Patent Application
20170232701
The invention concerns a thin glass film composite web according to the generic concept of claim 1 and a method for the storage of thin glass film webs.
Optoelectronic devices are being used with increasing frequency in commercial products or will soon be introduced onto the market. Such devices comprise inorganic or organic electronic structures such as organic, organometallic, or polymeric semiconductors or combinations thereof. Depending on the desired application, the corresponding products have a stiff or flexible configuration, and there is an increasing demand for flexible devices. The production of such devices is often carried out by printing processes such as surface printing, roller printing, silkscreen printing, flat printing, or so-called “non-impact printing” processes such as thermal transfer printing, inkjet printing, or digital printing. However, vacuum processes such as chemical vapor deposition (CVD), physical vapor deposition (PVD), plasma-enhanced chemical or physical deposition processes (PECVD), sputtering, (plasma) etching, or vaporization are also used. Structuring is carried out by masking.
Examples of optoelectronic applications that are already commercially available or interesting in their market potential include electrophoretic or electrochromic structures or displays, organic or polymeric light-emitting diodes (OLEDs or PLEDs) in lighting and display devices or as illumination, as well as electroluminescent lamps, light-emitting electrochemical cells (LEECs), organic solar cells such as dye or polymer solar cells, inorganic solar cells, particularly thin-layer solar cells, for example based on silicon, germanium, copper, indium and selenium, perovskite solar cells, organic field effect transistors, organic elements, organic optical amplifiers, organic laser diodes, organic or inorganic sensors, or organically or inorganically based RFID transponders.
In the effort to achieve sufficient useful life and functioning of optoelectronic devices in the area of inorganic and organic optoelectronics, and particularly in organic optoelectronics, protection of the components contained therein from permeates is to be seen as a particular technical challenge. In this case, permeates are generally considered to be gaseous or liquid substances that penetrate into a solid and may pass or permeate through it. Accordingly, many low-molecular-weight organic or inorganic compounds can be permeates, with water vapor and oxygen being of particular importance in this connection.
A number of optoelectronic devices—particularly when organic materials are used—are sensitive to both water vapor and oxygen. Protection by means of encapsulation during the useful life of electronic devices is therefore necessary in order to prevent performance from decreasing over the period of use. If protection is insufficient, for example because of oxidation or hydrolysis processes, there may be sharp reductions in the luminosity of electroluminescent lamps (EL lamps) or organic light-emitting diodes (OLED), the contrast of electrophoretic displays (EP displays), or the efficiency of solar cells within a short period of time.
In inorganic and/or organic (opto)electronics, particularly in organic (opto)electronics, there is therefore a need for flexible substrates that protect electronic components and constitute a permeation barrier against permeates such as oxygen and/or water vapor.
Glass provides particularly favorable protection from permeates. For some time, therefore, highly thin and flexible types of glass have been available on the market, with the product Willow® Glass manufactured by Corning being an example. This extremely thin and flexible glass can be used for electronic structures, and may significantly change the form of mobile terminal devices such as smartphones and tablets.
Thin glass films are supplied as films 100 μm in thickness on 1 m wide rolls having a length of up to 300 m.
For mechanical stabilization purposes, a thin glass film is often equipped with a protective polymer film. The protective film may remain permanently on the glass, or may be removed prior to use of the OLEDs in the final application. Protective films are ordinarily applied using an adhesive to the thin glass film. Measures to maintain stability are of essential importance in wide-ranging use of thin glass on rolls; on the one hand, such measures serve in particular to prevent stress corrosion cracking during storage of the roll, and on the other, however, a further important aspect of stabilizing the thin glass film is stabilization of the glass edge.
In the method of producing the thin glass film by the so-called down-draw process, the edge is initially thickened as a border, cf. WO 00/41978 A1. However, the border makes it more difficult to wind the thin glass film onto a roll, because on the one hand, this thickening allows only a small bending radius to be achieved, and on the other hand, the layers do not lie against one another in planar fashion. As a rule, therefore, the border on the thin glass film is cut off prior to winding onto a roll. The cut edge then remains as an extremely sensitive area, from which glass cracks tend to propagate into the interior of the thin glass film. In the handling and separation processes to which thin glass films are subjected during production, highly precise positioning of the thin glass film is often required. In particular, in lateral web guidance of the thin glass film in a roll-to-roll process, particularly strong forces act on the edge, increasing the risk of web cracks.
Glass is known to show a strong permeation-blocking effect against water vapor and oxygen, and it is therefore suitable for the encapsulation of OLEDs, which are sensitive to water vapor and oxygen. Flexible or bendable OLEDs require flexible encapsulation, which can advantageously be achieved using a flexible thin glass film. Thin glass films are bendable to a limited extent, and are therefore also suitable for the production of flexible or bendable devices. However, the thin glass film is highly sensitive, and damage may occur, originating in particular from the glass edge of the thin glass film, especially when this glass edge has been cut. Devices and methods used for stabilization, particularly of the edge of the thin glass film, are known from the prior art.
WO 2011/014606 discloses a flexible polymeric glass coating that projects at its edge beyond the glass. The coating can cover the glass over its entire width, or over only a portion thereof. The coating material can be reinforced with polymer or glass fibers. The coating can be applied as a liquid or as a preformed film. Both polymers and metal, also in combination with a polymer, are suggested as materials for the preformed film. The flexible glass film projecting laterally on the glass film allows simpler handling, i.e. the glass film can be picked up and transported using the two lateral coating projections.
A drawback of the glass coating is that it has an elastic modulus that is less than that of glass, and it therefore yields to tensile loads in the longitudinal direction of the thin glass film, so that the load is transferred directly to the edge of the thin glass film. Moreover, reinforcing materials in the form of polymer or glass fibers are applied along the entire width of the glass coating, causing its overall flexibility to decrease. Even when glass or polymer fibers are added in the maximum amount of 30 percent by weight, which is common for coatings or polymer films, the overall elastic modulus of the glass coating remains significantly lower than that of the glass film itself.
WO 2008/069930 A2 discloses a composite material of a glass layer and a flexible polymeric carrier layer. The glass layer is arranged on the polymer layer, with the polymer layer as a carrier material projecting beyond the edges of the glass layer.
The drawback in this case as well is that the polymer layer has a significantly lower elastic modulus than that of the thin glass film and therefore yields to tensile stress at the edge of the thin glass film, causing the stress to be transferred to the edge of the glass.
U.S. Pat. No. 6,815,070 B1 describes a glass-plastic composite for stabilizing thin glass. The thin glass is coated with liquid polymers. The polymer layer is applied to a thin glass film by spinning, spraying, pouring, rolling, or dipping. The polymer coating can also enclose the edge of the thin glass. However, the coating is of a homogeneous material, and it is extremely thin at the edge, making it incapable of absorbing the tensile forces generated at the edge of the thin glass film during web guidance. In this case as well, the polymer coating enclosing the edge shows a significantly lower elastic modulus than that of the glass itself and therefore yields to tensile stress at the edge of the glass, causing the stress to be transferred to the edge of the thin glass film.
EP 2336048 A1 discloses composites of a thin glass film and a polymeric carrier film in which the carrier film extends beyond the thin glass in the direction of the web not only in the front and rear, but also laterally. A drawback in this case as well is that the flexible polymeric carrier film has a significantly lower elastic modulus than glass, and therefore yields to a tensile stress at the edge of the thin glass film, with the result that the stress is transferred to the edge of the glass, where it can lead to crack formation.
US 2010/0260964 A1 concerns a composite of a thin glass film and a carrier material wound onto a roll, with the carrier material extending laterally beyond the edges of the thin glass film in this case as well. The polymer carrier material or the protective film is/are configured homogenously over their entire surface.
U.S. Pat. No. 6,592,969 B1 also discloses a composite that can be wound onto a roll composed of a thin glass film and a carrier material, with the carrier material also extending laterally beyond the edges of the thin glass film. In this case as well, the carrier material is homogenously composed of the same material over its entire surface.
US 2005/0053768 A1 discloses a glass protective film having embossed protruding features. The protective film may consist of a composite of a smooth polymer layer and a rough layer of paper or fabric, or may also be a pure polymer layer. The embossing provides the protective film with areas of differing tensile strength, which, however, are randomly distributed over the surface and show areas of lower tensile strength precisely at the edge. Moreover, the protective film does not extend beyond the edges. Fabrics and paper as reinforcing materials show a significantly lower elastic modulus than glass and therefore yield to tensile stress at the edge of the glass, so that in this case as well, the stress is transferred to the edge of the glass. The protective film is not suitable for protecting the edge by absorbing tensile forces acting from the edge.
EP 2548730 A1 discloses a composite of a thin glass film and a polymer carrier material that can be wound onto a roll, with the carrier material extending laterally beyond the edges of the glass film. Again, in this case, the polymer carrier material has a significantly lower elastic modulus than that of the glass, and the polymer carrier material is composed of a single material over its entire length.
US 2013/0196163 A1 discloses a composite of a thin glass film wound onto a roll having a reinforcing layer, with the thickness of the reinforcing layer being selected so that when the composite is bent toward the glass side, the neutral surface does not lie within the glass layer. This is the case when the thickness of the reinforcing layer is greater than the thickness of the thin glass film multiplied by the root of the quotient of the elastic modulus of the glass divided by the elastic modulus of the reinforcing layer. A drawback is that because of the high tensile strength of the entire reinforcing layer, the resulting composite is extremely rigid, i.e., the flexibility of the composite material is significantly reduced compared to the pure glass film.
The object of the invention is to provide a thin glass film composite web that allows improved protection of the edge of the thin glass film and nevertheless does not excessively increase bending stiffness.
It is also the object of the invention to provide a method for the storage of a thin glass film web.
In its first aspect, the object is achieved by means of the thin glass film composite web mentioned above that has the characterizing features of claim 1.
The object is achieved in its second aspect by a method having the features of claim 16.
The thin glass film composite web according to the present invention has a thin glass film web with a first and second surface and two thin glass film edges running in the longitudinal direction of the thin glass film web. The thin glass film composite web also has a protective film web of a first material that extends at least along a portion of the first surface of the thin glass film. According to the invention, at least one reinforcing strip of a second material is provided that runs along at least one of the two thin glass film edges and is different from the first material, with the protective film web and the at least one reinforcing strip being connected to one another such that they can be applied together to the thin glass web. The at least one reinforcing strip also shows a higher relative tensile strength than the thin glass film web.
First, a film web is understood to be a sheetlike structure whose dimensions in one spatial direction, i.e. height or thickness, are significantly smaller than in the other two spatial directions. The main extension is defined by length and width. In a film web, moreover, width and thickness are specified. As a rule, however, the length of the film is not specifically defined. The length of the film web is ordinarily at least 10 times greater than the width. The film web can have a simple continuous configuration, or it may also be interrupted. It can consist of a single material or areas of different materials, but can either have a constant thickness over its entire surface area or have areas of different thicknesses. The film web can consist of one or a plurality of layers that are arranged in congruent fashion, or may have an at least partially non-overlapping configuration.
A thin glass film web in understood to refer to a film web having a height of 10 to 200 μm, preferably 20 to 100 μm, more preferably 25 to 75 μm, and particularly preferably 30 to 50 μm. The entire thin glass film web is preferably composed of thin glass. Thin glass films are highly suitable as impermeable substrates. Examples of available thin glasses include D263 from Schott or Willow® Glass from Corning.
A borosilicate glass such as D263 T from Schott, an alkali-alkaline earth-silicate glass, or an aluminum borosilicate glass such as AF 32 eco, also from Schott, is preferably used for the thin glass film composite web according to the invention. An alkali-free thin glass such as AF 32 eco is advantageous because its UV transmission is greater. For UV-curing adhesive systems, therefore, initiators with absorption maxima in the UV-C range can be more favorably used, which increases the stability of the uncrosslinked adhesives with respect to daylight.
An alkali-free thin glass such as D263 T eco is advantageous because its thermal expansion coefficient is higher, and it is more compatible with the polymer components of an organoelectronic device such as an OLED unit.
Such thin glass can be manufactured by the down-draw process, as referenced in WO 00/41978 A1, or by methods such as those disclosed for example in EP 1832558 A1. In the former document, further methods are disclosed for producing composites of thin glass and polymer layers or films. In thin glass films or thin glass film webs, because of the intrinsically high barrier properties of the glass against oxygen and hydrogen, further barrier coating is unnecessary.
The protective film web of a first material extends along at least a portion of the first surface of the thin glass film web. The protective film web preferably covers the first surface completely or at least in some areas, and preferably at least along a strip on each of the two edges of the thin glass film web.
The first surface of the thin glass film web is preferably completely covered, because in this case, the protective film web protects the entire surface of the thin glass film web, for example against mechanical, chemical, or physical damage.
As the material of the protective film web of the thin glass film composite web according to the invention, sheetlike materials, papers, plastic-coated papers, or films can be used, with said films in particular being dimensionally stable plastic or metal films. Non-limiting examples thereof include metal films of aluminum or plastic films of polyolefins such as polyethylene (PE) or polypropylene (PP), cyclic olefin copolymers (COC), polyvinyl chloride (PVC), polyesters—particularly polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polymethyl pentene (PMP), ethylene vinyl alcohol (EVOH), polyvinylidene chloride (PVDC), fluoropolymers such as polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polycarbonate (PC), polyamide (PA), polyether sulfone (PES), polyether imide (PEI), polyarylate (PAR), cellulose triacetate (TAC), polymethacrylate (PMMA), or polyimide (PI).
The protective film web preferably consists of polyesters, particularly polyethylene terephthalate, for example biaxially oriented polyethylene terephthalate, or polyolefins, particularly polybutene, cycloolefin copolymer, polymethyl pentene, polypropylene, or polyethylene, for example monoaxially oriented polypropylene, biaxially oriented polypropylene, or biaxially oriented polyethylene or copolymers thereof. Polyester films are advantageous in that they provide temperature stability and increased mechanical stability. Therefore, it is most particularly preferred for the protective film web to consist of a polyester film such as biaxially oriented polyethylene terephthalate. Polyolefins are advantageous because of their low water vapor permeation rate and reduced water content. Therefore, it is most particularly preferred for the protective film web to consist of a film comprising cycloolefin copolymer or polymethyl pentene, materials that also show higher temperature stability than other polyolefin films.
The protective film web may also be composed of composites, particularly layered composites, of the above-mentioned materials with one another or with other materials.
In a preferred embodiment, the protective film web has a barrier function. The barrier function prevents one or more specific permeate(s), particularly water vapor, from penetrating the thin glass film composite and promoting stress corrosion cracking in the thin glass web.
The barrier function is preferably provided by a barrier layer. The barrier layer is favorably configured on a surface of the protective film web, but can also be contained therein as a layer.
Such a barrier layer can consist of organic or inorganic materials, for example a metal layer, an organic layer, or a sol-gel layer.
The barrier layer is preferably provided on an inner side of the protective film web facing the glass film, as this allows better protection of the barrier layer from mechanical damage.
Particularly preferably, the protective film web comprises at least one inorganic barrier layer. Particularly suitable as inorganic barrier layers are metals deposited in a vacuum (for example by evaporation, CVD, PVD, or PECVD) or under atmospheric pressure (for example by means of atmospheric plasma, reactive corona discharge, or flame pyrolysis) such as aluminum, silver, gold, nickel, or particularly metal compounds such as metal oxides, nitrides, or hydronitrides, for example oxides or nitrides of silicon, boron, aluminum, zirconium, hafnium, or tellurium or indium tin oxide (ITO). Layers of the aforementioned variants doped with further elements are also suitable.
Examples of particularly suitable methods for applying an inorganic barrier layer include high-power impulse magnetron sputtering and atomic layer deposition, by means of which highly impermeable layers can be produced with low temperature stress on the protective film. Preferred is a permeation barrier of the protective film web having a barrier function or a composite of the protective film web and the barrier layer that has a water vapor transmission rate (WVTR) of <1 g/(m2·d) and/or an oxygen transmission rate (OTR) of <1 cm3/(m2·d·bar), with this value referring to the respective thickness of the protective film web having a barrier function, i.e., not being standardized to a specific thickness. Here, WVTR is measured at 38° C. and 90% relative humidity according to ASTM F-1249, and OTR is measured at 23° C. and 50% relative humidity according to DIN 53380 Part 3.
The reinforcing strips composed of a second material different from the first material are arranged along each or at least one of the two edges of the thin glass film web, preferably along its entire extension in the longitudinal direction. The reinforcing strips run essentially parallel, and preferably exactly parallel to the edge of the thin glass film web. In this case, the reinforcing strips run parallel to the ideal edge of the thin glass film web, as the real edge of the thin glass film web has tolerances in its straightness such as camber or edge waviness. The reinforcing strips have a specified width and thickness or height. Their length is as a rule not specifically defined, but is based on the length of the thin glass film web. The length of the reinforcing strips is preferably identical to the length of the thin glass film web.
The width and height of the reinforcing strips should preferably remain constant over the entire length of the reinforcing strips, i.e., the cross section should remain identical over the entire length. However, it is also conceivable to configure the height and/or width in a variable manner over said length.
The reinforcing strips can be configured along their entire length on the edge of the thin glass film web. However, the reinforcing strips can also be discontinuous over their length, for example if the glass film web consists of individual sections in the longitudinal direction, with the reinforcing strips being configured only along the edge of the thin glass film web.
According to the invention, the reinforcing strips of the protective film run only in the area of the edge of the thin glass film, i.e., the reinforcing strips do not extend in their width over the entire width of the thin glass film web and/or the protective film web. The sum of the widths of the reinforcing strips along one edge of the thin glass film web should be less than half the entire width of the thin glass film web, preferably less than a third, and particularly preferably less than a quarter of the entire width of the thin glass film web.
As at least one reinforcing strip runs along at least one of the two edges, the projection of the reinforcing strips parallel to the surface of the thin glass film web in the plane thereof will lie at last partially outside of the surface of the thin glass film web. Here, ‘partially outside’ also includes contact of the edge of the projection of the reinforcing strips with the edge of the thin glass film web. Preferably, the projection of the reinforcing strips lies outside the surface of the thin glass web with at least half of its area, and particularly preferably is completely outside the surface of the thin glass film web.
More clearly, this means that a reinforcing strip in the projection covers or is flush with (lies exactly on the edge of) the glass edge, or lies outside the thin glass film web adjacent to the glass edge. The projection of the reinforcing strips can also be at an external distance from the edge of the thin glass film web. The figures show both arrangements according to the invention and arrangements not according to the invention.
The reinforcing strips may have different external dimensions, particularly in width and height, and in their arrangement with respect to the edge of the thin glass film web.
The reinforcing strips are preferably arranged at a distance from the thin glass film edge, and said reinforcing strips are advantageously arranged along the entire length at a distance from the thin glass film edge. The distance allows tolerances in the straightness of the thin glass film web reinforcing strips, particularly camber and waviness of the edge of the thin glass film web, to be buffered. Within the separation zone between the reinforcing strips and the thin glass film web, an area is formed which consists solely of the partial area of the protective film web, is reinforced neither by the reinforcing strips nor the thin glass web itself, and as a rule shows greater flexibility than the reinforcing strips and the thin glass film web. This makes it possible to elastically buffer force peaks and web offset and to gently transfer unilateral stresses on the thin glass film composite web, for example by means of web edge control, to the thin glass film web without placing excessive stress on the thin glass film edge. The distance d is limited at its lower boundary by the usual tolerances in the straightness of the thin glass web. These are approximately 0.5 mm to 10 mm. In principle, the distance is not limited at its upper boundary, but a distance of 10 to 50 mm is preferred, because if the distance is greater, web guiding forces transferred to the reinforcing strips may lead to the formation of folds in the exposed area of the protective film web.
The reinforcing strips are preferably completely arranged in a space spanned by the intended lateral prolongation of the first and second surface of the thin glass film web, i.e. the thin glass film layer.
Preferably, the first and second surface of the thin glass film web have a planar configuration, and each forms one layer. The intended lateral projections of the layers beyond the respective edge of the thin glass film web open up a space in which the thin glass film is arranged, said space having a height corresponding to that of the thin glass film, which as a rule is not limited in its width, unless the two surfaces are inclined at angles to each other and intersect along a lateral line, and has a length corresponding to the length of the thin glass film composite web. This space is also referred to here as the thin glass film layer. Accordingly, a protective layer in which the protective film web is arranged is formed.
The reinforcing strips are preferably arranged completely within the thin glass film layer, which means that an outermost end or a free end of the reinforcing strips facing away from the protective film has a height above the protective film web that is equal to or less than the height of the second surface of the thin glass film web above the protective film web.
In a further preferred embodiment of the invention, an upper free side of the reinforcing strips aligns with the second surface of the thin glass film web. This allows the thin glass film composite web to be wound onto the roll without being offset along its width.
In another embodiment, the height of the reinforcing strips is greater than the height of the thin glass film web above the protective film web. This provides particularly rigid reinforcing strips. However, it is preferable if the height of the reinforcing strips is not greater than five times the thickness of the thin glass film web, and particularly preferably not greater than three times this thickness, as the bending stiffness will otherwise become too great, making it difficult to wind the thin glass film composite onto a roll.
The reinforcing strips can have cross-sectional areas that are of the same size and thus the same tensile strength but are nevertheless of different heights. The reinforcing strips with the greater height then have a higher bending stiffness.
In a further preferred embodiment of the invention, however, the height of the reinforcing strips is lower than the height of the thin glass film web, so that in this embodiment, lower bending stiffness is achieved, with the result that the thin glass film composite remains particularly flexible and can thus be favorably wound onto a roll using only minimal force.
In preferred embodiments of the invention, an adhesive layer, particularly a pressure-sensitive adhesive layer, is provided between the thin glass film web and the protective film web. The protective film web can enclose the adhesive layer, but it can also be separately applied to the glass film or the protective film. The adhesion may be provided by the protective film material itself or by a layer of an adhesive, preferably a pressure-sensitive adhesive or an activatable adhesive.
The protective film web can be coated with a fluid phase onto the thin glass film web or can be applied as a prefabricated layer, for example as a film, to the thin glass film web. The protective film web is advantageously an adhesive tape with at least one carrier material layer and at least one adhesive layer and is connected with at least one reinforcing strip.
According to the invention, the protective film web and the at least one reinforcing strip are connected to one another such that they can be applied together to the thin glass web. Applied together means that a composite of the protective film web and the reinforcing strips can first be formed, and this composite can then be brought into contact with the thin glass film web.
The reinforcing strips can be formed by introducing reinforcing material into a protective film web, particularly into the carrier material layer thereof, for example by methods such as coextrusion or pultrusion. Examples of suitable reinforcing materials include metal or carbon fibers, carbon nanotubes, graphene, and crystalline or amorphous mineral fibers. The introduced reinforcing materials should preferably have a higher elastic modulus than the thin glass, particularly an elastic modulus that is greater than that of the thin glass by a factor of 1.5. This makes it possible to produce reinforcing strips that are thin in height, which thus have a lesser overall effect on the bending flexibility of the composite.
The reinforcing strips can be applied as a further layer to the protective film web and bonded thereto. However, they can also be introduced into the protective film web in sections and thus form a further web within the protective film web. Production of the composite of the protective film web and the at least one reinforcing strip is preferably carried out before applying the protective film web to the thin glass film web, but it can also take place thereafter.
The configuration with the protective film web composed of the first material and the reinforcing strips composed of the second material means that the chemical or physical composition of the two webs is different. This difference can also result from the physical introduction of further components into the first material, causing this area as a whole, into which the components are introduced, to constitute a second material. For example, from a chemical standpoint, the second material can completely contain the first material. Nevertheless, the two materials as a whole show different elastic moduli. According to the invention, the reinforcing strips have a relative tensile strength that is at least equivalent to the relative tensile strength of the glass film web. Here, tensile strength is understood to refer to the elastic modulus multiplied by the cross-sectional area A of the reinforcing strips or the glass film web. The relative tensile strength relates to the respective web or the strip and is therefore equal to the tensile strength divided by the width B. If the cross-section of the reinforcing strip is not rectangular, the maximum width is taken as the width.
The reinforcing strips may by all means be configured with multiple layers or coatings. When the reinforcing strips are composed of multiple layers, the total tensile strength is equal to the total of the tensile strengths of the individual layers.
The elastic modulus of thin glass is approximately 70 to 80 GPa, which means that in order to achieve the relative tensile strength according to the invention in the reinforcing strips, the thickness of the reinforcing strips can be increased with respect to that of the glass film, or the elastic modulus of the second material is increased. As the thickness of the reinforcing strips should preferably not exceed the thickness of the thin glass film, because otherwise the thin glass films will not entirely cover the radially adjacent inner wraps of the roll on winding of the thin glass film composite web onto said roll, causing tensions in the roll, it is preferably provided that the elastic modulus of the reinforcing strips is greater than that of the thin glass.
Materials with an elastic modulus at 23° C. and relative humidity of 50% of more than 80 GPa, and particularly more than 100 GPa, are preferably used as the material of the reinforcing strips, as this allows the thickness of the reinforcing strips to be kept low, with the result that the bending flexibility of the entire composite of the thin glass film composite web is impaired to a lesser degree. The reinforcing materials can be provided as a continuous layer in fiber or plate form. They can essentially be present in the reinforcing strips as a pure material or embedded in a matrix material, for example a polymer, a metal, or a ceramic. In addition to metals, examples of known materials include S-glass fibers, carbon fibers, aramid fibers (such as Kevlar 49), carbon nanotubes, graphene, and crystalline or amorphous mineral fibers (such as Saffil aluminum oxide fibers). As the material of the reinforcing strips, a metal layer, for example in the form of a metal film or metal fibers, is preferably used. Because of their high elastic moduli, iron, steel, copper, brass, bronze, titanium, nickel, and alloys thereof are preferred. The elastic moduli of several fibers are shown below, with particular examples of suitable materials selected for the reinforcing strips being S-glass, alumina, carbon and Kevlar 49.
The relative tensile strength of the reinforcing strips is greater than the relative tensile strength of the protective film web.
The protective film web is preferably glued onto the thin glass film web with an adhesive.
The adhesive applied to the protective film web is preferably a pressure-sensitive adhesive or an activatable adhesive, particularly a reversible and/or transparent adhesive. Particularly preferably, the adhesive placed on the carrier material layer is a pressure-sensitive adhesive.
Pressure-sensitive adhesives are adhesives whose cured film remains permanently tacky and adherent at room temperature in a dry state. Pressure-sensitive adhesives allow lasting bonding to the adhesive substrate with only relatively weak application pressure.
A distinction is generally made between pressure-sensitive adhesives for permanent applications and for reversible applications (reversibly configured pressure-sensitive adhesives). While the former generally can only be removed using a high degree of force and often with destruction of the adhesive substrate or the adhesive tape, the latter can generally be completely removed with relatively little force, leaving no residue, and without destroying the adhesive substrate.
According to the invention, the adhesive on the protective film web of the adhesive tape used in the method according to the invention is preferably reversibly configured.
The reversibility of a pressure-sensitive adhesive can be described by means of its viscoelastic properties.
In terms of its viscoelastic properties, a substance is generally considered suitable for pressure-sensitive adhesive applications if the memory modulus G′ is in the range of 103 to 106 Pa and the loss modulus G″ is also in this range at room temperature in the frequency range of 10° to 101 rad/s, and ideally 10−1 to 102 rad/s. Within this range, which can also be referred to in a matrix plot of G′ and G″ (G′ plotted against G″) as the viscoelastic window for pressure-sensitive adhesive applications or as the pressure-sensitive adhesive window according to viscoelastic criteria, there are also various sectors or quadrants that more specifically characterize the expected pressure-sensitive adhesive properties of the relevant substances. According to Chang (J. Adhesion, 1991, Vol. 34, pp. 189-200), reversible pressure-sensitive adhesives are characterized by G′ in the range of 103 to 3×104 Pa and G″ in the range of 103 to 3×104 Pa at room temperature and a measurement frequency of 10−2 rad/s respectively.
Here, the memory modulus and loss modulus of pressure-sensitive adhesives are determined in an oscillatory shear test (dynamic mechanical analysis, DMA) under torsional loading at a temperature of 23° C. and a frequency of 0.01 rad/s. This test is used to investigate rheological properties and is described in detail in Pahl et al., “Practical Rheology of Plastics and Elastomers,” VDI Publishing, 1995, pp. 57-60 and 119-127). The test is conducted in a shear rate-controlled rheometer under torsional loading using a plate-plate geometry with a plate diameter of 25 mm.
Generally speaking, according to the invention, an adhesive is preferably to be considered reversible if it shows an adhesive strength on steel of <3 N/cm, and preferably <2.2 N/cm.
According to the invention, all pressure-sensitive adhesives known to the person skilled in the art may be used, with examples including those based on acrylate and/or methacrylates, polyurethanes, natural rubbers, and synthetic rubbers; styrene block copolymer adhesives having an elastomer block of unsaturated or hydrogenated polydiene blocks such as polybutadiene, polyisoprene, copolymers of the two, polybutylene, particularly polyisobutylene, as well as elastomer blocks known to the person skilled in the art; polyolefins, particularly poly-α-olefins and/or polyisobutylenes; and fluoropolymers and/or silicones. The term “pressure-sensitive adhesive” also includes other adhesives possessing pressure-sensitive adhesive properties, as described in the “Handbook of Pressure Sensitive Adhesive Technology” by Donatas Satas (Satas & Associates, Warwick 1999).
When the term acrylate-based pressure-sensitive adhesives is used in this specification, it is also understood to comprise pressure-sensitive adhesives based on methacrylates or acrylates and methacrylates, without these having to be further specified, unless expressly stated otherwise.
Adhesive systems in which the generation of adhesive force in general is carried out by increasing or reducing the adhesive force using energy input, such as actinic radiation or heat, or by means of a material interaction, are considered to be activatable adhesives. This activation is preferably used in order to make the adhesive bonding reversible, particularly in cases where a pressure-sensitive adhesive does not fall into the category of reversible pressure-sensitive adhesives prior to its activation (Chang, J. Adhesion, 1991, Vol. 34, pp. 189-200). For example, such activatable pressure-sensitive adhesives are known from the area of grinding and dicing of adhesive tapes used in wafer processing.
In general, all commonly-used activated adhesive systems can be used as activatable adhesives. According to the invention, this activation is generally carried out by means of energy input, for example and particularly preferably using actinic radiation or heat (heat-activated debondable adhesives).
According to the invention, so-called “autoadhesive” layers are also considered to be reversibly configured pressure-sensitive adhesives. Autoadhesive layers are used for example in protective films for displays. They show very little or no initial tack and adhere particularly well to extremely smooth surfaces. Autoadhesive layers are described for example in WO 2005/044560 A1 or DE 19742805 A1.
The adhesive preferably contains at least one silane. Silanes are often used as coupling agents in order to increase adhesive bonding to glass. Examples are presented in U.S. Pat. No. 6,195,608, WO 2008/036222 A1, JP 2000-003782 A1, U.S. Pat. No. 6,501,014 B1, WO 2011/084323 A1, and EP 0924761 A1. The silane is not only applied to the thin glass film web prior to adhesion, but may also be contained in the adhesive itself. Silanes may be used that contain chemical groups which show favorable compatibility with the adhesive, or can even form covalent, ionic, or coordinative bonds with the adhesive. In cases where the protective film web adheres permanently to the thin glass film web, the adhesive preferably contains a silane showing favorable compatibility with said adhesive. In another embodiment of the invention in which the protective film web is again detached from the thin glass film web, reversible adhesives are used. These may contain a silane that is incompatible with the adhesive or a silane that cannot form covalent, ionic, or coordinative bonds with the adhesive. This largely prevents any increase in the adhesion of the reversible adhesive to the thin glass film web. Because of the incompatibility of the silane with the adhesive, the silane molecules capable of migration are deposited on the surface of the adhesive and therefore come into contact with the glass film web in large amounts. By means of the silane film formed in this manner on the second surface of the thin glass film web, microcracks can even be bridged over, improving the stability of the glass. The adhesive preferably contains a hydrophobic silane, with the term hydrophobic silane referring here to silanes with more than eight connected carbon atoms, such as octadecyldimethyl chlorosilane.
The invention also concerns a method for the storage of thin glass film webs, in which
Advantageous variants can be found in the attached claims 18 to 26.
A method is further disclosed in which the area of the protective film containing the reinforcing zones is removed after processing or handling of the glass film, for example in a roll-to-roll process. Other areas of the protective film remain at least temporarily on the glass. The other areas should preferably remain on the glass web permanently. In this way, the glass film can be provided with a permanent protective film whose reinforcing zones remain in the composite material only temporarily. In this method, it is particularly preferred for the reinforcing zones to be arranged adjacent to the glass web so that they can be removed simply by cutting them off along the web.
The invention is described in several embodiments in 18 figures which show the following:
The thin glass film web 10 has a first surface 11 and a second surface 12. A second surface 22 of the protective film web 20 is applied to completely cover the first surface 11. “Completely cover” in this case means that the first surface 11 of the thin glass film web 10 is completely covered by the protective film web 20.
The protective film web 20 projects laterally along width B on both sides beyond the thin glass film web 10. The thin glass film web 10 shows two lateral edges 15, 16 running in a longitudinal direction L. The two edges 15, 16 are highly sensitive, because as in this case, thin glass film webs 10 ordinarily have a thickened border on the longitudinal sides after production which is cut from the thin glass film web 10 in the longitudinal direction L for better handling of said thin glass film web 10. The resulting cut edges 15, 16 of the thin glass film web 10 according to
In the embodiment according to
In the embodiment of the thin glass film composite web of the invention 1 according to
An advantage of the embodiment of
In the embodiments of
In an advantageous method, the protective film web is separated from the thin glass film together with the at least one reinforcing strip after use of the thin glass film composite, for example for constructing or encapsulation of an electronic device. In this case, the use of a non-permanent adhesive is advantageous.
In a further advantageous method, only the at least one reinforcing strip is separated from the thin glass film after use of the thin glass film composite, wherein a part of the protective film is optionally also separated. This can take place, for example, by lateral edge cutting. Particularly well-suited for this purpose are structures in which the reinforcing strip is arranged at a distance from the thin glass edge, for example according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 221 245.6 | Oct 2014 | DE | national |
This application is a 371 of PCT/EP2015/071498, filed Sep. 18, 2015, which claims foreign priority benefit under 35 U.S.C. §119 of the German Patent Application No. 10 2014 221 245.6 filed Oct. 20, 2014, the disclosures of which patent applications are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/071498 | 9/18/2015 | WO | 00 |
