Glazing having electrically switchable optical properties

Abstract

A glazing having electrically adjustable optical properties is described, including an outer pane and an optically adjustable element which is connected to the outer pane in a planar fashion via at least one thermoplastic film, wherein the thermoplastic film contains at least one luminescent material.

Claims

1. A glazing having electrically adjustable optical properties, comprising: an outer pane; and an optically adjustable element that is areally bonded to the outer pane via at least one thermoplastic film, wherein the at least one thermoplastic film contains at least one luminescent material, the at least one thermoplastic film containing from 0.1 kg/m.sup.3 to 20 kg/m.sup.3 of the at least one luminescent material.

2. The glazing according to claim 1, wherein the at least one thermoplastic film contains no UV blockers.

3. The glazing according to claim 1, wherein the optically adjustable element contains at least one organic material.

4. The glazing according to claim 1, wherein the optically adjustable element is areally arranged between two carrier films and wherein one of the carrier films is bonded to the outer pane via the at least one thermoplastic film.

5. The glazing according to claim 1, wherein a barrier film is arranged on a surface of the at least one thermoplastic film facing away from the outer pane.

6. The glazing according to claim 5, wherein the barrier film contains polyethylene terephthalate (PET).

7. The glazing according to claim 1, wherein the thermoplastic film contains one or both of ethylene vinyl acetate (EVA) and polyvinyl butyral (PVB).

8. The glazing according to claim 1, wherein the luminescent material has an excitation maximum in the range from 350 nm to 450 nm.

9. The glazing according to claim 1, wherein the luminescent material has an emission maximum in the range from 410 nm to 600 nm.

10. The glazing according to claim 1, wherein the at least one luminescent material contains at least one hydroxyalkyl terephthalate with the formula
R1-COO-Ph(OH)xCOOR2, where R1, R2 is an alkyl or allyl radical having 1 to 10 C atoms, Ph is a phenyl ring, OH is a hydroxyl group bonded to the phenyl ring, and x is an integer from 1 to 4.

11. The glazing according to claim 1, wherein the at least one thermoplastic film has transmittance less than or equal to 10% in the wavelength range from 380 nm to 410 nm.

12. The glazing according to claim 1, wherein an active layer of the optically adjustable element selected from the group consisting of a suspended particle device, a polymer dispersed liquid crystal, an electrochromic material, and an electroluminescent material.

13. The glazing according to claim 1, further comprising an inner pane forming a composite pane, wherein the optically adjustable element is arranged areally between the outer pane and the inner pane.

14. The glazing according to claim 1, further including a barrier film positioned between the at least one thermoplastic film and the optically adjustable element.

15. The glazing according to claim 1, wherein the at least one thermoplastic film has a thickness from 0.2 mm to 2 mm.

16. The glazing according to claim 1, wherein the at least one luminescent material is contained within the at least one thermoplastic film.

17. The glazing according to claim 1, wherein the at least one luminescent material is distributed homogeneously over an entire area of the at least one thermoplastic film.

18. The glazing according to claim 1, wherein the at least one luminescent material has an excitation maximum in the range from 380 nm to 420 nm.

19. The glazing according to claim 1, wherein the at least one luminescent material has an emission maximum in the range from 430 nm to 500 nm.

20. The glazing according to claim 1, wherein the at least one luminescent material contains diethyl 2,5-dihydroxy terephthalate.

21. The glazing according to claim 1, wherein the at least one thermoplastic film contains from 1 kg/m.sup.3 to 7 kg/m.sup.3 of the at least one luminescent material.

22. The glazing according to claim 1, wherein the at least one thermoplastic film contains a material selected from the group consisting of ethylene vinyl acetate, polyvinyl butyral, polyurethane, polyethylene, polyethylene terephthalate, polypropylene, polycarbonate, polymethyl methacrylate, polyacrylate, polyvinyl chloride, polyacetate resin, casting resins, acrylates, fluorinated ethylene propylenes, polyvinyl fluoride, and ethylene tetrafluoroethylene.

23. A method for producing a glazing having electrically adjustable optical properties, comprising: providing a thermoplastic film; applying at least one luminescent material on the thermoplastic film or incorporating at least one luminescent material into the thermoplastic film, the at least one thermoplastic film containing from 0.1 kg/m.sup.3 to 20 kg/m.sup.3 of the at least one luminescent material; arranging the thermoplastic film between an outer pane and an optically adjustable element; and bonding the optically adjustable element to the outer pane via the thermoplastic film.

24. A protection method for a glazing, comprising: providing an optically adjustable element; and areally bonding the optically adjustable element to an outer pane via a thermoplastic film, wherein the thermoplastic film contains at least one luminescent material, the at least one thermoplastic film containing from 0.1 kg/m.sup.3 to 20 kg/m.sup.3 of the at least one luminescent material, thus protecting the optically adjustable element against UV radiation and radiation in the short wavelength visible range.

25. The method of claim 24, wherein protecting the optically adjustable element includes protection against radiation having a wavelength less than 410 nm.

26. The method of claim 24, wherein protecting the optically adjustable element includes protection against radiation in the wavelength range from 380 nm to 410 nm.

Description

(1) The invention is explained in detail with reference to drawings and exemplary embodiments. The drawings are schematic representations and are not true to scale. The drawings in no way restrict the invention. They depict:

(2) FIG. 1 a cross-section through a first embodiment of the glazing according to the invention having electrically switchable optical properties,

(3) FIG. 2 a cross-section through another embodiment of the glazing according to the invention,

(4) FIG. 3 a cross-section through another embodiment of the glazing according to the invention.

(5) FIG. 4 a cross-section through another embodiment of the glazing according to the invention,

(6) FIG. 5 the aging of switchable functional elements without and with protection against UV radiation and short wavelength radiation of the visible range referring to a diagram,

(7) FIG. 6 the transmittance of thermoplastic films of the prior art and according to the invention referring to a diagram, and

(8) FIG. 7 an exemplary embodiment of the method according to the invention referring to a flowchart.

(9) FIG. 1 depicts a cross-section through an embodiment of the glazing according to the invention having electrically switchable optical properties. The glazing includes one outer pane 1 and is intended as a window glazing, for example, a shop window. The outer pane is made of soda lime glass.

(10) The glazing further includes a switchable functional element 4. The functional element 4 contains an active layer 5 between an outer flat electrode 6 and an inner flat electrode 7. The flat electrodes 6, 7 are connected to an external power supply via busbars (not shown) and connection cables (not shown). The functional element 4 was provided at the time of production of the composite pane as a multilayer film 8 having electrically switchable optical properties. The multilayer film 8 includes the functional element 4 between a first carrier film 9 and a second carrier film 10. The carrier films 9, 10 are made of polyethylene terephthalate (PET) and have a thickness of 0.125 mm. The functional element is, for example, an electrochromic functional element or an SPD functional element.

(11) The first carrier film 9 is bonded to the outer pane via a thermoplastic film 12 made of polyvinyl butyral (PVB). The functional element 4 is arranged on the interior side of the outer pane 1. This means that, in the installed position, the outer pane 1 faces the external environment and the multilayer film 8 faces the building interior. A luminescent material 3 with a concentration of roughly 3.9 kg/m.sup.3 is incorporated into the thermoplastic film 12. The luminescent material 3 is diethyl-2,5-dihydroxy terephthalate.

(12) FIG. 2 depicts a cross-section through an embodiment of the glazing according to the invention having electrically switchable optical properties. The glazing is a composite pane. The composite pane includes a outer pane 1, which is bonded to an inner pane 2 via an intermediate layer 11. The composite pane is provided as a component of a window glazing of a building and is arranged, in the installed position, such that the outer pane 1 faces the external environment and the inner pane 2 faces the building interior. The outer pane 1 and the inner pane 2 are made of soda lime glass and have thicknesses of, for example, 1.6 mm.

(13) A switchable functional element 4 is incorporated into the intermediate layer 11. The functional element 4 is, for example, a PDLC functional element with an active layer 5 between an outer flat electrode 6 and an inner flat electrode 7. Alternatively, the functional element 4 can be, for example, an SPD functional element. The functional element 4 is arranged on the surface of the inner pane 2 facing the outer pane 1, with a circumferential edge region of the inner pane 2 not provided with the functional element 4. The flat electrodes 6, 7 are connected to an external power supply via busbars (not shown) and connection cables (not shown). The flat electrodes 6, 7 are made of indium tin oxide (ITO) and have a thickness of roughly 100 nm. The active layer 5 contains liquid crystals that are incorporated into a polymer matrix. When a voltage is applied on the flat electrodes 6, 7, the liquid crystals align themselves in a common direction and the scattering of light on the liquid crystals is reduced. The optical properties of the active layer 5 are, consequently, electrically switchable.

(14) The intermediate layer 11 is formed by a thermoplastic film 12. The thermoplastic film 12 is made of polyvinyl butyral (PVB) into which a luminescent material 3 is incorporated. The thermoplastic film 12 has a thickness of, for example, 0.76 mm. The luminescent material 3 is diethyl-2,5-dihydroxy terephthalate. The luminescent material 3 has, in the thermoplastic film 12, a concentration of roughly 3.9 kg/m.sup.3.

(15) In the edge region not provided with the functional element 4, the inner pane 2 is bonded directly to the outer pane 1 via the thermoplastic film 12. The functional element is thus advantageously protected against corrosion in the interior of the intermediate layer 11.

(16) FIG. 3 depicts a cross-section through another embodiment of the glazing according to the invention having electrically switchable optical properties. The glazing is a composite pane. The composite pane comprises an outer pane 1 that is bonded via an intermediate layer 11 to an inner pane 2. The composite pane is provided as a roof panel of a motor vehicle and is arranged in the installed installation such that the outer pane 1 faces the external environment and the inner pane 2 faces the vehicle interior. The outer pane 1 and the inner pane 2 are made of soda lime glass and have thicknesses of 2.1 mm.

(17) A switchable functional element 4 is incorporated into the intermediate layer 11. The functional element 4 is an SPD functional element with an active layer 5 between an outer flat electrode 6 and an inner flat electrode 7. The flat electrodes 6, 7 are connected to an external power supply via busbars (not shown) and connection cables (not shown). The flat electrodes 6, 7 are made of indium tin oxide (ITO) and have a thickness of, for example, roughly 50 nm. The active layer 5 contains polarized particles suspended in a resin. As a function of the voltage applied on the flat electrodes 6, 7, the suspended particles align themselves along a common spatial direction. By means of the alignment of the particles, the absorption of visible light is reduced. The transmittance of visible light through the composite pane can, consequently, be conveniently controlled electrically.

(18) The functional element 4 was provided, at the time of production of the composite pane, as a multilayer film 8 having electrically switchable optical properties. The multilayer film 8 includes the functional element 4 between a first carrier film 9 and a second carrier film 10. The carrier films 9, 10 are made of polyethylene terephthalate (PET) and have a thickness of 0.125 mm.

(19) The multilayer film 8 is bonded via a first thermoplastic film 12 to the outer pane 1 and via a second thermoplastic film 13 to the inner pane 2. The first thermoplastic film 12 is made of polyvinyl butyral (PVB) and has a thickness of 0.76 mm. The second thermoplastic film 13 is made of ethylene vinyl acetate (EVA) and has a thickness of 0.38 mm. The intermediate layer 11 thus comprises the first thermoplastic film 12, the multilayer film 8 (with the first carrier film 9, the outer flat electrode 6, the active layer 5, the inner flat electrode 9, and the second carrier film 10), and the second thermoplastic film 13.

(20) A luminescent material 3 is incorporated into the first thermoplastic film 12. The thermoplastic film 12 has a thickness of, for example, 0.76 mm. The luminescent material 3 is diethyl-2,5-dihydroxy terephtalate. The luminescent material 3 has, in the thermoplastic film 12, a concentration of roughly 3.9 kg/m.sup.3. By means of the luminescent material 3, the transmittance of the thermoplastic film 12 in the wavelength range from 380 nm to 410 nm is less than 10%.

(21) Radiation components of the sunlight passing through the composite pane in the UV range and in the short wavelength visible range, in particular radiation components with wavelengths less than roughly 410 nm are absorbed by the thermoplastic film 12. Consequently, these radiation components cannot lead to aging of the functional element 4, by which means the long-term stability of the functional element 4 is advantageously increased. The radiation energy absorbed by the luminescent material 3 is emitted again with a greater wavelength. Compared to the use of prior art UV blockers, this reduces the color change of the light passing through the composite pane and increases the transmittance of the composite pane. The fact that improved protection of the functional element 4 against aging is provided by the thermoplastic film 12 with the luminescent material was unexpected and surprising for the person skilled in the art.

(22) FIG. 4 depicts a cross-section through another embodiment of the glazing according to the invention having electrically switchable optical properties. The glazing is a composite pane. The outer pane 1, the inner pane 2, the first thermoplastic film 12, the second thermoplastic film 13, and the multilayer film 8 are configured as in FIG. 3. The multilayer film 8 has a smaller surface area than the outer pane 1 and the inner pane 2, with a circumferential edge region of the composite pane not provided with the multilayer film 8 when looked through. Thus, the multilayer film 8 does not extend to the side edges of the composite pane. Consequently, the multilayer film 8 has no contact with the surrounding atmosphere and is advantageously protected against corrosion in the region of the side edges by the films of the intermediate layer 11. The multilayer film 8 is also provided with a circumferential edge sealing 15. The edge sealing 15 is implemented as polyimide film, which runs circumferentially around the side edges of the multilayer film 8 and extends, starting from the side edges, a few millimeters beyond the surfaces of the carrier films 9, 10 facing away from the active layer 5. The edge sealing prevents the diffusion of plasticizers and other adhesive components of the thermoplastic films 12, 13 into the active layer 5, by which means the aging of the functional element 4 is reduced.

(23) A barrier film 14 is arranged between the first thermoplastic film 12 with the luminescent material 3 and the multilayer film 8. The barrier film 14 is made of PET and prevents diffusion of the luminescent material 3 out of the first thermoplastic film 12 into the second thermoplastic film 13. The barrier film 14 is also provided with an infrared protection coating (not shown). This protects the functional element 4 against aging due to infrared components of sunlight.

(24) FIG. 5 shows a diagram of aging measurements on composite panes having electrically switchable optical properties. The composite panes were subjected to a standardized Weather-Ometer (WOM) Test. The composite panes were irradiated with a xenon arc lamp whose radiation simulates the solar spectrum. The outer pane 1 was arranged facing the light source. After the irradiation, the value E was determined. The value E indicates the changes in brightness and color of the composite pane, in particular of the functional element 4 as a result of the WOM Test. The value E is thus a measure of the aging of the functional element 4. It is calculated with the following formula:

(25) $E=\sqrt{{\left(\frac{L^{*}}{2}\right)}^2+a^{{*}^2}+b^{{*}^2}}$
L*is the brightness value, a* and b* are the color coordinates in the L*a*b* Color Space. A refers to the difference in the respective variable before and after the WOM Test.

(26) The values E were determined for an example according to the invention and two comparative examples and are plotted in FIG. 5 as a function of the irradiation period. The Example according to the invention was a composite pane in accordance with FIG. 3. The luminescent material 3 was incorporated into the first thermoplastic film 12. The Comparative Example 1 differed from the Example through the first thermoplastic film 12. The thermoplastic film 12 in the Comparative Example 1 was made of ethylene vinyl acetate (EVA), had a thickness of 0.38 mm, and contained no luminescent material 3. The composite pane in the Comparative Example 2 was configured exactly like that in the Comparative Example 1. However, during the irradiation in the Comparative Example 2, an optical filter that was not transparent to UV radiation or to radiation in the visible range with a wavelength of less than 500 nm was arranged between the radiation source and the composite pane.

(27) From FIG. 5, it is evident that the protection of the composite pane against UV radiation and radiation in the short wavelength visible range results in significantly less aging of the functional element 4. The values E in the Comparative Example 2 are significantly lower for all observation times than in the Comparative Example. The values E in the Example according to the invention are approximately on the same best-fit straight line as the values E of the Comparative Example 2. Thus, by means of the thermoplastic film according to the invention 12 with the luminescent material 3, equally effective protection against UV radiation and radiation in the short wavelength range is obtained as with an optical filter. This result was unexpected and surprising for the person skilled in the art.

(28) FIG. 6 shows the transmittance of a thermoplastic film made of EVA, of a thermoplastic film made of PVB, and of a thermoplastic film 12 according to the invention with luminescent material 3 incorporated. The thermoplastic film according to the invention 12 is made of PVB and contains diethyl-2,5-dihydroxy terephtalate as the luminescent material 3 at a concentration of roughly 3.9 kg/m.sup.3. Each thermoplastic film has transmittance of roughly 0% for UV radiation up to a certain wavelength. However, as the wavelength increases, the transmittance of the thermoplastic film increases up to a maximum value of roughly 90%. If the thermoplastic film is arranged between the outer pane 1 and the switchable functional element 4 of a glazing having electrically switchable optical properties, the transmitted UV radiation as well as radiation in the short wavelength visible range results in aging of the functional element 4. It is evident from the diagram that a film made of PVB transmits a smaller range of the UV spectrum than a film made of EVA. When a luminescent material is incorporated into the film, the radiation component transmitted in the UV range and in the short wavelength visible range is further reduced. Table 1 summarizes the transmittance of the films at 380 nm, 390 nm, 400 nm, and 410 nm. Through the use of the PVB film with luminescent material as the thermoplastic film 12 of a glazing having electrically switchable optical properties, the aging of the switchable functional element 4 can be effectively reduced (cf. FIG. 5). This result was unexpected and surprising for the person skilled in the art.

(29) TABLE-US-00001 TABLE 1 PVB with Diethyl-2,5-dihydroxy terephtalate EVA PVB (3.9 kg/m.sup.3) 380 nm 1.9% 0.0% 0.0% 390 nm 18.6% 2.0% 0.0% 400 nm 56.6% 29.5% 0.2% 410 nm 79.7% 70.3% 6.5%

(30) FIG. 7 depicts an exemplary embodiment of the method according to the invention for producing a glazing having electrically switchable optical properties. The exemplary embodiment results in a composite pane in accordance with FIG. 3. First, the luminescent material 3 is applied in a solvent on a surface of the first thermoplastic film 12. The concentration of the luminescent material 3 on the thermoplastic film 12 is, for example, 3 g/m.sup.2. The second thermoplastic film 13 is placed on the inner pane 2. The multilayer film 8 is electrically contacted and placed on the second thermoplastic film 13. The first thermoplastic film 12 is placed on the multilayer film 8. The outer pane 1 is placed on the first thermoplastic film 12. Then, the stack is laminated under the action of temperature, pressure, and/or vacuum to form the composite pane.

LIST OF REFERENCE CHARACTERS

(31) (1) outer pane (2) inner pane (3) luminescent material (4) functional element having electrically switchable optical properties (5) active layer of the functional element 4 (6) outer flat electrode of the functional element 4 (7) inner flat electrode of the functional element 4 (8) multilayer film having electrically switchable optical properties (9) carrier film of the multilayer film 8 (10) carrier film of the multilayer film 8 (11) intermediate layer (12) thermoplastic film (13) thermoplastic film (14) barrier film (15) edge sealing