Device for operating functional elements having electrically controllable optical properties

Abstract

A device having a functional element having electrically controllable optical properties, includes an electrical energy source having an output voltage U, a functional element having electrically controllable optical properties, and at least two supply lines, by means of which the electrical energy source and the functional element are connected. The output voltage U has an alternating voltage having a frequency f from 40 Hz to 210 Hz, a maximum amplitude U.sub.max from 24 V to 100 V, and a slope in the range of the output voltage U between 80% U.sub.max and 80% U.sub.max from 0.05*U.sub.max/100 s to 0.1*U.sub.max/100 s and in the range of the output voltage U between 80% U.sub.max and 80% U.sub.max from 0.05*U.sub.max/100 s to 0.1*U.sub.max/100 s.

Claims

1. A device having at least one functional element having electrically controllable optical properties, comprising: an electrical energy source having an output voltage U, at least one functional element having electrically controllable optical properties, and at least two supply lines, by means of which the electrical energy source and the functional element are connected, wherein the output voltage U has an alternating voltage having a frequency f of 40 Hz to 210 Hz, a maximum amplitude U.sub.max of 24 V to 100 V, a slope in the range of the output voltage U between 80% U.sub.max and 80% U.sub.max of 0.05*U.sub.max/100 s to 0.1*U.sub.max/100 s and in the range of the output voltage U between 80% U.sub.max and 80% U.sub.max of 0.05*U.sub.max/100 s to 0.1*U.sub.max/100 s, wherein a thermometer is arranged on the functional element and the thermometer is coupled to the power supply.

2. The device according to claim 1, wherein the functional element is planar.

3. The device according to claim 1, wherein the functional element is a suspended particle device film or a polymer-dispersed liquid crystal film.

4. The device according to claim 1, wherein the frequency f is from 45 Hz to 105 Hz.

5. The device according to claim 1, wherein the maximum amplitude U.sub.max is from 50 V to 75 V.

6. The device according to claim 1, wherein the slope in the range between 100% U.sub.max to 80% U.sub.max as well as between 80% U.sub.max to 100% U.sub.max is less than 0.05*U.sub.max/100 s and between 100% U.sub.max to 80% U.sub.max as well as between 80% U.sub.max to 100% U.sub.max is greater than 0.05*U.sub.max/100 s.

7. The device according to claim 1, wherein the slope in the range between 90% U.sub.max and 80% U.sub.max as well as in the range from 80% U.sub.max to 90% U.sub.max is from 0.05*U.sub.max/100 s to 0.1*U.sub.max/100 s.

8. The device according to claim 1, wherein the slope in the range between 100% U.sub.max and 90% U.sub.max as well as in the range from 90% U.sub.max to 100% U.sub.max is less than 0.05*U.sub.max/100 s.

9. The device according to claim 1, wherein the functional element is arranged inside a composite pane.

10. A method for controlling the device according to claim 1, wherein a) a temperature T is measured at the thermometer, and b) the maximum amplitude U.sub.max of the output voltage U is adapted to the temperature, wherein from a certain threshold temperature T.sub.S as the temperature T increases at the thermometer, the maximum output voltage U.sub.max is lowered and up to a certain threshold temperature T.sub.S as the temperature T drops, the maximum output voltage U.sub.max is increased.

11. A method for controlling a device according to claim 1, wherein the temperature T is measured at the thermometer and the maximum amplitude U.sub.max of the output voltage U is adapted as a function of the temperature T, wherein for T<T.sub.S: U.sub.max=U.sub.max,k=constant at 50 V<U.sub.max,k<75 V and for T>T.sub.S: 50 V1.5 V/ C.*(TT.sub.S)<U.sub.max<75 V0.5 V/ C.*(TT.sub.S) and T.sub.S=constant at 40 C.<T.sub.S<60 C.

12. The method according to claim 11, wherein for T<T.sub.S: U.sub.max=U.sub.max,k=constant at 50 V<U.sub.max,k<75 V and for T>T.sub.S: U.sub.max=U.sub.max,k+g (TT.sub.S) with 1.5 V/ C.<g<0.5 V/ C. and T.sub.S=constant at 40 C.<T.sub.S<60 C.

13. The method according to claim 11, wherein for T<T.sub.S: U.sub.max=U.sub.max,k=constant at 60 V<U.sub.max,k<70 V and for T>T.sub.S: U.sub.max=U.sub.max,k+g (TT.sub.S) with g=constant and 1.5 V/ C.<g<0.5 V/ C. and T.sub.S=constant at 40 C.<T.sub.S<60 C.

14. A method comprising utilizing a device according to claim 1 for controlling a functional element in a vehicle on water, on land, or in the air, or in an interior glazing or an exterior glazing of a building, as a sun screen or as a privacy screen.

15. The device according to claim 4, wherein the frequency f is from 49 Hz to 69 Hz.

16. The device according to claim 5, wherein the maximum amplitude U.sub.max is from 60 V to 70 V.

17. The device according to claim 9, wherein the thermometer is arranged inside the composite pane.

18. The method according to claim 14, wherein the device includes a windshield or a roof panel of a motor vehicle.

Description

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

(2) FIG. 1A a plan view of an embodiment of a device according to the invention for operating functional elements having electrically controllable optical properties,

(3) FIG. 1B a cross-section through the composite pane of FIG. 1A along the section line X-X,

(4) FIG. 1C an enlarged representation of the region Z of FIG. 1B,

(5) FIG. 2A a diagram of the output voltage U as a function of the time t,

(6) FIG. 2B an enlarged detail of output voltage U as a function of the time t from the diagram of FIG. 2A,

(7) FIG. 3 depicts a diagram of the maximum output voltage U.sub.max as a function of the temperature T.

(8) FIG. 1A depicts a device 100 for operating a functional element 2 having electrically controllable optical properties. The device 100 includes an electrical energy source 1, which is electrically conductively connected to a functional element 2 via two supply lines 3. The functional element 2 is arranged here, for example, inside a composite pane 10.

(9) FIG. 1B depicts a cross-section through a composite pane 10 according to the invention. The composite pane 10 comprises an outer pane 11 and an inner pane 12 that are joined to one another via a first intermediate layer 13a and a second intermediate layer 13b. The outer pane 11 has a thickness of 2.1 mm and is made, for example, of clear soda lime glass. The inner pane 12 has a thickness of 1.6 mm and is also made, for example, of clear soda lime glass. The composite pane 10 can be arranged, for example, as vehicle glazing as a roof panel in the roof of the motor vehicle. In another exemplary embodiment, the composite pane 10 can be arranged as architectural glazing in the frame of a window with other panes to form an insulating glazing.

(10) A functional element 2 that is controllable in its optical properties via an electrical voltage is arranged between the first intermediate layer 3a and the second intermediate layer 3b.

(11) The controllable functional element 2 is, for example, a PDLC multilayer film consisting of an active layer 21 between two surface electrodes 22, 23 and two carrier films 24, 25. The active layer 21 contains a polymer matrix with liquid crystals dispersed therein that are oriented as a function of the electrical voltage applied on the surface electrodes, by which means the optical properties can be controlled. The carrier films 24, 25 are made of PET and have a thickness of, for example, 0.125 mm. The carrier films 24, 25 are provided with a coating of ITO facing the active layer 21 and having a thickness of approx. 100 nm that form the surface electrodes 22, 23. The surface electrodes 22, 23 are electrically connected to the supply lines 3 via busbars (not shown) (formed, for example, by a silver-containing screen print) and, via them, to the energy source 1.

(12) The intermediate layers 13a, 13b comprise in each case a thermoplastic film with a thickness of 0.38 mm. The intermediate layers 13a, 13b are made, for example, of 78 wt.-% polyvinyl butyral (PVB) and 20 wt.-% triethylene glycol bis(2-ethyl hexanoate) as plasticizer.

(13) The electrical energy source 1 outputs an output voltage U that is applied via the supply lines 3 on the surface electrodes 22, 23 of the surface element 2 and that controls, by the voltage level, the optical properties of the surface element 2, i.e., in this case the transparency to visible-light.

(14) FIG. 2A shows a diagram of the output voltage U of the energy source 1 as a function of the time t. The output voltage U is outputted by the energy source 1 during operation of the device, i.e., when the functional element is connected.

(15) FIG. 2B shows an enlarged detail of the diagram of FIG. 2A. The output voltage U is essentially a trapezoidal voltage with slightly oblique edges and rounded corners. The output voltage U changes between a minimum value of U.sub.max (negative maximum output voltage) and a maximum value of U.sub.max (positive maximum output voltage) and, for example, between 65 V and +65 V.

(16) The frequency is, for example, 50 Hz such that the period duration P=20 ms.

(17) The slope of the rising edge between 80% U.sub.max and +80% U.sub.max, i.e., between 52 V and +52 V is 0.075*U.sub.max/100 s, i.e., 4.875 V/100 s. The rise time t.sub.1, i.e., the temporal length of the rising edge von 52 V to +52 V, is, consequently, 1066.6 s. The slope of the rising edge between 80% U.sub.max and 80% U.sub.max, i.e., between +52 V and 52 V is, for example, 0.075*U.sub.max/100 s, i.e., 4.875 V/100 s. The temporal length of the rising edge from +52 V to 52 V is, consequently, likewise 1066.6 s.

(18) The slope decreases for values between 80% U.sub.max and 100% U.sub.max and is significantly less than 0.075*U.sub.max/100 s. This applies correspondingly to the range between 100% U.sub.max to 80% U.sub.max, 80% U.sub.max to 100% U.sub.max, and 100% U.sub.max to 80% U.sub.max. The rounding of the corners of the rectangular signal improves the electromagnetic compatibility (EMC) of the device 100 and significantly reduces interference, for example, in electronics in the surroundings.

(19) The reduced slope in the range between 80% U.sub.max and +80% U.sub.max as well as between 80% U.sub.max and 80% U.sub.max reduces the charge/discharge currents of the layer system and thus reduces heating of the supply lines and of the active layer. Thus, significant aging resistance can be achieved.

(20) FIG. 3 shows a diagram of the temperature-dependent maximum amplitude U.sub.max of the output voltage U as a function of the temperature T.

(21) According to one embodiment of the method according to the invention, the maximum output voltage U.sub.max of the output voltage U is adapted to the temperature T of the functional element 2. The temperature T is measured by a thermometer 5 that is arranged here, for example, directly on the functional element 2 (see, for example, FIGS. 1A, 1B, and 1C).

(22) In the example presented here, below a threshold voltage T.sub.S, the maximum amplitude U.sub.max of the output voltage U is constant (=U.sub.max,k). Above a threshold temperature T.sub.S of, for example, 50 C., the maximum amplitude U.sub.max is lowered. The maximum amplitude U.sub.max is, for temperatures T that are greater than the threshold temperature T.sub.S, for example, U.sub.max1.0 V/ C.*(TT.sub.S). In other words, with a maximum output voltage U.sub.max (in the temperature range T.sub.S) of 65 V and a temperature T of 75 C., the temperature-dependent maximum output voltage U.sub.max is, for example, 65 V1.0 C.*(75 C.50 C.)=40 V.

(23) As investigations by the inventors showed, such a temperature-dependent maximum output voltage U.sub.max suffices for achieving the desired switching result in terms of the ultimate optical properties, i.e., for achieving comparable transparency values and opacity values as with higher maximum output voltages in the lower temperature range. At the same time, energy for operation is saved and unnecessary additional heating of the functional element is reduced, thus increasing its service life.

(24) Without intending to subscribe to a theory, this behavior can be understood in a simple model: PDLC films contain a polymer liquid crystal film that is embedded between two transparent films. Randomly oriented electrically polarized liquid crystal molecules are situated within the solid polymer, which crystals align themselves in their electrical field when a specific voltage is applied.

(25) PDLC films are very sensitive to temperature changes. Two competing effects then occur. With rising temperatures, the intrinsic movement of the polarized liquid crystal molecules increases, making their alignment in the electrical field more difficult. However, at the same time, the viscosity of the liquid crystals is greatly reduced, in other words, the liquid crystal molecules can be more readily polarized and aligned in the electrical field. Furthermore, phase transitions occur in the liquid crystal molecules.

(26) As the inventors surprisingly found, at higher temperatures, on the whole, a smaller electrical field and thus a lower voltage are necessary to achieve comparable transparency values and opacity values than with higher maximum output voltages in the lower temperature range. Thus, energy can be saved at elevated temperatures and the PDLC film is protected through the avoidance of high voltages, resulting in increased service life.

LIST OF REFERENCE CHARACTERS

(27) 1 voltage source 2 functional element having electrically controllable optical properties 3 supply line 5 thermometer 6 signal line 10 composite pane 11 outer pane 12 inner pane 13a first intermediate layer 13b second intermediate layer 21 active layer of the functional element 5 22 surface electrode of the functional element 5 23 surface electrode of the functional element 5 24 carrier film 25 carrier film 100 device f frequency g temperature coefficient g.sub.o upper temperature coefficient g.sub.u lower temperature coefficient P period duration t time t.sub.1 rise time T temperature T.sub.S threshold temperature U output voltage U.sub.max the maximum amplitude of the output voltage U U.sub.max,o upper maximum amplitude of the output voltage U U.sub.max,u lower maximum amplitude of the output voltage U U.sub.max,k the maximum amplitude of the output voltage U for temperatures TT.sub.S X-X section line Z enlarged region