MULTIFUNCTIONAL OPTICALLY HIGHLY TRANSPARENT FILMS AND METHOD FOR THEIR PRODUCTION

Abstract

Multifunctional optically highly transparent films based on cellulose esters are disclosed, having the following components within a film a) cellulose esters preferably based on cellulose triacetate which can be processed into a highly transparent film with Haze value of < than 0.4% by virtue of a high degree of purity and optical quality and which is defined by the following properties b) at least one organic or inorganic material which acts as a plasticizer and as a spacer between the molecule chains of the cellulose esters and additionally introduced additives in a synergistically effective manner c) at least three organic or inorganic materials with a transmission influencing absorptive function in the wave length range of 300 nm to 2500 nm, the films having protective strain reducing function for the retina of the human eye.

Claims

16. A multifunctional highly transparent film based on cellulose esters comprising the following components forming a cellulose matrix, a) a cellulose ester or a mixture of cellulose esters of cellulose triacetates suitable for processing into a highly transparent film; b) at least an organic or inorganic substance which acts as a distance holder between molecule chains of the cellulose ester and residual solvents in a film drying process and acting as a synergistically effective mediator for integrating additional additives into the matrix; c) at least three organic or inorganic light transmission reducing substances to reduce light that penetrate a film in the wave length range of 300 nm to 2500 nm, wherein said substances act synergistically as plasticizer equivalent and as a distance holder between the molecule chains of the cellulose matrix; wherein a) comprises: cotton-linters as a raw material, 300 ppm of birefringent particles with a size of 20 m, 1% water, 300 ppm free acetic acid, 0.5% of gel forming components, an amount of yellow dye having a low Haze-color number (APHA value)70 (determined by a 16% solution of cellulose triacetate dissolved in methylene chloride after the method ASTM D-1209), 0.5% of foreign fibers and derivatized particles of a size of 40 m.

17. The multifunctional highly transparent film of claim 16, wherein b) is selected from the group consisting of phosphoric acid ester, phthalic acid ester, acetic acid ester, citric acid ester, fatty acid ester, glycols, polyester and adipic acid ester.

18. The multifunctional highly transparent film of claim 16, wherein the components of c) are suitable amount of compounds having the following properties: UV-light absorbing, IR-light absorbing, visible light absorbing dyes, light absorbing or reflecting nano-scale substances in a wave length range of 300 nm to 1000 nm of median particle size of 250 nm that influence the Haze-value with Haze of 0.1, in addition to suitable amounts of photochromic dyes, thermochromic dyes, luminescence dyes, stabilizers, adhesion promoters and cross-linking agents.

19. The multifunctional highly transparent film of claim 16, wherein the synergistically effective components of c) are compounds soluble or dispersible in one or more solvents selected from the group of, water, glacial acetic acid, methanol, ethanol, propanol, butanol, hexanol, chloroform, dichloromethane, trichloromethane, tetrachloromethane, trichloroethane, acetone, methylethylketone, dioxane, tetrahydrofuran, methoxypropanol, ethoxypropanol, benzene, toluene, xylol, methylacetate, ethylacetate, propylacetate, butylacetate, di methylsulfoxide, aceto nitrl, n-heane and n-heptane.

20. The multifunctional highly transparent film of claim 16, wherein the synergistically effective components of c) are one or more dyes selected from the group consisting of the following dyes, nano-scale pigment dyes, metal complex dyes laser dyes, luminescence dyes, photochromic dyes and thermochromic dyes, anthrachinone based dyes, cyanin dyes, perionon dyes, and azodyes.

21. The multifunctional highly transparent film of claim 20, wherein synergistically effective single dyes of component c) have the following properties: at least one transmission minimum in the visible wave length range of 400 nm to 780 nm with a bandwidth of maximally 75 nm at 95% of the transmission minimum value, a molecular weight of 200 g/mol, a high long term stability of transmission properties in the end product, that is, the deviation of transmission- and color value of the starting values may maximally be 10%, if the storage or the material stress occurs under the following conditions: a relative air humidity of 50%, a temperature of 80 C., a storage time of 500 hours, a boiling point or degradation point: 105 C. and a transmission at 380 nm of 80%.

22. The multifunctional highly transparent film of claim 16, wherein the organic or inorganic substances c) are substances selected from the group consisting of benzophenone benzotriazole acetic acid ester, triazine and a nano-scale metal oxide with an average particle size of 250 nm or substances with a wave length transmission of 10% of the average transmission in the wave length range of 400 nm to 780 nm.

23. The multifunctional highly transparent film of claim 16, wherein the organic or inorganic substances of c) are substances which at a wave length of 800 nm10 nm have a transmission of 40% of the average transmission in the wave length range of 400 nm to 780 nm and thus act as IR absorber.

24. The multifunctional highly transparent film of claim 16, wherein the organic or inorganic substances are synergistically effective components of c) which after light impact of wave length ()400 nm show a reversible change of transmission in the range of the visible light and a reduction of the transmission in the area of the UV light and thus result in a reduction of the radiation energy impacting the eye in the range of 300 nm to 780 nm, wherein the films exhibit the following properties: a film thickness of 30 m to 300 m, a break stability of 95 N/mm.sup.2, stretching of 12% an elasticity module of 2.500 N/mm.sup.2, a temperature stability to 150 C. without degradation, melting or irreversible deformation, high longterm stability of the optical properties, that is, the level of Haze-values and transmission values deviate maximally 10% from the starting value after storage of more than 500 hrs at 80 C./50% relative humidity, a plasticizer content of 20 mass %, wherein the portion of triphenylphosphate does not exceed the value of 16 mass-% an additive content of 5 mass % a Haze-value 0.5%, relative to 180 m film thickness, a transmission prior to the impact of light at 400 nm at a Impact time of 300, transmission at 380 nm: 30%, transmission at 400 nm: 50% of transmission transmission at 550 nm: 50%

25. The multifunctional highly transparent film of claim 16, wherein the components of c) include antioxidants or HALS-compounds (Hindered Amine Light Stabilizers) for long term- and temperature stability.

26. The multifunctional highly transparent film of claim 16, wherein the components a) to c) are combined in such a way that a multi functionality Is already realized in a single layer which is defined by the following properties: a film thickness of 30 m to 300 m, a break stability of 95 N/mm.sup.2, stretching of 12% an elasticity module of 2.500 N/mm.sup.2, a temperature stability to 150 C. without degradation, melting or irreversible deformation, high longterm stability of the optical properties, that is, the level of Haze-values and transmission values deviate maximally 10% from the starting value after storage of more than 500 hrs at 80 C./50% relative humidity, a plasticizer content of 13 mass %, an additive content of 5 mass % a Haze-value 0.5%, relative to 180 m film thickness, a transmission at 400 nm of 50% and, color value according to CIE-Lab 1976; 10; D 65: L: 30 to 80 a: 100 to +100, b: 150 to +150.

27. The multifunctional highly transparent film of claim 16, wherein the components a) to c) are combined in such a way that an improved protection is realized at an absorption of light at a wave length of 580 nm and/or 490 nm and/or 435 nm, and wherein the film has the following property profile: a film thickness of 70 m to 270 m, a break stability of 95 N/mm.sup.2, stretching of 12% an elasticity module of 2.500 N/mm.sup.2, a temperature stability to 150 C. without degradation, melting or Irreversible deformation, high longterm stability of the optical properties at 500 hrs at 80 C./50% relative humidity, a plasticizer content of 13 mass %, an additive content of 5 mass % a Haze-value 0.7%, relative to 180 m film thickness, a transmission at 400 nm of 50% and, a transmission at 435 nm of 70% of the transmission value measured at a wave length of 450 nm, a transmission at 490 nm of 70% of the transmission value measured at a wave length of 525 nm, a transmission at 580 nm of 70% of the transmission value measured at a wave length of 550 nm, a transmission at 650 nm of 20%.

28. A method for the production of a multifunctional optically highly transparent film according to claim 16, comprising the following steps, providing the cellulose esters or the mixture of cellulose esters according to a) as starting material, adding of additives which are the components b) and c).

29. The method of claim 28, further comprising the steps of: dissolving the cellulose ester material according to a) In at least a solvent selected from the group consisting of halogen organic solvents, alcoholic solvents, carbonic acid esters, aromatic solvents, ether or ketone, homogenizing the resulting solution, filtrating the solution in a multistep filtration process to free the solution form foreign particulate, gel particles, fibers and undissolved raw material components, and adding the components b) and c).

30. The method of claim 29, wherein the components acting as plasticizer or plasticizer equivalents b) and c) are at least partially added to the product solution after the filtration step and before homogenizing the solution, wherein portion of the plasticizer in total is less or equal to 25% and the portion of plasticizers according to b) Is less or equal to 20%.

31. A method for the production of a multifunctional optically highly transparent film according to claim 16, comprising the following steps, dissolving the solid material in a solvent mixture of 93% dichloromethane and 7% methanol and stirring for at least 12 hours to realize a possibly highest homogeneity degree; four step filtration of the solution up to a filter mesh width of minimally 2.5 m; successive addition of the UV stabilizers 0.53% tinuvin 328, of the functional color component, 0.11% (5(6)-carboxy fluorescein of Sigma Aldrich and 0.055% PTCDI of the firm Organica Feinschemie (D-06766 Bitterfeld-Wolfen), into the finest filtered product solution wherein a period between the addition steps of a homogenizing duration is minimally 15 minutes. addition of suitable amount of plasticizer, triphenylphosphate, in this case of 8.53% for dissolution and homogenizing during a further 4 hour period. renewed multistep filtration of the solution, subsequent ultra sound degassing and placing the solution onto a circulating stainless steel band by means of a casting tool and drying of the film leaving the casting tool still moist from the solvent is in a multi step dryer at a temperature of maximally 150 C. until to reach the required residual moisture and coiling the film.

32. The method of claim 29, wherein component a) comprises at least: cotton-linters as a raw material, 300 ppm of birefringent particles with a size of 20 m, 1% water, 300 ppm free acetic acid, 0.5% of gel forming components, an amount of yellow dye having a low Haze-color number (APHA value)70 (determined by a 16% solution of cellulose triacetate dissolved in methylene chloride after the method ASTM D-1209), 0.5% of foreign fibers and derivatized particles of a size of 40 m.

Description

[0231] Further details, features and advantageous embodiments of the present invention are shown from the following description of embodiments with reference to the respective drawings: It is shown in:

[0232] FIG. 1: transmission spectrum of a multifunctional color film with UV-380 nm-filter function and several absorption maxima.

EXAMPLE A

[0233] Multifunctional Color-Film with UV-380 nm Filter Function and Several Absorption Maxima.

[0234] A film, comprising a cellulose triacetate at a possibly lowest Haze-value <0.4%, a plasticizer (triphenyl phosphate) in a concentration of less than 9% relative to the solid material and functional additives, is produced as follows: [0235] dissolving the solid material in a solvent mixture of 93% dichloromethane and 7% methanol and stirring for at least 12 hours to realize a possibly highest homogeneity degree; [0236] four step filtration of the solution up to a filter mesh width of minimally 2.5 m; [0237] successive addition of the UV stabilizers, for example 0.53% tinuvin 328, of the functional color component, for example, 0.11% (5(6)-carboxy fluorescein of Sigma Aldrich and 0.055% PTCDI of the firm Organica Feinschemie (D-06766 Bitterfeld-Wolfen), into the finest filtered product solution wherein a period between the addition steps of a homogenizing duration is minimally 15 minutes. [0238] addition of the required amount of plasticizer, for example triphenylphosphate, in this case of 8.53% for dissolution and homogenizing during a further 4 hour period. [0239] renewed multistep filtration of the solution, subsequent ultra sound degassing and placing the solution onto a circulating stainless steel band by means of a casting tool and [0240] drying of the film leaving the casting tool still moist from the solvent is in a multi step dryer at a temperature of maximally 150 C. until to reach the required residual moisture and then coiled.

[0241] The so produced multifunctional color film with a filter effect at a wave length of 380 nm and several absorption maxima has the following properties: [0242] basic color pink-violet coloration, [0243] Haze-value: <0.5%, [0244] film thickness: 80 m (5 m), [0245] break stability: >95 N/mm.sup.2, [0246] temperature stability of the film: up to 150 C., [0247] plasticizer content: 8 mass-%, [0248] transmission values, see Table 1:

TABLE-US-00001 TABLE 1 80 m Color Film with UV 380 nm- Filter Example A T380 % 28.8% T460 % 71.2% T582 % 62.4% L* 88,533 a* 5.0 b* 0.9 T(lum) % 72.9%

[0249] and transmission spectrum, which shows the transmission in [%] at a specific wave length in [nm], see FIG. 1.

EXAMPLE B

[0250] Multifunctional UV-Color Film with Photochrome Functionality

[0251] A film consisting of a cellulose acetate with lowest possible Haze-value, that is of 0.4%; a plasticizer in the form of triphenyl phosphate in a concentration of 12%, relative to the solid material, and a functional additive is produced by the following steps: [0252] dissolving the solid material in a solvent mixture of 95% dicloromethane and 5% methanol and stirring at least for 12 hours to attain a highest possible homogenization; [0253] four-step filtration of the solution up to a filter mesh width of 2.5 m; [0254] successively adding the UV-additive color stabilizers, for example benzophenone and timuvin, the dye components, for example Orasol-dyes of the company Kremer Pigments, inclusive of a photochrome dye, for example Reversacoal-dye of the company James Robinson, Into an amount of methanol which corresponds to 5% of the total amount of solvent, maximally to realize a concentration, which corresponds to 95% of the total saturation concentration of the additives in the solution, optionally also heating the solution up to maximally 60 C.; [0255] stirring the additive solution into the cellulose derivative solution and homogenization for approximately 4 hours; [0256] addition of the required amount of plasticizers, for example triphenyl phosphate, in this case 12% to the solution and homogenizing for a further 4 hours; renewed multistep filtration of the solution, subsequently ultra sound degassing and emergence of the solution onto a circulating stainless steel band by means of a casting tool and [0257] drying the still solvent-moist film emerging from the casting tool in a multi-step dryer to attain the required residual solvent moisture at a temperature of maximally 150 C. and coiling the film.

[0258] The so-produced multifunctional photochrome color film with UV protection exhibit the following properties: [0259] basic color: grey-blue, [0260] Haze-value: 0.3% [0261] film thickness: 180 m5 m, [0262] break stability: 95 N/mm.sup.2, [0263] expansion: 14%, [0264] elasticity module: 2.500 N/mm.sup.2, [0265] temperature stability of the film: up to 150 C., [0266] plasticizer content 12 mass % and [0267] transmission values, see Table 2:

TABLE-US-00002 TABLE 2 180 m Photochrome Color Film with UV-Protection inactive after UV-activation % T380 10% 10% % T490 18.3 12.1 % T550 50.0 33.2 % T584 15.7 9.0 L* 71.6 64.3 a* 0.7 3.0 b* 7.4 9.1 t.sub.1/2 51 s t.sub.1/4 158 s

EXAMPLE C

[0268] Multifunctional Color Film with UV-Protection and Retinal Cone Relief Function

[0269] A film consisting of a cellulose triacetate with the lowest possible

[0270] Haze-value 0.4%, a plasticizer (triphenylphosphate) In a concentration of 9%, relative to the solid material, and functional additives is produced as follows: [0271] dissolving the solid material in a solvent mixture of 93% dichloromethane and 7% methanol and stirring for at least 12 hours [0272] to attain a highest possible degree of homogenization; four-step filtration of the solution up to a filter mesh width of minimally 2.5 m: [0273] successive addition of the UV-stabilizers, for example Tinuvin 770 and Tinuvin 328, then the functional color components from the group of metal complex dyes (for example Orasol-dyes of the company Kremer Pigment (D-88317 Aichstetten), the group of luminescence dyes (for example (5(6)-Carboxyfluorescine of the company Sigma Aldrich Laborchemikalien GmbH, D-30926 Seelze) and the group of perylene dyes (for example PTCDI of the company Organica Feinchemie D-Bitterfeld-Wolfen) into the finest filtered product solution, wherein between the addition steps, a homogenization duration should be minimally 15 min.; [0274] addition of the required amount of plasticizer, for example triphenyl phosphate, in this case 8.5%, to the solution and homogenization of further 4 hours; [0275] renewed multistep filtration of the solution, subsequently ultra sound degassing and outputting the solution onto a circulating stainless steel band by means of a casting tool and [0276] drying the still solvent-moist film emerging from the casting tool in a multi-step dryer to attain the required residual solvent moisture at a temperature of maximally 150 C. and coiling the film.

[0277] The so-produced multifunctional color films with UV protection exhibit the following properties: [0278] basic color: dark grey with very little pink-violet coloration, [0279] Haze-value: 0.5% [0280] film thickness: 160 m5 m, [0281] break stability: 95 N/mm.sup.2, [0282] stretching: 14%, [0283] elasticity module: >2.500 N/mm.sup.2, [0284] temperature stability of the film: up to 150 C., [0285] plasticizer content: 8 mass % and [0286] transmission values, see Table 3:

TABLE-US-00003 TABLE 3 160 m Color Film with UV-Filter Example C T380 % 1% T490 % 6.0% T580 % 3.4% L* 48.95 a* 4.35 b* 0.75 T(lum) % 17.5%