Composite film with shielding areas

Abstract

The present invention relates to a composite film comprising a polyvinyl acetal having an opaque region disposed on a carrier film.

Description

[Technical Field]

[0001] The present invention relates to a composite film comprising a polyvinyl acetal having areas of obscuration disposed on a carrier film.

[0002] Interlayer films comprising polyvinyl acetal have long been known as adhesive layers for laminating glass. In particular, plasticized polyvinyl butyral (PVB) films are widely used as adhesive layers for glass-glass laminates, for example, for windshields in automotive applications.

[0003] It is also known to use an interlayer film that is opaque to visible light in certain areas of the windshield to protect the sealant or adhesive that mechanically connects the windshield to the chassis from UV radiation and to conceal the sensor system from view from the outside of the vehicle for aesthetic reasons.

[0004] It is further known to use patches of thin, non-transparent plastic film in combination with a typical plasticized PVB film to introduce this shielding. For example, WO 2019 / 038043 discloses a thin, non-plasticized PVB film with printed shielding areas.

[0005] However, there remains a need in the industry for improved means of providing laminated glass with obscured areas, particularly for use in vehicle windshields.

[0006] It is therefore an object of the present invention to provide a film having a shielding area with improved properties, including better processability, particularly during the printing process and during storage and / or transportation, lower manufacturing costs, and / or higher optical quality, particularly in terms of optical defects such as wrinkles, bubbles or grains, lower haze, and / or less yellowness.

[0007] This and other problems have been solved by the present invention.

[0008] In a first aspect, the present invention relates to a composite film comprising a film A containing polyvinyl acetal and optionally a plasticizer, and a carrier film, wherein film A is provided with a shielding region.

[0009] The amounts specified for the content of plasticizer and other ingredients in the individual films, as well as all dimensions such as thickness and surface roughness, refer to the "before lamination" state, i.e., the state of Film A and Film B before they are brought into contact with each other.

[0010] The term "shielding area" refers to an area of ​​film A having a light transmittance of less than 10% in the visible spectrum (380 nm to 780 nm). In a variant, the shielding area may fade to transparency, for example in the form of a dotted area or a gradient, or the shielding area may have a transparent area embedded therein, for example to provide a viewing area for a camera. In such a variant, at least a portion of the shielding area has a light transmittance of less than 10% in the visible spectrum.

[0011] The term "composite film" is intended to mean a film comprising at least two separate layers, one of which is deposited onto the other during manufacture. In the context of the present invention, film A is preferably deposited onto a carrier film by solution casting.

[0012] For a uniform blocking area, i.e., a blocking area that does not fade or have a dot pattern, a colorant (pigment or dye) can be added to the bulk polyvinyl acetal starting material prior to the manufacture of the composite film.

[0013] However, the masking areas are preferably provided by an ink layer printed or coated on the surface of film A facing away from the carrier film. This preferred embodiment allows for more complex patterns to be provided, for example dotted areas or fading, such as from black to grey or from black to transparent.

[0014] The carrier material can be selected from any material compatible with polyvinyl acetal and the manufacturing method used to provide the composite film. Thus, the carrier material can be glass or metal. However, it is preferred to use a polymer material selected from the group consisting of polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyamide, polycarbonate, polyethylene terephthalate (PET), polyethylene terephthalate copolymer, polyhydroxyalkanoate, polyurethane, polyolefin such as polyethylene or polypropylene, acrylonitrile styrene acrylate, polyacrylate and polymethacrylate, polyvinyl alcohol, and TAC (cellulose triacetate). Most preferably, the carrier contains polyethylene terephthalate (PET), and more specifically, the carrier is a film made of PET.

[0015] The thickness of the carrier film is preferably 10 μm to 500 μm, more preferably 25 μm to 250 μm, and most preferably 50 μm to 100 μm.

[0016] Also, preferably, film A is adhered to the carrier film with an adhesive strength of 0.05 N / 3 cm to 10 N / 3 cm, more preferably 0.1 N / 3 cm to 5 N / 3 cm, and most preferably 0.5 N / 3 cm to 3 N / 3 cm.

[0017] It has been found that using a composite film with this adhesive strength and carrier film thickness range makes it possible to provide a very thin film A with a shielding area. Film A should be as thin as possible because it is typically cut to shape and used only as a patch in a specific area of ​​the windshield. In one cutting variation, film A is cut with a steel die or laser while the carrier remains intact (also known as kiss cutting). In this way, the printed part can be cut to its final size and shape and protected from damage or contamination due to the stabilizing effect and protection provided by the carrier film. Cutting a freestanding film A without a carrier, on the other hand, would be extremely difficult for a very thin film. The thinner film A, the better, because the total thickness of the combined interlayer film for lamination will have less variability.

[0018] The thickness of the film A is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm, and specifically 20 μm to 40 μm.

[0019] When the surface of film A is printed or coated, it is advantageous to have a smooth surface to be printed on in order to provide a uniform printed pattern, while the opposite side of film A, which is not printed or coated, advantageously has a specific roughness Rz. This roughness allows for improved degassing during the lamination process and also makes it easier to handle patches of film A, because film A is less likely to stick to glass or plasticized polyvinyl acetal film B before lamination.

[0020] It has now been found that a specific roughness Rz of the carrier allows the production of a film A having one very smooth surface and one surface with a specific roughness, particularly when using a solution casting process. The specific roughness of the surface of film A can be adjusted by selecting a carrier with a complementary roughness, while the other surface of film A is very smooth due to the production conditions of the solution cast film.

[0021] Preferably, the surface roughness Rz of the surface of film A to be coated or printed, when measured before the surface is coated or printed, is from 0.01 μm to 10 μm, preferably from 0.1 μm to 3.0 μm.

[0022] Preferably, when measured before the carrier film and film A come into contact with each other, the surface roughness Rz of the carrier film on the surface side in contact with film A is 1.0 μm to 10 μm, and more preferably 2.0 μm to 6.0 μm.

[0023] The printed or coated layer contains an inorganic or organic pigment, which should not be soluble in the polyvinyl acetal so as to resist migration from film A to film B or bleeding out of the printed layer.

[0024] As pigments, carbon black, iron oxide, polyaniline, perylene or spinel pigments are preferably used. The pigments can be dispersed in a carrier fluid, such as water, alcohol or a mixture of alcohol and water.

[0025] Water-based printing inks are preferred over organic solvent-based printing inks because they do not swell or dissolve film A and / or cause film defects. Organic solvent-based printing inks can be used if the coating is thin and / or the drying process is fast and the solvent does not migrate into the PVB film.

[0026] Printing inks may be formulated and applied by techniques commonly known in the printing industry, such as offset printing, rotogravure printing, flexography and screen printing, usually followed by a drying step.

[0027] The dry film thickness of the printed layer varies from 1 μm to 50 μm, depending on the printing technique and the required opacity. Typically, the dry film thickness is between 2 μm and 20 μm. A sufficient full dry film thickness can be achieved by stacking ink layers in successive printing / coating steps.

[0028] Preferably, the ink comprises one or more binders selected from the group consisting of vinylpyrrolidone, water-soluble acrylic resin, alcohol-soluble resin, such as phenolic resin, acrylic resin, styrene-maleic acid resin, styrene acrylate resin, polyurethane resin, polyvinyl acetal resin, polyvinyl alcohol resin or ketone resin, and most preferably, the ink comprises a polyurethane resin binder.

[0029] Film A may contain alkali metal ions, preferably potassium, sodium, or lithium. The preferred concentration ranges of alkali metal ions are 7 ppm to 210 ppm, preferably 14 ppm to 140 ppm, and more preferably 21 ppm to 140 ppm for lithium, 23 ppm to 690 ppm, preferably 46 ppm to 460 ppm, and more preferably 69 ppm to 460 ppm for sodium, and 39 ppm to 1170 ppm, preferably 78 ppm to 780 ppm, and more preferably 117 ppm to 780 ppm for potassium. Furthermore, it is preferred to add alkali metal ions in the form of a salt of a carboxylic acid having 1 to 10 carbon atoms. Potassium acetate is particularly preferred as the adhesion control agent.

[0030] The total amount of alkali metal salt may be as low as 0.005 wt %, based on the weight of Film A. Preferred ranges of alkali metal salt are 0.01 wt % to 0.1 wt %, 0.02 wt % to 0.08 wt %, and 0.03 wt % to 0.06 wt %, based on the weight of Film A.

[0031] Film A used in the laminate of the present invention may further contain alkaline earth ions, although their effect on adhesion is limited and should be used in relatively small amounts compared to alkali ions. In a first embodiment of the present invention, film A contains 0 ppm to 100 ppm, preferably 10 ppm to 50 ppm, of alkaline earth ions.

[0032] Alternatively, the film A used in the laminate of the present invention may contain only alkaline earth ions as the adhesion control agent. That is, the film A does not contain any alkali metal ions. In this case, the concentration of alkaline earth metal ions is 500 ppm to 5000 ppm, preferably 750 ppm to 4000 ppm, and more preferably 1500 ppm to 3000 ppm. Magnesium ions are particularly preferred, and can be added in the form of a magnesium salt of a carboxylic acid, such as magnesium acetate and / or magnesium neoate.

[0033] To avoid haze, the amount of chloride ions and / or nitrate ions and / or sulfate ions in Film A can be reduced.

[0034] For this reason, the chloride content of film A may be less than 150 ppm, preferably less than 100 ppm, in particular less than 50 ppm. Ideally, the chloride content of film A is less than 10 ppm or even 0 ppm.

[0035] The nitrate content of film A may optionally be less than 150 ppm, preferably less than 100 ppm, in particular less than 50 ppm. Ideally, the nitrate content of film A is less than 10 ppm or even 0 ppm.

[0036] Further optionally, the sulfate content of Film A may be less than 150 ppm, preferably less than 100 ppm, in particular less than 50 ppm. Ideally, the sulfate content of Film A is less than 10 ppm or even 0 ppm.

[0037] Another aspect of the present invention relates to a free-standing film A that does not contain a carrier, which can be obtained by peeling the carrier from film A. Thus, one embodiment of the present invention is film A, which contains polyvinyl acetal and optionally a plasticizer, and which has a masking area provided by a printed or coated ink layer on one surface thereof, and which can be obtained by peeling the carrier from film A.

[0038] There are several ways in which the composite film of the present invention can be used to manufacture laminated windscreens together with a standard (=plasticized) polyvinyl acetal film B. In one simple way, the carrier film is removed and the peeled printed film A can be prepared for lamination by cutting to size, laminating and attaching it to the surface of a standard polyvinyl acetal film B or to one of the inner glass surfaces before final assembly of the glass and interlayer for the lamination process.

[0039] Alternatively, composite films can be processed together during processes such as cutting, laminating, and attaching to surfaces, taking advantage of the thicker, less elastic, and more melt-resistant properties of the carrier film material (e.g., PET). Even Film A with a thickness of less than 40 μm can be safely handled until the carrier film is removed just before or during the assembly process. It is also possible to remove the unwanted cut portion / frame of Film A from the carrier film and leave the printed portion attached to it in its final size. Such a printed "sticker" can be placed on a standard polyvinyl acetal film B or one of the interior glass surfaces, without touching Film A, along with a larger piece of carrier film. The release properties of the carrier film can be used to 1) pre-bond the printed surface of thin Film A to the cut-to-size surface of a standard polyvinyl acetal film B by applying heat and pressure or ultrasonic bonding, 2) optionally stack several of the combined blanks thus produced for storage, and 3) remove the carrier film from the backside of the "sticker" during assembly before starting the lamination process.

[0040] The carrier film with the printed patch attached in the form of a "sticker" can be easily stored in roll form and can help prevent the adhesion and transfer of ink or other surface contaminants to the backside of the printed film A.

[0041] Thus, one embodiment is a method for producing a windshield comprising two glass sheets laminated together by an interlayer film comprising film A containing polyvinyl acetal and optionally a plasticizer, and film B containing polyvinyl acetal and a plasticizer in an amount of at least 22% by weight, the method comprising: a) placing the composite film according to any one of claims 1 to 10 on a first glass sheet with film A facing the first glass sheet; b) peeling the carrier film from film A; c) placing Film B on Film A or on a second glass sheet; d) providing a stack of layers comprising, in this order: first glass sheet-Film A-Film B-second glass; e) laminating the stack obtained in step d) to produce a windshield; in that order.

[0042] Another embodiment of the present invention is a method for producing a windshield comprising two glass sheets laminated together by an interlayer film comprising film A containing polyvinyl acetal and optionally a plasticizer, and film B containing polyvinyl acetal and a plasticizer in an amount of at least 22% by weight, the method comprising: a) placing the composite film according to any one of claims 1 to 10 on film B so that film A faces film B; b) peeling the carrier film from film A; c) providing a stack of layers comprising, in this order: first glass sheet-Film A-Film B-second glass; d) laminating the stack obtained in step c) to produce a windshield; in that order.

[0043] Yet another embodiment of the present invention is a method for producing a windshield comprising two glass sheets laminated together by an interlayer film comprising film A containing polyvinyl acetal and optionally a plasticizer, and film B containing polyvinyl acetal and a plasticizer in an amount of at least 22% by weight, the method comprising: a) providing a composite film according to any one of claims 2 to 10, and peeling the carrier film from film A; b) placing film A on a first glass sheet such that the surface of film A having the printed or coated ink layer faces away from the first glass sheet; c) placing Film B on Film A or on a second glass sheet; d) providing a stack of layers comprising, in this order: first glass sheet-Film A-Film B-second glass; e) laminating the stack obtained in step d) to produce a windshield; in that order.

[0044] The alignment task requires a high degree of precision when aligning the printed area of ​​Film A with the ceramic print on either glass surface. To this end, a printed patch may be moved to the desired location by a human operator, who manually aligns the printed shape of the patch with the printed shape on the glass. This alignment may be performed on the patch alone (with or without a carrier film) and whether or not the patch is attached to a larger blank of regular PVB film (Film B). In another step, the edge of a second glass pane may be aligned to the edge of the first glass pane, as is common in the industry. Optical systems can be used to facilitate the alignment task. As an example, such an optical system may consist of a laser spot projected onto the regular PVB and an alignment mark printed on Film A as part of the main design or in a location that will be hidden by the ceramic frit in the final product. The alignment mark can also be an unprinted, transparent shape within the fully printed area of ​​Film A. A camera system is then used to monitor the good alignment of the laser spot and the alignment mark. In another variation of the described alignment, a robot is used to automatically pick up an individual patch (with or without carrier film) from the stack, place it in the correct position on a glass surface or regular PVB, optionally press, ultrasonically, or heat-solder to sufficiently secure it to the substrate, and then place the next layer (i.e., regular PVB or glass sheet) on top. Such a robot can use suction cups to lift and move the patch and / or the patch on the PVB sheet. Alternatively, a robot can provide the first laminate, and a second robot can provide precise alignment by moving the patch, the patch on the PVB sheet, or ceramic-printed glass under or over the PVB. In a preferred variation of the invention, the robot picks up the printed film A, cut to its final shape, still attached to the carrier film and with any surrounding matrix already peeled off.The robot then places the printed patch with the carrier film on the regular PVB sheet already placed on the first glass sheet, with the printed side facing the PVB sheet. As the robot arm moves up again, it peels the carrier film off the backside of the printed patch and attaches a heat solder point so that the patch remains temporarily attached to the surface of the PVB sheet. For final placement, the entire PVB sheet is then carefully moved over the first glass sheet until it is optimally aligned with the ceramic print on this glass sheet. This additional layer and the second glass sheet are then attached.

[0045] In another aspect, the invention relates to a windshield, or generally to a laminated glass component, obtained by one of the methods described above.

[0046] The films A and B used according to the invention contain polyvinyl acetal, which is produced by acetalization of polyvinyl alcohol or ethylene-vinyl alcohol copolymers.

[0047] The films can contain polyvinyl acetals, each having a different polyvinyl alcohol content, degree of acetalization, residual acetate content, ethylene ratio, molecular weight, and / or different chain lengths of the aldehyde in the acetal group.

[0048] In particular, the aldehydes used to prepare polyvinyl acetals may be linear or branched (i.e., "n" or "iso" type) containing 2 to 10 carbon atoms, which results in the corresponding linear or branched acetal groups. Polyvinyl acetals are referred to as "polyvinyl (iso)acetals" or "polyvinyl (n) acetals," as appropriate.

[0049] The polyvinyl acetals used according to the invention result in particular from the reaction of at least one polyvinyl alcohol with one or more aliphatic unbranched compounds containing 2 to 10 carbon atoms. For this purpose, n-butyraldehyde is preferably used.

[0050] The polyvinyl alcohol or ethylene-vinyl alcohol copolymer used to prepare the polyvinyl acetal in Film A or Film B may be the same or different, and may be pure or a mixture of polyvinyl alcohols or ethylene-vinyl alcohol copolymers having different degrees of polymerization or hydrolysis.

[0051] The polyvinyl acetate content of the polyvinyl acetal in Film A or Film B can be adjusted by using an appropriately saponified polyvinyl alcohol or ethylene-vinyl alcohol copolymer. The polarity of the polyvinyl acetal is affected by the polyvinyl acetate content, which in turn affects the plasticizer compatibility and mechanical strength of each layer. It is also possible to acetalize polyvinyl alcohol or ethylene-vinyl alcohol copolymer using a mixture of multiple aldehyde compounds.

[0052] Film A or film B preferably contains, the same or different, a polyvinyl acetal having a proportion of polyvinyl acetate groups of 0.1 mol % to 20 mol %, preferably 0.5 mol % to 3 mol % or 5 mol % to 8 mol %, respectively.

[0053] The polyvinyl alcohol content of the polyvinyl acetal PA used in film A may be 6% by weight to 26% by weight, 8% by weight to 24% by weight, 10% by weight to 22% by weight, 12% by weight to 21% by weight, 14% by weight to 20% by weight, or 16% by weight to 19% by weight, and preferably 16% by weight to 21% by weight or 10% by weight to 16% by weight.

[0054] Independently of film A, the polyvinyl alcohol content of the polyvinyl acetal PB used in film B may be 14% by weight to 26% by weight, 16% by weight to 24% by weight, 17% by weight to 23% by weight, and preferably 18% by weight to 21% by weight.

[0055] In a preferred embodiment of the present invention, film A comprises polyvinyl acetal PA having a proportion of vinyl alcohol groups of 6% to 26% by weight, and film B comprises polyvinyl acetal B having a proportion of vinyl alcohol groups of 14% to 26% by weight.

[0056] Film A and / or film B used according to the invention may contain, as plasticizer, one or more compounds selected from the following group: - esters of polyhydric aliphatic or aromatic acids: for example, dialkyl adipates such as dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, a mixture of heptyl and nonyl adipate, diisononyl adipate, heptylnonyl adipate and esters of adipic acid with alicyclic ester alcohols or ester alcohols containing ether compounds; dialkyl sebacates such as dibutyl sebacate and esters of sebacic acid with alicyclic ester alcohols or ester alcohols containing ether compounds; esters of phthalic acid such as butylbenzyl phthalate or bis-2-butoxyethyl phthalate. - esters or ethers of polyhydric aliphatic or aromatic alcohols or oligoether glycols having one or more unbranched or branched aliphatic or aromatic substituents: for example, esters of glycerol, diglycol, triglycol or tetraglycol with linear or branched aliphatic or cycloaliphatic carboxylic acids; examples of the latter group include diethylene glycol-bis-(2-ethylhexanoate), triethylene glycol-bis-(2-ethylhexanoate), triethylene glycol-bis-(2-ethylbutanoate), tetraethylene glycol-bis-n-heptanoate, triethylene glycol-bis-n-heptanoate, triethylene glycol-bis-n-hexanoate, tetraethylene glycol dimethyl ether and / or dipropylene glycol benzoate. - phosphates with aliphatic or aromatic ester alcohols: for example tris(2-ethylhexyl) phosphate (TOF), triethyl phosphate, diphenyl-2-ethylhexyl phosphate and / or tricresyl phosphate. - Esters of citric, succinic and / or fumaric acid.

[0057] By definition, plasticizers are organic liquids with a high boiling point. Therefore, additional types of organic liquids with boiling points above 120° C. can also be used as plasticizers.

[0058] However, film A preferably does not contain any added plasticizers.

[0059] The present invention is also advantageous for laminates including thin glass sheets, since sintering enamel onto thin glass is more likely to produce irregularly bent sheets with optical defects. In preferred embodiments of the present invention, at least one of the glass sheets has a thickness of less than 2.1 mm, e.g., less than 1.8 mm, less than 1.8 mm, less than 1.6 mm, less than 1.4 mm, less than 1.0 mm, or less than 0.9 mm. The term "glass sheet" shall be interpreted as any material useful in the manufacture of windshields, including polycarbonate sheets.

[0060] The plasticizer-containing film B used according to the present invention contains, in the starting state before lamination, at least 22% by weight, for example 22.0% to 45.0% by weight, preferably 25.0% to 32.0% by weight, in particular 26.0% to 30.0% by weight, of plasticizer.

[0061] Film A or film B preferably contains, the same or different, a polyvinyl acetal having a proportion of polyvinyl acetate groups of 0.1 mol % to 20 mol %, preferably 0.5 mol % to 3 mol % or 5 mol % to 8 mol %, respectively.

[0062] The thickness of film B in the initial state is 450 μm to 2500 μm, preferably 600 μm to 1000 μm, preferably 700 μm to 900 μm. In the present invention, a plurality of films B can be used, and they may be stacked on top of each other or separated by films A.

[0063] If film B is stretched before the production of the sandwich and / or additionally conforms to the shape of the screen (e.g., windshield) in a curved manner, the specific thickness at the moment of lamination may be further reduced by up to 20%.

[0064] In addition, Film A and Film B may contain further additives, such as remaining amounts of water, UV absorbers, antioxidants, adhesion modifiers, optical brighteners or fluorescent additives, stabilizers, colorants, processing aids, inorganic or organic nanoparticles, pyrogenic silicic acid and / or surface-active substances.

[0065] In particular, film B may contain 0.001% to 0.1% by weight of an alkali metal salt and / or alkaline earth salt of a carboxylic acid as an adhesion control agent. Film B preferably contains magnesium ions in an amount of at least 10 ppm, preferably 20 ppm, and most preferably 30 ppm.

[0066] The lamination process for producing laminated glass is preferably carried out such that Film A and Film B are placed between two sheets of glass and the laminate so produced is pressed under high or low pressure and elevated temperature to form the laminate.

[0067] Methods familiar to those skilled in the art for laminating the layers can be used with or without prior fabrication of a prelaminate.

[0068] The so-called "autoclave process" is carried out at high pressures of about 10-15 bar and temperatures of 100-150° C. for about 2 hours. For example, the vacuum bag or vacuum ring process according to EP 1235683 operates at about 200 mbar and 130-145° C.

[0069] Vacuum laminators can also be used. These consist of a chamber that can be heated and evacuated. In this chamber, the laminated glass can be laminated within 30 to 60 minutes. Vacuum pressures of 0.01 mbar to 300 mbar and temperatures of 100 to 200°C, especially 130 to 160°C, have proven to be useful in practice.

[0070] Film B can also have a wedge-shaped thickness profile. The laminated glass of the present invention, even with the plane-parallel thickness profile of Film A, can still obtain a wedge-shaped thickness profile and be used in automotive windshields for HUD displays.

[0071] The laminated glass according to the invention can be used in windshields, backlights and side glazing for automobiles, buses, trucks, ships, trains or airplanes. [Example]

[0072] [Preparation of composite film] A polyethylene terephthalate (PET) film (Grade #50-X42G, commercially available from Toray Industries, Inc.) having a thickness of 50 μm and a matte surface was used as the carrier. The surface roughness (Rz) was 4.0 μm.

[0073] A 15.5 wt% solution of polyvinyl butyral (PVB) powder (a 45:55 mixture of commercial grades Mowital® B30H and Mowital® B75H) dissolved in a 50:50 wt% mixture of methanol / methyl acetate was used as the coating solution.

[0074] A standard commercial solvent coating apparatus, including an unwinder, coater, dryer, and winder, was used in slot-die coating mode. The substrate speed was 1.1 m / min, and the wet thickness on the moving substrate was 200 μm. Coating was carried out at a temperature of 26° C. The gap between the coating lip and the moving substrate was 300 μm.

[0075] Drying was carried out in three zones, with temperatures in the drying zones set at 60° C., 70° C. and 125° C. The total drying time was about 4 minutes.

[0076] A composite film comprising PVB Film A and a PET carrier was wound into a roll. Visual inspection revealed no wrinkles in the composite film. To measure the thickness of the dried Film A, the carrier was peeled from the composite sample. The measurement showed that Film A had a thickness of 25 μm.

[0077] Five sets of specimens, 3 cm wide and 15 cm long, were cut from the composite film and the t-peel adhesion strength was measured by a tensile tester at 20°C and a pulling rate of 500 mm / min. The average of the five measurements was found to be 1.5 N / 3 cm.

[0078] [Printing on composite film] The composite film used in the first step was used in the following printing process.

[0079] An aqueous printing ink containing a carbon black pigment and a polyurethane binder was used in the printing process. The printing ink had a viscosity of 20 DIN seconds (20°C, DIN 4 mm cup).

[0080] The printing ink was applied to Film A of the composite film using a flexographic printing press. In a first step, the composite film was passed through an in-line corona treater to improve ink adhesion to the surface of Film A. The corona-treated film then passed through four printing units, all equipped with flexible Kodak Flexcel NX relief plates. Furthermore, the first printing unit was equipped with a Zecher 160 L / cm, 10 g / m² (60°) anilox roller, the second printing unit was equipped with a Zecher 220 L / cm, 10 g / m² (60°), the third printing unit was equipped with an Apex 180 L / cm, 12 g / m² (open), and the fourth printing unit was equipped with a Zecher 120 L / cm, 20 g / m² (60°). The drying temperature in the printing units was set to 55°C. After passing through the printing unit, the composite film also passed through an additional drying zone (4 m) set at 70° C. During the entire printing process, the composite film passed through the press at a speed of approximately 80 m / min.

[0081] At the end of the printing process, the composite film was wound onto a 6 inch diameter PVC roll core.

[0082] Thanks to the PET carrier film, the wet ink did not transfer to the bottom surface of the PVB film in the wound polymer film roll. The dried ink formed a uniform, closed layer (approximately 7 μm dry film thickness) on the PVB substrate, which appeared completely opaque upon visual inspection. The optical density of the dried ink layer was measured with a transmission densitometer (x-rite, model 331C) to be greater than 3.5.

Claims

1. A composite film, a film A containing polyvinyl acetal and optionally a plasticizer; Career film and Including, Film A is provided with a shielding area, the shielding area is provided by an ink layer printed or coated on the surface of film A that does not face the carrier film; The thickness of the film A is 15 μm to 40 μm. Composite film.

2. 2. The composite film of claim 1, wherein the carrier film contains a polymer selected from the group consisting of polylactic acid, acrylonitrile-butadiene-styrene copolymer, polyamide, polycarbonate, polyethylene terephthalate, polyethylene terephthalate copolymer, polyhydroxyalkanoate, polyurethane, polyolefin, acrylonitrile styrene acrylate, polyacrylate and polymethacrylate, polyvinyl alcohol, and TAC (cellulose triacetate).

3. 3. The composite film according to claim 1, wherein the carrier film contains polyethylene terephthalate.

4. 4. The composite film according to claim 1, wherein the thickness of the carrier film is from 25 μm to 250 μm.

5. 5. The composite film according to claim 1, wherein film A is adhered to the carrier film with an adhesive strength of 0.05 N / 3 cm to 10 N / 3 cm.

6. 6. The composite film according to claim 1, wherein the surface to be coated or printed of film A has a surface roughness Rz of 0.01 μm to 10 μm when measured before the surface is coated or printed.

7. The surface roughness Rz of the carrier film on the surface side in contact with film A is 1.0 μm to 10 μm when measured before the carrier film and film A come into contact. A composite film according to any one of claims 1 to 5.

8. A composite film described in any one of claims 1 to 5, wherein the surface roughness Rz of the surface to be coated or printed of film A is 0.01 μm to 10 μm when measured before the surface is coated or printed, and the surface roughness Rz of the carrier film on the surface side in contact with film A is 1.0 μm to 10 μm when measured before the carrier film and film A come into contact.

9. 9. The composite film according to claim 1, wherein the ink layer comprises a binder selected from the group consisting of vinylpyrrolidone, a water-soluble acrylic resin, an alcohol-soluble resin, a phenolic resin, an acrylic resin, a styrene-maleic acid resin, a styrene-acrylate resin, a polyurethane resin, a polyvinyl acetal resin, a polyvinyl alcohol resin, or a ketone resin.

10. Film A, Contains polyvinyl acetal and optionally a plasticizer, A shielding area provided by a printed or coated ink layer is provided on one surface of the film A, The film A is obtained by peeling off the carrier film from the film A, The thickness is 15 μm to 40 μm. Film A.

11. 10. A method for producing a composite film according to any one of claims 1 to 9, comprising: a) providing a carrier film; b) coating one surface of the carrier film with a solution containing a solvent, polyvinyl acetal or polyvinyl ethylene acetal, and optionally a plasticizer; c) evaporating the solvent to obtain a film A on the one surface of the carrier film; d) providing a shielding area by printing or coating the surface of the film A that is not in contact with the carrier film with an ink layer; in this order.

12. 1. A method for manufacturing a windshield comprising two glass sheets joined together by an interlayer film comprising: a film A containing polyvinyl acetal and optionally a plasticizer; and a film B containing polyvinyl acetal and a plasticizer in an amount of at least 22% by weight, the method comprising: a) placing a composite film according to any one of claims 1 to 9 on a first glass sheet with film A facing the first glass sheet; b) peeling the carrier film from the film A; c) placing the film B on the film A or on a second glass sheet; d) providing a stack of layers comprising, in that order: first glass sheet-Film A-Film B-second glass; e) laminating the stack obtained in step d) to produce the windshield; in this order.

13. 1. A method for manufacturing a windshield comprising two glass sheets joined together by an interlayer film comprising: a film A containing polyvinyl acetal and optionally a plasticizer; and a film B containing polyvinyl acetal and a plasticizer in an amount of at least 22% by weight, the method comprising: a) placing the composite film according to any one of claims 1 to 9 on film B such that film A faces film B; b) peeling the carrier film from the film A; c) providing a stack of layers comprising, in that order: first glass sheet-Film A-Film B-second glass; d) laminating the stack obtained in step c) to produce the windshield; in this order.

14. 1. A method for manufacturing a windshield comprising two glass sheets joined together by an interlayer film comprising: a film A containing polyvinyl acetal and optionally a plasticizer; and a film B containing polyvinyl acetal and a plasticizer in an amount of at least 22% by weight, the method comprising: a) providing a composite film according to any one of claims 1 to 9, and peeling the carrier film from the film A; b) placing the film A on the first glass sheet so that the surface of the film A on which the printed or coated ink layer is provided faces away from the first glass sheet; c) placing the film B on the film A or on a second glass sheet; d) providing a stack of layers comprising, in that order: first glass sheet-Film A-Film B-second glass; e) laminating the stack obtained in step d) to produce the windshield; in this order.

15. A windscreen obtained according to the method of claim 12, 13 or 14.