WO2025168391A1

WO2025168391A1 - Light modulator comprising fluid-distributing protrusions

Info

Publication number: WO2025168391A1
Application number: PCT/EP2025/052112
Authority: WO
Inventors: Romaric Mathieu Massard; Anthony John Slack; Anatolie MITIOGLU
Original assignee: Elstar Dynamics Patents BV
Current assignee: Elstar Dynamics Patents BV
Priority date: 2024-02-07
Filing date: 2025-01-28
Publication date: 2025-08-14
Anticipated expiration: 2026-08-07
Also published as: WO2025168392A1

Abstract

Some embodiments are directed to a light modulator, comprising a first substrate, a second substrate arranged opposite the first substrate, at least one electrode applied to at least the first substrate on a surface facing the second substrate, with an optical layer extending between the first substrate and the second substrate. The light modulator further comprises a plurality of fluid-distributing protrusions regulating the flow of the fluid in the optical layer, distributed across a region of a surface of at least one of the first substrate and the second substrate, wherein the region has a density of at least 10 fluid-distributing protrusions per mm² and/or wherein the combined area of the fluid-distributing protrusions is at least 0.1% of the surface of the first substrate.

Description

LIGHT MODULATOR COMPRISING FLUID-DISTRIBUTING PROTRUSIONS

BACKGROUND

A known light modulator is disclosed in W02022023180, included herein by reference. The known light modulator comprises transparent or reflective substrates. Multiple electrodes are applied to the substrates in a pattern across the substrate. A controller may apply an electric potential to the electrodes to obtain an electro-magnetic field between the electrodes providing electrophoretic movement of the particles towards or from an electrode.

SUMMARY

A light modulator, a substrate for use in a light modulator, a method of modulating light and a manufacturing method for a light modulator are described in the accompanying claims. Specific embodiments of the invention are set forth in the dependent claims.

In an embodiment, the light modulator comprises a first substrate, a second substrate arranged opposite the first substrate, and at least one electrode applied to at least the first substrate on a surface facing the second substrate, and an optical layer extending between the first substrate and the second substrate, the optical layer comprising a fluid comprising particles.

The light modulator may be configured to apply an electric potential to the at least one electrode, causing modulation of an electric field in the optical layer, providing electrophoretic and/or dielectrophoretic movement of the particles in the optical layer, causing modulation of light passing through the optical layer.

The light modulator may further comprise a plurality of fluid-distributing protrusions regulating the flow of the fluid in the optical layer, the plurality of fluiddistributing protrusions being distributed across a region of a surface of at least one of the first substrate and the second substrate, wherein the region has a density of at least 10 fluid-distributing protrusions per mm² and/or wherein the combined area of the fluiddistributing protrusions is at least 0.1% of the surface of the first substrate. BRIEF DESCRIPTION OF DRAWINGS

Further details, aspects, and embodiments will be described, by way of example only, with reference to the drawings. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals. In the drawings,

Figure la schematically shows an example of an embodiment of a building block,

Figure lb schematically shows an example of an embodiment of a substrate, Figure 1c schematically shows an example of an embodiment of a substrate, Figure Id schematically shows an example of an embodiment of a substrate, Figure le schematically shows an example of an embodiment of a substrate, Figure If schematically shows an example of an embodiment of a substrate, Figure 1g schematically shows an example of an embodiment of a light modulator,

Figures 2a-2f schematically show an example of an embodiment of a substrate,

Figure 3a schematically shows an example of an embodiment of a light modulator,

Figure 3b schematically shows an example of an embodiment of a light modulator,

Figure 3c schematically shows an example of an embodiment of a car,

Figures 4a-4c schematically show an embodiment of a light modulator,

Figure 5a-5d schematically show examples of embodiments of a substrate for use in an embodiment of a light modulator,

Figure 6a-6c schematically show side-views of examples of embodiments of a light modulator,

Figure 7a-7e schematically show side-views of examples of embodiments of a light modulator,

Figure 7f schematically shows examples of embodiments of a fluiddistributing protrusions,

Figure 8a schematically shows an example of an ink droplet being dropped on a substrate without spacers,

Figure 8b schematically shows an example of an ink droplet being dropped on a substrate with spacers, Figure 8c shows a result of the spreading of an ink droplet after being dropped on a substrate without spacers,

Figure 8d shows the result of the spreading of an ink droplet after being dropped on a substrate with spacers,

Figure 9a schematically shows an example of an embodiment of a light modulator without spacers,

Figure 9b schematically shows an example of an embodiment of a light modulator with spacers,

Figure lOa-lOb schematically show examples of embodiments of a substrate,

Figure 11 schematically shows an example of a method of modulating light according to an embodiment,

Figure 12 schematically shows an example of a method of manufacturing a light modulator according to an embodiment.

Reference signs list

The following list of references and abbreviations corresponds to the figures, and is provided for facilitating the interpretation of the drawings and shall not be construed as limiting the claims.

10 a light modulator

11 a first substrate

12 a second substrate

13, 13a, 13b electrodes

14, 14a, 14b electrodes

15 a fluid

16 a controller

30 particles

20 a car

21 a light modulator

40 a light modulator

41 a first substrate

42 a second substrate

43 a third substrate

46 a controller 100-102 a substrate

111-114 a main line

121-124 a main line

131-134 interdigitated electrodes

140 a building block

141-144 a building block

110, 120 a driving bus

110’, 120’ a driving bus

119, 129 a connecting zone

191, 192 a direction

203-204 a substrate

211-222 a building block

251-262 a building block

18, 18a-18k. fluid-distributing protrusions

18’ a spacer

19, 19a, 19b surface regions of substrates

45 a seal

71 distance

72 distance

72’ substrate gap width

73, 73’ height of a protrusion

74, 74’ diameter of a protrusion

81 ink droplet

DESCRIPTION OF EMBODIMENTS

While the presently disclosed subject matter is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail one or more specific embodiments, with the understanding that the present disclosure is to be considered as exemplary of the principles of the presently disclosed subject matter and not intended to limit it to the specific embodiments shown and described.

In the following, for the sake of understanding, elements of embodiments are described in operation. However, it will be apparent that the respective elements are arranged to perform the functions being described as performed by them. Further, the subject matter that is presently disclosed is not limited to the embodiments only, but also includes every other combination of features described herein or recited in mutually different dependent claims.

In an embodiment, a light modulator is provided with fluid-distributing protrusions in the light modulator. Fluid-distributing protrusions in the light modulator are advantageous as they improve the flow of the fluid, e.g., liquid, in the optical layer. This is advantageous both during manufacture, where overflowing of seal by the fluid is avoided, as well as during operative use. In an embodiment, a light modulator may have fluid-distributing protrusion of low density; a light modulator may have fluid-distributing protrusion of high density.

Substrates are disclosed, e.g., for use in a light modulator, in particular, dynamic glazing. The substrate is transparent, and at least one electrode is applied to a side of the substrate, the electrode extending in a pattern across the side of the first substrate. At least one of the first and second substrates is transparent. In a glazing application both substrates are transparent. In other applications, e.g., a display, one of the two substrates may be opaque. The electrode may comprise non-transparent material, in particular reflective metal.

Dynamic glazing, also known as smart glazing, may comprise a system wherein the transparency or optical properties of a glazing material are altered in response to an external electrical input. This system may allow for active control over light and heat transmission, thereby enhancing energy efficiency and user comfort in various architectural or vehicular applications.

Figures la- 4c provide various examples of the electrode system on the first and second substrate and how they may be implemented or used in a light modulator. These examples may be provided with fluid-distributing protrusions in the light modulator.

Some of the known light modulators which may be provided with fluiddistributing protrusions in the light modulator are based on the electrophoretic principle. For example, the substrate may comprise multiple interdigitated electrodes applied to the substrate, e.g., two electrodes, each of the multiple electrodes being arranged in a pattern across the substrate, the multiple interdigitated electrodes being arranged altematingly with respect to each other on the substrate. Having multiple interdigitated electrodes allows local control over the electric field enabling electrophoretic control of particles. Electrophoretic light modulators are explained more extensively herein and are used as the motivating example. In an embodiment, a light modulator comprises a first substrate and a second substrate. At least one of the first and second substrate may be according to an embodiment, e.g., having fluid-distributing protrusions in the light modulator. For example, the first and second substrates may be arranged with inner sides opposite to each other, using a substrate according to an embodiment. An optical layer is arranged between the first and second substrates. The electrode is arranged to modulate an electrical field in the optical layer. The optical layer comprises a fluid, e.g., liquid, comprising particles, wherein the particles are electrically charged or chargeable. The particles may be moved under control of the electrical field. For example, a controller may be configured to apply an electric potential to the electrode to obtain an electromagnetic field at the electrode providing electrophoretic movement of the particles towards or from one of the at least one electrode causing modulation of the optical properties of the light modulator. For example, optical properties may include a transition between a high-transparent state and a low-transparent state or vice versa. Note that a transition may also alter thermal properties of the light modulator.

Below a number of known light modulators are reviewed, showing some of the options in technology and electrodes. These known substrates can advantageously be modified by adding fluid-distributing protrusions in the light modulator according to an embodiment. These examples also show light modulators with varying numbers of electrodes on a substrate.

International patent applications WO2011012499 Al, included herein by reference, and WO2011131689, included herein by reference, disclose light modulators in the form of electrophoretic display devices, e.g., e-Ink displays. A pixel of the display comprises an accumulation electrode and a field electrode, the accumulation electrode being arranged at a storage area for accumulating charged particles away from an aperture area, and the field electrode occupying a field-electrode area being at least a part of an aperture area of the pixel, the charged particles being movable between the accumulation electrode and the field electrode. In an embodiment, two electrodes are applied on a single substrate. The substrate with the accumulation electrode and/or field electrode may be provided with fluid-distributing protrusions. Fluid-distributing protrusions may be provided on the substrate having electrodes, on the opposite electrode or both.

US patent 10921678 with title ‘Electrophoretic device’, included herein by reference, shows an electrophoretic device having only one patterned electrode on one of two substrates. For example, the one substrate with an electrode according to US 10921678 may be replaced with a substrate according to an embodiment comprising one single electrode. For example, an embodiment comprises a first transparent substrate with a field electrode, and a second substrate opposite of the first substrate, with an accumulation electrode. The first substrate and the second substrate enclose a pixel with a fluid and particles. In use an applied electro-magnetic field to the field electrode and the accumulation electrode provides movement of the particles from the field electrode and the accumulation electrode and vice versa. Any of these cited electrophoretic or di electrophoretic light modulators may be adapted by including fluid-distributing protrusions in the light modulator.

US patent 8054535B2, included herein by reference, and US patent 8384659B2, included herein by reference, show alternative example of electrophoretic light modulators in one of two substrates have two patterned electrodes.

Patterned electrodes are also used in dielectrophoretic light modulators. For example, US patent application US2005185104A1, included herein by reference, and US20180239211A1, included herein by reference, show a dielectrophoretic light modulators having a substrate with a patterned electrode. Any of these cited electrophoretic or dielectrophoretic light modulators may be adapted by including fluiddistributing protrusions in the light modulator.

The paper “Reversible Metal Electrodeposition Devices: An Emerging Approach to Effective Light Modulation and Thermal Management,” included by reference, also shows a substrate on which a patterned electrode is applied. Fluiddistributing protrusions in the light modulator may be included herein

An embodiment of a substrate may be used in an electrochromic device (ECD). An electrochromic device (ECD) controls optical properties such as optical transmission, absorption, reflectance and/or emittance in a continual but reversible manner on application of voltage (electrochromism). This property enables an electrochromic device to be used for applications like smart glass, electrochromic mirrors, and electrochromic display devices. Fluid-distributing protrusions in the light modulator may be included herein.

An electrochromic device is described, e.g., in the paper “Silver grid electrodes for faster switching ITO free electrochromic devices” by Antonio California et al ., included herein by reference. The paper describes the preparation of an electrochromic device, in this case one which is ITO free. Fluid-distributing protrusions in the light modulator may be included herein. An electrochromic device uses electrically conductive electrodes applied on a substrate. The cited paper uses silver grids, made using silver ink, as electrically conductive electrodes. An electrochromic device may comprise an electrochromic material. The cited paper uses poly(3,4-ethylenedi oxythiophene) polystyrene sulfonate (PEDOT:PSS). In an electrochromic device, at least one electrode, e.g., the electrically conductive electrode, is applied to a substrate. The electrode being arranged in a pattern across the substrate. The cited paper discloses two different grid patterns a regular hive and a regular ladder design. See table 1 and figure 3 of the cited paper. Fluid-distributing protrusions in the light modulator may be included herein.

Electrodes may be applied to a substrate by screen-printing on a substrate, in the case of the cited paper, polyethylene terephthalate (PET). The electrodes are typically an electrically conductive material, e.g., a metal or metal oxide. In the cited paper, silver ink was used to screen print the grids on PET using a RokuPrint RP 2.2 equipment and a 180 wired mesh. The samples were allowed to dry in an oven at 130 °C during 15 min. On top of these silver grids, one or two layers of PEDOT:PSS SV3 were posteriorly printed by screen printing. Fluid-distributing protrusions in the light modulator may be included herein.

Another example of an electrochromic device is given in US patent 5161048, with title “Electrochromic window with metal grid counter electrode and acidic polyelectrolyte”, included herein by reference. For example, an electrochromic device may comprise a transparent electrochromic film and an ion-conductive layer disposed between a pair of electrodes. The metal grid electrode is issued for the electrodes. Figure 1 of the patent shows a metal grid according to the cited patent. To form the counter electrode, a metal grid is disposed adjacent to the second glass substrate.

For example, in an embodiment of an electrochromic device, the electrochromic device may comprise a transparent substrate, an electroconductive electrode member, a transparent electrochromic film in contact with said electroconductive electrode member, an ion-conductive polymer in contact with said electrochromic film; and a patterned conductive electrode in contact with said ion- conductive polymer. Fluid-distributing protrusions in the light modulator may be included herein.

A substrate according to an embodiment can be beneficially applied in a number of other technologies. For example, the light modulator may be di electrophoretic light modulator, e.g., as shown in US20050185104 Al, included herein by reference. Fluid-distributing protrusions in the light modulator may be included herein. A substrate as in an embodiment may also be used in other electrowetting and OLED applications. In OLED and electrowetting one needs electrodes on only one of the substrates. The substrate with electrodes may be according to an embodiment. An OLED layer may be combined with a light modulator as in an embodiment, in addition or instead.

Yet other dynamic glass technologies may be used.

For example, an optical layer for a light modulator, e.g., in dynamic glazing, may use LCD (Liquid Crystal Display) technology. For example, the optical layer may comprise liquid crystal molecules that can be aligned to control the amount of light passing through the display. When an electric current is applied to the liquid crystal molecules, they change their alignment and modify the way that light passes through the material. The optical layer with LCD material may be placed between two layers of glass or plastic and connected to an electrical circuit. By controlling the electric current applied to the LCD material, the amount of light passing through the glazing may be adjusted. Fluid-distributing protrusions in the light modulator may be included herein.

An optical layer for a light modulator, e.g., in dynamic glazing, may use Suspended Particle Device (SPD) technology. The optical layer may comprise particles suspended within a thin fdm or laminate. By applying an electrical current to the SPD fdm, the particles align and modify the amount of light passing through the material, allowing for dynamic control of the glazing. When the electrical current is turned off, the suspended particles randomize and allow more light to pass through, creating a clear or transparent effect. When the electrical current is turned on, the particles align and absorb more light, creating a darker or tinted effect. Fluid-distributing protrusions in the light modulator may be included herein.

In an application of the light modulator for glazing both substrates are typically transparent. In other application, e.g., in television, e-readers, etc., only one substrate may be transparent.

Figure lb schematically shows an example of an embodiment of a substrate. The substrate is in particular useful for use in a light modulator, e.g., of a kind described herein. Across the substrate an electrode system is applied in the form of multiple interdigitated electrodes. Shown in figure lb are two interdigitated electrodes. The substrate may comprise fluid-distributing protrusions as in an embodiment.

A contact area may be arranged to enable electrical connection to at least the one or more driving electrodes applied on the substrate. The motivating example use of the substrate is in an electrophoretic light modulator. Typically, an electrophoretic light modulator comprising at least two substrates, each having at least two electrodes at each of the substrates; this is not necessary though, for example, an electrophoretic light modulator may comprise a single substrate with 2 electrodes and an opposite substrate with 1 electrode. In any case, preferably, at least one of the substrates in the light modulator is according to an embodiment.

An embodiment of a light modulator comprises a first substrate according to an embodiment and a second substrate. The first and second substrates are arranged with inner sides opposite to each other. At least one electrode is applied to the inner side of the first substrate. An optical layer is arranged between the first and second substrates. A controller is configured to apply an electric potential to the at least one electrode causing modulation of the optical properties of the light modulator. One or both of the first and second substrates are transparent and/or translucent.

There are many different kinds of light modulators that use at least one electrode applied to a substrate. The optical layer and controller may be arranged to modulate optical properties using effects that depend on the potential on the electrode; examples including the dielectrophoretic effect and the electrophoretic effect. For example, optical modulation may comprise the modulation of particles arranged in the optical layer. The number of electrodes may range from one on a single substrate, to multiple electrodes on one or both substrates.

The optical layer arranged between the first and second substrates may comprise particles, e.g., suspended in a fluid. The controller may be configured to apply an electric potential to the electrodes causing the particles to move thus modulating the optical properties of the light modulator.

In an embodiment, the particles comprise electrically charged or chargeable particles, and the controller is configured to apply an electric potential to the electrode to obtain an electro-magnetic field providing electrophoretic movement of the particles. In an embodiment, the electro-magnetic field is arranged between at least two electrodes arranged on the same substrate or arranged on different substrates.

In an embodiment, the particles comprise dielectric particles, and the controller is configured to apply an electric potential to the electrode to apply an electric field gradient to the particles enabling the particles to be moved under the action of dielectrophoretic forces. The controller may apply an electric signal to one or more of the electrodes. Embodiments that control di electrophoretic forces may use a signal that comprises a DC signal and/or an AC signal. Embodiments that control electrophoretic forces may use a signal that comprises a DC signal and/or an AC signal.

Shown in figure lb are two electrodes on the same surface. The two electrodes are indicated in figure lb in two different dashing styles. There could be more than two electrodes on the same side of the substrate, e.g., to facilitate more fine-grained control of voltage differences across the substrate. The electrodes are applied to a same side of the substrate. Applying electrodes to a substrate may be done lithographically, e.g., using a mask representing the electrodes pattern. Electrodes may also be applied by embedding them in the substrate.

An electrode is electrically connected, e.g., has the same electric potential everywhere. An electrode may comprise a driving bus and main lines. At least, the main lines are interdigitated with main lines of a further electrode. Typically, the electrodes extend in a substantially straight line across the substrate, while the main lines are convoluted.

In an embodiment, the two substrates of a light modulator each have two electrodes arranged at its inner surface. Though, as mentioned, multiple electrodes on one or both substrates are not needed. For example, an embodiment of a light modulator comprises a first substrate and a second substrate. For example, the first substrate may comprise one electrode, the second substrate may not comprise electrodes. For example, the first substrate may comprise two electrodes, the second substrate may comprise one electrode. For example, the first substrate may comprise two electrodes, the second substrate may comprise two electrodes. For example, the first substrate may comprise more than two electrodes, the second substrate may comprise two or more electrodes.

Light modulators, wherein each substrate comprises two electrodes are used as a motivating example, though. Designs of substrates featuring two electrodes may be adapted to have a single electrode, e g., by connecting the two electrodes, or by removing one of the electrodes. Adapting a substrate in such a manner may make it suitable for use in different technologies.

Each of the multiple electrodes are arranged in a pattern across the substrate. The multiple electrodes are arranged alternatingly with respect to each other on the substrate. Typically, an electrode comprises multiple main lines, that each stretch across the substrate. The main lines of the electrodes alternate, e.g., interdigitate. For example, in figure lb the first electrode comprises main lines 111-114, and the second electrode comprises main lines 121-124. The electrodes are each driven by its driving bus. Figure lb shows two driving buses: driving bus 110 and driving bus 120. The electrodes also serve to connect the main lines together. For example, in figure lb, the driving bus 110 drives and connects main lines 111-114; and the driving bus 120 drives and connects main lines 121-124. There can be more main lines than the four shown in this example. The use of main lines is advantageous as it reduces the length of the electrodes, but it is not necessary. A design using only one main line per electrode is not impossible, though having multiple is advantageous.

The driving buses may be adapted to form a contact area to enable electrical connection to at least the one or more driving electrodes applied on the first substrate, e.g., a connection from outside the light modulator. This is not necessary, and a separate contact area, e.g., additional to driving buses 110 and 120 may be provided as in an embodiment.

The multiple main lines of the first and second electrode are arranged alternatingly with respect to each other on the substrate.

In this example, there are no other connections between the main lines of an electrode than through the common driving bus. In an embodiment, an electrode comprises a mesh electrode, that is, it may have additional electrical connection may be added between electrode lines of the same electrode. This increases the reliability of the electrode. Such additional connections typically cross an electrode line of another electrode, which may be resolved by placing the additional electrical connection in part on a different level with respect to the substrate than the electrode line being crossed. For example, one may place the entire electrodes at a different level than another electrode. In this way, additional connections may be placed without short circuits arising.

A motivating application for a substrate such as substrate 100 is in smart glazing, e.g., a light modulator, which may be applied in domestic housing, offices, green houses, cars, and the like. The level of transparency or reflectivity of the smart glazing can be adapted electrically. For example, in smart glazing two substrates such as substrate 100 would be stacked so that the sides on which the two electrodes are applied face each other. A fluid with particles is enclosed between the two substrates. Smart-glazing embodiments are further discussed below. In an embodiment, electrodes, e.g., two or more electrodes are applied to one surface of each substrate. There could also be one, two or more electrodes on the other surface of substrate 100, e.g., to facilitate stacking of three or more substrates.

Some embodiments below show examples of modulating a transparency or reflectivity level. Light modulators may be adapted for other optical effects. For example, if desired, embodiments could be modified to different levels of translucency instead of different levels of transparency. If desired, the type of particle that is used in an embodiment can be varied, e.g., to particles that differ in which wavelengths they absorb or reflect, and how specular of diffuse the reflection is. For example, in an embodiment, a light modulator can modulate different levels of reflection. Particles can also emit light. Stacking multiple optical layers further increases the possibilities.

Having two sets of alternating main lines is sufficient to provide electrically adaptable glazing; due to the alternating two sets the electric field at any part of the substrate can be controlled as two opposite electrodes border the part from two opposing sides.

Interestingly, the pattern in which the electrodes stretch across the substrate may be created by multiple repeated building blocks. Shown in figure lb, the electrodes on substrate 100 shows four blocks: blocks 141, 142, 143 and 144 which are all substantially the same. The number of building blocks may be larger than four. The building blocks repeat in both directions across the substrate, e.g., a first direction 191, e g., an x-direction, shown horizontally in the figure, and a second direction 192, e g., a y-direction, shown vertically in the figure. Using building blocks is advantageous as it allows manufacture using a stepper machine; using building blocks is not necessary.

For example, figure la schematically shows an example of an embodiment of a building block 140. Building block 140 comprises multiple interdigitated electrodes extending in at least 2 directions across the building block. Shown in figure la are four electrodes: electrode 131-134. When the building blocks are repeated across a substrate in two directions, the electrodes in the building block will form the electrodes, e.g., form the multiple main lines of the electrodes. Note that the building blocks are typically connected in a substrate-electrode design tool. Typically, a building block comprises more than four electrode lines. For example, in a range of embodiments between 8 and 12 main lines are used. The number of electrode lines can be much higher though. For example, a building block may comprise many short electrode lines near the edges that connect to lines of other building blocks when the block is repeated. Taking such short offshoots into account, the number of lines could go up to, say, 50. Clearly, when using larger building blocks, the number of electrode lines may go up as well. In an embodiment, the number of electrode lines in a building block is between 8 and 50, or between 8 and 25, etc.

The electrodes that are formed by repeating building blocks are connected to the driving buses. Typically, electrode lines in a building block are connected to electrode lines in neighboring blocks by mering corresponding electrode lines; this is not necessary though, between repeated building blocks connection zones can be inserted that connect corresponding electrode lines.

This step can connect up multiple of the main lines together thus forming a single electrode. Figure lb shows two connecting zones 119 and 129 in which the main lines belonging to the same electrode are connected to driving bus 110 and driving bus 120, respectively.

The electrodes that are shown in figure la are alternately dashed in the same dashing style of figure lb. Indeed, it happens to be the case in this example, that a particular electrode of the building block of figure la will always end up in the first electrode or in the second electrode, e.g., as indicated in this case by the dashing style. This is, however, not necessarily the case. An electrode in a building block may end up as part of the first electrode or as part of the second electrode. This can change, e g., as a result of the parity of the number of electrodes in the building block, the pattern in which the building blocks are repeated, etc.

For example, a particular pattern of repeated building blocks may be used for a light modulator with two electrodes, in which one might assign alternating main lines to the two electrodes. However, the same pattern of repeated building blocks may be used for a light modulator with three electrodes, in which one might assign every next set of three main lines to the three electrodes.

Furthermore, the building block shown in figure la is square, but this is also not needed. For example, a building block may be rectangular. In an embodiment, building block shape(s) could form a so-called tessellation. For example, a building block may be a triangle, a hexagon or even a combination of plane-filling shapes.

As said, figures la and lb are schematic. This is especially the case for the depiction of the electrodes. An electrode as shown in figure la is straight, however, in an embodiment, an electrode on the building block is more convoluted, e.g., curved. By adapting the shape of the electrodes undesirable diffraction effects can be altered.

In an embodiment, a dimmable mirror comprises a light modulator according to an embodiment. For example, the dimmable mirror comprises a transparent substrate, an optical layer, and a reflective substrate. One or both of the substrates is according to an embodiment. The dimmable mirror may be electrophoretic. Typically, each substrate has two electrodes, but this is not necessary.

Figure 1c schematically shows an example of an embodiment of a substrate

101. Substrate 101 is similar to that of substrate 100, except for how the main lines are connected that formed from the electrodes on the building blocks to the driving buses. In figure la, a connection zone is inserted between the repeated building blocks and the driving buses 110 and 120. In the connection zone, the main lines belonging to the same electrode are connected to the same driving bus. In figure 1c, the driving bus is directly adjacent to the building blocks. To avoid that a driving bus connects to a main line of a different electrode, some of the building blocks are modified. Driving buses 110 and 120 may be configured as contact areas.

For example, building block 141 may be a copy of building block 140, but the electrode 134 is shortened so that the main line 122 of which line 134 is a part does not connect to bus 110. In figure 1c the building blocks are substantially the same except that a disconnect is introduced in some electrodes of building blocks next to the driving bus to avoid connecting a main line with the driving bus. Although all building blocks shown in figure 1c are modified in this way, in an embodiment the majority of building blocks would not be modified, e.g., the building blocks that are not adjacent to driving buses 110, 120.

Figure Id schematically shows an example of an embodiment of a substrate

102. In an embodiment, the electrodes in a building block each connect the same opposite sides of the building block. This has the consequence that the main lines that are formed by the electrodes on the building block connect opposite sides of the substrate. In such a situation having only two driving buses, e.g., each extending along an opposite side of the substrate, is sufficient to connect and drive the electrodes.

It is however not required for the electrodes in a building block to connect opposite sides of the building block. Although typically all electrodes in a building block will connect two sides of the building block, it is not required that these two sides are opposite. The reason for this, is that an electrode may be continued by a next building block. In such a situation, most main lines will still connect the same two opposite sides, but at the edge of the substrate this may not happen, as there are no further building blocks there to carry the electrode forward. To allow for more intricate electrode designs on the building blocks, the main line may be connected to a driving bus from two sides, e.g., two sides of the substrate that are adjacent to the same comer of the substrate. Shown in figure Id, is a driving bus 110’ extending along two sides of the substrate and a driving bus 120’ extending along the other two sides of the substrate.

An advantage of this configuration is that the driving buses can be made in the same plane. This is not necessary though. A driving bus could connect from three or all four sides if desired, e.g., to further increase design freedom for the building blocks. Various examples are given herein.

Note that electrodes, e.g., driving buses, and/or main lines are allowed to overlap. This is possible, e g., by causing a part of dielectric material between the electrodes. For example, such overlapping electrodes could be partly or fully in different planes of the substrate.

For example, in an embodiment one might depose the first electrode. Then locally depose a dielectric, and finally depose a second electrode. The dielectric is arranged to cover at least the points where the first and second electrode cross. A via could be used to the lower first electrode, e.g., to connect to it. The deposing of the electrodes may include the deposing of the driving buses.

Figure le schematically shows an example of an embodiment of a substrate

203. In figure le, a building block has been copied multiple times.

Building block 211 has been mirrored in the y-direction to form building block 221. Building block 221 has been arranged directly at the bottom of building block 211. Building block 211 has been mirrored in the x-direction to form building block 212. Building block 212 has been arranged directly to the right of building block 211. Building block 211 has been mirrored in the x-direction as well as in the y-direction to form building block 222. For example, the mirroring may have as mirroring axis a side of the building block.

By mirroring the building block, it is ensured that driving buses of the same electrode end up next to each other on the substrate.

Figure If schematically shows an example of an embodiment of a substrate

204. In substrate 204 the building block is repeated across the substrate, in a different manner. Building block 251 has been mirrored in the y-direction to form building block

261. Building block 261 has been arranged directly at the bottom of building block 251. Building block 251 has been point reflected, e.g., rotated over 180 degree, to form building block 252. Building block 252 has been arranged directly to the right of building block 251. Building block 251 has been mirrored in the x-direction to form building block

262.

It is also possible to arrange building blocks without mirroring the pattern. Figure 1g schematically shows an example of an embodiment of a light modulator, illustrating spacers. Shown is one of the two substrates together with an electrode system, in this case two interdigitated electrodes. For example, the other substrate of the light modulator of figure 1g may have a similar design. Shown in figure 1g are spacers. One such spacer is labeled 151. Spacers are small structures placed around the substrate to keep the two substrates at a constant distance. A spacer may be a dielectric, e.g., formed from the same material as one of the substrates. The spacers are an example of fluid-distributing protrusions in the light modulator.

Figures 2a-2f schematically show examples of substrates with interdigitated electrodes. These may be embodied on a substrate with two electrodes, e.g., by alternatingly connected electrodes. Figures 2a-2d may also be embodied on a substrate with multiple electrodes, e.g., by connecting in sequences of 3 or 4 or more electrodes.

Figures 2e and 2f show designs with two electrodes on the surface of the substrate. Either design could be modified to have only a single electrode on the surface of the substrate, e.g., by removing one of the two electrodes. For example, such a modified design could be used in a light modulator that uses a substrate with a single electrode.

The designs shown can be realized in a single plane, without having crossing electrodes. In particular if these designs are connected to two driving buses, no crossing electrodes are needed. When more than two electrodes are used, or if more complicated electrode patterns are used, then crossing of the electrodes may be used, or may even become necessary. Such crossings are possible however for example, at the location where two electrode lines cross a dielectric material may be arranged between the electrodes. For example, such an insulator may be deposited at the crossing location. For example, a first electrode is in a first plane of the substrate and a second electrode is in a second plane of the substrate.

Two substrates according to an embodiment may be combined to form a light modulator. The light modulator is particularly suited to glazing. An exemplary embodiment of a light modulator is shown below.

Figure 3a schematically shows an embodiment of a light modulator 10, which may be applied in smart glazing.

Reference is made to patent application PCT/EP2020/052379, which is included herein by reference; this application comprises advantageous designs for light modulator, which may be further improved, e.g., by including electrodes, building blocks, and/or substrates as explained herein.

Light modulator 10 can be switched electronically between a transparent state and a non-transparent state and vice versa, or between a non-reflective state and a reflective state and vice versa. Light modulator 10 comprises a first substrate 11 and a second substrate 12 arranged opposite to each other. On an inner-side of first substrate 11 at least two electrodes are applied: shown are electrodes 13a, 13b. These at least two electrodes are together referred to as electrodes 13. On an inner-side of second substrate 12 at least two electrodes are applied: shown are electrodes 14a, 14b. These at least two electrodes are together referred to as electrodes 14. One or more of substrates 11 and 12 may be provided with one or more contact areas to enable electrical connection to at least the one or more electrodes applied on the substrate(s).

A fluid 15 is provided in between said substrate. The fluid comprises particles 30, e.g., nanoparticles and/or microparticles, wherein the particles are electrically charged or chargeable. For example, particles may carry a charge on their surface intrinsically. For example, the particle may be surrounded by a charged molecule. The fluid may be a liquid

The electrodes are arranged for driving particles 30 to move towards or away from electrodes, depending on the electric field applied. The optical properties, in particular the transparency or reflectivity of the light modulator depend on the location of particles 30 in the fluid. For example, a connection may be provided for applying an electro-magnetic field to the electrodes.

Light modulator 10 may be provided with fluid-distributing protrusions, e.g., on first substrate 11 and/or on second substrate 12, facing the optical layer.

The electrodes 13 and 14 are shown schematically in the figures. They may be implemented in a number of ways, e.g., as shown in figures 2.

In an example, substrate 11 and substrate 12 may be optically transparent outside of the electrodes, typically > 95% transparent at relevant wavelengths, such as >99% transparent. Taking electrodes into account, transparency can be much lower, e.g., 70%. The term “optical” may relate to wavelengths visible to a human eye (about 380 nm- about 750 nm), where applicable, and may relate to a broader range of wavelengths, including infrared (about 750 nm - 1 pm) and ultraviolet (about 10 nm-380 nm), and subselections thereof, where applicable. In an exemplary embodiment of the light modulator a substrate material is selected from glass, and polymer. In another example, one substrate, such as a bottom substrate 12, may be reflective or partially reflective, while the top substrate 11 is transparent. The optical properties, in particular the reflectivity of the light modulator depends on the location of particles 30 in the fluid. When the panel is in the open state (vertical drive), the particles will mostly be located between opposite electrodes of the two substrates, such that incident light can pass through the transparent top substrate and the optical layer relatively unhindered and is reflected or partially reflected on the bottom substrate.

The distance between the first and second substrate is typically smaller than 30 pm, such as 15 pm. In an exemplary embodiment of the light modulator a distance between the first and second substrate is smaller than 500 pm, preferably smaller than 200 pm, preferably less than 100 pm, even more preferably less than 50 pm, such as less than 30 pm.

In an example the modulator may be provided in a flexible polymer, and the remainder of the device may be provided in glass. The glass may be rigid glass or flexible glass. If required, a protection layer may be provided on the substrate. If more than one color is provided, more than one layer of flexible polymer may be provided. The polymer may be polyethylene naphthalate (PEN), polyethylene terephthalate (PET) (optionally having a SiN layer), polyethylene (PE), etc. In a further example the device may be provided in at least one flexible polymer. As such the modulator may be attached to any surface, such as by using an adhesive.

Particles 30 may be adapted to absorb light and therewith preventing certain wavelengths from passing through. Particles 30 may reflect light; for example, the reflecting may be specular, diffusive, or in between. A particle may absorb some wavelengths and reflect others. Particles may also or instead emit light, e.g., using phosphorescence, fluorescence, or the like. Even the fluid may emit light, which emittance is modulated by changing the location of particles.

In an exemplary embodiment of the light modulator a size of the nanoparticles is from 20-1000 nm, preferably 20-300 nm, more preferably smaller than 200 nm. In an exemplary embodiment of the light modulator the nanoparticles/microparticles may comprise a coating on a pigment, and preferably comprise a core. In an exemplary embodiment of the light modulator the coating of the particles is made from a material selected from conducting and semiconducting materials.

In an exemplary embodiment of the light modulator the particles are adapted to absorb light with a wavelength of 10 nm-1 mm, such as 400-800 nm, 700 nm -1 pm, and 10-400 nm, and/or are adapted to absorb a part of the light with a wavelength-range falling within 10 nm-1 mm (filter), and combinations thereof.

In an exemplary embodiment of the light modulator the particles are electrically charged or chargeable. For example, a charge on the particles may be 0. le to lOe per particle (5*10'⁷-0.1 C/m²).

In an exemplary embodiment of the light modulator the fluid is present in an amount of 1-1000 g/m², preferably 2-75 g/m², more preferably 20-50 g/m², such as 30-40 g/m². It is a big advantage that with the present layout much less fluid, and likewise particles, can be used.

In an exemplary embodiment of the light modulator the particles are present in an amount of 0.01-70 g/m², preferably 0.02-10 g/m², such as 0.1 -3 g/m².

In an exemplary embodiment of the light modulator the particles have a color selected from cyan, magenta, and yellow, and from black and white, and combinations thereof.

The light modulator can be also configured to only, or primarily, modulate non-visible light such UV or near-IR, e.g., respectively in the range of about 10 nm-380 nm, and in the range of about 750 nm - 1 pm.

In an exemplary embodiment of the light modulator the fluid comprises one or more of a surfactant, an emulsifier, a polar compound, and a compound capable of forming a hydrogen bond.

Fluid 15 may be an apolar fluid with a dielectric constant less than 15. In an exemplary embodiment of the light modulator the fluid has a relative permittivity e_r of less than 100, preferably less than 10, such as less than 5. In an exemplary embodiment of the light modulator, fluid 15 has a dynamic viscosity of above 10 mPa.s.

Electrodes 13a, 13b and electrodes 14a, 14b are in fluidic contact with the fluid. The fluid may be in direct contact the electrodes, or indirectly, e.g., the fluid may contact a second medium with the electrode, such as through a porous layer. In an embodiment, the electrodes cover about 1-30% of the substrate surface. In an embodiment, the electrodes comprise an electrically conducting material with a resistivity of less than 100 nflm (at 273K; for comparison typically used ITO has 105 nflrn), which is similar to an electrical conductivity >l*10⁷ S/m at 20°C).

In an embodiment of the light modulator, electrodes comprise copper, silver, gold, aluminum, graphene, titanium, indium, and combinations thereof, preferably copper. The electrodes may be in the form of microwires embedded in a polymer-based substrate; for example, copper microwires. A connection for applying an electro-magnetic field to the electrodes, wherein the applied electro-magnetic field to the electrodes provides movement of the nano- and microparticles from a first electrode to a second electrode and vice versa. A connection for applying an electro-magnetic field to the electrodes may be provided. For example, in an exemplary embodiment of the light modulator an electrical current is between -100- +100pA, preferably -30-+30 pA, more preferably -25-+25 pA. For example, a power provider may be in electrical connection with the at least two electrodes. The power provider may be adapted to provide a waveform power. At least one of amplitude, frequency, and phase may be adaptable to provide different states in the light modulator. For example, these aspects of the power may be adapted by a controller 16. The controller 16 may be connected to the contact areas of the light modulator.

Light modulator 10 may comprise one or more segments, a segment being a single optically switchable entity, which may vary in size. The substrates enclose a volume, which may be a segment, at least partly.

The present device may comprise a driver circuit for changing the appearance of (individual) segments by applying an electro-magnetic field. As such also the appearance of the light modulator, or one or more parts thereof, may be changed. For example, a segment may have an area of at least 1 mm². The present design allows for stacking to allow for more colors; e.g., for full color applications a stack of two or three modulators could provide most or all colors, respectively.

Having one or more segments allows the light modulator to be controlled locally; this is advantageous for some applications, but not necessary. For smart glazing, a light modulator may be used with or without segments. For example, applied in smart glazing, transparency or reflectivity may be controlled locally, e.g., to block a sun-patch without reducing transparency or reflectivity in the whole window. Segments may be relatively large, e.g., having a diameter of at least 1 mm, or at least 1 cm, etc.

In an exemplary embodiment of the light modulator substrates (11, 12) are aligned, and/or electrodes (13, 14) are aligned. For example, electrodes 13a, 13b and electrodes 14a, 14b may be aligned to be opposite each other. In aligned substrates, electrodes on different substrates fall behind each other when viewed in a direction orthogonal to the substrates. When the light modulator is disassembled, and the substrates are both arranged with electrodes face-up, then the electrode patterns are each other’s mirror image.

Aligning substrates may increase the maximum transparency or reflectivity of the light modulator, on the other hand, when selecting a light modulator for more criteria than the range of transparency or reflectivity, etc., it may be better not to align or not fully align the two substrates. Light modulators can be stacked. For example, two stacked light modulators can be made from three substrates, wherein the middles one has electrodes on both its surfaces. In an embodiment of the light modulator optionally at least one substrate 11, 12 of a first light modulator is the same as a substrate 11, 12 of at least one second light modulator. For stacked modulators, alignment may also increase maximum transparency or reflectivity, but it may be detrimental to other considerations, e.g., diffraction.

Figure 3b schematically shows an example of an embodiment of a light modulator 40. Light modulator 40 is similarto light modulator 10, except that it comprises multiple optical layers; in the example as shown two optical layers. There may be more than two optical layers. Each optical layer is arranged between two substrates. Light modulator 40 can be regarded as a stack of two-substrate light modulators as in figure 3 a. As shown, light modulator 40 comprises three substrates: first substrate 41, second substrate 42 and third substrate 43. Between substrates 41 and 42 is an optical layer, and between substrates 42 and 43 is an optical layer. The optical layers may be similar to those in light modulator 10. A controller 46 is configured to control electrical current on the electrodes of the substrates. For example, in figure 3b, controller 46 may be electrically connected to at least 4 times 2 equals 8 electrodes.

Interestingly, the particles in the multiple optical layers may be different so that the multiple layers may be used to control more optical properties of the light modulator. For example, particles in different optical layers may absorb or reflect at different wavelengths, e g., may have a different color. This can be used to create different colors and/or different color intensities on the panel by controller 46. For example, a four- substrate panel may have three optical layers with different color particles, e.g., cyan, yellow, and magenta, respectively. By controlling the transparency or reflectivity for the different colors a wide color spectrum may be created.

The surfaces of the substrates that face another substrate may be supplied with two or more patterns, e.g., as in an embodiment. For example, the outer substrates 41 and 43 may receive electrodes only on an inner side, while the inner substrate, e.g., substrate 42, may have electrodes on both sides.

Substrates 41 and 42 may together be regarded as an embodiment of a light modulator. Likewise, substrates 42 and 43 may together be regarded as an embodiment of a light modulator. One or more of substrates 41, 42, and 43 may be provided with a contact area for electrical connection to the electrodes, e.g., for control by controller 46.

Light modulator 40 may be provided with fluid-distributing protrusions, e.g., on first substrate 41 facing second substrate 42, on second substrate 42 facing first substrate 41, on second substrate 42 facing third substrate 43, and/or on third substrate 43 facing second substrate 42.

Figure 3c schematically shows an example of an embodiment of a car 20 having smart glazing for windows 21. This is a particularly advantageous embodiment, since while driving the level of incident lighting can change often and rapidly. Using smart glazing in a car has the advantage that light levels can be maintained at a constant level by adjusting the transparency of the car windows. Moreover, the reduced diffraction effect improves safety as it reduces driver distraction. Car 20 may comprise a controller configured for controlling the transparency or reflectivity of windows 21.

Smart glazing can also be used in other glazing applications, especially, where the amount of incident light is variable, e.g., buildings, offices, houses, green houses, skylights. Skylights are windows arranged in the ceiling to allow sunlight to enter the room.

The light modulator may have two optical states, e.g., a transparent state and a non-transparent state, or a non-reflective state and a reflective state. The light modulator, e.g., light modulator 10 or light modulator 40 may be configured to

- switch to the second optical state, e.g., the non-transparent state or to the reflective state by creating an alternating voltage on at least one of the first and second substrates, applying an alternating current between at least a first electrode and a second electrode on the first substrate and/or between a first electrode and a second electrode on the second substrate, and

- switch to the first optical state, e g., the transparent state or to the non- reflective state by creating an alternating voltage between the first and second substrate, applying an alternating current between a first electrode on the first substrate and a first electrode on the second substrate, and/or between a second electrode on the first substrate and a second electrode on the second substrate.

The electrode pattern on the first substrate is arranged at least in part in the same pattern as a second electrode on the second substrate. Typically, the electrodes oppose each other, but the pattern of the first electrode and second electrode may also be shifted with respect to each other. A protective coating may be provided on at least a part of the inner surface area of at least one of the first substrate and the second substrate is provided.

A driving signal applied to electrodes typically has a varying voltage. For example, a power provider may be operated at an AC frequency for switching to a transparent state or to a non-transparent state. Such a signal may have a frequency between, say, 1-1000 Hz. A balanced electrolysis current may be obtained by continuously switching the polarity of oppositely charged electrodes on the first and on the second substrates and/or between the first and the second substrates.

Figures 4a-4b schematically show a side view of an embodiment of a light modulator in use. In this figure only the electrodes are shown. The contact area(s) are not separately shown in these figures.

Applying an electric field to the electrodes on the substrates causes an electrical force on the particles. Using this effect, the particles can be moved around, and so different transparency or reflectivity states can be caused in the light modulator. A controller may control the electric field, e.g., its amplitude, frequency, and phase. In an embodiment, the controller is connected to at least four electrodes: two for each substrate. But more electrodes may be used and connected to the controller; for example, more than 2 electrodes may be used for a substrate to better fine-tune grayscaling and driving to nontransparent or reflective state. Multiple electrodes may also be used to support multiple segments on the substrate.

Figure 4a shows the light modulator without an electric field being applied. No electric force is yet applied on particles 30 suspended in fluid 15, in figure 4a.

In the configuration shown in figure 4a, a conducting electrode pattern, arranged on the top substrate is completely or substantially aligned with a conducting electrode pattern on the bottom substrate. The conducting electrode pattern may be deposited on a transparent or (partially) reflective glass substrate or may be embedded in a plastics substrate, etc.

Alignment between the top-electrode pattern and the bottom electrode pattern contributes to a wider range of achievable levels of transparency or reflectivity. However, alignment is not needed, as similar effects can be obtained without alignment. Without alignment, a range of transparency or reflectivity is likewise obtained.

Note that in these examples, reference is made to the top substrate and the bottom substrate to refer to substrate that is higher or lower on the page. The same substrates could also be referred to, e.g., as the front substrate and back substrate, since in a glazing application, the substrates would be aligned vertically rather than horizontally.

Figure 4b shows the light modulator wherein, say at an instance Pl, a potential +V 1 is applied to each microwire electrode on the top substrate, while a negative voltage, say -VI, is applied to each microwire electrode of the bottom substrate. Thus, in this case, the same positive potential is applied to all electrodes 13, and the same negative potential is applied to electrodes 14. The difference in potential causes negatively charged particles to flow to the vicinity of the electrodes of the top substrate, where the particles will substantially align with the top electrodes. As a result, if both the top and bottom substrate are transparent, the transparency of light modulator 10 will increase. Likewise, if, e.g., the top substrate is transparent and the bottom substrate is reflective, the reflectivity of light modulator 10 will increase If the solution contains positively charged particles they will flow to the vicinity of the electrodes of the bottom substrate, where those particles will substantially align with the bottom electrodes.

A similar transparency can be achieved, when in a second instance, P2, of the on-state, the voltages of the top electrodes and bottom electrodes are reversed in contrast to the instance of Pl In the instance P2, the voltage of each electrode on of the top substrate are now supplied with a negative potential -VI while the voltages of the aligned electrodes of the bottom substrate are supplied with a positive potential. This state is similar to the state shown in figure 4b, but with top and bottom substrates reversed. In this configuration, the transparency of light modulator 10 is also high. If reflective particles are used, then reflectivity is low.

Interestingly, by switching between a positive potential at electrodes at the top substrate, e.g., as shown as electrodes 13 in figure 4b (and a negative potential on electrodes 14), and a positive potential at electrodes at the bottom substrate, e.g., as shown as electrodes 14 in figure 4b, the transparency or non-refl ectivity can be maintained, while decreasing corrosion damage to the electrodes. This alternating electric field can be achieved by applying alternating electric potentials to the top and bottom electrodes.

Applying an AC waveform is optional, but it is a useful measure to increase the lifetime of the light modulator by reducing corrosion. Corrosion can form for example, when using copper electrodes, since copper ions dissolve in an ionic fluid at one substrate and flow to electrode on the opposite substrate, where they deposit. By applying a waveform, the direction of copper ion transport is frequently reversed, thus reducing corrosion damage. Between the two instances Pl and P2 the corrosion current between the two substrates is balanced or substantially, e.g., >95%, balanced, e.g., as corrosion rate of an electrode of the top plate occurs there is a balancing deposition of copper on the bottom electrode between each instance of time, Pl and vice versa in instance P2. Therefore, the particles are transitioning or migrating continuously between top and bottom electrode, and the light modulator or smart window is always in the on-state while the dynamic electrolysis current between the top and bottom electrode is constant thus there is no or a negligible net loss of electrode material on the top and bottom substrates.

Figure 4c shows how a state of decreased transparency or increased reflectivity can be obtained. An alternating voltage is applied on the same substrate. For example, in an embodiment a potential +V2 is applied to a first electrode and the next immediate neighboring electrode has an opposite potential -V2 etc., as shown in fig. 4c. This can be obtained by applying the potential +V2 to electrode 13a and the opposite potential -V2 to electrode 13b. On the opposite substrate the potential +V2 may be applied to electrode 14a and the opposite potential -V2 to electrode 14b. For example, the electrodes may be arranged so that the electrodes on the substrates are aligned; an electrode on the top substrate having an opposite electrode on the bottom substrate, and vice versa. For example, to decrease transparency or increase reflectivity, the opposite electrode may receive the same potential, while neighboring electrodes receive an opposite potential. An embodiment is shown in figure 4c, wherein four electrodes are indicated with the reference numbers 13a, 13b, 14a and 14b, and the rest of the electrodes continue to alternate.

By using this AC drive cycle between top and bottom substrates, diagonal and lateral electric fields are generated between the two substrates thereby causing haphazard diffusion of the particles thereby creating the closed state of the light modulator. As a result of this configuration, the particles migrate diagonally and laterally between the top and bottom substrate and diffusion of particles into the visible aperture of the light modulator contributes to the closed, opaque state of the light modulator.

As for the transparent state shown in figure 4b, a waveform may be applied to the electrodes, e.g., so that electrodes that are shown in figure 4b with a positive potential become negative and vice versa. As in figure 4b applying a waveform, e.g., between electrodes 13a and 13b and between 14a and 14b reduces corrosion damage to the electrodes. In an embodiment, electrodes 14, e.g., 14a, 14b are reflective, while electrodes 13, e g., 13a, 13b may or may not be. The AC drive cycle may be implemented by using an interdigitated line configuration combining the top and bottom electrode configuration shown in plan view in figures la, lb, 2a-2f, etc.

The extent with which transparency or reflectivity is increased or decreased in figures 4b and 4c depends on the voltage and frequencies difference. By varying the voltage difference, the amount by which the transparency or reflectivity increases, respectively, decreases, is controlled. For example, a curve representing light transmission versus voltage may be determined, e.g., measured. To obtain a particular level of light transmission, e g., a particular transparency, e.g., a particular gray scale level, the corresponding voltage, e.g., AC voltage may be applied. By interpolating the signals for a transparent or for a non-transparent state, levels in between transparent and nontransparent may be obtained. Likewise, a curve representing light reflection versus voltage may be determined, e.g., measured. To obtain a particular level of reflectivity, the corresponding voltage, e.g., AC voltage may be applied. By interpolating the signals for a reflective or for a non-reflective state, levels in between reflective and non-refl ective may be obtained.

Different electrode patterns may be used for a light modulator. The electrode patterns may each provide a range of grayscales, e.g., levels of transparency or reflectivity, that the light modulator can attain. However, the particular range of grayscale for any particular electrode pattern may be different from another electrode pattern. In other words, although different patterns give an increased transparency or reflectivity or an increased opacity, the exact response to a drive signal depends on many factors, including the particular pattern that is used. The variations in the optical properties of a light modulator may have a fine resolution, e.g., below 1 mm. Note that no pixilation of the light modulator is needed to achieve different optical patterns, e.g., logos, visible in the light modulator.

This effect may be used to embed visible images in the light modulator by locally changing the electrode pattern on the substrates of a light modulator. For example, one may locally have grayscales that have a permanent off-set in grayscale relative to each other, because of a different electrode pattern. For example, by locally changing the electrode pattern or its pitch, the maximum transparency or reflectivity can be altered.

The result is an area on the light modulator which has a different intensity of grayscale, e g., a different grayscale, or of coloring. The area may have the same colorpoint, though. In an embodiment, they may switch together with the rest of the window, although at a different rate. For example, even if the same voltage is applied to the electrodes in two different areas, they cause a different transparency state, e.g., different transmission level, due to different electrode patterns. For example, a curve representing transmission versus voltage may be shifted. For example, if voltage control is changed in the same way in both areas, then in both areas light transmission may change, but with a different amount. An area may also be made less response to a drive signal by reducing the density of electrodes; in particular, an area may be made not to switch at all, e.g., by not applying electrodes in the area.

For example, the electrode material may be copper, aluminum, gold, indiumtin oxide (ITO), etc. ITO is transparent while Cu/Al is reflective, thus using a different electrode material, a different appearance may be obtained, irrespective of the voltage driving. Likewise, different materials with a different resistance will give rise to a different electric field. For example, ITO will have a smaller electric field, even though driven with the same voltage.

An embodiment of a method of modulating light, comprises applying an electric potential to multiple electrodes applied to two opposing substrates according to an embodiment to obtain an electro-magnetic field between the multiple electrodes providing electrophoretic movement of the particles towards or from one of the multiple electrodes causing modulation of light shining through the substrates, wherein the two opposing substrates are as in an embodiment.

Various modes of operation are supported by an embodiment of a four- electrode light modulator system.

Horizontal drive

Horizontal drive is a mode in which lateral electric fields are created along the substrate. The light modulator may apply alternating voltage on the interdigitated electrodes to cause the particles in the optical layer to move parallel to the substrate, thus decreasing transparency.

Vertical drive

Vertical drive is a mode in which particles are aligned orthogonally to the substrates. Electrodes opposite to each other on opposite substrates receive a different voltage.

Maintaining a grayscale The light modulator drive system may apply 0 voltage on the electrodes most of the time, but if the grayscale is dropping, due to the particles dispersing, then briefly the electrodes and may be driven as in vertical drive.

In all three modes, the driving may use DC or AC signals. Preferably, AC signals are used.

In what follows, figures, claims, and a description are set forth for fluiddistributing protrusions. Nevertheless, an embodiment of a light modulator having fluiddistributing protrusions may be manufactured in a same machine, e.g., a one drop fill (ODF) machine, using the same processes as a light modulator having, e.g., a low- pressure layer to obtain an energy efficient light modulator with limited size and weight.

It would be advantageous to have an improved light modulator, and an improved substrate that may be used therein.

Some embodiments are directed to a light modulator. The light modulator may comprise an optical layer extending between a first and a second substrate, the second substrate being arranged opposite the first substrate. Particles in a fluid in the optical layer may be modulated thus changing the optical properties of the light modulator. The light modulator may be configured to modulate light passing through the optical layer by applying an electric potential to at least one electrode applied to at least the first substrate on a surface facing the second substrate, the electric potential causing modulation of an electric field in the optical layer, providing electrophoretic and/or di electrophoretic movement of the particles in the optical layer The fluid in the optical layer may comprise ink, and/or the particles in the optical layer may comprise ink particles.

In a typical embodiment, two electrodes are applied on the inner side of each of substrates. As described herein, other light modulators are applicable. Optical properties of the light modulator can be modified by applying an electric potential to the at least one electrode.

For example, the at least one electrode may be arranged across the substrate in multiple lines, which are not necessarily straight. Multiple electrodes are typically interdigitated, e.g., arranged altematingly on the surface.

The optical layer may comprise a fluid, e.g., a liquid. The fluid may comprise particles. By applying an electric potential to the at least one electrode, a modulation is caused of the electric field in the optical layer providing electrophoretic and/or di electrophoretic movement of the particles in the optical layer causing modulation of light passing through the substrates. Typically, the first substrate and the second substrate are transparent. The first and second substrate typically have the same dimensions. The substrates of the light modulator, may be glass, e.g., tempered glass, or plastic. For example, the distance between substrates of the light modulator may be at most 100 micrometer, e g., at most 50 micrometer, e.g., at most 30 micrometer.

The electrode(s) are typically patterned using a photolithographic process.

The light modulator may further comprise a plurality of fluid-distributing protrusions which regulate the flow of the fluid in the optical layer. The plurality of fluiddistributing protrusions may be distributed across a region of a surface of at least one of the first substrate and the second substrate, wherein the region has a density of at least 10 fluid-distributing protrusions per mm², and/or wherein the combined area of the fluiddistributing protrusions is at least 0.1% of the surface of the first substrate.

For example, the distribution of the plurality of fluid-distributing protrusions may be as follows. The region of a surface may comprise at least one of the first substrate and the second substrate as a whole. The density of fluid-distributing protrusions may be at least 50 per mm², and/or the combined area of the regions of a surface may be at least 0.2% of the surface of the first substrate For example, the combined area may be at least 0.3% of the surface of the first substrate

The distribution may be across multiple regions of fluid-distributing protrusions of various densities and/or coverage. The distribution may be across multiple regions of fluid-distributing protrusions, with the fluid-distributing protrusions having a distribution of shapes, heights and/or sizes. For example, fluid-distributing protrusions may be triangular-shaped, rectangular-shaped, cylindrical-shaped and/or hill-shaped. For example, fluid-distributing protrusions in the plurality of fluid-distributing protrusions may be of two or more different heights. For example, fluid-distributing protrusions of a first height are comprised in the first substrate and fluid-distributing protrusions of a second height are comprised in the second substrate.

Fluid-distributing protrusions in the plurality of fluid-distributing protrusions may have a diameter of a cross section of at least 1 pm, and/or have a height of at least 6 pm, and/or a sum of at least a part of heights of corresponding fluid-distributing protrusions in the plurality of fluid-distributing protrusions in the first substrate and in the second substrate may add up to a width of a gap between the first substrate and the second substrate.

The distribution may be such, that the fluid-distributing protrusions in the region are at least 20 pm away from each other, and/or at most 1 mm away from each other. The distribution may be such that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions in the region of the surface of the first substrate is vertically aligned with corresponding fluid-distributing protrusions in the second substrate, or shifted parallel to the second substrate with respect to a corresponding fluid-distributing protrusion in the second substrate. Such a shift of a fluid-distributing protrusions parallel to the second substrate with respect to a corresponding fluiddistributing protrusion in the second substrate may for example comprise a distance of at least the width of fluid-distributing protrusions in the plurality of fluid-distributing protrusions. A shift may for example comprise a distance of at most twice a maximal diameter of a cross section of fluid-distributing protrusions in the plurality of fluiddistributing protrusions. A shift may for example comprise a distance of at least 0.5 pm.

Having a distribution of the fluid-distributing protrusions across a region of a surface of at least one of the first substrate and the second substrate, wherein the region has a density of at least 10 fluid-distributing protrusions per mm², and/or wherein the combined area of the fluid-distributing protrusions is at least 0.1% of the surface of the first substrate, may be advantageous to the light modulator in the following ways. In general, a distribution involving such a relatively high density of fluid-distributing protrusions compared to the state of the art may improve the reliability performance and/or the longevity of the light modulator.

A distribution involving a relatively high density of fluid-distributing protrusions compared to the state of the art may limit and control the fluidic flow during the process and the device operations in an improved manner. The fluid may be distributed more evenly, efficiently and/or in other improved ways, for example more homogeneously. The distribution may limit the flowability of the fluid, which for example may be ink, within the device, which may be advantageous in maintaining a homogeneous distribution of chemicals in the ink. By such a distribution, less sedimentation, for example ink sedimentation, may occur. With limiting and/or avoiding sedimentation of the fluid and maintaining a homogeneous distribution of chemicals in the fluid, the longevity of the light modulator may be increased.

Furthermore, a distribution involving a relatively high density of fluiddistributing protrusions compared to the state of the art may improve process conditions during the process of manufacturing and/or use of the light modulator, as the distribution may add to the stability of the light modulator during the process. In particular, the processing of the one-drop filling (ODF), which may be used in manufacturing displays for electrophoretic light modulators, such as liquid crystal displays (LCDs), may be supported. Moreover, a distribution involving a relatively high density of fluiddistributing protrusions compared to the state of the art may add to the mechanical robustness of the light modulator, as the first substrate and the second substrate may be less likely to break, shift and/or tilt in an undesired manner when process conditions may change under which the process of manufacturing and/or use of the light modulator may take place. In particular, by increasing capillary forces, a distribution involving a relatively high density of fluid-distributing protrusions compared to the state of the art may limit a bulging effect which may occur in a vertical orientation of the substrates, for example, glass substrates which may be implemented in a setting of a window.

In an embodiment, the fluid-distributing protrusions may comprise spacers, which are arranged between the first substrate and the second substrate. The spacers may be applied to at least the first substrate on a surface facing the second substrate. The spacers may maintain a cell gap between the first substrate and the second substrate. In an embodiment, spacers may be applied on the first substrate and/or the second substrate on a side facing the optical layer. Spacers may be arranged between second substrate 12 and first substrate 11; during manufacture the spacers may be applied on second substrate 12, or on substrate 11, and/or partially on both. The spacers may be very thin. For example, in an embodiment, a ratio between a diameter of the spacers and a height of the spacers is at most 1, or at most 3/4, or at most 1/2, or at most 1/4. Spacers may be manufactured in a number of ways. For example, spacers may be obtained by an imprinting process, embossing process, and/or etching process, etc. Spacers may be created using a photolithography process. We refer to such spacers as photospacers. Using photospacers may allow a precise placement of spacers, smaller dimensions, higher density, and larger coverage of spacers. This may maintain stronger stability and flatness of the device. In an embodiment, the spacers are photospacers and are UV-curable, e.g., composed of a UV-curable resin. In an embodiment, the spacers are photospacers, composed of a UV-curable resin selected from the group consisting of epoxy-based, acrylic-based, polyurethane-based, and silicone-based resins. For example, manufacturing the photospacers may use the following process. First, applying UV- curable material at predetermined spacer locations on the substrate. This step needs not to be too accurate, as too much UV-curable material may be deposited as is needed for the spacer. Then second, the UV-curable material is exposed to ultraviolet (UV) light through a photomask to cure the spacers. After the curing, the additional uncured material may be removed, e.g., washed away. In an embodiment, the alignment of spacers may be controlled. For example, in an embodiment the first substrate and/or second substrate may contain visible micropattern elements, and all or part of the spacers may be aligned with the visible micropattern elements. This reduces the optical visibility of the spacers. The visible micropattern elements may be electrodes, in particular electrodes in the light modulator. The visible micropattem elements may also include other elements than electrodes. For example, the visible micropattem elements may be a visible pattern applied for aesthetic reasons. For example, the visible micropattern elements may be a pattern configured to visible to birds, to cause birds to avoid flying into the light modulator.

In an embodiment, the light modulator may be sealed: a seal may be applied between the first substrate and the second substrate, positioned at an edge of at least one of the substrates. The seal may seal the optical layer. One way to do sealing is to use a UV-curable seal, e g., a UV-curable resin such as indicated above. The UV-curable seal may be applied around the edges between the at least one insulating substrate and the light modulator, and/or between the substrates of the light modulator. For example, seal may be applied on first substrate facing the optical layer, before second substrate is applied. The distribution of the plurality of fluid-distributing protrusions may be such that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions is positioned at an edge around the seal.

In an embodiment, the distribution of the plurality of fluid-distributing protrusions may be such, that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions is aligned with the at least one electrode. In such a distribution, the region across which the fluid-distributing protrusions may be distributed may overlap with the region across which the at least one electrode may be distributed, and the fluid-distributing protrusions may be overshadowed by the at least one electrode. The at least one electrode may be wholly or partly non-transparent. Such a distribution of the fluid-distributing protrusions may then avoid wholly or partly any possibly negative impact the fluid-distributing protrusions and/or their distribution may otherwise have on the optical characteristics of the light modulator device, such as increasing the diffraction effect, and/or may be beneficial for the contrast characteristics of the light modulator device. The distribution of the plurality of fluid-distributing protrusions may be such that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions is aligned with the at least one electrode may be beneficial for the optical performance of the light modulator.

An aspect is a substrate for use in a light modulator, wherein the substrate may comprise at least one electrode applied to the substrate, and a plurality of fluid-distributing protrusions, wherein the plurality of fluid-distributing protrusions may be distributed across a region of a surface of the substrate with a density of at least 50 fluid-distributing protrusions per mm² in the region.

Another aspect is a method of modulating light, wherein the method may comprise applying an electric potential to at least one electrode, wherein the at least one electrode may be applied to at least one of two opposing substrates, wherein at least one of the two opposing substrates may be according to an embodiment. The applying of the electric potential may cause modulation of an electric field in an optical layer, wherein the optical layer may extend between the two opposing substrates and the optical layer may comprise a fluid comprising particles, and may provide electrophoretic and/or di electrophoretic movement of particles in the optical layer, which movement may cause modulation of light passing through the optical layer.

Another aspect is a method of manufacturing a light modulator according to an embodiment, wherein the method may comprise providing a first substrate according to an embodiment, applying a seal along an edge of the first substrate, providing a fluid comprising particles onto the first substrate within a sealed area, and providing a second substrate opposite the first substrate, thus forming an optical layer between the first substrate and the second substrate, wherein the optical layer may be sealed by the seal.

Embodiments of light modulators are described herein that comprise a plurality of fluid-distributing protrusions, which are arranged to regulate the flow of a fluid in the optical layer of the light modulator, wherein the plurality of fluid-distributing protrusions (is distributed across a region of a surface of at least one of the first substrate and the second substrate, with the region having a density of at least 10 fluid-distributing protrusions per mm², and/or wherein the combined area of the fluid-distributing protrusions is at least 0.1% of the surface of the first substrate.

Such fluid-distributing protmsions are useful to improve the flowability of the fluid in the optical layer, thereby limiting the fluidic flow in the optical layer and decreasing possible sedimentation of the fluid, for example ink. In general, a distribution involving such a relatively high density of fluid-distributing protmsions compared to the state of the art may improve the reliability performance and/or the longevity of the light modulator this way.

A light modulator comprises a first substrate, a second substrate arranged opposite the first substrate, an electrode system extending across at least the first substrate on a side facing the second substrate. Extending between the first and second substrate is an optical layer that comprises a fluid that comprises particles. For example, the light modulator may be a conventional light modulator, e.g., as described herein. For example, the light modulator may be as described with respect to figure 3 a By applying an electric potential to the electrode system an electric field in the optical layer is modulated which in turn causes movement of the particles in the optical layer. As a result of a new distribution of the particles in the optical layer, light that passes through the substrates is modulated — typically visibly so. An electrode system extending across a substrate may comprise one or more electrodes extending across the substrate. An electrode system may be applied to one of the first and second substrates, or to both of the first and second substrates. Typically, the electrode systems are applied to a side of a substrate facing the optical layer, and may be in fluidic contact, though neither is necessary.

Many embodiments of light modulators are possible. For example, the particles may be moved through electrophoretic and/or through dielectrophoretic forces. For example, various types of optical layers, and electrode system are possible. Some types of optical layers use an electrode system with two electrodes, one on each side, some use three electrodes, with 2 on one side and 1 on the other. Some optical layers and electrode system use 4 or even more electrodes. We will refer to embodiments as a two- electrode, three-electrode, or four-electrode to refer to the type of optical layer.

Furthermore, the fluid-distributing protrusions may be of various types, and variously arranged on various regions of a surface with different densities. For example, the fluid-distributing protrusions may be applied on a region of a surface which may comprise at least one of the first substrate and the second substrate as a whole. The density of fluid-distributing protrusions may be at least 50 per mm², and/or the combined area of the regions of a surface may be at least 0.2% of the surface of the first substrate. For example, the combined area may be at least 0.3% of the surface of the first substrate. The distribution may be across multiple regions of fluid-distributing protrusions of various densities and/or coverage. The distribution may be across multiple regions of fluiddistributing protrusions, with the fluid-distributing protrusions being of various types, having a distribution of shapes, heights and/or sizes. For example, fluid-distributing protrusions may be triangular-shaped, rectangular-shaped, cylindrical-shaped and/or hillshaped. For example, fluid-distributing protrusions in the plurality of fluid-distributing protrusions may be of two or more different heights. For example, fluid-distributing protrusions of a first height are comprised in the first substrate and fluid-distributing protrusions of a second height are comprised in the second substrate.

For example, the distribution of the plurality of fluid-distributing protrusions may be such, that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions is aligned with the at least one electrode. Having electrodes on the optical layer-side is advantageous as it increases the effect of the electrode system in the optical layer, but this placement is not necessary, e.g., an electrode system could be placed on the opposite side.

Figure 5a-5d schematically show examples of embodiments of a substrate 11 for use in an embodiment of a light modulator according to an embodiment.

In Figure 5a, a substrate 11 is shown, on which a seal 45 is arranged. In implementation in a light modulator, seal 45 may be applied between substrate 11 and a possible second substrate 12. Seal 45 may seal an optical layer 17 which may extend between substrate 11 and possible second substrate 12. Seal 45 may be positioned at an edge of substrates 11. Seal may at the same time be positioned at and edge of possible substrate 12. Optical layer 17 may comprise a fluid 15 comprising particles 30. Seal 15 may, by sealing optical layer 17, avoid and/or limit fluidic flow, such that it does not run out, spread out, leak out and/or does not behave otherwise in a desired manner near the edge in the light modulator during processing. Fluid 15 may comprise ink, for example electrophoretic ink, and/or particles 30 may comprise ink particles, for example electrophoretic particles.

With the current physical characteristics of electrophoretic inks as fluids, such as a low viscosity, and/or a low surface tension, it may be challenging to fill light modulator devices, such as devices in the liquid-crystal display (LCD) line, in a proper manner, such that the fluid does not spread too fast. In general, ink droplets may tend to spread too fast, also near the edges. By spreading too fast near the edges, the ink droplets will run over the sealed region. By running over the sealed region, the quality of the sealing may decrease, for example, by ink remaining at the interface of the seal at the end.

In Figure 5b, a substrate 11 is shown, on which a seal 45 as well as a plurality of fluid-distributing protrusions 18 are arranged. Fluid-distributing protrusions 18 are distributed across a region 19 of a surface of substrate 11. Region 19 may have a density of at least 10 fluid-distributing protrusions 18 per mm², and/or the combined area of the fluid-distributing protrusions 18 may be at least 0.1% of the surface of substrate 11.

By adding fluid-distributing protrusions in a higher density on substrate 11, there are multiple advantages noticeable during the filling process. First, when a droplet of a fluid, for example an ink droplet, may be places on substrate 11, the spreading of the droplet will be limited due to a reduced surface tension, which is caused by applying the fluid-distributed protrusions 18 on the surface of substrate 11, compared to the surface tension of substrate 11, which may for example be a glass substrate, when no fluid- distributing protrusions 18 are applied to it. Additionally, when a network of fluiddistributing protrusions may be placed on substrate 11, the fluidic flow, for example a flow ink, may take place through the light modulator device by capillary forces, though in a limited manner, as the fluidic flow will then be limited to the height of the fluiddistributing protrusions 18. Since the height of the fluidic flow will be limited, it may not flow over seal 45, as well as the fluidic flow may stop once reaching the sealed area as a whole. Both of these advantageous aspects may maintain a good sealing quality. At least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions 18 may be positioned at an edge around seal 45 in order to reach the effects.

Region 19 of the surface may comprise substrate 11 as a whole. The density of fluid-distributing protrusions 18 may be at least 50 per mm², and/or the combined area 19 may be at least 0.2% of the surface of substrate 11, and/or the combined area 19 may be at least 0.3% of the surface of substrate 11. Fluid-distributing protrusions 18 in region

19 may be distributed in such a way, that fluid-distributing protrusions 18 may be at least

20 pm away from each other, and/or at most 1 mm away from each other.

In Figure 5c, a substrate 11 is shown, on which a seal 45 as well as a plurality of fluid-distributing protrusions 18 are arranged. Here, fluid-distributing protrusions 18 are distributed across multiple regions 19a, 19b of a surface of substrate 11. A further region 19b of a further surface outside of the region further comprises a further plurality of fluid-distributing protrusions 18, wherein the further plurality of fluid-distributing protrusions 18 may be distributed with a density of at least 10 fluid-distributing protrusions 18 per mm² in further region 19b. Region 19a may comprise fluid-distributing protrusions 18 which are positioned near the edge of the sealed area around seal 45, whilst region 19b may comprise fluid-distributing protrusions which are closer to the mid region of substrate 11. Region 19a may have a different density and/or coverage of fluiddistributing protrusions 18 per mm² from the density and/or coverage of fluid-distributing protrusions 18 per mm² in region 19b. The combined area of 19a, 19b of the fluiddistributing protrusions 18 may be at least 0.1% of the surface of substrate 11. For example, in region 19a the density of fluid-distributing protrusions 18 may be at least 50 per mm², and in region 19b the density of fluid-distributing protrusions 18 may be at least 10 per mm². The combined area of 19a and 19b may be at least 0.2% of the surface of substrate 11, and/or the combined area 19 may be at least 0.3% of the surface of substrate 11. Fluid-distributing protrusions 18 in region 19a may be distributed in such a way, that fluid-distributing protrusions 18 in 19a may be closer to a distance of at least 20 pm away from each other, and/or fluid-distributing protrusions 18 in 19a may be closer to a distance of at most 1 mm away from each other.

In Figure 5d, a substrate 11 is shown, on which a seal 45 as well as a plurality of fluid-distributing protrusions 18 are arranged. Here, fluid-distributing protrusions 18 are distributed across multiple regions 19a, 19b of a surface of substrate 11. Region 19a may be of a different shape from region 19b, and/or both shapes may take more free and unusual forms, such as the depicted regions, which deviate from the regions 19a, 19b in Figure 5c which were regular rectangular shapes. It may be desirable to have substrate 11 these shapes of regions 19a, 19b, for example, for the purpose of recognizability and/or distinction such as in the case of logos, watermarks and other prints which may be applied in for example branding purposes. Region 19a may comprise fluid-distributing protrusions 18 which are located in a different larger region, such as here a larger region on the left of substrate 11, from a different larger region in which fluid-distributing protrusions region 19b may be located, such as here a larger region on the right region of substrate 11. Regions 19a, 19b may comprise various densities and/or coverage of fluiddistributing protrusions 18. Substrate 11 may comprise multiple regions 19a, 19b, 19c, &c. of fluid-distributing protrusions 18, which may all be of various densities and/or coverage. In multiple regions 19a, 19b, 19c, &c., fluid-distributing protrusions 18 may have a distribution of size, height and/or shapes. Concentration and/or density of fluiddistribution protrusions 18 may not be uniform in regions 19a, 19b.

Figure 6a-6c schematically show side-views of examples of embodiments of a light modulator.

In Figure 6a, substrates 11, 12 are shown. A seal 45 may be applied between substrates 11, 12. Fluid-distributing protrusions 18 may be applied at substrate 11. Fluiddistributing protrusions 18 may be applied at least one of substrates 11, 12 in order to have an impact on processing and operations of the light modulator.

In Figure 6b, fluid-distributing protrusions 18 may be applied at both substrates. Fluid-distributing protrusions 18 at substrates 11, 12 may face each other; fluid-distributing protrusions 18 at substrate 11 may face fluid-distributing protrusions 18 at substrate 12, and vice versa. Fluid-distributing protrusions may be placed at both substrates 11, 12, but may not necessarily share height and/or positions.

In Figure 6c, the plurality of fluid-distributing protrusions 18 may comprise spacers 18’. Spacers 18’ may be applied to at least the first substrate 11 on a surface facing the second substrate 12. Spacers 18’ may maintain a cell gap between first substrate 11 and second substrate 12. The functionality of spacers 18’ will mainly be shown in Figures 8b and 9b.

Figure 7a-7e schematically show side-views of examples of embodiments of a light modulator.

In Figure 7a, substrates 11, 12 are shown. Here, fluid-distributing protrusions 18 of two separate heights may be applied to substrate 11. More generally, fluiddistributing protrusions 18 in the plurality of fluid-distributing protrusions 18 may be of two or more different heights. The usage of two separate heights may be advantageous in the following way. The higher of the two separate heights may be primarily used for improving mechanical strength and robustness between substrates 11, 12 and therefore of the light modulator, and/or maintaining cell gap maintenance. The lower one of the two heights may be primarily used for limiting and/or avoiding the fluidic flow. In the case of placements of fluid-distributing protrusions 18 at an electrode area, fluid-distributing protrusions may hide part or parts of the electrode where pigments may be supposed to group. When then two separate types of heights are used in fluid-distributing protrusions 18, this may be beneficial to limit and/or avoid fluidic flow, whilst sacrificing less electrode area surface. In the case of the usage of spacers, fluid-distributing protrusions of the lower height may be called subspacers.

In Figure 7b, fluid-distributing protrusions 18 may be applied to both of the substrates 11, 12, which may all be vertically aligned with each other; this may mean that fluid-distributing protrusions which may be applied to substrate 11 may be aligned with corresponding fluid-distributing protrusions which may be applied to substrate 12 Here, for a fluid-distributing protrusion 18 which is applied at substrate 11, a corresponding fluid-distributing 18 which is applied at substrate 12 may be one of the plurality of fluiddistributing protrusions which are applied at substrate 12 which may be closest in distance, using a Riemannian distance in the 3D space and/or a Hausdorff distance between the plurality of fluid-distributing protrusions in substrate 11 and the plurality of fluid-distributing protrusions in substrate 12.

In Figure 7c, fluid-distributing protrusions 18 may be distributed over different heights, size and/or shapes. First, fluid-distributing protrusions 18a, 18b, 18c may be distributed over different sizes. Secondly, fluid-distributing protmsions 18d, 18e, 18f may be of different heights. The usage of separate heights may be beneficial as discussed at Figure 7a. Thirdly, fluid-distributing protrusions 18g, 18h, 18i may be of different shapes. For example, fluid-distributing protrusion 18 may be of a cylindrical shape. Fluid-distributing protrusion 18g may also, for example, be of any free form shape with a narrowing head; fluid-distributing protrusion 18h may also for example be of a triangular shape; and/or fluid-distributing protrusion 18i may for example be of a hill shape. Of course, combinations of size, height and/or shapes may be used, by which fluiddistributing may differ in both size, height and/or shape.

In Figure 7d, a part of the fluid-distributing protrusions 18 applied to the first substrate 11 may be vertically aligned with corresponding fluid-distributing protrusions 18 in second substrate 12. Here, for a fluid-distributing protrusion 18 applied to first substrate 11, a corresponding fluid-distributing protrusion applied second substrate 12 is the fluid-distributing protrusion out of the plurality of fluid-distributing protrusions 18 applied to second substrate 12 which may be closest in distance, using a Riemannian distance in the 3D space and/or a Hausdorff distance between the plurality of fluiddistributing protrusions in substrate 11 and the plurality of fluid-distributing protrusions in substrate 12. At least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions 18 in a region of the surface of first substrate 11 may be vertically aligned with respect to a corresponding fluid-distributing protrusion 18 in second substrate 12. This distance may be a vertical distance 72 between two corresponding fluid-distributing protrusions 18 in the first and the second substrate 11, 12.

Furthermore, fluid-distributing protrusions 18 of a first height may be comprised in the first substrate 11, and fluid-distributing protrusions 18 of a second height may be comprised in the second substrate 12. The first and the second height may be different from each other This means that fluid-distributing protrusions 18 in first substrate 11 may be of a separate height from fluid-distributing protrusions 18 in second substrate 12. A sum of at least a part of heights of corresponding fluid -distributing protrusions 18 in the plurality of fluid-distributing protrusions 18 in the first substrate 11 and in the second substrate 12 may add up to a width 72’ of a gap between the first substrate 11 and the second substrate 12.

In Figure 7e, a part of the fluid-distributing protrusions 18 applied to the first substrate 11 may be shifted parallel to the second substrate 12 with respect to a corresponding fluid-distributing protrusion 18 in the second substrate 12. At least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions 18 in a region of the surface of first substrate 11 may be shifted parallel to second substrate 12 with respect to a corresponding fluid-distributing protrusion 18 in second substrate 12. Such a shift 71 may comprise a distance of at least the width of a fluid-distributing protrusion. A shift 71 may also comprise a distance of at most twice a maximal diameter of a cross section of fluid-distributing protrusions 18 in the plurality of fluid-distributing protrusions 18. A shift 71 may for example comprise a distance of at least 0.5 pm. Such shifts 71 may ensure a better processability of a light modulator device, as they may account for alignment errors which may occur during a production process of a device, for example of a one drop fill (ODF) device.

In an embodiment, the shifts between the fluid-distributing protrusions from substrate 11 to the ones of substrate 12 are not equal for all fluid-distributing protrusions. For each fluid-distributing protrusion or group of fluid-distributing protrusions, the shift may be in any direction parallel to substrate 11 or 12. Considering the whole or part of the population of fluid-distributing protrusions on substrate 11 or 12, there may be multiple shift directions and distances. This is helps to compensate for production misalignment between substrate 11 and substrate 12. Shifting to various directions and distances the fluid-distributing protrusions of substrate 11 or 12, a sufficient physical contact between the fluid-distributing protrusions of substrate 11 and 12 is more likely, if not ensured, during the alignment process in production and for the final light modulator. The shift distances distribution range of the fluid-distributing protrusions is comprised between no shift to the maximum distance corresponding to the alignment tolerance of the alignment production machine.

Figure 7f schematically shows examples of embodiments of a fluiddistributing protrusions. Fluid-distributing protrusion 18j may be of a cylindrical shape. Fluid-distributing protrusion 18k may be of a triangular shape.

A diameter 74, 74’ of a fluid-distributing protrusion may be the maximal distance between all possible points across cross sections of the shape of the fluid-distributing protrusion. In the case of the cylindrical shape of fluid-distributing protrusion 18j , this is the diameter 74 of the circle which forms the cross surfaces. In the case of the triangular shape of fluid-distributing protrusion 18k, this is the diameter 74’ of the square which forms the cross surface at the bottom, which is the length of the diagonal side which is formed by the line which cross the center of the square by connecting the overlying corners. A diameter 74, 74’ of a fluid-distributing protrusion 18 may typically be 1 pm. The height 73, 73’ of a fluid-distributing protrusion 18 may generally be less than the thickness of a light modulator, which may typically be 10 pm. Fluid-distributing protrusions 18 may have a diameter of a cross section of at least 1 pm. Fluid-distributing protrusions 18 may have a height of at least 6 pm. Figure 8a schematically shows an example of an ink droplet 81 being dropped on a substrate 11 without spacers, and Figure 8c shows a result of the spreading of an ink droplet 81 after being dropped on substrate 11 without spacers.

. With the current physical characteristics of electrophoretic inks as fluids, such as a low viscosity, and/or a low surface tension, it may be challenging to fill light modulator devices, such as devices in the liquid-crystal display (LCD) line, in a proper manner, such that the fluid does not spread too fast. In general, ink droplets 81 may tend to spread too fast on substrate 11, also near the edges. By spreading too fast near the edges, the ink droplets will run over the sealed region, and over seal 45. By running over the sealed region, the quality of the sealing may decrease, for example, by ink remaining at the interface of seal 45 at the end.

Figure 8b schematically shows an example of an ink droplet 81 being dropped on a substrate 11 with spacers 18’, and Figure 8d shows the result of the spreading of an ink droplet 81 after being dropped on substrate 11 with spacers 18’. By adding spacers 18’ on substrate 11, this may be advantageous in the filling process. When ink droplet 81 may be placed on substrate 11, the spreading of ink droplet 81 will be limited due to a reduced surface tension, which is caused by applying spacers 18’ on the surface of substrate 11, compared to the surface tension of substrate 11 in the case of Figures 8a and 8c, when no spacers 18’ are applied to it. Now, the flow of ink particle 81 may be limited, as the flow may not rise above the height of spacers 18’. Since the height of the fluidic flow may be limited, it may not flow over seal 45, as well as the flow may stop once reaching the sealed area as a whole. These advantageous aspects may maintain a good sealing quality.

Figure 9a schematically shows an example of an embodiment of a light modulator without spacers. The light modulator may comprise substrates 11, 12, and a fluid 15 comprising particles 30 which may flow through an optical layer which extends between substrates 11, 12. The light modulator may be vertically orientated, for example, for use in a window. The process conditions during the process of manufacturing and/or use of the light modulator may be such that the stability of the light modulator during the process may not be maintained. In particular, the processing of the one-drop filling (ODF), which may be used in manufacturing displays for electrophoretic light modulators, such as liquid crystal displays (LCDs), may be prone to the bulging effect, which means that the mechanical robustness of the light modulator may be little, even such that substrates 11, 12 may be likely to break during the processes, and/or shift and/or tilt in an undesired manner when process conditions may change under which the process of manufacturing and/or use of the light modulator may take place.

Figure 9b schematically shows an example of an embodiment of a light modulator, comprising substrates 11, 12, now with spacers 18’. Now, the fluidic flow of fluid 15 comprising particles 30 may take place through the light modulator device by capillary forces, A distribution involving a relatively high density of spacers 18’ compared to the state of the art may improve the mentioned process conditions during the process of manufacturing and/or use of the light modulator, as the distribution may add to the stability of the light modulator during the process. In particular, the processing of the one-drop filling (ODF), which may be used in manufacturing displays for electrophoretic light modulators, such as liquid crystal displays (LCDs), may be supported. Moreover, a distribution involving a relatively high density of spacers 18’ compared to the state of the art may add to the mechanical robustness of the light modulator, as substrates 11, 12 may be less likely to break, shift and/or tilt in an undesired manner when process conditions may change under which the process of manufacturing and/or use of the light modulator may take place. In particular, by increasing capillary forces, a distribution involving a relatively high density of spacers 18’ compared to the state of the art may limit the bulging effect, which may especially occur in a vertical orientation of substrates 11, 12, for example, glass substrates which may be implemented in a setting of a window. As spacers 18’ may maintain the cell gap between substrates 11, 12 during the lifetime of the light modulator, increasing its longevity and reliability, the bulging effect may also be limited, adding to the mechanical stability and robustness of substrates 11, 12 and thus of the light modulator.

Figure lOa-lOb schematically show examples of embodiments of a substrate 11 on which electrodes 13a, 13b, &c. as well as fluid-distributing protrusions 18a, 18b, &c. may be applied.

In Figure 10b, a substrate 11 is shown on which electrodes 13a, 13b, &c. as well as fluid-distributing protrusions 18a, 18b, &c. may be applied. Here, there may not be a clear distribution of the plurality of fluid-distributing protrusions may be such, that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions may be aligned with electrodes 13a, 13b, &c.

In Figure 10a, the distribution of the plurality of fluid-distributing protrusions may be such that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions may be aligned with electrodes 13a, 13b. In such a distribution, the region across which the fluid-distributing protrusions may be distributed may overlap with the region across which the at least one electrode may be distributed, and the fluid-distributing protrusions may be overshadowed by the at least one electrode. The at least one electrode may be wholly or partly non-transparent. Such a distribution of the fluid-distributing protrusions may then avoid wholly or partly any possibly negative impact the fluid-distributing protrusions and/or their distribution may otherwise have on the optical characteristics of the light modulator device, such as increasing the diffraction effect, and/or may be beneficial for the contrast characteristics of the light modulator device. The distribution of the plurality of fluid-distributing protrusions may be such that at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions is aligned with the at least one electrode may be beneficial for the optical performance of the light modulator.

Figure 11 schematically shows an example of a method 900 of modulating light according to an embodiment. Method 900 may comprise applying an electric potential to at least one electrode in a step 910, wherein the at least one electrode may be applied to at least one of two opposing substrates, wherein at least one of the two opposing substrates may be according to an embodiment. The applying of the electric potential may cause modulation of an electric field in an optical layer, wherein the optical layer may extend between the two opposing substrates and the optical layer may comprise a fluid comprising particles, and may provide electrophoretic and/or di electrophoretic movement of particles in the optical layer, which movement may cause modulation of light passing through the optical layer.

Figure 12 shows an example of a method 1000 of manufacturing a light modulator according to an embodiment. Method 1000 may comprise providing a first substrate according to an embodiment in a step 1010; applying a seal along an edge of the first substrate in a step 1020; providing a fluid comprising particles onto the first substrate within a sealed area in a step 1030; and providing a second substrate opposite the first substrate in a step 1040. In this way, an optical layer between the first substrate and the second substrate is formed, wherein the optical layer may be sealed by the seal. In the described manufacturing method, ink jet printer technology may be used. The method may be performed in a one drop fill (ODF) machine. It should be noted that the above-mentioned embodiments illustrate rather than limit the presently disclosed subject matter, and that those skilled in the art will be able to design many alternative embodiments.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb ‘comprise’ and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article ‘a’ or ‘an’ preceding an element does not exclude the presence of a plurality of such elements. Expressions such as “at least one of’ when preceding a list of elements represent a selection of all or of any subset of elements from the list. For example, the expression, “at least one of A, B, and C” should be understood as including only A, only B, only C, both A and B, both A and C, both B and C, or all of A, B, and C. The presently disclosed subject matter may be implemented by hardware comprising several distinct elements, and by a suitably programmed computer. In the device claim enumerating several parts, several of these parts may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

In the claims references in parentheses refer to reference signs in drawings of exemplifying embodiments or to formulas of embodiments, thus increasing the intelligibility of the claim. These references shall not be construed as limiting the claim.

Claims

Claim 1. A light modulator (10), comprising

- a first substrate (11),

- a second substrate (12) arranged opposite the first substrate (11),

- at least one electrode (13, 13a, 13b, 14, 14a, 14b) applied to at least the first substrate

(11) on a surface facing the second substrate (12),

- an optical layer (17) extending between the first substrate (11) and the second substrate

(12), the optical layer (17) comprising a fluid (15) comprising particles (30), wherein the light modulator (10) is configured to apply an electric potential to the at least one electrode (13, 13a, 13b, 14, 14a, 14b), causing modulation of an electric field in the optical layer (17), providing electrophoretic and/or dielectrophoretic movement of the particles (30) in the optical layer (17), causing modulation of light passing through the optical layer (17), and

- a plurality of fluid-distributing protrusions (18, 18a, 18b) regulating the flow of the fluid (15) in the optical layer (17), the plurality of fluid-distributing protrusions (18, 18a, 18b) being distributed across a region (19) of a surface of at least one of the first substrate and the second substrate, wherein the region (19) has a density of at least 10 fluid-distributing protrusions (18, 18a, 18b) per mm² and/or wherein the combined area of the fluiddistributing protrusions (18, 18a, 18b) is at least 0.1% of the surface of the first substrate (11).

Claim 2. A light modulator (10) as in claim 1, wherein the region (19) of a surface comprises at least one of the first substrate (11) and the second substrate (12) as a whole.

Claim 3. A light modulator (10) as in any of the preceding claims, wherein the density of fluid-distributing protrusions (18, 18a, 18b) is at least 50 per mm² , and/or the combined area (19) is at least 0.2% of the surface of the first substrate (11), and/or the combined area (19) is at least 0.3% of the surface of the first substrate (11).

Claim 4. A light modulator (10) as in any of the preceding claims, wherein the fluiddistributing protrusions (18, 18a, 18b) in the region (19) are distributed to be at least 20pm away from each other, and/or at most 1 mm away from each other.

Claim 5. A light modulator (10) as in any of the preceding claims comprising multiple regions (19, 19a, 19b) of fluid-distributing protrusions (18, 18a, 18b) of various densities and/or coverage.

Claim 6. A light modulator (10) as in any of the preceding claims comprising one or multiple regions (19, 19a, 19b) where fluid-distributing protrusions (18, 18a, 18b) have a distribution of size, height and/or shapes.

Claim 7. A light modulator (10) as in any of the preceding claims, wherein at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions (18, 18a, 18b) is aligned with the at least one electrode (13, 13a, 13b, 14, 14a, 14b).

Claim 8. A light modulator (10) as in any of the preceding claims, further comprising a seal (45) applied between the first substrate (11) and the second substrate (12), sealing the optical layer (17), the seal (45) positioned at an edge of at least one of the substrates (11, 12).

Claim 9. A light modulator (10) as in Claim 8, wherein at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions (18, 18a, 18b) is positioned at an edge around the seal (45).

Claim 10. A light modulator (10) as in any of the preceding claims, wherein at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions (18, 18a, 18b) in the region (19) of the surface of the first substrate (11) is vertically aligned with corresponding fluid-distributing protrusions (18, 18a, 18b) in the second substrate (12).

Claim 11. A light modulator (10) as in any of Claims 1-9, wherein, at least 10%, preferably 50%, more preferably 80% of the plurality of fluid-distributing protrusions (18, 18a, 18b) in the region (19) of the surface of the first substrate (11) is shifted parallel to the second substrate (12) with respect to a corresponding fluid-distributing protrusion (18, 18a, 18b) in the second substrate (12). Claim 12. A light modulator (10) as in Claim 11, wherein the shifts distances and directions parallels to the substrate are not equal for all fluid-distributing protrusions.

Claim 13. A light modulator (10) as in Claim 11, wherein the shifts distances and directions are randomly distributed across the substrate.

Claim 14. A light modulator (10) as in any one of Claims 11-13, wherein a shift comprises a distance of at least a tenth of the width of the spacer.

Claim 15. A light modulator (10) as in any of Claims 11-14, wherein a shift comprises a distance of at most twice a maximal diameter of a cross section of fluid-distributing protrusions (18, 18a, 18b) in the plurality of fluid-distributing protrusions (18, 18a, 18b).

Claim 16. A light modulator (10) as in any one of Claims 11-15, wherein a shift comprises a distance of at least 0.5 pm.

Claim 17. A light modulator (10) as in any of the preceding claims, wherein

- fluid-distributing protrusions (18, 18a, 18b) in the plurality of fluid-distributing protrusions (18, 18a, 18b) have a diameter of a cross section of at least 1 pm, and/or

- fluid-distributing protrusions (18, 18a, 18b) in the plurality of fluid-distributing protrusions (18, 18a, 18b) have a height of at least 6 pm, and/or

- a sum of at least a part of heights of corresponding fluid-distributing protrusions (18, 18a, 18b) in the plurality of fluid-distributing protrusions (18, 18a, 18b) in the first substrate (11) and in the second substrate (12) adds up to a width of a gap between the first substrate (11) and the second substrate (12).

Claim 18. A light modulator (10) as in any of the preceding claims, wherein fluiddistributing protrusions (18, 18a, 18b) in the plurality of fluid-distributing protrusions (18, 18a, 18b) are triangular-shaped, rectangular-shaped, cylindrical-shaped and/or hillshaped.

Claim 19. A light modulator (10) as in any of the preceding claims, wherein fluiddistributing protrusions (18, 18a, 18b) in the plurality of fluid-distributing protrusions (18, 18a, 18b) are of two or more different heights. Claim 20. A light modulator (10) as in Claim 19, wherein fluid-distributing protrusions (18, 18a, 18b) of a first height are comprised in the first substrate (11) and fluiddistributing protrusions (18, 18a, 18b) of a second height are comprised in the second substrate (12).

Claim 21. A light modulator (10) as in any of the preceding claims, wherein the plurality of fluid-distributing protrusions (18, 18a, 18b) comprises spacers, the spacers being applied to at least the first substrate (11) on a surface facing the second substrate (12).

Claim 22. A light modulator (10) as in any of the preceding claims, wherein a region (19) of a surface of at least one of the first substrate (11) and the second substrate (12) is hydrophilic, and/or has a surface energy between 30-50 mJ/mm².

Claim 23. A light modulator (10) as in any of the preceding claims, wherein the fluid (15) comprises ink, and/or the particles (30) comprise ink particles.

Claim 24. A substrate (11) for use in a light modulator (10), the substrate (11) comprising

- at least one electrode (13, 13a, 13b, 14, 14a, 14b) applied to the substrate (11), and

- a plurality of fluid-distributing protrusions (18, 18a, 18b), which is distributed across a region (19) of a surface of the substrate (11) with a density of at least 50 fluid-distributing protrusions (18, 18a, 18b) per mm² in the region (19).

Claim 25. A method (900) of modulating light, comprising

- applying (910) an electric potential to at least one electrode (13, 13a, 13b, 14, 14a, 14b) applied to at least one of two opposing substrates (11, 12), causing modulation of an electric field in an optical layer (17) extending between the two opposing substrates (11, 12) and comprising a fluid (15) comprising particles (30), providing electrophoretic and/or dielectrophoretic movement of particles (30) in the optical layer (17), causing modulation of light passing through the optical layer (17), wherein at least one of the two opposing substrates (11, 12) is as in Claim 24.

Claim 26. A method (1000) of manufacturing a light modulator (10), the method comprising

- providing (1010) a first substrate (11) as in Claim 22,

- applying (1020) a seal (45) along an edge of the first substrate (11), - providing (1030) a fluid (15) comprising particles (30) onto the first substrate (11), within a sealed area,

- providing (1040) a second substrate (12) opposite the first substrate (11), thus forming an optical layer (17) between the first substrate (11) and the second substrate (12) which optical layer (17) is sealed by the seal (45).