WO2024012955A1

WO2024012955A1 - Method for structuring an electrode layer of a functional element in the form of a film

Info

Publication number: WO2024012955A1
Application number: PCT/EP2023/068554
Authority: WO
Inventors: Li-Ya Yeh; Alexandre FESSEMAZ; Nadine HECKER; Florence JACQUES
Original assignee: Saint-Gobain Glass France
Priority date: 2022-07-13
Filing date: 2023-07-05
Publication date: 2024-01-18

Abstract

The invention relates to a method for structuring an electrode layer (3) of an electrically controllable functional element (1) in the form of a film, comprising the following steps: a) providing an electrically controllable functional element (1) in the form of a film, which has a liquid crystal-based functional layer (2), wherein the functional layer (2) is embedded between two transparent electrode layers (3, 4) and wherein a transparent plastics carrier film (5, 6) is arranged on the side of each electrode layer (3, 4) facing away from the functional layer (2), b) creating at least one electrically insulating separation line (8) in at least one electrode layer (3) using a laser beam (10), wherein the laser beam (10) is directed at an outer side, which faces away from the functional layer (2), of the plastics carrier film (5) situated on the same side of the functional layer (2) as the electrode layer (3) and wherein the at least one electrically insulating separation line (10) is created with a specifiable energy per unit length of the laser beam such that – less than 20%, more particularly less than 10%, of the energy per unit length of the laser beam (10) is absorbed by the plastics carrier film (5), and – more than 40% of the energy per unit length of the laser beam (10) is absorbed by the electrode layer (3), and – less than 20% of the energy per unit length of the laser beam (10) is absorbed by the functional layer (2).

Description

Method for structuring an electrode layer of a functional element in film form

The present invention lies in the technical field of electrically controllable functional elements and relates to a method for structuring an electrode layer of an electrically controllable functional element in film form, which has a functional layer based on a liquid crystal.

Composite panes usually consist of two individual panes, typically made of glass, which are firmly connected to one another via at least one thermoplastic intermediate layer. Modern composite windows, especially windshields of motor vehicles, can have complex curvatures in the horizontal and/or vertical directions in order to meet aerodynamic requirements and design specifications of the automobile manufacturers. They increasingly also include electrically controllable functional elements that display information for the driver and/or front passenger, serve as lighting devices and/or can change the optical transparency of the window, for example in the manner of a sun visor. Electrically controllable functional elements in film form are advantageously integrated into the composite pane. In particular, electro-optical functional elements in film form with a functional layer based on liquid crystal, which are based on the so-called “guest-host” effect, represent an interesting possibility to implement an electro-optical switching function in a composite pane in a simple, space-saving, cost-effective and to be implemented reliably in the application. Here and below, electro-optical functional elements in film form with a liquid crystal-based functional layer, which are based on the “guest host” effect, are referred to as “guest host films” for the sake of simplicity.

Guest-host films typically comprise a nematic liquid crystal (host) in unpolymerized form, which is provided with an additive (guest), with dichroic dye molecules, for example, which absorb light anisotropically being used as an additive. Since the molecules of the additive have an elongated shape, their orientation can be controlled by the orientation of the molecules of the liquid crystal, ie host, which in practice is achieved by applying an electric field to the liquid crystal. In this way, for example, the optical transparency of the guest-host film can be controlled very precisely using an external electric field. For example, windshields can very advantageously be provided with an electrically switchable transparency in the manner of a sun visor. Electrically controllable functional elements in film form include, in addition to the functional layer based on a liquid crystal, two electrode layers located on both sides of the functional layer, which serve as surface electrodes and can be used to electrically switch the functional layer. Typically, the functional layer based on a liquid crystal is embedded in two plastic carrier films, on each of which one of the two electrode layers is deposited. Such functional elements in film form form a prefabricated composite.

For more complex switching functions, in particular for switching individual areas of the electrically controllable functional element in film form, it is desirable for a surface electrode to be divided into several sections that can be controlled in a targeted manner. This represents a particular challenge with guest-host films, since such functional layers, due to their physical properties of being similar to a liquid, react very sensitively to locally different mechanical loads and heating. Basically, when structuring or electrically subdividing a surface electrode, there is a risk that undesirable local optical defects (e.g. cloudiness) will be generated in the functional layer.

Structuring electrode layers using laser writing, whereby trenches are created, is well known to those skilled in the art and is described, for example, in WO 2011/101427. However, ordinary laser writing is not suitable for structuring electrode layers of functional layers based on liquid crystals.

US2021/0141259 A1 shows a method in which surface electrodes of a functional layer based on a polymer network of liquid crystals are structured by a laser beam.

To date, however, there is no known method in the prior art for structuring surface electrodes of electrically switchable functional elements in film form, through which the structuring of surface electrodes of functional layers based on a liquid crystal, in particular guest-host films, with usable optical quality is possible.

In contrast, the object of the present invention is to provide an improved method for structuring a surface electrode of an electrically controllable functional element with a functional layer based on a liquid crystal in film form. These and other tasks are solved according to the proposal of the invention by a method for structuring an electrode layer of an electrically controllable functional element in film form according to the independent patent claim. Advantageous embodiments of the invention result from the subclaims.

According to the invention, a method for structuring an electrode layer of an electrically controllable functional element in film form is shown. The functional element comprises a functional layer based on a liquid crystal. For the purposes of the invention, the term “structuring” means the electrical division of the electrode layer into sections that are electrically insulated from one another and can be electrically applied separately. The electrically controllable functional element in film form is used in or on a flat body, in particular a glass flat body. The functional element in film form is preferably used for integration into a particularly glass composite pane.

The method according to the invention comprises the following steps, which are carried out in the order given according to the alphabetical name:

Step a)

Providing an electrically controllable functional element in film form, which has a functional layer based on a liquid crystal, the functional layer being embedded between two transparent electrode layers, and a transparent plastic carrier film being arranged on each electrode layer on the side facing away from the functional layer.

step b)

Generating at least one electrically insulating dividing line in at least one electrode layer with a laser beam, the laser beam being directed onto an outside of the plastic carrier film located on the same side of the functional layer as the electrode layer, facing away from the functional layer, the at least one electrically insulating dividing line having a predefinable (certain) path energy of the laser beam is generated in such a way that less than 20%, in particular less than 10%, of the path energy of the laser beam is absorbed by the plastic carrier film, and more than 40% of the path energy of the laser beam is absorbed by the electrode layer, and less than 20% of the laser beam energy is absorbed by the functional layer.

Accordingly, in the method according to the invention, an electrically controllable functional element is provided in film form, which has a functional layer based on a liquid crystal, the functional layer being embedded between two plastic films, and a transparent electrode layer being located between a respective plastic carrier film and the functional layer. The transparent electrode layers serve as surface electrodes for electrically switching the functional layer.

By means of the method according to the invention, at least one, in particular exactly one, electrode layer is structured, i.e. electrically divided into two or more sections, the sections each being separately subjected to an electrical voltage and serving as surface electrodes. The sections are electrically isolated from each other. For this purpose, at least one electrically insulating dividing line (isolation line) is introduced into the electrode layer to be structured using a laser beam. The laser beam is directed from the external environment onto the functional element in film form and in particular onto the plastic carrier film which is located on the same side of the functional layer as the electrode layer that is to be structured. The laser beam therefore hits the outer surface of the plastic carrier film that faces the external environment (away from the functional layer).

The laser beam emerges from a terminal jet nozzle of a jet head. As usual, the laser beam is designed in the form of a focused, rotationally symmetrical beam cone with a central beam axis. The beam head serves to guide the laser beam so that it can be moved relative to the functional element in a typically horizontal plane parallel to the functional element, as well as in a perpendicular, typically vertical direction. From a local perspective, however, it is irrelevant whether the jet head or the functional element or both are moved. In this respect, it would be equally possible for the functional element to also be moved as an alternative to the moving jet head, or for both the jet head and the functional element to be moved.

The energy of the laser beam depends on the specific design of a laser source generating the laser beam and is typically specified in joules (J). The power of the laser beam (i.e. energy per time), typically measured in joules per second (J/s) or in watts (W), describes the optical output power of a continuous wave (CW) laser or the average power of a pulsed laser or pulsed laser. Pulsed lasers are also characterized by their pulse energy, which is directly proportional to the average power and inversely proportional to the repetition rate of the laser. The energy of the laser beam related to the irradiated area is referred to as “energy density”. The energy density is measured, for example, in J/mm ² . The power of the laser beam related to the irradiated area is referred to as “power density”. The power density is measured, for example, in W/mm ² .

In addition to the energy density or power density, what is important for the laser beam processing of an electrode layer is the travel speed of the beam head or laser beam, i.e. the time period for how long a specific area of the electrode layer is irradiated by the laser beam. It is common to use the term “distribution energy” for this. This is the power of the laser beam absorbed by the electrode layer per speed of the beam head or laser beam, e.g. measured in watts/(mm/s). The speed of the beam head or laser beam is measured, for example, in “mm/s” (millimeters/second). If the power of the laser beam in watts (W) is given as joules per second (J/s), the distance energy is therefore measured in J/mm. The path energy therefore depends on the speed of the laser beam, i.e. the travel speed of the beam head or cutting nozzle, also referred to as the “feed speed”. The higher the feed speed, the shorter a certain area of the functional element is irradiated, and vice versa. Thus, with an increase in the feed speed, the path energy of the laser beam is reduced, and vice versa. It is understood that the energy density and thus also the path energy can be changed by changing the power of the laser beam itself.

In general, when laser beam processing a layer, the distance energy of the laser beam is important, with the energy absorbed by the layer depending on the energy density. The energy absorbed by the layer depends, for a certain power of the laser beam, on the size of the beam spot on the layer, corresponding to the beam diameter at the point where the laser beam hits the surface of the layer. The beam diameter of the laser beam on the surface of the layer results from the focus position, ie the position of the focus of the laser beam relative to the layer (vertical shortest distance), in particular relative to the surface of the layer to which the laser beam is directed. If the layer is in the divergent region of the beam cone (focus above the surface of the layer on which the laser beam hits), increasing the distance between the focus and the layer can increase the beam diameter on the layer, and vice versa. The larger the beam diameter on the layer, the smaller the energy absorbed by the layer, and vice versa. With a laser, the steel intensity outside the focus is not constant relative to the cross section. Ideally the power intensity is a Gaussian profile. In any case, the energy density towards the edge is relatively low, especially outside of focus.

Preferably, the travel speed of the laser beam when structuring the electrode layer is constant, so that only the energy density of the laser beam is important when structuring the electrode layer. Preferably, the irradiated area of the functional element or the plastic carrier film is constant when structuring the electrode layer, so that only the energy of the laser beam is important when structuring the electrode layer.

According to the invention, the laser beam used to structure the electrode layer has such a distance energy that the least possible thermal damage to the functional layer occurs. As experiments by the inventors have shown, where the insulation line is created, in a vertical view through the functional element, if the functional layer is heated excessively, increased bubble formation occurs in the functional layer. This bubble formation significantly impairs the optical quality of the functional layer, as it creates optical errors (e.g. local clouding). In order to avoid this, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with a specific, but predeterminable, path energy of the laser beam in such a way that less than 20% of the path energy of the laser beam is absorbed by the functional layer. With a constant travel speed of the laser beam, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with a specific but predeterminable energy (i.e. energy density) of the laser beam related to the irradiated surface in such a way that less than 20% of the energy density of the laser beam comes from the functional layer is absorbed. With a constant travel speed of the laser beam and a constant irradiated area of the functional element, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with a specific, but predeterminable, energy of the laser beam in such a way that less than 20% of the energy of the laser beam is absorbed by the functional layer.

The distance energy (or energy density or energy) of the laser beam is selected so that the following additional conditions for the plastic carrier film and the electrode layer are also met. The laser beam used to structure the electrode layer hits the functional element, ie it hits the plastic carrier film arranged adjacent to the electrode layer and passes through it. It is therefore necessary that the plastic carrier film is damaged as little as possible. For this purpose, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with the specific (predeterminable) path energy of the laser beam in such a way that less than 20%, in particular less than 10%, of the path energy of the laser beam is absorbed by the plastic carrier film . With a constant travel speed of the laser beam, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with the specific (predeterminable) energy density of the laser beam in such a way that less than 20%, in particular less than 10%, of the energy density of the laser beam is absorbed by the plastic carrier film becomes. With a constant travel speed of the laser beam and a constant irradiated area of the functional element, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with the specific (predeterminable) energy of the laser beam in such a way that less than 20%, in particular less than 10%, of the energy density of the laser beam is absorbed by the plastic carrier film.

On the other hand, the electrode layer must be structured as effectively as possible by the laser beam. This is achieved by generating the at least one electrically insulating dividing line of the electrode layer to be structured with the specific (predeterminable) path energy of the laser beam in such a way that more than 40% of the path energy of the laser beam is absorbed by the electrode layer. With a constant travel speed of the laser beam, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with the specific (predeterminable) energy density of the laser beam in such a way that more than 40% of the path energy of the laser beam is absorbed by the electrode layer. With a constant travel speed of the laser beam and a constant irradiated area of the functional element, the at least one electrically insulating dividing line of the electrode layer to be structured is generated with the specific (predeterminable) energy of the laser beam in such a way that more than 40% of the path energy of the laser beam is absorbed by the electrode layer.

From the above explanations it follows that with a constant travel speed of the laser beam, the energy density of the laser beam and, additionally, with a constant beam area, the energy of the laser beam can be considered. According to the invention, the conflict of objectives is resolved by choosing the path energy or energy density or energy of the laser radiation so that, on the one hand, the functional layer based on a liquid crystal and the plastic carrier film are damaged as little as possible and, on the other hand, the electrode layer is structured efficiently and reliably. The present invention therefore advantageously shows a way in which this conflict of objectives can be resolved in a satisfactory manner.

In an advantageous embodiment, the width of the at least one dividing line with which the electrode layer is electrically divided is from 30 μm to 200 gm. Such thin dividing lines allow safe and sufficiently high electrical insulation and at the same time do not or only slightly disturb the view through the electrode layer.

According to an advantageous embodiment of the method according to the invention, the laser beam used to structure the electrode layer has a wavelength whose transmission through the plastic carrier film is more than 80%, in particular more than 90%, and through the electrode layer is less than 60%, and through the functional layer more than 80%.

Through this measure, the absorptions claimed according to the invention of the various layers of the functional element in film form can be achieved in a particularly simple manner. For this purpose, the laser beam preferably has a wavelength in the infrared wavelength range. The laser beam particularly preferably has a wavelength of more than 800 nm, in particular more than 1000 nm. As the inventors have found, the energy of the laser beam is absorbed relatively little by the functional layer based on a liquid crystal and the plastic carrier film (in particular made of polyethylene terephthalate), but relatively strongly by the electrode layer (in particular made of indium tin oxide), so that the The above-mentioned conflict of objectives can be resolved particularly well.

In the method according to the invention, a continuous wave laser beam can be used. A pulsed laser beam or pulse laser is preferably used, the pulse duration of a laser pulse advantageously being more than 200 femtoseconds (fs) and in particular less than 10 picoseconds (ps), in order to ensure, on the one hand, a sufficiently high energy absorption by the electrode layer and, on the other hand, to avoid disadvantageous damage the Avoid functional layer. In particular, the travel speed of the laser beam and the irradiated surface of the functional element can be constant. As experiments by the inventors have shown, these advantageous effects can be achieved reliably and safely using a pulse duration in the specified range.

According to an advantageous embodiment of the method according to the invention, a power density of the laser beam is less than 1 kW/m ² and is in particular in the range from 700 W/m ² to less than 1 kW/m ² . This measure allows the effects according to the invention to be achieved particularly well.

The functional layer based on a liquid crystal can in principle be of any design. The method according to the invention can be used particularly advantageously for guest-host films with a functional layer made of a liquid-crystalline material with an embedded additive. Reference is made to the above statements regarding guest-host slides. Guest-host foils as such are well known to those skilled in the art, so there is no need to go into them in more detail here. Guest-host films are commercially available, for example under the term “Light Control Film”, for example from Dai Nippon Printing Co., Ltd., Japan, under the product name LCF005(EU).

According to the invention, the functional layer is preferably formed on the basis of a non-polymerized liquid-crystalline material, i.e. the functional layer is liquid or flowable, which is typically the case with guest-host films. The method according to the invention can be used particularly advantageously for guest-host films with a functional layer made of a non-polymerized, liquid-crystalline material with an embedded additive.

The optically transparent electrode layers can in principle be of any design, as long as they can be electrically contacted in order to electrically control the functional layer. These are preferably transparent conductive oxide layers (TCO = Transparent Conductive Oxide). Suitable electrode materials are, for example, indium tin oxide (ITO), fluorine-doped tin oxide (SnO2:F) or aluminum-doped zinc oxide (ZnO:Al), with indium tin oxide (ITO) being preferred.

The electrode layers are preferably deposited onto a carrier material, preferably onto one of the two plastic films, by one or more deposition processes. The electrode layers are advantageously deposited using vacuum processes such as Vacuum evaporation or PVD processes (PVD = Physical Vapor Deposition) such as magnetic field-assisted cathode sputtering, in particular sputtering, or CVD processes (CVD = Chemical Vapor Deposition).

The plastic films can in principle consist of any plastic, for example polyimide (PI) or polyethylene terephthalate (PET), with plastic films made of polyethylene terephthalate (PET) being preferred.

For the purposes of the present invention, “transparent” means a transmission in the visible spectral range (light) of more than 70% and in particular more than 75%. Accordingly, “opaque” means a transmission in the visible spectral range (light) of less than 15%, preferably less than 5%, in particular 0%.

The various embodiments of the invention can be implemented individually or in any combination. In particular, the features mentioned above and explained below can be used not only in the specified combinations, but also in other combinations or on their own, without departing from the scope of the present invention.

The invention is explained in more detail below using exemplary embodiments, with reference being made to the attached figures. It shows in a simplified, not true-to-scale representation:

1 shows a cross-sectional view of an exemplary electrically controllable functional element;

Fig. 2 is a diagram to illustrate the transmission (%) of a guest-host film as a function of the wavelength (nm);

3 is a diagram to illustrate the transmission (%) of an ITO electrode layer as a function of the wavelength (nm);

Fig. 4 is a diagram to illustrate the transmission (%) of a PET plastic film as a function of the wavelength (nm);

Fig. 5 is a flow chart of the method according to the invention.

First, consider Figure 1, in which an exemplary embodiment of an electrically controllable functional element 1 is shown in film form using a schematic cross-sectional representation. The Functional element comprises a functional layer 2 based on a typically non-polymerized liquid crystal with embedded additive (guest host effect). The functional layer 2 is embedded between an optically transparent first electrode layer 3 and an optically transparent second electrode layer 4. The functional layer 3 and the two electrode layers 3, 4 are embedded between an optically transparent first plastic carrier film 5 and an optically transparent second plastic carrier film 6. The first plastic carrier film 5 is arranged on the side of the first electrode layer 3 facing away from the functional layer 2. The second plastic carrier film 6 is arranged on the side of the second electrode layer 4 facing away from the functional layer 2. The first electrode layer 3 is located on the (inner) surface of the first plastic carrier film 5 facing the functional layer 2 and is deposited on this surface by a PVD process, in particular sputtering. In a corresponding manner, the second electrode layer 4 is located on the (inner) surface of the second plastic carrier film 6 facing the functional layer 2 and is deposited on this surface by a PVD process, in particular sputtering. It is also possible for the two electrode layers 3, 4 to be applied to the respective plastic carrier film 5, 6 using a roll-to-roll process.

The functional layer 2 is applied to a carrier film, which is not shown in more detail in Figure 1. In the functional layer 2 there are spacers 7, through which a size (height) of the functional layer 2, which is measured perpendicular to the extent of the functional layer 2, can be precisely adjusted. The optical properties of the functional layer 2 depend heavily on a uniform (constant) height of the functional layer 2. There is a defined working distance and the task of the spacers 7 is to optimally maintain this working distance. The two electrode layers 3, 4 can be used to switch optical properties of the functional layer 2, in particular its transparency.

In the present exemplary embodiment, the functional layer 2 is based on a liquid crystal and has an additive for the guest-host effect. The two electrode layers 3, 4 are indium tin oxide (ITO) layers. The two plastic carrier films 5, 6 are polyethylene terephthalate (PET) films.

In order to improve the electrical controllability of the functional layer 2, at least one electrically insulating dividing line 8 (insulation line) is introduced into the first electrode layer 3. The dividing line 8 divides the first electrode layer 3 into two electrically insulated sections 9, 9 ', each of which can be separately supplied with an electrical voltage and serve as surface electrodes for controlling the functional layer 2. The dividing line 8, for example, has a closed, in particular circular, course. However, it is also conceivable, for example, that the dividing line 8 has a straight or curved course and completely divides the first electrode layer 3. The course of the dividing line 8 is basically arbitrary as long as it is ensured that the first electrode layer 3 is divided into at least two electrically separated sections. The at least one dividing line 8 enables selective switching in different designs. The arrangement of the at least one dividing line 8 depends on the design selected, although in principle many different designs can be realized.

The at least one dividing line 8 is generated by a laser beam 10, as illustrated schematically in FIG. The laser beam 10 is directed onto the surface of the first plastic carrier film 5 facing away from the functional layer 2. The laser beam 10 penetrates the first plastic carrier film 5 and serves to structure the first electrode layer 3.

To explain the wavelength of the laser beam 10 used in the structuring, reference is made to the diagrams in FIGS. 2, 3 and 4.

2 shows a diagram in which the transmission (%) of an exemplary guest-host film is plotted against the wavelength (nm). To determine the transmission, the percentage of the transmitted radiation (e.g. light intensity) based on the incident radiation (e.g. light intensity) is stated in the usual way. The transmission of the guest-host film is shown when switched off (OFF), ie without applied voltage, and when switched on (ON), ie with applied voltage. In the diagram, the abscissa shows the wavelength in nanometers (nm) and the ordinate shows the corresponding transmission value in % (percent). As can be seen from the diagram, applying a voltage significantly increases the transmission of the guest-host film in the visible spectral range (approx. 400 nm to approx. 800 nm). Above the visible spectral range, at least no significant difference between applied and non-applied voltage can be seen. In the visible spectral range it is clearly visible that when an operating voltage is applied, the transmission values increase from less than a few percent to values of over 30%. In this way, a viewer can easily switch between an opaque and a transparent operating state of the guest-host film. A particularly high transmission occurs at wavelengths in the infrared wavelength range. A local maximum of transmission in the infrared range can be seen at around 1030 nm and is marked by the vertical line in the diagram. The transmission there is around 85%, with the transmission in the infrared being significantly more than 80%. This means that infrared radiation can pass through the guest-host film very easily without there being a high absorption of the radiation energy.

3 shows a diagram in which the transmission (%) of a glass pane coated with an indium-tin oxide layer is plotted against the wavelength (nm). The transmission of an uncoated glass pane is also shown as a reference. In the diagram of Figure 3, analogous to Figure 2, the wavelength in nanometers (nm) is given on the abscissa and the corresponding transmission in % (percent) is given on the ordinate. As can be seen in the diagram, applying an ITO layer changes the transmission depending on the wavelength. Starting with the infrared wavelength range, the transmission drops significantly, i.e. the absorption increases accordingly. From a wavelength of around 1000 nm, the transmission is a maximum of around 70% and decreases continuously. This means that radiation with a wavelength in the infrared can only pass through the ITO layer with difficulty, i.e. there is high absorption. This applies, for example, to wavelengths of approximately 1000 nm, 9.6 pm or 10.6 pm.

A diagram is shown in Figure 4, in which different transmission spectra are shown. In the diagram of Figure 4, analogous to Figure 2, the wavelength in nanometers (nm) is given on the abscissa and the corresponding transmission in % (percent) is given on the ordinate. According to the legend, the transmission spectrum of a PET layer is shown in particular. From a wavelength of around 300 nm, the transmission is constantly high and amounts to more than 80%. This means that radiation with a wavelength in the visible spectral range and in the infrared can easily pass through the PET layer without high absorption.

Accordingly, the first electrode layer 3 of the functional element 1 of Figure 1 was structured with a pulsed laser beam with a wavelength of 1030 nm. This made it possible, on the one hand, to achieve good absorption in the ITO electrode layer 3 (transmission approx. 40%), and on the other hand, good transmission in the functional layer 2 (>80%) and in the first PET plastic carrier film 5 (>80%) , so that the ITO electrode layer 3 could be structured well without damaging the functional layer 2 and the first PET plastic carrier film 5. The focus diameter was 58 pm and the repetition rate (pulse frequency) was 100 kHz. The overlap of the laser pulses was 50%. The travel speed was 2.9 m/s. The Laser power was 1 -2 W. The inventors were able to show that only slight bubble formation occurred in the functional layer 2, but the bubbles disappeared again after some time and the functional layer 2 showed no optical damage. The travel speed of the laser beam 10 was constant. Likewise, the irradiated area of the functional element 1 was constant. The parameters mentioned are only to be understood as examples.

In Figure 5, the method according to the invention is illustrated again using a flow chart. It includes the following steps in this order: a) providing an electrically controllable functional element 1 in film form, which has a functional layer 2 based on a non-polymerized liquid crystal, the functional layer being embedded between two transparent electrode layers 3, 4, and on each Electrode layer 3, 4, a transparent plastic carrier film 5, 6 is arranged on the side facing away from the functional layer. b) generating at least one electrically insulating dividing line 8 in at least one electrode layer 3 with a laser beam 10, the laser beam 10 being directed onto an outside of the plastic carrier film 5 located on the same side of the functional layer 2 as the electrode layer 3, facing away from the functional layer 2, wherein the at least one electrically insulating dividing line 8 is generated with a predeterminable (determined) path energy of the laser beam 10 in such a way that less than 20%, in particular less than 10%, of the path energy of the laser beam 10 is absorbed by the plastic carrier film 5, and more than 40% of the path energy of the laser beam 10 is absorbed by the electrode layer 3, and less than 20% of the path energy of the laser beam 10 is absorbed by the functional layer 2.

The laser beam 10 advantageously has a wavelength of more than 800 nm, with a pulsed laser beam 10 being advantageously used, in which a pulse duration of a laser pulse is more than 200 femtoseconds and less than 10 picoseconds. The travel speed and the irradiated surface of the functional element 1 are advantageously constant.

From the above statements it follows that the invention provides an improved method for structuring an electrically controllable functional element in film form, in which the laser beam used to structure the electrode layer has such a distance energy has that an electrode layer can be structured reliably, with no or at most tolerable, very little damage to the functional layer occurring.

Reference symbol list

1 functional element

2 functional layer 3 first electrode layer

4 second electrode layer

5 first plastic carrier film

6 second plastic carrier film

7 spacers 8 dividing line

9, 9' section

10 laser beam

Claims

Patent claims

1 . Method for structuring an electrode layer (3) of an electrically controllable functional element (1) in film form, which comprises the following steps: a) providing an electrically controllable functional element (1) in film form, which has a functional layer (2) based on a liquid crystal, wherein the functional layer (2) is embedded between two transparent electrode layers (3, 4), and a transparent plastic carrier film (5, 6) is arranged on each electrode layer (3, 4) on the side facing away from the functional layer (2), b) generating at least one electrically insulating dividing line (8) in at least one electrode layer (3) with a laser beam (10), the laser beam (10) being directed onto an outside facing away from the functional layer (2) on the same side of the functional layer (2). how the electrode layer (3) is aligned with the plastic carrier film (5), and the at least one electrically insulating dividing line (10) is generated with a predeterminable path energy of the laser beam in such a way that less than 20%, in particular less than 10%, the path energy of the laser beam (10) is absorbed by the plastic carrier film (5), and more than 40% of the path energy of the laser beam (10) is absorbed by the electrode layer (3), and less than 20% of the path energy of the laser beam (10 ) is absorbed by the functional layer (2).

2. The method according to claim 1, in which the laser beam (10) has a wavelength whose transmission through the plastic carrier film (5) is more than 80%, in particular more than 90%, and through the electrode layer (3) less than 60% , and through the functional layer (2) is more than 80%.

3. The method according to claim 1 or 2, in which the laser beam (10) has a wavelength in the infrared wavelength range.

4. The method according to claim 3, in which the laser beam (10) has a wavelength of more than 800 nm, in particular more than 1000 nm.

5. Method according to one of claims 1 to 4, in which a pulsed laser beam (10) is used.

6. The method according to claim 5, in which a pulse duration of a laser pulse is more than 200 femtoseconds and in particular less than 10 picoseconds.

7. Method according to one of claims 1 to 6, in which a power density of the laser beam (10) is less than 1 kW/m ² and is in particular in the range from 700 W/m ² to less than 1 kW/m ² .

8. The method according to any one of claims 1 to 7, in which the electrically controllable functional element (1) comprises a functional layer (2) based on a liquid crystal with an embedded additive.

9. The method according to any one of claims 1 to 8, in which the electrically controllable functional element (1) comprises a functional layer (2) based on a non-polymerized liquid crystal.

10. The method according to claim one of claims 1 to 9, in which the electrode layers (3, 4) are each designed in the form of a transparent, conductive oxide layer (TCO), in particular an indium-tin oxide layer.

1 1 . Method according to one of claims 1 to 10, in which the electrode layers (3, 4) are each applied to one of the plastic films (5, 6), for example in the roll-to-roll process.

12. The method according to any one of claims 1 to 11, in which the plastic films (5, 6) consist of polyethylene terephthalate (PET).