymeric film, a second substrate, a polymeric film, a third substrate, etc. in that order or in other configurations.
• each bond in a laminate i.e., the bond at each interface
• the substrates may be any suitable type of material.
• substrates may be metal, ceramic, glass, polymeric, composites, and the like.
• the type of material used for the substrates generally depends on the application in which the laminate article will be used. As mentioned in the background, certain properties (e.g., transparency for optical applications) are needed when using laminate articles in particular applications.
• the laminated articles are used in applications where it is desirable, or necessary, to see through the substrate.
• the substrates are typically transparent (e.g., glass or polymeric, typically glass or polycarbonate).
• the dimensions and surface topography of the substrates generally depend on the application in which the laminate article will be used.
• the surface of the substrate to be bonded may be at least partially structured. For example, methods of structuring polymeric films of the invention are discussed infra, under the subsection "Polymeric Film.” These same principles can be applied to structuring surfaces of substrates to be bonded.
• the surface topography of a substrate may also be roughened in a non-structured way, such as by scratching or abrading (e.g., by vandalism).
• transparent substrates e.g., glass or polycarbonate
• blemish e.g., scratch or abrasion
• U.S. Patent Application Serial No. 09/181 ,198 assigned to the assignee of the present application and entitled "Repaired Scratched and/or Abraded Transparent Substrates Having Protective Removable Sheets Thereon and a Method of Making”
• blemish e.g., scratch or abrasion
• blemish is essentially invisible to the unaided human eye after bond formation.
• Substrates having rough surface topographies e.g., concrete pavement and woven fabrics
• substrates having rough surface topographies are more difficult to bond due to their uneven surfaces, which may also make it more difficult to remove entrapped air bubbles from the laminate if the topography of the surface is not structured, or otherwise roughened, in configurations to allow for escape of air bubbles.
• the substrate does not compete effectively with the polymeric film in absorbing the plasticizer. That is, preferably the substrate does not absorb a significant amount of the plasticizer during bond formation, preventing an adhesive bond from forming.
• the type and amount of the plasticizer may also be adjusted to compensate for any abso ⁇ tion of the plasticizer by the substrate.
• the plasticizer is an organic compound that acts to increase flexibility and toughness of the polymeric film by internal modification
• a plasticizer is not capable of forming a significant bond (i.e., a bond having a 180° peel adhesion value of greater than about 3 N/dm after aging for 30 minutes) by itself.
• the plasticizer may be solid or liquid at room temperature and atmospheric pressure. If solid, the plasticizer can be softened or liquified, before, during, or after the laminate is assembled by thermal activation (e.g., heating) to cause the plasticizer to melt. If solid, the plasticizer is typically a crystalline solid, displaying a measurable melting temperature when measured using Differential Scanning Calorimetry (DSC). It is preferred that the melting temperature of solid plasticizers used in the present invention is relatively low (i.e., less than about 60°C) so as to minimize any heating that may be required in lamination methods of the present invention.
• DSC Differential Scanning Calorimetry
• the plasticizer is liquid at room temperature so that an elevated temperature step is not necessary.
• Viscosity of the plasticizer may be tailored for application. It is preferred that the viscosity of the plasticizer is sufficiently low to facilitate spreading of the plasticizer over the substrate surface to be bonded and to facilitate abso ⁇ tion of the plasticizer into the polymeric film.
• viscosity of the plasticizer is less than about 1,000 centiPoise (cP) when liquified, more preferably, the viscosity of the plasticizer is less than about 500 cP, and most preferably, less than about 200 cP when liquified.
• the plasticizer is compatible with the polymeric film.
• the polymeric film is a blend of more than one polymer, it is preferred that the plasticizer is compatible with each polymer in the blend.
• “Compatible” refers to a plasticizer that: ( 1 ) exhibits essentially no gross phase separation after abso ⁇ tion of the plasticizer into the polymeric film when the bond is formed, and (2) exhibits essentially no gross phase separation from the polymeric film upon aging.
• phase separation it is meant that by Differential Scanning Calorimetry
• DSC DSC
• a melting or glass transition temperature can be found for the pure plasticizer in the polymeric film.
• Some migration of the plasticizer from or throughout the polymeric film can be tolerated, such as minor separation due to composition equilibrium or temperature influences, but the plasticizer does not migrate to the extent of phase separation between the polymeric film and the plasticizer. Haziness may also be evidence of gross phase separation.
• Compatibility of the plasticizer with the polymeric film helps to minimize the amount of time needed for bond formation. Furthermore, compatibility of the plasticizer with the polymeric film enhances long term effectiveness of the bond within the laminate article.
• the plasticizer is non-volatile.
• “Non-volatile” refers to plasticizers that do not substantially vaporize under bond formation conditions. That is, the plasticizers generate less than 3% VOC (volatile organic content).
• the VOC content can be determined analogously to ASTM D 5403-93 by exposing the plasticizer coated substrate or polymeric film to 100°C ⁇ 5°C in a forced draft oven for one hour. If less than
• plasticizer 3% of the plasticizer is lost from the coating, then the plasticizer is considered “nonvolatile.”
• water for example, is a volatile plasticizer and evaporates under most bond formation conditions used in preferred embodiments of the present invention.
• the plasticizer is non-reactive with other components in the system or atmospheric components.
• the plasticizer is inert with respect to other components in the system, including the substrate(s) and polymeric film.
• alteration e.g., crosslinking
• loss of optical properties such as by hazing or yellowing, may be minimized.
• the plasticizer is preferably non-reactive with itself. That is, preferably the plasticizer is already substantially polymerized, if polymerization is to occur at all. This obviates the need for a subsequent polymerization step after assembling the laminate.
• plasticizers have a broad range of molecular weights and architectures.
• the plasticizers may be polymeric or monomeric.
• Monomeric plasticizers are typically derived from mono- or multi-functional, low molecular weight acids or alcohols that are esterified with a mono-functional alcohol or mono-functional acid, respectively.
• esters of mono- or di-basic acids such as myristate esters, phthalate esters, adipate esters, phosphate esters, citrates, trimellitates, glutarates, and sebacate esters (e.g., dialkyl phthalates, such as dibutyl phthalate, diisoctyl phthalate, dibutyl adipate, dioctyl adipate; 2-cthylhexyl diphenyl diphosphatc; t-butylphenyl diphenyl phosphate; butyl benzylphthalates; dibutoxyethoxyethyl adipate; dibutoxypropoxypropyl adipate; acetyltri-n-butyl citrate; dibutylscbacate; etc.).
• dialkyl phthalates such as dibutyl phthalate, diisoctyl phthalate, dibutyl adipate, dioct
• Phosphate ester plasticizers arc commercially sold under the trade designation SANTICIZER from Monsanto; St. Louis, MO. Glutarate plasticizers are commercially sold under the trade designation PLASTHALL 7050 from CP. Hall Co.; Chicago, LL.
• Polymeric plasticizers are typically derived from cationic, free-radical, condensation, or ring-opening polymerizable monomers. If polymeric, the plasticizers are typically relatively low molecular weight (i.e., preferably less than about 5,000, more preferably less than about 1,500 weight average molecular weight). In general, the lower the molecular weight of the plasticizer, the higher the compatibility of the plasticizer with the polymeric film. Common among polymeric plasticizers are polybutenes, polyvinylethers, polyethers (including polyalkylene oxides and functionalized polyalkylene oxides), polyesters, polymeric adipates (e.g., polyester adipates), polyols (e.g., glycerin), and the like.
• Polyester plasticizers are commercially sold under the trade designation PARAPLEX from CP. Hall Co.; Chicago, IL.
• Benzoyl-functionalized polyethers are commercially sold under the trade designation BENZOFLEX from Velsicol Chemicals; Rosemont, LL (e.g., BENZOFLEX 400, a polypropylene glycol dibenzoate).
• Alkyl- functionalized polyalkylene oxides are commercially sold under the trade designation PYCAL from ICI Chemicals; Wilmington, DE (e.g., PYCAL 94, a phenyl ether of polyethylene oxide).
• the chemistry of the plasticizer is selected from the group consisting of monoalkyl esters of aliphatic carboxylic acids, monoalkyl esters of aromatic carboxylic acids, polyalkyl esters of aliphatic carboxylic acids, polyalkyl esters of aromatic carboxylic acids, polyalkyl esters of aliphatic alcohols, polyalkyl esters of phosphonic acids, poly(alkoxylated) esters of aliphatic carboxylic acids, poly(alkoxylated) esters of aromatic carboxylic acids, poly(alkoxylated) ethers of aliphatic alcohols, poly(alkoxylated) ethers of phenols, and mixtures thereof.
• the amount of plasticizer used depends on the materials comprising the substrates and polymeric film, as well as their dimensions. Generally, the amount of plasticizer used is up to about 50 milligrams per square centimeter of substrate area. Preferably from about 0.5 to about 10 milligrams per square centimeter is used to provide useful bonding times and minimize the change in physical properties (e.g., shear modulus) of the polymeric film.
• the plasticizer may be diluted in, for example, water or another solvent, preferably a solvent with a relatively high volatility (e.g., isopropanol and the like). Dilution can provide a lower viscosity and more uniform spreading of the plasticizer onto the substrate. If diluted, a drying step is typically performed before the laminate is assembled.
• a solvent with a relatively high volatility e.g., isopropanol and the like.
• the polymeric film is capable of absorbing the plasticizer when the plasticizer is in the liquid state. Upon abso ⁇ tion of the plasticizer, the polymeric film forms a measurable bond to the substrate.
• the bond exhibits a 180° peel adhesion value of greater than about 3 N/dm after aging for 30 minutes. More preferably, the bond exhibits a 180° peel adhesion value of greater than about 25 N/dm, even more preferably greater than about 40 N/dm, after aging for 30 minutes.
• the polymeric film is amo ⁇ hous. That is, the amo ⁇ hous polymeric film does not exhibit a measurable melting temperature when measured using Differential Scanning Calorimetry (DSC). Amo ⁇ hous polymeric films enable more rapid bond formation than many of their crystalline counte ⁇ arts.
• DSC Differential Scanning Calorimetry
• polymeric films prepared from free radically polymerizable monomers are amo ⁇ hous.
• free radically polymerized polymeric films are preferred.
• Specific examples of polymeric films prepared as such include: poly(meth)acrylates and copolymers derived from (meth)acrylate monomers, styrene-butadiene copolymers, polyvinyl esters (e.g., polyvinyl acetates) and copolymers derived from vinyl ester (e.g., vinyl acetate) monomers, and the like.
• the polymeric film is a poly(meth)acrylate, copolymer derived from (meth)acrylate monomers, polyvinyl ester, or copolymer derived from vinyl ester monomers, as these materials tend to be the most environmentally stable (e.g., oxidation- resistant, hydrolysis-resistant, etc.) and when preparing laminate articles for use in applications where clarity is needed, they tend to provide the most optically clear laminate articles. Due to their widespread availability, (meth)acrylate-dcrived polymers (i.e.,
• (meth)acrylate polymers and copolymers derived from (meth)acrylate monomers) are preferred.
• any (meth)acrylate monomers can be used to prepare the (meth)acrylate-derived polymers (including copolymers) can be used.
• the number of carbons in the (meth)acrylate monomers is less than about 14, more preferably less than about 12. Longer carbon chains tend to result in more crystalline materials, which crystalline materials are not as preferred as their amo ⁇ hous counterparts.
• Any suitable styrene-butadiene copolymer may be used.
• Useful styrene-butadiene copolymer materials include those available from BASF Co ⁇ oration, Charlotte, NC, under the trade designation, BUTOFAN, and those available from Mallard Creek Polymers, Inc., Charlotte, NC under the trade designation, ROVENE.
• Any suitable vinyl ester-derived polymer i.e., polyvinyl ester (e.g., polyvinyl acetate) or copolymers derived from vinyl ester monomers (e.g., vinyl acetate-ethylene copolymer)
• the comonomer content e.g., ethylene content
• Useful polyvinyl acetate materials include those available from Air Products; Allentown, PA under the trade designation, VLNAC
• Useful vinyl acetate-ethylene copolymer materials include those available from Bayer Co ⁇ oration; Akron, OH, under the trade designation, LEVAPREN.
• the polymeric film may also comprise a blend of two or more polymers. If more than one polymer is used, preferably the polymers form a compatible blend having good optical clarity. "Compatible" blends are those that exhibit essentially no gross phase separation when blended together at room temperature and atmospheric pressure.
• the glass transition temperature (Tg) of the polymeric film is close to the temperature at which the bond is formed.
• the Tg of the polymeric film is preferably less than about 60°C, more preferably less than about 50°C
• the bond is assembled at room temperature.
• the Tg of the polymeric film is less than about 35°C
• the polymeric film may be tacky, tackiness is not required.
• the Tg of the polymeric film may be greater than -20°C, more preferably greater than about 0°C
• the polymeric film may be more easily handled when assembly the laminate layers due to its relatively low tackiness.
• the polymeric film may be crosslinked. However, to speed absorption of the plasticizer into the polymeric film, relatively low crosslinking is preferred. Crosslinking tends to decrease the abso ⁇ tion rate of plasticizer into a polymeric film.
• Topography of the polymeric film may influence the absorption rate of the plasticizer.
• a structured surface may be used.
• one or more surfaces of the polymeric film to be bonded can be at least partially structured (e.g., polymeric films having a microstructured surface), for example, such as those described in PCT Patent Publication No.
• Microreplication can be achieved by at least any of (1) casting the polymeric film using a tool having a microembossed pattern, (2) coating of the polymeric film onto a release liner having that microembossed pattern, or (3) passing through a nip roll to compress the polymeric film against a release liner having that microembossed pattern.
• Desired embossing topography can be formed in tools via any of a number of well- known techniques, selected depending in part upon the tool material and features of the desired topography.
• Illustrative techniques include etching (e.g., via chemical etching, mechanical etching, or other ablative means such as laser ablation or reactive ion etching, etc.), photolithography, stereolithography, micromachining, knurling (e.g., cutting knurling or acid enhanced knurling), scoring or cutting, etc.
• knurling e.g., cutting knurling or acid enhanced knurling
• scoring or cutting etc.
• the presence of such surface structural topography can also beneficially impact the ability for air bubbles to escape from between laminate layers. As discussed above, air bubbles can undesirably lead to "defects" in the final laminate article.
• the structured topography can reside on a portion or all of at least one major surface of the polymeric film and can optionally reside on a portion or all of both major, opposing surfaces of the polymeric film affecting the properties of the interface(s) in the same or different manners, as desired by those skilled in the art.
• the substrate surface to be bonded may be at least partially structured or otherwise roughened.
• the polymeric film surface to be bonded may or may not also be at least partially structured or otherwise roughened.
• the thickness of the polymeric film depends on the topography of the substrate being bonded.
• the polymeric film should be of sufficient thickness to absorb the plasticizer and form a measurable bond to the substrate (i.e., a bond having a 180° peel adhesion of greater than about 3 N/dm after aging for 30 minutes).
• the polymeric film is typically greater than about 10 micrometers thick. Generally, the polymeric film is also about 1,000 micrometers thick or less. Preferably, the polymeric film has a thickness of about 25 to about 500 micrometers.
• the polymeric film may contain any suitable additive.
• the polymeric film may include further plasticizers and tackifiers.
• Plasticizers and tackifiers can lower the modulus of the film and thus, increase the abso ⁇ tion rate of the bonding plasticizer into the polymeric film.
• Use of such additives may depend on the particular application. For example, when longer bonding times are desired (e.g., when multiple repositioning is needed after activation of the bonding mechanism), the use of tackifiers and plasticizers may not be preferred. Those of ordinary skill in the art can determine the suitability of particular additives for their particular application. A wide variety of other additives known to those skilled in the art, for example, adhesion promoters, can also be used in the polymeric film. Bonding
• the bonding time can be as short as several seconds or up to one day. Any suitable method of forming a laminate from the materials of the invention can be used.
• preferred embodiments of the invention do not require the use of elevated temperatures (i.e., those above 60°C, or in most preferred embodiments, those above room temperature (about 25°C)) for timely bonding.
• elevated temperatures i.e., those above 60°C, or in most preferred embodiments, those above room temperature (about 25°C)
• timely bonding may differ depending on the application and the user's desires, for pu ⁇ oses of describing this invention timely bonding is about 12 hours or less, more preferably about 8 hours or less, even more preferably about 4 hours or less, even more preferably about 1 hour or less, and most preferably less than about 30 minutes.
• preferred embodiments of the invention do not require the use of non- atmospheric pressure, such as that provided by an autoclave or otherwise.
• Preferred embodiments of the invention include those where lamination occurs at essentially atmospheric pressure. This enables lamination to easily occur in certain applications where essentially defect-free lamination was previously impossible (e.g., bulk structures, such as windows in buildings, etc.). However, increased/decreased pressure may be used if desired.
• At least one major surface of the substrate or the polymeric film is coated with the plasticizer.
• each of the major substrate surface and the major surface of the polymeric film is coated with the plasticizer.
• Any suitable coating method can be used.
• the plasticizer may be applied to the surface of the substrate or polymeric film to be bonded by: spraying, brushing, pouring, dripping, etc. the plasticizer onto the surface to be bonded.
• the substrate is positioned with the polymeric film such that at least one of the plasticizer-coated surfaces resides at the substrate/polymeric film interface.
• a polymeric film is placed between at least one set of adjacent substrates.
• more than one polymeric film may be used (e.g., when multiple substrate/polymeric film interfaces are bonded using the method of the invention). For example, a first polymeric film may be placed between a first and second substrate and a second polymeric film may be placed between the second substrate and a third substrate.
• each substrate/polymeric film interfaces are bonded using the method of the invention.
• the plasticizer used at each interface may or may not be the same, both in terms of chemistry and amount.
• the substrates and polymeric films may or may not be the same throughout the entire laminate.
• substrates may be bonded to the substrate and/or polymeric film using any suitable bonding method.
• suitable bonding methods include those using mechanical (e.g., nails, rivets, etc.), chemical (e.g., adhesives, etc.), and physical (e.g., ultrasonic welding, etc.) means.
• excess air and plasticizer is squeezed from the substrate/polymeric film interface or multiple substrate/polymeric film interfaces.
• the excess air and plasticizer may be squeezed from the interface by using no more than hand pressure.
• a squeegee or roller is applied to the sandwich assembly to remove the excess air and plasticizer.
• no visible air bubbles remain in the assembled laminate article for optical laminate articles of the invention.
• Migration also referred to as abso ⁇ tion or diffusion
• migration of the plasticizer is enabled and enhanced by using an amo ⁇ hous polymeric film.
• This enables laminates to be formed at atmospheric pressure without the use of elevated temperatures.
• Further preferred for enhancing migration of the plasticizer into the bulk polymeric film is the use of a plasticizer that is compatible with the polymeric film.
• the plasticizer is dispersed substantially uniformly throughout the plasticized polymeric film when bonding of the laminate is complete.
• the storage modulus at the surface of the polymeric film decreases during bond formation, typically to a value lower than that of the Dahlquist criterion (Sung Gun Chu, Chapter 8, Handbook of Pressure Sensitive Adhesive Technology. Second Edition, Donatas Satas, Editor, 1989).
• the storage modulus Upon migration of the plasticizer into the bulk polymeric film, the storage modulus then increases to its equilibrium value.
• the resulting laminate article includes a polymeric film adhesively bonded to at least one major surface of at least one substrate.
• Kits of the invention are particularly useful for practicing the method of the invention.
• the kits typically comprise a polymeric film, preferably an amo ⁇ hous polymeric film, and a sufficient amount of a plasticizer (preferably a non- volatile plasticizer) for forming a laminate comprising the polymeric film and a substrate.
• a plasticizer preferably a non- volatile plasticizer
• the amount of plasticizer must be great enough to form measurable bond between a first major surface of the polymeric film and substrate.
• the kits may further comprise a substrate to be bonded to a second major surface of the polymeric film.
• Laminate articles of the present invention can be used in a wide variety of applications. As described above, bonds at interfaces in the laminate may have a wide variety of strengths, from pressure-sensitive to structural strengths can be formed in a timely manner using materials and methods of the invention. "Pressure-sensitive” strengths are those that are about 3 N/dm to about 300 N/dm upon complete bond formation, as measured using a 90° peel adhesion test. "Structural” strengths are those that are greater than about 300 N/dm upon complete bond formation, as measured using a 90° peel adhesion test.
• Particularly preferred laminate articles are optical laminate articles. That is, they can be used in application where it is desired or necessary to be able to see through the laminate article without a distorted view. For example, computer screens, television screens, automobile windows, architectural windows, and a wide variety of other applications can benefit from the present invention.
• preferred polymeric film materials for use in laminate articles are poly(meth)acrylates and copolymers derived from (meth)acrylate monomers, as well as polyvinyl esters and copolymers derived from vinyl ester monomers.
• a clean glass plate was uniformly coated with a 10% solids isopropanol solution of plasticizer using a #12 wire wound rod, resulting in a 27-micron thick wet plasticizer coating.
• the coating was air-dried at room temperature to nominally give a 2.7 micron thick coating (approximately 0.3 mg/cm ⁇ ) of the dried plasticizer film.
• a 12.7-millimeter wide strip of a polyester backing coated with a transparent polymeric film was laminated to the dried plasticizer film using a 1.8-kilogram rubber roller. After dwelling at room temperature for 30 minutes, the free end of the polymer- coated polyester backing was doubled back nearly touching itself, so that the angle of removal was 180°. The free end was then attached to an adhesion tester scale.
• ROVENE 9413 (a carboxylated styrene-butadiene emulsion polymer, commercially available from Rohm and Haas; Spring House, PA) was knife-coated onto a 37-micrometer thick polyester backing to provide a polymeric film having a thickness of
• n-butyl acryl ate/acrylic acid (nBA/AA) solution copolymer was prepared by charging 18 grams butyl acrylate and 2 grams acrylic acid into a 100 mL glass bottle along with a solution of 0.06 gram VAZO 64 (a 2,2'-azo-bis(isobutyronitrile) initiator, commercially available from E.I. duPont de Nemours & Co.; Wilmington, DE) in 30 grams of acetone.
• VAZO 64 a 2,2'-azo-bis(isobutyronitrile) initiator
• Polymeric Film 3 A 98/2 (weight ratio) ethyl acrylate/acrylic acid (EA/AA) solution copolymer was prepared following the procedure in Polymeric Film 2, except ethyl acetate solvent was used as the solvent. After diluting to 20% solids with ethyl acetate, the resulting solution was coated to provide a polymeric film having a thickness of 23 micrometers after drying at 65° C for 10 minutes and conditioning for 24 hours at 23°C and 50% relative humidity. Performance in plasticizer-assisted lamination was assessed with the test method described above using the plasticizers found in Table 1.
• ELVACE 734 (a vinyl acetate-ethylene emulsion polymer, commercially available from Reichhold; Research Triangle Park, NC) was knife-coated onto a 37-micrometer thick polyester backing to a dry polymeric film having a thickness of 66 micrometers after drying at 65° C for 10 minutes and conditioning for 24 hours at 23°C and 50% relative humidity. Performance in plasticizer-assisted lamination was assessed with the test method described above using the plasticizers found in Table 1.
• Polymeric Film 5 Into a 100 mL glass jar charged with 10 grams 1 J APREN 500 (a vinyl acetate- ethylene copolymer, commercially available from BASF; Mt. Olive, NJ) and 15 grams FORAL 85 (a glycerine rosin ester tackifying resin, commercially available from Hercules, Inc.; Wilmington, DE), 83.3 grams toluene was added. After rolling for 16 hours at room temperature on a ball mill, the resulting solution was coated onto a polyester backing to produce a dry polymeric film having a thickness of 33 micrometers after drying at 65° C for 10 minutes and conditioning for 24 hours at 23 °C and 50% relative humidity. Performance in plasticizer-assisted lamination was assessed with the test method described above using the plasticizers found in Table 1.
• 1 J APREN 500 a vinyl acetate- ethylene copolymer, commercially available from BASF; Mt. Olive, NJ
• FORAL 85 a glycerine rosin ester tackifying resin
• a 96/4 (weight ratio) isooctyl acrylate/acrylamide (IOA/Acm) solution copolymer was prepared following the procedure in Polymeric Film 2. After diluting to 20% solids with acetone, the resulting solution was coated to provide a dry polymeric film having a thickness of 23 micrometers after drying at 65° C for 10 minutes and conditioning for 24 hours at 23°C and 50% relative humidity. Performance in plasticizer-assisted lamination was assessed with the test method described above using the plasticizers found in Table 1. Polymeric Film 7
• plasticizers listed in Table 1 were coated, dried, laminated to the polymeric film samples and tested for adhesion as described above.
• IOA isooctyl acrylate
• LBOA isobornyl acrylate
• AA acrylic acid
• a 90/10 IOA/AA copolymer was prepared by blending 45 grams IOA monomer with 5 grams AA monomer and 0.1 gram IRGACURE 651 (a 2,2-dimethoxy-2- phenylacetophenone photoiniator, commercially available from Ciba Specialty Chemicals Co ⁇ ; Tarrytown, NY) in a 100 mL jar.
• IRGACURE 651 a 2,2-dimethoxy-2- phenylacetophenone photoiniator, commercially available from Ciba Specialty Chemicals Co ⁇ ; Tarrytown, NY
• a portion of the resulting moderate viscosity, partially polymerized fluid was coated to a thickness of 45 micrometers between a 37-micrometer thick polyester film and a 51 -micrometer thick siliconized polyester release liner.
• the resulting assembly was further exposed to the fluorescent bulbs for 10 minutes to complete polymerization.
• a 75/15/10 IOA/LBOA AA te ⁇ olymer (Polymeric Film 9) was prepared by blending 10 grams of the fluid from Polymeric Film 8 with 5 grams of the fluid from Polymeric Film 1 1.
• a 60/30/10 IOA/LBOA/AA te ⁇ olymer (Polymeric Film 10) was prepared with 5 grams of the fluid from Polymeric Film 8 and 10 grams of the fluid from Polymeric Film 11.
• Examples 21 and 22 An 80/20 LBOA AA copolymer containing 40% added TERG ⁇ OL 15-S-9 plasticizer (Plasticizer L) was prepared by blending 48 grams LBOA monomer with 12 grams AA monomer, 40 grams of TERGITOL 15-S-9 and 0.08 grams IRGACURE 651. After purging and partial polymerization by exposure to light as described above for Polymeric Films 8 through 14, the resulting fluid was degassed by placing in a vacuum desiccator for one hour.
• TERG ⁇ OL 15-S-9 plasticizer Plasticizer L
• the composition was coated to a thickness of 90 micrometers between a 180 micrometer-thick, louvered cellulose (acetate-co-butyrate) privacy film (similar to those described in U.S. Patent No. 5,254,388) and a 51 micrometer-thick, siliconized polyester release liner. After further exposure to the fluorescent bulbs to complete polymerization, the opposite side of the louvered film was similarly coated with a 90 micrometer-thick coating of the composition to give a coating (Polymeric Film 15) on each side.
• a second doubly coated louvered film (Polymeric Film 16) was similarly prepared using a te ⁇ olymer of 35/55/10 butyl acrylate (BA)/LBOA AA containing 20% added
• the siliconized polyester release liner was removed from one side of each construction, which was then laminated onto a puddle of plasticizer on a clean glass plate (14.0 centimeters by 15.2 centimeters). Excess plasticizer and trapped air was squeegeed out and the second siliconized polyester release liner was removed from the side of the polymeric film-coated louvered privacy film opposite to the side laminated to the glass plate.
• a puddle of plasticizer was poured at one end of each exposed polymeric film and a second clean glass plate was pivoted down onto each polymeric film surface, allowing the fluid front to exhaust the air. Adjustment was made as necessary to align the assembly.
• the resulting laminates were evaluated in a cyclic temperature-humidity test involving 10 cycles of two hours at 25"C, 47.5% relative humidity; four hours at 65°C, 92.5% relative humidity; and eleven hours at 65°C, 47.5% relative humidity.
• the laminates maintained their essentially defect-free characteristics after such vigorous testing.

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