GREENHOUSE SCREEN

Abstract

A greenhouse screen comprising strips of film material that are interconnected by a yarn system of transverse threads and longitudinal threads by means of a knitting, warp-knitting or weaving process to form a continuous product is provided. At least some of the strips comprise a polyester film having a transparency of at least 93%, said polyester film having at least one base layer B comprising a thermoplastic polyester and a UV stabilizer. The polyester film has a first and a second surface, wherein a permanent anti-fog coating is applied to at least one of the first or second surfaces of the polyester film. The anti-fog coating has a lower refractive index than the base layer B.A process for producing said film is also disclosed.

Claims

1. A greenhouse screen comprising strips (11) of film material that are interconnected by a yarn system of transverse threads (12, 14, 18) and longitudinal threads (13a, 13b; 15; 19) by means of a knitting, warp-knitting or weaving process to form a continuous product, wherein at least some of the strips (11) comprise a polyester film having a transparency of at least 93%, said polyester film having at least one base layer B comprising a thermoplastic polyester and a UV stabilizer, said polyester film has a first and a second surface, wherein a permanent anti-fog coating is applied to at least one of the first or second surfaces of the polyester film, and characterized in that said anti-fog coating has a lower refractive index than the base layer B.

2. The greenhouse screen according to claim 1, characterized in that the polyester film is a multi-layer film comprising a layer A applied to the base layer, or a layer A and a layer C applied to the base layer B, the base layer B being located between the layer A and the layer C, and wherein the layers A and/or C comprise a thermoplastic polymer and a UV stabilizer.

3. The greenhouse screen according to claim 1 or 2, characterized in that a total thickness of the polyester film is at least 10 m and at most 40 m, such as at least 14 m and at most 25 m, such as at least 14.5 m and at most 20 m.

4. The greenhouse screen according to any one of the preceding claims, characterized in that the base layer B consists of at least 70% by weight of a thermoplastic polyester, the thermoplastic polyester comprising at least 85 mol %, such as at least 90 mol % such as at least 92 mol % units derived from ethylene glycol and terephthalic acid.

5. The greenhouse screen according to any one of the preceding claims, characterized in that the polyester film has a Standard Viscosity (SV) value greater than 600, such as greater than 650, such as greater than 700, the SV value of the film being less than 950, such as less than 850.

6. The greenhouse screen according to any one of the preceding claims, characterized in that the UV stabilizer is selected from the group consisting of triazines, benzotriazoles, benzoxazinones, and the base layer B and, if present, the layer A and/or the layer C contain the UV stabilizer in an amount of 0.3 to 3% by weight, such as 0.75 to 2.8% by weight, based on the weight of the respective layer.

7. The greenhouse screen according to any one of the preceding claims, characterized in that the refractive index of the anti-fog coating is below 1.64, such as below 1.60 such as below 1.58 at a wavelength of 589 nm in the machine direction of the film.

8. The greenhouse screen according to any one of the preceding claims, characterized in that the thickness of the anti-fog coating is at least 60 nm and at most 150 nm, such as at least 70 nm and at most 130 nm, such as at least 80 nm and at most 120 nm.

9. The greenhouse screen according to one or more of claims 1 to 7, characterized in that an anti-fog coating is applied to the first or second surface of the polyester film, and a surface of the polyester film opposite to the anti-fog coating is provided with an antireflection modification layer, said antireflection modification layer is an antireflective coating, or is formed by an topcoat layer modification and has a lower refractive index than polyethylene terephthalate.

10. The greenhouse screen according to claim 9, characterized in that the anti-fog coating has a thickness of at least 30 nm, such as at least 40 nm, such as at least 50 nm and at most 60 nm

11. The greenhouse screen according to claim 9 and 10, characterized in that the refractive index of the antireflective coating is below 1.64, such as below 1.60 such as below 1.58 at a wavelength of 589 nm in the machine direction of the film.

12. The greenhouse screen according to any one of claims 9-11, characterized in that the anti-reflective coating contains more than 70 wt. %, such as more than 80 wt. %, and ideally more than 93 wt. % of methyl methacrylate and ethyl acrylate repeating units.

13. The greenhouse screen according to any one of claims 9-12, characterized in that the anti-reflective coating comprises at least 1% by weight of a UV stabilizer (based on the dry weight of the anti-reflective coating).

14. The greenhouse screen according to any one of claims 9-13, characterized in that the anti-reflective coating has a thickness of at least 60 nm, such as at least 70 nm such as at least 80 nm, such as at least 87 nm, such as at least 95 nm and is at most 130 nm, such as at most 115 nm, such as at most 110 nm.

15. The greenhouse screen according to claim 9, characterized in that the topcoat layer modification is formed by co-extrusion on the base layer B, and the topcoat layer modification comprises a polyester which has a lower refractive index than the polyester of the base layer B.

16. The greenhouse screen according to claim 15, characterized in that the refractive index of the topcoat layer modification is below 1.70, such as below 1.65 such as below 1.60 at a wavelength of 589 nm in the machine direction of the film.

17. The greenhouse screen according to any one of claims 15-16, characterized in that the polymer of the topcoat layer modification contains a co-monomer fraction of at least 2 mol %, preferably at least 3 mol % and particularly preferably at least 6 mol % (in each case calculated with regard to the total mol % of the polymer in the topcoat layer).

18. The greenhouse screen according to any one of claims 15-17, characterized in that the topcoat layer modification comprises more than 8 mol %, such as more than 10 mol %, but less than 20 mol %, such as less than 19 mol % such as less than 15 mol % of isophthalic acid (in each case calculated with regard to the dicarboxylic acid component of the polyester).

19. The greenhouse screen according to any one of claims 15-18, characterized in that the anti-fog coating has a thickness of at least 60 nm and at most 150 nm, preferably at least 70 nm and at most 130 nm, particularly preferably at least 80 nm and at most 120 Nm.

20. The greenhouse screen according to any one of claims 1-8, characterized in that both the first and second surfaces of the polyester film are provided with anti-fog coatings.

21. The greenhouse screen according to any one of the preceding claims, characterized in that the anti-fog coating is a dispersion composition and comprises, a) a hygroscopic, porous material; b) a polymer-based crosslinker; c) an adhesion-promoting organofunctional silane; and d) one or more surfactants.

22. The greenhouse screen according to any one of the preceding claims, characterized in that the anti-fog and/or anti-reflective coatings are applied in-line during production of the biaxially oriented polyester film.

23. The greenhouse screen according to any one of the preceding claims, characterized in that the anti-fog and/or anti-reflective coatings are applied to the first and/or second surfaces of the polyester film by means of off-line technology in an additional process step downstream of the film production.

24. The greenhouse screen according to any one of the preceding claims, characterized in that one or more of said strips of film material (11) has a width that is smaller than the distance between the longitudinal threads (13a, 13b; 15; 19).

25. The greenhouse screen according to claim 24, characterized in that a gap is formed between said one or more strips of film material (11) and the adjacent strip(s) of film 11, said gap permitting ventilation through said screen.

26. The greenhouse screen according to any one of the preceding claims, characterized in that at least 10%, preferably at least 20%, more preferably at least 30%, more preferably at least 40%, more preferably at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90% of the strips of film material (11) in the greenhouse screen comprise said single- or multilayer polyester film.

27. The greenhouse screen according to any one of the preceding claims, characterized in that all strips of film material (11) in the greenhouse screen are of said single- or multilayer polyester film.

28. Use of the greenhouse screen according to any one of the preceding claims as a convection barrier.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0110] The greenhouse screen will below be described with reference to some embodiments shown in the drawings.

[0111] FIG. 1 shows on an enlarged scale part of warp-knitted screen according to one embodiment.

[0112] FIG. 2 shows a part of a warp-knitted screen according to a further embodiment.

[0113] FIG. 3 shows on an enlarged scale a part of a woven screen.

[0114] FIG. 4 shows a part of a woven screen according to a further embodiment.

[0115] FIG. 5 shows the contact angle during measurement of hydrophilicity of the film surface.

DETAILED DESCRIPTION

[0116] The greenhouse screen 10 according as disclosed herein comprises a plurality of narrow strips of film material 11 held together by a yarn framework 12, 13a, 13b; 14, 15; 18, 19.

[0117] The strips of film material 11 are preferably arranged closely edge to edge, so that they form a substantially continuous surface. The screen has a longitudinal direction, y, and a transverse direction, x, wherein the strips of film material 11 extend in the longitudinal direction. In some embodiments strips of film material 11 may extend also in the transverse direction. A typical width of the strips is between 2 mm and 10 mm.

[0118] In FIG. 1 strips of film material 11 are interconnected by a warp knitting procedure as described in EP 0 109 951. The yarn framework comprises warp threads 12 forming loops or stitches and primarily extending in the longitudinal direction, y. The warp threads 12 are connected to one another by weft threads 13a and 13 b extending across the film strips.

[0119] FIG. 1 shows an example of a mesh pattern for a fabric manufactured through a warp knitting process in which four guide bars are used, one for the strips of film material 11, two for the connecting weft threads 13a and 13b extending transversely to the film strips and one for the longitudinal warp threads 12.

[0120] The spaces between the strips of film material 11 have been strongly exaggerated in order to make the mesh pattern clear. Usually the strips of film material 11 are located closely edge to edge. The longitudinal warp threads 12 are arranged on one side of the screen, the underside, while the transverse connecting weft threads 13a and 13b are located on both sides of the fabric, the upper and the underside. The term transverse in this respect is not restricted to a direction perpendicular to the longitudinal direction, but means that the connecting weft threads 13a and 13b extends across the strips of film material 11 as illustrated in the drawings. The connection between the longitudinal warp threads 12 and the transverse weft threads 13a and 13b are preferably made on the underside of the fabric. The strips of film material 11 can in this way be arranged closely edge to edge without being restricted by the longitudinal warp threads 12.

[0121] The longitudinal warp threads 12 in FIG. 1 extend continuously in unbroken fashion along opposite edges of adjacent strips of film material 11, in a series of knitted stitches, in a so called open pillar stitch formation.

[0122] The transverse weft threads 13a and 13b pass above and below the strips of film material 11 at the same location, i.e. opposed to each other, to fixedly trap the strips of film material. Each knitted stitch in the longitudinal warp threads 12 has two such transverse weft threads 13a and 13b engaging with it.

[0123] FIG. 2 shows another example of a mesh pattern for a fabric similar to the one shown in FIG. 1. The difference is that the transverse weft threads 13a and 13b pass over one and two strips of film material 11 in an alternating way.

[0124] FIG. 3 shows a woven screen in which the strips of film material 11 are interconnected by warp threads 14 extending in longitudinal direction, y, and interwoven with weft threads 15 extending across the strips of film material 11 primarily in the transverse direction, x.

[0125] FIG. 4 shows another embodiment of a woven screen as described in U.S. Pat. No. 5,288,545 comprising strips of film material 11 (warp strips) extending in longitudinal direction, y, and strips of film material 11 (weft strips) extending in transverse direction, x. The weft strips 11 in the transverse direction may as shown in FIG. 4 always be on the same side of the warp strips 11 in longitudinal direction or may alternate on the upper and underside of the warp longitudinal strips 11. The warp and weft strips 11 and 11 are held together by a yarn framework comprising longitudinal and transverse threads 18 and 19. The screen may comprise open areas that are free from strips to reduce heat build-up under the screen.

[0126] Polyester Film Production Process

[0127] The polyester polymers of the individual layers are prepared by polycondensation, either from dicarboxylic acids and diol or else from the esters of the dicarboxylic acids, preferably the dimethyl esters, and diol. Suitable polyesters preferably have SV values in the range from 500 to 1300, the individual values being less important, but the average SV value of the raw materials used must be greater than 700 and such as greater than 750.

[0128] The particles, as well as UV stabilizers, can already be added during the preparation of the polyester. For this purpose, the particles are dispersed in the diol, optionally ground, decanted and/or filtered and added to the reactor, either in the (Re) esterification or polycondensation step. Preferably, a concentrated particle-containing or additive-containing polyester masterbatch can be produced in a twin-screw extruder and thereafter diluted during the film extrusion with particle-free polyester. It has proven to be advantageous if no masterbatches are used which contain less than 30% by weight of polyester. In particular, the masterbatch containing SiO.sub.2 particles should not be more than 20% by weight of SiO.sub.2 (as a result of the risk of gel formation). A further possibility is to add particles and additives directly during the film extrusion in a twin-screw extruder.

[0129] When single-screw extruders are used, it has been found to be advantageous to dry the polyesters beforehand. When a twin-screw extruder with a degassing zone is used, the drying step can be dispensed with.

[0130] First, the polyester or the polyester mixture of the layer or in the case of multilayer films of the individual layers is compressed and liquefied in extruders. The melt is then formed into flat melt films in a single-layer or multi-layer nozzle, pressed through a slot die and drawn off on a cooling roll and one or more take-off rolls, where it cools and solidifies.

[0131] The film as described herein is biaxially oriented, that is, biaxially stretched. The biaxial stretching of the film is most frequently carried out sequentially. In this case, it is preferably first stretched in the longitudinal direction (i.e., in the machine direction, MD direction) and subsequently in the transverse direction (i.e., perpendicular to the machine direction, TD direction). The stretching in the longitudinal direction can be carried out with the aid of two rollers running at different speeds according to the desired stretching ratio. For transverse stretching, a corresponding tenter frame is generally used.

[0132] The temperature at which the stretching is carried out can vary within a relatively wide range and depends on the desired properties of the film. In general, the longitudinal stretching is carried out in a temperature range from 80 to 130 C. (heating temperatures 80 to 130 C.) and in the transverse direction in a temperature range from 90 C. (beginning of stretching) to 140 C. (end of stretching). The longitudinal stretching ratio is in the range from 2.5:1 to 4.5:1, such as from 2.8:1 to 3.4:1. A stretching ratio above 4.5 leads to a markedly deteriorated manufacturability (tear-off). The transverse stretching ratio is generally in the range from 2.5:1 to 5.0:1, such as from 3.2:1 to 4:1. A higher cross-draw ratio than 4.8 leads to a markedly deteriorated manufacturability (tear-off) and should therefore preferably be avoided.

[0133] In order to achieve the desired film properties, it has proven to be advantageous if the stretching temperature (in MD and TD) is below 125 C., such as below 118 C. Prior to the transverse stretching, one or both surfaces of the film can be coated in-line according to the processes known per se. The in-line coating can preferably be used for applying a coating for increasing the transparency (antireflex).

[0134] In the subsequent thermofixing, the film is held under tension at a temperature of 150 to 250 C. for a period of time of about 0.1 to 10 seconds, in order to achieve the preferred shrinkage and elongation values of at least 1%, such as at least 3%, such as at least 4% in the transverse direction. This relaxation preferably takes place in a temperature range from 150 to 190 C. To reduce the transparency bow, the temperature in the first fixing field is preferably below 220 C., and more preferably below 190 C. In addition, for the same reason as stated above, at least 1%, preferably at least 2%, of the total transverse stretching ratio should be in the first fixing field after which it is usually not stretched any further. Subsequently, the film is wound up in a conventional manner.

[0135] In a particularly economical way of producing the polyester film, the blended material (regenerate) can be fed to the extrusion in an amount of up to 60% by weight, based on the total weight of the film, without adversely affecting the physical properties of the film.

[0136] The greenhouse screen is explained in more detail below with reference to the following: [0137] Examples 1-9, and [0138] Comparative Examples 1-7

[0139] The exemplary embodiments serve to further illustrate the greenhouse screen as disclosed herein, without restricting it to this. Rather, all of the features mentioned are freely combinable in any form which appears suitable for a person skilled in the art, and all of these forms are encompassed by the present greenhouse screen as disclosed herein.

Examples 1-9

[0140] The polymer mixtures were melted at 292 C. and electrostatically applied to a cooling drum heated to 50 C. by means of a slot die. The following raw materials were melted in one extruder per layer and extruded through a three-layered slot die onto a cooled take-off roll. The amorphous preform thus obtained was then stretched longitudinally. The longitudinally stretched film was corona-treated in a corona discharger and then coated by reverse-coating with the following dispersion. Thereafter, the film was stretched, fixed, and rolled. The conditions in the individual process steps were as seen in Table 1:

TABLE-US-00001 TABLE 1 Longitudinal Heating temperature 75-115 C. stretching (MD) Stretching temperature 115 C. Longitudinal stretching ratio 3.8 Transverse Heating temperature 100 C. stretching (TD) Stretching temperature 112 C. Transverse stretching ratio (including 3.9 Stretching in first fixing field) Fixation Temperature 237-150 C. Duration 3 s Relaxation in TD at 200-150 C. 5 % Fixation Temperature in first fixing field 170 C.

[0141] The following starting materials were used to prepare the films described in table 2 below:

[0142] PET1=polyethylene terephthalate raw material of ethylene glycol and terephthalic acid with an SV value of 820 and DEG content of 0.9% by weight (diethylene glycol content as monomer).

[0143] PET2=polyethylene terephthalate raw material having an SV value of 700 containing 20% by weight of Tinuvin 1577. The UV stabilizer has the following composition 2-(4,6-diphenyl-1,3,5-triazyn-2-yl)-5-(hexyl) oxy-phenol (Tinuvin 1577 from BASF, Ludwigshafen, Germany). Tinuvin 1577 has a melting point of 149 C. and is thermally stable at 330 C.

[0144] PET3=polyethylene terephthalate raw material having an SV value of 700 and 15% by weight of silica particles Sylysia310 P with a d50 of 2.7 m (manufacturer FUJI SILYSIA CHEMICAL LTD. Greenville N.C./USA). The SiO.sub.2 was incorporated into the polyethylene terephthalate in a twin-screw extruder

[0145] PET4=polyethylene terephthalate raw material having an SV value of 710 containing 25 mol % of isophthalic acid as comonomer.

[0146] Composition of the coating dispersions used

[0147] Coating 1

[0148] The following composition of the coating solution was used: [0149] 88.95% by weight of deionized water [0150] 3.50% by weight of Elecut AG 100 (16.5% by weight, Takemoto Oil and Fat Co. Ltd.) [0151] 4.50% by weight of Elecut AG 200 (13.5% by weight, Takemoto Oil and Fat Co. Ltd.) [0152] 2.50% by weight of EPOCROS WS-700 (25% by weight, Nippon Shokubai) [0153] 0.50% by weight of Z-6040 (90-100% by weight, Dow Corning) [0154] 0.05% by weight of BYK-DYNWET 800 (100% by weight, BYK-Chemie GmbH)

[0155] The individual components were slowly added to deionized water with stirring and stirred for at least 30 minutes before use.

[0156] Coating 2

[0157] The following composition of the coating solution was used: [0158] 88.45% by weight of deionized water [0159] 2.50% by weight of Elecut AG 100 (16.5% by weight, Takemoto Oil and Fat Co. Ltd.) [0160] 3.50% by weight of Elecut AG 200 (13.5% by weight, Takemoto Oil and Fat Co. Ltd.) [0161] 5.00% by weight of EPOCROS WS-700 (25% by weight, Nippon Shokubai) [0162] 0.50% by weight of Z-6040 (90-100% by weight, Dow Corning) [0163] 0.05% by weight of BYK-DYNWET 800 (100% by weight, BYK-Chemie GmbH)

[0164] The individual components were slowly added to deionized water with stirring and stirred for at least 30 minutes before use. Unless otherwise described, the coatings are applied in the in-line process.

[0165] The following Table 2 summarizes the formulations, production conditions and resulting film properties:

TABLE-US-00002 TABLE 2 Properties for films in Examples 1-9 Example 1 Example 2 Example 3 Example 4 Example 5 Layer Film 15 15 15 15 15 (m) thickness Thickness 0.8 0.8 0.8 0.8 0.8 layer A Thickness 13.4 13.4 13.4 13.4 13.4 layer B Thickness 0.8 0.8 0.8 0.8 0.8 layer C Coating on Dry thickness Dry thickness Dry thickness Dry thickness Dry thickness surface A 65 nm. 65 nm. 65 nm. 65 nm. 65 nm. Anti-fog coat. 1 Anti-fog coat. 2 Anti-fog coat. 2 Anti-fog coat. 1 Anti-fog coat. 1 (off-line proc.) Coating on Dry thickness surface C 75 nm. Acrylate coat. and application method as in example 1 of EP 0144948 A-layer PET 1 89 89 89 89 89 PET 2 10 10 10 10 10 PET 3 1 1 1 1 1 PET 4 B-layer PET 1 95 95 95 95 95 PET 2 5 5 5 5 5 C-layer PET 1 34 34 89 89 34 PET 2 15 15 10 10 15 PET 3 1 1 1 1 1 PET 4 50 50 50 Transparency in % 93.2 93.8 93.0 95.0 94.0 (web center) Haze 10.5 9.8 13.0 13.0 15.5 UV-stability in % 70 64 65 65 64 UTS Flame test Grade 4 4 4 4 4 E-Modul MD N/mm.sup.2 4360 3950 3950 3950 4000 Young's Modulus MD E-Modul TD N/mm.sup.2 4800 4350 4300 4300 4500 Young's Modulus TD F5 MD N/mm.sup.2 110 115 104 104 105 F5 TD N/mm.sup.2 110 100 117 117 115 Shrinkage in % 1.5 1.3 1.3 1.3 1.5 MD Shrinkage TD in % 0.1 0.4 0.4 0.4 0.3 Expansion in % 0.1 0 0 0 -0.2 MD at 100 C. Expansion in % 0 0 0 0 0 TD at 100 C. SV film 738 728 738 738 740 Surface mN/m 58.4 50.5 55.6 55.6 56.4 tension (total) (surface A) Cold fog test A A A A A Hot fog test A B B A A Example 6 Example 7 Example 8 Example 9 Layer Film 15 15 15 15 (m) thickness Thickness 0.8 0.8 0.8 0.8 layer A Thickness 13.4 13.4 13.4 13.4 layer B Thickness 0.8 0.8 0.8 0.8 layer C Coating on Dry thickness Dry thickness Dry thickness Dry thickness surface A 130 nm. 65 nm. 40 nm. 40 nm. Anti-fog coat. 1 Anti-fog coat. 1 Anti-fog coat. 1 Anti-fog coat. 1 (off-line proc.) Coating on Dry thickness Dry thickness Dry thickness surface C 150 nm. 65 nm. 75 nm. Acrylate coat. Anti-fog coat. 1 Acrylate coat. and application and applicat. method as in method as in example 1 of example 1 of EP 0144948 EP 0144948 (off-line proc.) A-layer PET 1 89 89 89 89 PET 2 10 10 10 10 PET 3 1 1 1 1 PET 4 B-layer PET 1 95 95 95 94.2 PET 2 5 5 5 5 C-layer PET 1 89 89 34 89 PET 2 10 10 15 10 PET 3 1 1 1 1 PET 4 50 Transparency in % 95.5 95.3 93.1 94.5 (web center) Haze 17.8 17.8 10.5 9.8 UV-stability in % 63 63 70 64 UTS Flame test Grade 4 4 4 4 E-Modul MD N/mm.sup.2 4100 4100 4360 3950 Young's Modulus MD E-Modul TD N/mm.sup.2 4550 4550 4800 4350 Young's Modulus TD F5 MD N/mm.sup.2 1015 1015 110 115 F5 TD N/mm.sup.2 102 102 110 100 Shrinkage in % 1.4 1.4 1.5 1.3 MD Shrinkage TD in % 0.2 0.2 0.1 0.4 Expansion in % 0 0 0.1 0 MD at 100 C. Expansion in % 0.1 0.1 0 0 TD at 100 C. SV film 735 735 738 728 Surface mN/m 56.5 56.5 58.4 50.5 tension (total) (surface A) Cold fog test A A* B B Hot fog test A A* B B Note *Results apply to both film surfaces

Comparative Examples 1-7

[0166] The starting compositions and process for preparing the films in the comparative examples were as described for EXAMPLES 1-9 but the films were coated by the coating as described in in EP 1777251 A1 consisting of a hydrophilic coating in which the drying product of the coating composition contains water, a sulfopolyester, a surfactant and, optionally, an adhesion-promoting polymer. The resulting films have a hydrophilic surface which prevents short-term fogging of the films with water droplets.

[0167] Coating 3

[0168] The following composition of the coating solution was used: [0169] 1.0% by weight of sulfopolyester (copolyester of 90 mol % of isophthalic acid and mol % of sodium sulfoisophthalic acid and ethylene glycol) [0170] 1.0% by weight of acrylate copolymer consisting of 60% by weight of methyl methacrylate, 35% by weight of ethyl acrylate and 5% by weight of N-methylolacrylamide [0171] 1.5% by weight of diethylhexyl sulfosuccinate sodium salt (Lutensit A-BO BASF AG).

[0172] Table 3 summarizes the formulations, production conditions and resulting film properties for the films in the comparative examples 1-7:

TABLE-US-00003 TABLE 3 Properties for films in comparative examples 1-7 Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Layer Film thickness 15 15 15 15 (m) Thickness layer A 0.8 0.8 0.8 0.8 Thickness layer B 13.4 13.4 13.4 13.4 Thickness layer C 0.8 0.8 0.8 0.8 Coating on surface A Dry thickness Dry thickness Dry thickness Dry thickness 40 nm. 40 nm. 40 nm. 40 nm. Anti-fog coating 3 Anti-fog coating 3 Anti-fog coating 3 Anti-fog coating 3 (In-Line) (In-Line) (Off-Line) (Off-Line) Coating on surface C Dry thickness 75 nm. Acrylate coating and application method as in example 1 of EP0144948 A-layer PET 1 89 89 89 89 PET 2 10 10 10 10 PET 3 1 1 1 1 PET 4 B-layer PET 1 95 95 95 95 PET 2 5 5 5 5 PET 1 34 89 89 89 C-layer PET 2 15 10 10 10 PET 3 1 1 1 1 PET 4 50 Transparency in % 92.3 9.6 91.8 94.4 (web center) Haze 10.2 10.9 11.3 11.0 UV-stability UTS in % 65 70 64 65 Flame test Grade 4 4 4 4 E-Modul MD N/mm2 4250 4300 3900 4000 Young's Modulus MD E-Modul TD N/mm2 4820 4750 4400 4350 Young's Modulus TD F5 MD N/mm2 100 115 110 118 F5 TD N/mm2 112 105 113 117 Shrinkage MD in % 1.4 1.7 1.5 1.3 Shrinkage TD in % 0.4 0.1 0.4 -0.1 Expansion MD at in % 0 0.1 0 0 100 C. Expansion TD at in % 0.1 0 0 0 100 C. SV Film 720 738 728 738 Surface tension mN/m 46.7 49.8 51.5 50.2 (total) (surface A) Cold fog Test C C C C Hot fog Test D D D D Comparative Comparative Comparative Example 5 Example 6 Example 7 Layer Film thickness 15 15 15 (m) Thickness layer A 0.8 0.8 0.8 Thickness layer B 13.4 13.4 13.4 Thickness layer C 0.8 0.8 0.8 Coating on surface A Dry thickness Dry thickness Dry thickness 25 nm. 40 nm. 25 nm. Anti-fog coating 1 Anti-fog coating 1 Anti-fog coating 1 Coating on surface C Dry thickness 75 nm. Acrylate coating and application method as in example 1 of EP0144948 A-layer PET 1 89 89 89 PET 2 10 10 10 PET 3 1 1 1 PET 4 B-layer PET 1 95 95 95 PET 2 5 5 5 PET 1 34 89 89 C-layer PET 2 15 10 10 PET 3 1 1 1 PET 4 50 Transparency in % 92.5 91.8 94.3 (web center) Haze 11.8 11.8 11.8 UV-stability UTS in % 65 65 65 Flame test Grade 4 4 4 E-Modul MD N/mm2 4200 4200 4200 Young's Modulus MD E-Modul TD N/mm2 4750 4750 4750 Young's Modulus TD F5 MD N/mm2 103 103 103 F5 TD N/mm2 112 112 112 Shrinkage MD in % 1.4 1.4 1.4 Shrinkage TD in % 0.3 0.3 0.3 Expansion MD at in % 0 0 0 100 C. Expansion TD at in % 0.1 0.1 0.1 100 C. SV Film 720 720 720 Surface tension mN/m 45.4 58.2 45.4 (total) (surface A) Cold fog Test B B B Hot fog Test C B C Note

[0173] Description of Test Methods

[0174] The following measurement methods were used to characterize the raw materials and films

[0175] Measurement of Average Particle Diameter d50

[0176] The average particle size d50 was determined using a Malvern Master Sizer 2000. For this purpose, the particles to be used were dispersed in water and transferred into a cuvette which was analyzed in the measuring device, the size determination being effected by means of laser diffraction. In general, the detector takes an intensity image of the diffracted laser light, from which the particle size distribution is calculated by means of a mathematical correlation function from its angle-dependent light intensity. The particle size distribution is characterized by two parameters, the median value d50 (=position measurement for the mean value) and the degree of scattering SPAN98 (=measure for the particle diameter spread). The measurement was performed automatically and also included the mathematical determination of the d50 value.

[0177] Measurements on the film produced with these particles result in a 15-25% lower d50 value compared to the initial value of the particles before the start of production.

[0178] UV/Vis Spectra or Transmission at Wavelength x

[0179] Transmission of the films was measured in a UV/Vis double beam spectrophotometer (Lambda 12 or 35) Perkin Elmer USA. An approximately (35) cm wide film specimen is inserted into a flat sample holder perpendicular to the measurement beam in the beam path. The measurement beam was directed via a 50 mm integrating sphere toward the detector where the intensity is used to determine the transparency at the desired wavelength. The background was air. The transmittance is read at the desired wavelength.

[0180] Opacity/Transparency

[0181] The test serves to determine the opacity and transparency of plastic films in which the optical clarity or opacity is essential for the use value. The measurement is carried out on the Hazegard Hazemeter XL-21 1 from BYK Gardner according to ASTM D 1003-61. The transparency was measured according to ASTM-D 1003-61 (method A) using haze-gard plus from BYK-Gardner GmbH Germany,

[0182] SV Value (Standard Viscosity)

[0183] The standard viscosity SV, was measured based on DIN 53 728 part 3, in an Ubbelohde viscometer at (250.05) C. which measures the time required for the test solution to pass through a capillary. Dichloroacetic acid (DCE) was used as a solvent. The concentration of the dissolved polymer was 1 g of polymer/100 ml of pure solvent. The polymer was dissolved at 60 C. for 1 hour. If the samples were not completely dissolved after this time, the dissolution procedure was repeated twice for 40 min at 80 C. and the solutions were then centrifuged for 1 hour at a rotational speed of 4100 min-1.

[0184] From the relative viscosity (.sub.rel=(/(.sub.s), the dimensionless SV value is determined as follows:

SV=(rel-1)1000

[0185] To be able to compare the chain lengths of polymers used in an unfilled film versus a filled film, the amount of insoluble material has to be taken into account in case the film contains such particles. Polymer raw materials or film containing insoluble particles were dissolved in DCA and the insoluble pigments centrifuged off before measuring. The proportion of insoluble particles was determined by ash determination. In case a filled film is to be analyzed, a larger amount of filled film has to be dissolved in dichloroacetic acid compared to unfilled film. The following formula is used to calculate the weight of the sample to be dissolved in DCA in case the film contains insoluble particles:

[0186] Total weight of sample (filled film) to be dissolved in DCA=(weight of the sample for an unfilled film)/((100insoluble particle content of filled film in wt. %)/100). For example if 0.4 g of standard unfilled film is dissolved in 40 ml DCA, and the filled film to be analyzed contains 5% insoluble particles (as determined by ash determination), 0.42 g of filled film has to be dissolved in DCA to compensate for the weight of insoluble particles:

[0187] 0.4 g/((1005)/100)=0.42 g

[0188] Mechanical Properties

[0189] The mechanical properties were determined by tensile test based on DIN EN ISO 572-1 and -3 (test specimen type 2) on film strips measuring 100 mm15 mm.

[0190] Shrinkage

[0191] The thermal shrinkage was determined on square film samples with an edge length of 10 cm. The samples were cut in such a way that one edge ran parallel to the machine direction and one edge perpendicular to the machine direction. The samples were measured precisely (edge length L.sub.0 was determined for each machine direction TD and MD, i.e. L.sub.0 TD and L.sub.0 MD) and annealed 15 min at the stated shrinkage temperature (here 150 C.) in a forced-air drying cabinet. The samples were removed and measured precisely at room temperature (edge length L.sub.TD and L.sub.MD). Shrinkage is calculated from the equation:

Shrinkage [%] MD=100(L.sub.0 MDL.sub.MD)/L.sub.0 MD, or

Shrinkage [%] TD=100(L.sub.0 TDL.sub.TD)/L.sub.0 TD

[0192] Expansion

[0193] The thermal expansion was determined on square film samples with an edge length of 10 cm. The samples were measured precisely (edge length L.sub.0), annealed for 15 minutes at 100 C. in a forced-air drying cabinet, and then accurately measured at room temperature (edge length L). The expansion results from the equation:

Expansion [%]=100(LL.sub.0)/L.sub.0

[0194] and was determined separately in each direction on the film.

[0195] UV Stability

[0196] The UV stability and the UTS value was determined and specified in % of initial value as in DE69731750 on page 8 (DE of WO9806575), except that the exposure time was not 1000 h but 2000 h.

[0197] Flame Resistance

[0198] A 3030 cm piece of film was fastened with two clips at the corners and hung vertically. Generally, it must be ensured that at the point of suspension, there is no air movement, which moves the piece of film. A slight air from above is acceptable. The film piece was then exposed to a flame from below in the center of the lower side. For flame treatment, a commercial cigarette lighter, or better a Bunsen burner is used. The flame must be longer than 1 cm and less than 3 cm. The flame was held long enough to the film until this continued to burn without an ignition flame (at least 3 seconds). The flame was thereby held maximally for 5 seconds at the most, after which the burning and shrinkage was examined. Four such ignition processes were performed.

[0199] In the examples given here, the flame resistance is evaluated with the following grades: 1=the film was ignited during 4 ignitions, and never burned more than 3 seconds.

[0200] 2=the film ignited and extinguished after less than 15 seconds, and more than 30% of the film surface remained.

[0201] 3=the film ignited and extinguished after less than 20 seconds, and more than 30% of the film surface remained.

[0202] 4=the film ignited and extinguished after less than 40 seconds, and more than 30% of the film surface remained.

[0203] 5=the film ignited and extinguished after less than 40 seconds and more than 10% of the film surface remained.

[0204] 6=the film ignited and burned more than 40 seconds, or less than 10% of the film surface remained after extinction.

[0205] Determination of the Refractive Index as a Function of Wavelength

[0206] To determine the refractive index of a film substrate and an applied coating or a coex layer which has a refractive index other than that of the base material as a function of wavelength, one uses spectroscopic ellipsometry. Background information and theory behind can for example be found in following publication: J. A. Woollam et al, Overview of variable angle spectroscopic ellipsometry-(VASE): I. Basic theory and typical applications, Proc. SPIE Vol. CR72, p. 3-28, Optical Metrology, Ghanim A. AI-Jumaily; Ed.

[0207] First one analyzes the base film without coating or modified coextruded layer. To suppress the back reflection of the film the back (side which is not analyzed) is roughened by a sandpaper with a fine grain size (for example, P1000). The sheet is then measured with a spectroscopic ellipsometer equipped with a rotating compensator, e.g. a M-2000 from J. A. Woollam Co., Inc. The machine direction of the sample film is parallel to the light beam. The measured wavelength is in the range of 370 to 1000 nm, the measurement angle is 65, 70 and 75.

[0208] The ellipsometric data and are then modeled to match the experimental data. The Cauchy model is suitable in the present case

[00001]$n\left(\right)=A+\frac{B}{{}^2}+\frac{C}{{}^4}.Math..Math.\left(\mathrm{wavelength}.Math..Math..Math..Math.\mathrm{in}.Math..Math.\mathrm{microns}\right).$

[0209] where n() is the refractive index at wavelength . The parameters A, B and C are varied such that the data matches as closely as possible the measured spectrum and . To test the quality of the model the MSE value may be included to compare Model with measured data (() and A ()). MSE should be minimized.

[00002]$\mathrm{MSE}=\sqrt{\frac{1}{3.Math.n-m}.Math.\underset{i=1}{\overset{n}{.Math.}}.Math.\left[\begin{array}{c}{\left(N_{E,i}-N_{G,i}\right)}^2+{\left(C_{E,i}-C_{G,i}\right)}^2+\\ {\left(S_{E,i}-S_{G,i}\right)}^2\end{array}\right]}.Math.1000$

[0210] n=number of wavelengths,

[0211] m=number parameter fit

[0212] N=cos (2),

[0213] C=sin (2) cos (),

[0214] S=sin (2) sin () [1]

[0215] The resulting Cauchy parameters A, B and C for the base film allow the calculation of the refractive index n as a function of wavelength, valid in the measured range from 370 to 1000 nm.

[0216] The coating or a modified coex layer can be analyzed similarly. The parameters of the base film are now already analyzed and well known and should be kept constant during the modeling of the additional layer. Also for determining the refractive index of a coating or a coextruded layer the back of the film has to be roughened, as described above. Again, one can use the Cauchy model to describe the refractive index depending on the wavelength of the additional layer. The layer is now on the substrate, which has to be accounted for in the modeling. The thickness of the layer affects the spectrum obtained and must also be included in the modeling process.

[0217] Surface Tension

[0218] The surface free energy (surface free energy) was calculated from the contact angles using the Owens-Wendt-Rabel-Kaelble method according to DIN 5560-1,2. The test liquids are water, 1,5-pentanediol and diiodomethane (see Table 4). The contact angle was determined by means of a DSA-100 measuring device from Kruss GmbH, Germany. The evaluation according to Owens-Wendt-Rabel-Kaelble was carried out using the DSA software belonging to the device (as of 2005). For 1,5-pentanediols, values for the polar and dispersed fraction were taken over according to Gebhardt, for water and diiodomethane values according to Strm.

TABLE-US-00004 TABLE 4 Interfacial Dispersive Polar tension IFT) interactions interactions (mN/m) (mN/m) (mN/m) Water 72.8 21.8 51 1,5-Pentanediol 43.3 27.6 15.7 Diiodomethane 50.8 50.8 0

[0219] Measurement of the Contact Angle (See FIG. 5)

[0220] As a measure of the hydrophilicity of the film surface (A), a static contact angle measurement of distilled water according to DIN 55660-1.2 is used. For measurement on static drops (B), the measuring instrument DSA-100 from the company Krss GmbH with the software Ver. 4 is used. The determination takes place at 23 C. and 50% relative humidity on unfilled film samples conditioned in standard climate at least 16 hours beforehand. Using an automated dosage syringe type ME41, 3-5 l of distilled water are applied to the film surface. The contact angle is automatically determined every 5 seconds over a period of 20 seconds. Measurements are taken for four drops and the mean value of the contact angle is formed from the 16 individual values.

[0221] Determination of the Anti-Fog Effect

[0222] Cold Fog Test: The anti-fogging properties of the polyester films are determined as follows: In a laboratory temperature controlled room at 23 C. and 50% relative humidity, film samples with anti-fog coatings were applied to a tray (length approx. 17 cm, width approx. 12 cm, height approx 3 cm) of amorphous polyethylene terephthalate (APET) containing approximately 50 ml of water (uncoated films are used as reference). The trays are stored in a refrigerator at a temperature of 4 C. and are placed at an angle of 30. The films are evaluated after 12 h, 24 h, 1 week, 1 month, and 1 year. A film equipped with a permanent anti-fogging agent is also transparent after the condensation since the condensate forms a cohesive, transparent film. Without effective anti-fog agent, the formation of a fine droplet mist on the film surface leads to a reduced transparency of the film; in the worst case, the content of the tray is no longer visible.

[0223] A further investigation method is the so-called hot-steam or hot-fog test. A QCT condensation tester from Q-Lab is used. This simulates the anti-fogging effects of climatic moisture influences by condensing warm water directly on the film. In a few days or weeks, results can be reproduced which are caused by moisture within months or years. For this purpose, the water in the QCT condensation unit is heated to 60 C. and the film is clamped in the corresponding holder. The stretched film has an inclination angle of approximately 30. The judgment is the same as described above. This test can be used to test the long-term anti-fogging effect or the washing-up resistance of the film, since the steam constantly condenses on the film and drains again and/or drips off. Easily soluble substances are washed off in this way and the effect of the anti-fogging effect is reduced. This test is also performed in a laboratory temperature controlled room at 23 C. and 50% relative humidity.

[0224] The evaluation of the anti-fog effect (anti-fog test) takes place visually.

[0225] Rating:

[0226] A: A transparent film that does not show any visible water, is completely transparentexcellent anti-fog effect

[0227] B: Some random, irregularly distributed water drops on the surface, discontinuous water filmacceptable anti-fog effect

[0228] C: A complete layer of large-translucent water droplets, poor transparency, lens formation, and drop formationpoor anti-fog effect

[0229] D: An opaque or transparent layer of large water droplets, no transparency, poor light transmissionvery poor anti-fog effect