WO2006067650A1

WO2006067650A1 - Method of manufacturing an electrophoretic display device and electrophoretic display device

Info

Publication number: WO2006067650A1
Application number: PCT/IB2005/054082
Authority: WO
Inventors: Mark T. Johnson; Roland M. Schuurbiers
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2004-12-20
Filing date: 2005-12-06
Publication date: 2006-06-29
Also published as: TW200628954A

Abstract

The method of manufacturing an electrophoretic display device including a plurality of microcapsules (10) comprises the following steps. The microcapsules are arranged on a relatively flexible first substrate (1) in a regular two-dimensional manner. The relatively flexible first substrate is provided with first alignment structures (21) registering with the microcapsules. A plurality of pixel electrodes (15) is arranged on a relatively rigid second substrate (2) in a similar regular two-dimensional manner. The relatively rigid second substrate is provided with second alignment structures (22) registering with the pixel electrodes. The shape of the second alignment structures is complementary with that of the first alignment structures. The relatively flexible first substrate is contacted to one side of the relatively rigid second substrate, such that a row of the microcapsules is aligned with a row of pixel electrodes. The relatively flexible first substrate is rolled in a rolling direction (30) across the relatively rigid second substrate such that engagement between the first and second alignment structures is provided.

Description

Method of manufacturing an electrophoretic display device and electrophoretic display device

The invention relates to a method of manufacturing an electrophoretic display device including a plurality of microcapsules, each microcapsule encapsulating an insulating fluid and a plurality of charged electrophoretic particles dispersed in the insulating fluid.

The invention also relates to an electrophoretic display device. Electrophoretic display devices are non-emissive devices based on the electrophoresis phenomenon influencing charged particles suspended in a suspension fluid. The suspension fluid is, for example, a liquid or a gas. Electrophoretic display devices are based on light absorbing and/or reflecting electrophoretic particles moving under the influence of an electric field between electrodes provided on opposite substrates or at spatially-separated portions on a substrate at one side of a microcapsule. The charged electrophoretic particles usually are colored particles or black and white particles. With these display devices, dark (colored) characters can be imaged on a light (colored) background, and vice versa. Electrophoretic display devices are notably used in display devices taking over the function of paper and are often referred to as "electronic paper" or "paper white" applications such as, for example, electronic newspapers and electronic diaries.

For mobile display applications, electrophoretic display devices offer an advantageous performance including relatively low power consumption due to long-term image stability, relatively high white state reflectivity and contrast, and "paper- like" optics enhancing readability and legibility. The optical performance of these reflective display devices makes them relatively insensitive to ambient lighting intensity and direction.

Electrophoretic display devices provide a viewing angle which is practically as wide as that of normal paper. The performance is such that supplemental illumination solutions such as front lights are not required for many devices.

Optical materials based on microencapsulated electrophoretic ink have been successfully integrated with traditional amorphous-Si thin- film transistors (TFTs), on a glass substrate, amorphous-Si TFTs built on conformable steel foils or organic TFTs. Facile mechanical integration of the material to active matrices leads to substantial simplifications in their cell assembly process compared to that of liquid crystal display (LCD) devices. In monochrome electrophoretic display devices, for example, a flexible plastic front sheet coated with indium tin oxide (ITO) and the electrophoretic medium is laminated directly to a thin- film transistor backplane. After lamination, an edge seal is applied around the perimeter of the display device. In principle, no polarizer films, alignment layers, rubbing processes, or spacers are required.

From US Patent Application US-A 2003/0152849 it is known to provide a process for manufacturing an electrophoretic display device or a liquid crystal display device. The known electrophoretic display device comprises micro-cups of well-defined shape, size and aspect ratio and the micro-cups are filled with charged pigment particles dispersed in an optically contrasting dielectric solvent. A roll-to-roll process and apparatus permits the display manufacture to be carried out continuously by a synchronized photo-lithographic process. The synchronized roll-to-roll process and apparatus permits a pre-patterned photomask, formed as a continuous loop, to be rolled in a synchronized motion in close parallel alignment to a web which has been pre-coated with a radiation sensitive material, so as to maintain image alignment during exposure to a radiation source. The radiation sensitive material may be a radiation curable material, in which the exposed and cured portions form the micro-cup structure. Exposure of a selected subset of the micro-cups via the photo-mask image permits selective re-opening, filling and sealing of the micro-cup subset. Repetition with additional colors permits the continuous assembly of a multicolor electrophoretic display device.

A disadvantage of the known method is that the individual microcapsules are provided at locations where an electrode structure has already been provided.

The invention has for its object to eliminate the above disadvantage wholly or partly. According to the invention, this object is achieved by a method of manufacturing an electrophoretic display device, the electrophoretic display device including a plurality of microcapsules, each microcapsule encapsulating an insulating fluid and a plurality of charged electrophoretic particles dispersed in the insulating fluid, the method comprising: arranging the plurality of microcapsules on a relatively flexible first substrate in a substantially regular two-dimensional manner, the relatively flexible first substrate being provided with first alignment structures, the first alignment structures registering with the arrangement of the microcapsules, arranging a plurality of pixel electrodes on a relatively rigid second substrate in a substantially similar regular two-dimensional manner, the relatively rigid second substrate being provided with second alignment structures, the second alignment structures registering with the arrangement of the pixel electrodes, the shape of the second alignment structures being complementary with the shape of the first alignment structures, bringing the relatively flexible first substrate into contact with the relatively rigid second substrate such that engagement between the first alignment structures and the complementary second alignment structures is provided.

The bringing together of the relatively flexible first substrate and the relatively rigid second substrate can be achieved by stamping the relatively flexible first substrate onto the relatively rigid second substrate. The engagement of the first alignment structures and the complementary second alignment structures provides the alignment between the the relatively flexible first substrate and the relatively rigid second substrate. In a favorable embodiment of the method, the method further comprises the following steps: contacting the relatively flexible first substrate to one side of the relatively rigid second substrate, such that a row of the microcapsules on the relatively flexible first substrate is aligned with a row of pixel electrodes at said one side of the relatively rigid second substrate, rolling the relatively flexible first substrate in a rolling direction across the relatively rigid second substrate starting from the one side of the relatively rigid second substrate, such that engagement between the first alignment structures and the complementary second alignment structures is provided. In this manner a relatively flexible first substrate is prepared with a two- dimensional array of completely encapsulated microcapsules filled with charged electrophoretic particles dispersed in an insulating fluid. The relatively flexible first substrate comprises, for instance, a foil, preferably, a thin plastic film. On the other hand a relatively rigid second substrate is prepared provided with a plurality of pixel electrodes arranged in a substantially similar regular two-dimensional manner, for instance, an active matrix structure. The relatively rigid second substrate comprises, for instance, a glass plate. If the relatively flexible first substrate with microcapsules and the relatively rigid second substrate with the pixel electrode structure are made independently of each other, the microcapsules on the relatively flexible first substrate will not be perfectly aligned with the pixel electrodes on the relatively rigid second substrate. Normally, there will some mismatch between the microcapsules and the electrode structure. This difference probably results from some small differences in pitch of the microcapsules, which are probably caused by tolerances in preparing or laminating the relatively flexible first substrate. Any such difference in pitch may result in a misalignment of the microcapsules with respect to the electrode structure on the relatively rigid second substrate upon laminating the relatively flexible first substrate and the relatively rigid second substrate. If the relatively flexible first substrate with the array of microcapsules is attached to the relatively rigid second substrate without carefully aligning the microcapsules with respect to the corresponding electrodes, this may give rise to pixels with a reduced brightness or may result in pixels which are non-operational. In a monochrome electrophoretic display device, generally, the electrophoretic particles are moving in a "vertical" manner from a position close to the relatively flexible first substrate towards the relatively rigid second substrate and vice versa. If the pixel electrodes are misaligned and partly overlap with walls between two microcapsules, such a pixel might be less bright than when the pixel electrode is perfectly aligned with the microcapsule, because the effective pixel aperture will be a somewhat reduced. However, in an electrophoretic display device relying upon in-plane ("horizontal") motion of electrophoretic particles, such as, for example, in full-color electrophoretic display devices, pixels with a wall of a microcapsule running through their centre will be practically non-operational. According to the invention, a method of manufacturing an electrophoretic display device comprises the step of carrying out a lamination process of the relatively flexible first substrate with the array of microcapsules on the relatively rigid second substrate with the pixel electrode structure using a rolling technique. To this end, the relatively flexible first substrate is provided with first alignment structures wherein the first alignment structures register with the arrangement of the microcapsules. In addition, the relatively rigid second substrate is provided with second alignment structures, wherein the second alignment structures register with the arrangement of the pixel electrodes. The second alignment structures are chosen to be such that the shape is complementary with the shape of the first alignment structures. Generally, the first and second alignment structures are topographic structures. The lamination process starts with contacting the relatively flexible first substrate with the array of microcapsules to one side of the relatively rigid second substrate with the electrode structure, in such a manner that a row of the microcapsules on the relatively flexible first substrate brought in alignment with a row of pixel electrodes at said one side of the relatively rigid second substrate. Preferably, the alignment procedure is carried out using traditional optical alignment techniques. Following this alignment step, the relatively flexible first substrate with the array of microcapsules is rolled in a rolling direction across the relatively rigid second substrate with the electrode structure starting from the one side of the relatively rigid second substrate in such a manner that engagement between the first alignment structures and the complementary second alignment structures is achieved. During the rolling process, the alignment structures running parallel to the rolling direction serve to maintain the correct rotational alignment, whilst the alignment structures in the perpendicular direction serve to maintain the correct pitch of the relatively flexible first substrate. In this manner, correct alignment is achieved and maintained. As the alignment of the first row of pixels is established to be correct, the complementary alignment structures allow only a miniscule misalignment between adjacent pixels.

If extremely robust topographic structures are created, it may be possible to achieve alignment, in stead of employing a rolling technique, by stamping the relatively flexible first substrate with the microcapsules onto the relatively rigid second substrate with the electrode structure. In this case, the topographic structures must have sufficient strength to induce alignment by distorting the relatively flexible first substrate at all points across the display. The structures need to be robust as extremely high levels of stress may be created during this stamping process. In addition, the topographic structures will also need to be relative large to allow for a misalignment of around a full pixel pitch i.e. they will themselves need to extend across almost the entire pixel. From this it appears that a stamping technique is impractical. By employing a rolling technique, the requirements on the mechanics of the topographic structures are relatively low as compared to the stamping technique.

As was already mentioned hereinabove, the alignment structures running parallel to the rolling direction serve to maintain the correct rotational alignment, whilst the alignment structures in the perpendicular direction serve to maintain the correct pitch of the relatively flexible first substrate. As a consequence, the density of the alignment structures can be different in the direction parallel to the rolling direction as compared to the density of the alignment structures in the direction perpendicular to the rolling direction. To this end a preferred embodiment of the method of manufacturing an electrophoretic display device according to the invention is characterized in that the density of the first alignment structures is higher in the rolling direction than in a direction perpendicular to the rolling direction.

A favorable embodiment of the method of manufacturing an electrophoretic display device according to the invention is characterized in that the second alignment structures have an elongate shape in a direction perpendicular to the rolling direction, each second alignment structure engaging with more than one first alignment structure. In this embodiment the second alignment structures act as a kind of trenches, each second alignment structure receiving a plurality of the first alignment structures.

In a monochrome electrophoretic display device, generally, the electrophoretic particles are moving in a "vertical" manner from a position close to the relatively flexible first substrate towards the relatively rigid second substrate and vice versa. To this end a preferred embodiment of the method of manufacturing an electrophoretic display device according to the invention is characterized in that the relatively flexible first substrate is provided with a common electrode between the microcapsules and the relatively flexible first substrate. In the situation where an electrophoretic display device relies upon in-plane ("horizontal") motion of electrophoretic particles, such as, for example, in full-color electrophoretic display devices, a common electrode on the relatively flexible first substrate is optional. In this case, a matrix arrangement of first and second electrodes is provided on the relatively rigid second substrate. Preferably, the first alignment structures are protruding ("male") alignment structures and the second alignment structures are indented ("female") alignment structures. The invention also relates to an electrophoretic display device. According to the invention, an electrophoretic display device comprising a plurality of microcapsules, each microcapsule encapsulating an insulating fluid and a plurality of charged electrophoretic particles dispersed in the insulating fluid, is characterized in that the plurality of microcapsules is arranged on a relatively flexible first substrate in a substantially regular two-dimensional manner, the relatively flexible first substrate being provided with first alignment structures, the first alignment structures registering with the arrangement of the microcapsules, a plurality of pixel electrodes is arranged on a relatively rigid second substrate in a substantially similar regular two-dimensional manner, the relatively rigid second substrate being provided with second alignment structures, the second alignment structures registering with the arrangement of the pixel electrodes, the shape of the second alignment structures being complementary with the shape of the first alignment structures. Preferably, the density of the first alignment structures is higher in one direction than in a direction perpendicular to said one direction. Preferably, the second alignment structures have an elongate shape, each second alignment structure engaging with more than one first alignment structure. In this favorable embodiment the second alignment structures act as a kind of trenches, each second alignment structure receiving a plurality of the first alignment structures. Preferably, the relatively flexible first substrate is provided with a common electrode between the microcapsules and the relatively flexible first substrate.

The dimensions of the electrophoretic display device are relatively low thereby obtaining an image on the display device with a relatively high resolution. To this end a preferred embodiment of the electrophoretic display device according to the invention is characterized in that a characteristic dimension of the microcapsules is between 5 and 50 μm. Preferably, the characteristic dimension of the microcapsules is between 5 and 20 μm.

Electrophoretic display devices can form the basis of a variety of applications where information may be displayed, for example in the form of information signs, public transport signs, advertising posters, pricing labels, billboards etc. In addition, they may be used where a changing non- information surface is required, such as wallpaper with a changing pattern or colour, especially if the surface requires a paper like appearance.

These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

In the drawings:

Figure IA is a cross-section of an embodiment of an electrophoretic display device according to the invention;

Figure IB is a cross-section of an alternative embodiment of an electrophoretic display device according to the invention;

Figure 2 shows how the relatively flexible first substrate is rolled on the relatively rigid second substrate during manufacturing of the electrophoretic display device according to the invention;

Figure 3 A shows an embodiment of the relatively rigid second substrate provided with pixels and second alignment structures in the shape of trenches;

Figure 3B shows an embodiment of the relatively flexible first substrate provided with protrusions for engagement with the relatively rigid second substrate as shown in Figure 3 A;

Figure 4A is a cross-section of a relatively flexible first substrate of an alternative embodiment of an electrophoretic display device according to the invention, and

Figure 4B is a cross-section of a relatively flexible first substrate of a further alternative embodiment of an electrophoretic display device according to the invention. The Figures are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly. Similar components in the Figures are denoted by the same reference numerals as much as possible.

Figure IA very schematically shows a cross-section of an embodiment of an electrophoretic display device according to the invention. The electrophoretic display device comprises a plurality of microcapsules 10. Each of the microcapsules 10 encapsulates an insulating fluid 11 and a plurality of charged electrophoretic particles 12 dispersed in the insulating fluid 11. Side walls 5 arranged perpendicular to the relatively flexible first substrate 1 and a seal layer 6 provide confinement of the insulating fluid 11 with the charged electrophoretic particles 12 in the microcapsules 10.

Electrophoretic display devices are based on light absorbing and/or reflecting electrophoretic particles 12 moving under the influence of an electric field. In the example of Figure IA, pixel electrodes 15 arranged at the relatively rigid second substrate 2 and a common electrode 16 provided on the relatively flexible first substrate 1 in between the relatively flexible first substrate 1 and the insulating fluid 11. The charged electrophoretic particles usually are colored particles or black and white particles. In the left part of Figure IA, the charged electrophoretic particles 12 are attracted towards the plurality of pixel electrodes 15, in the right part of Figure IA, the charged electrophoretic particles 12 are attracted towards the common electrode 16. In the example of Figure IA, the electrophoretic particles 12 are moving in a "vertical" manner. This manner of movement is typical for a monochrome electrophoretic display device. Preferably, the pixel electrodes 15 and the common electrode 16 are made from indium tin oxide (ITO) or any other suitable transparent conductive material.

The plurality of microcapsules (10) is arranged on a relatively flexible first substrate 1 in a substantially regular two-dimensional manner (in Figure IA only one dimension is shown). Preferably, the relatively flexible first substrate 1 comprises, a foil, for example, a thin plastic film with a typical thickness of 100 μm. The relatively flexible first substrate 1 is provided with first alignment structures 21. The first alignment structures 21 register with the arrangement of the microcapsules 10. In the example of Figure IA the first alignment structures 21 are "female" topographic structures and are provided at an edge portion of the side wall 5, the edge portion facing the relatively rigid second substrate 2. The plurality of pixel electrodes 15 on the relatively rigid second substrate 2 is arranged in a substantially similar regular two-dimensional manner (in Figure IA only one dimension is shown). In addition, the relatively rigid second substrate 2 is provided with second alignment structures 22. These second alignment structures 22 register with the arrangement of the pixel electrodes. In particular, the shape of the second alignment 22 structures is complementary with the shape of the first alignment structures 21. In the example of Figure IA the second alignment structures 22 are "male" topographic structures and are provided adjacent the pixel electrodes 15 on the relatively rigid second substrate 2. A technology for creating the microcapsules 12 on a substrate is the so-called embossing technology. Preferably, this embossing technology is also employed to create the first alignment structures 21.

Preferably, these first alignment structures 21 are made after the manufacturing of the relatively flexible first substrate 1 with the microcapsules 10. In an alternative embodiment the alignment structures are created by other well-known structuring methods such as lithography or printing methods. In this manner, both male and female structures may be created. The form of the alignment structures shown in Figure IA is purely illustrative and in no way limiting for the present invention. In general, it is advantageous if the groove structures taper from a relative broad opening towards a relative narrow end. Such shaping facilitates an efficient alignment of the relatively flexible first substrate 1 with the relatively rigid second substrate 2.

Figure IB very schematically shows a cross-section of an alternative embodiment of an electrophoretic display device according to the invention. The electrophoretic display device comprises a plurality of microcapsules 10 with side walls 5 and a seal layer 6 confining the insulating fluid 11 with the charged electrophoretic particles 12. In the left part of Figure IB, the charged electrophoretic particles 12 are attracted towards one of the walls 5 while in the right part of Figure IB, the charged electrophoretic particles 12 are evenly spread along the seal layer 6. In the example of Figure IB, the electrophoretic particles 12 are moving in a "horizontal" manner. This manner of movement is typical for a full-color electrophoretic display device. Note that the common electrode 16 as shown in Figure IB is optional.

Figure 2 very schematically shows how the relatively flexible first substrate is rolled on the relatively rigid second substrate during manufacturing of the electrophoretic display device according to the invention. In the method of manufacturing the electrophoretic display device, one side of the relatively flexible first substrate 1 upon which the plurality of microcapsules 10 is arranged in a substantially regular two-dimensional manner is brought into contact with one side of the relatively rigid second substrate 2 upon which the plurality of pixel electrodes 15 is arranged in a substantially similar regular two-dimensional manner. Upon establishing contact between the relatively flexible first substrate 1 and the relatively rigid second substrate 2, an alignment procedure is carried out using traditional optical alignment techniques. The result of the alignment procedure is that the first row of microcapsules 10 is aligned with the first row of pixel electrodes 15. Following this alignment step, the relatively flexible first substrate 1 with the array of microcapsules 10 is rolled in a rolling direction (indicated by the dash-dotted arrow 30 in Figure 2) across the relatively rigid second substrate 2 with the electrode structure starting from the one side of the relatively rigid second substrate 2 in such a manner that engagement between the first alignment structures 21 and the complementary second alignment 22 structures is achieved. During the rolling process, the alignment structures 21, 22 running parallel to the rolling direction serve to maintain the correct rotational alignment, whilst the alignment structures 21 , 22 in the perpendicular direction serve to maintain the correct pitch of the relatively flexible first substrate (also see Figure 4). In this manner, perfect alignment of the microcapsules 10 with respect to the corresponding pixel electrodes 15 is achieved and maintained.

Figure 3 A very schematically shows an embodiment of the relatively rigid second substrate 2 provided with pixels 20 and second alignment structures 22, 22' in the shape of "trenches". Only a limited number of pixels 20 is indicated. A typical size of the pixels 20 is in the range from approximately 100x100 μm to approximately 1000x1000 μm. The width of the trenches is 10 to 30 μm. The rolling direction 30 is indicated with the arrow. It can be seen that the density of the second alignment structures 22, 22' is higher in the rolling direction 30 than in a direction perpendicular to the rolling direction 30.

Figure 3B very schematically shows an embodiment of the relatively flexible first substrate 1 provided with protrusions 21 for engagement with the relatively rigid second substrate as shown in Figure 3 A. The width of the protrusions is 5 to 25 μm. The rolling direction 30 is indicated with the arrow. It can be seen that the density of the first alignment structures 21 is higher in the rolling direction 30 than in a direction perpendicular to the rolling direction 30.

Figure 4A very schematically a cross-section of a relatively flexible first substrate 1 of an alternative embodiment of an electrophoretic display device according to the invention. The shape of the microcapsules 10 has been modified in order to create self- aligned topographic structures without requiring additional processing steps. In the example of Figure 4A, the microcapsules 10 have been deliberately under- filled with the electrophoretic fluid. In the case of a deliberate under-fill, there is insufficient fluid to completely fill the micro-cup. After the self-sealing process has been completed whereby a polymeric sealing layer 6 is formed on the top of the insulating fluid 11, the walls 5 of the microcapsules 10 protrude towards the relatively rigid second substrate (the latter is not shown in Figure 4A). Such protrusions form natural topographic first alignment structures, which can be aligned with the second alignment structures etched into the relatively rigid second substrate with the electrode structure. Figure 4B very schematically a cross-section of a relatively flexible first substrate of a further alternative embodiment of an electrophoretic display device according to the invention. Also in this embodiment, the shape of the microcapsules 10 has been modified in order to create self-aligned topographic structures without requiring additional processing steps. In the example of Figure 4B, the microcapsules 10 have been deliberately over-filled with the electrophoretic fluid. In the case of a deliberate over-fill, there is an excess of insulating fluid 11 in the microcapsules 10. After the self-sealing process has been completed whereby a polymeric sealing layer 6 is formed on the top of the insulating fluid 11, the seal layer 6 protrudes beyond the walls 5 of the microcapsules 10. In this case the walls 5 appear as indentations in the relatively flexible first substrate. In this embodiment the wall form the first alignment structures. These indentations form natural topographic alignment structures, which can be aligned with the second alignment structures created on the relatively rigid second substrate.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. 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. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means 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.

Claims

CLAIMS:

1. A method of manufacturing an electrophoretic display device, the electrophoretic display device including a plurality of microcapsules (10), each microcapsule encapsulating an insulating fluid (11) and a plurality of charged electrophoretic particles (12) dispersed in the insulating fluid (11), the method comprising: arranging the plurality of microcapsules (10) on a relatively flexible first substrate (1) in a substantially regular two-dimensional manner, the relatively flexible first substrate (1) being provided with first alignment structures (21), the first alignment structures (21) registering with the arrangement of the microcapsules (10), arranging a plurality of pixel electrodes (15) on a relatively rigid second substrate (2) in a substantially similar regular two-dimensional manner, the relatively rigid second substrate (2) being provided with second alignment structures (22), the second alignment structures (22) registering with the arrangement of the pixel electrodes (15), the shape of the second alignment structures (22) being complementary with the shape of the first alignment structures (21), bringing the relatively flexible first substrate (1) into contact with the relatively rigid second substrate (2) such that engagement between the first alignment structures (21) and the complementary second alignment structures (22) is provided.

2. A method of manufacturing as claimed in claim 1, the method further comprising: contacting the relatively flexible first substrate (1) to one side of the relatively rigid second substrate (2), such that a row of the microcapsules (10) on the relatively flexible first substrate (1) is aligned with a row of pixel electrodes (15) at said one side of the relatively rigid second substrate (2), rolling the relatively flexible first substrate (1) in a rolling direction (30) across the relatively rigid second substrate (2) starting from the one side of the relatively rigid second substrate (2), such that engagement between the first alignment structures (21) and the complementary second alignment structures (22) is provided.

3. A method of manufacturing as claimed in claim 2, wherein the density of the first alignment structures (21) is higher in the rolling direction (30) than in a direction perpendicular to the rolling direction (30).

4. A method of manufacturing as claimed in claim 2 or 3, wherein the second alignment structures (22) have an elongate shape in a direction perpendicular to the rolling direction (30), each second alignment structure (22) engaging with more than one first alignment structure (21).

5. A method of manufacturing as claimed in claim 1 or 2, wherein the relatively flexible first substrate (1) is provided with a common electrode (16) between the microcapsules (10) and the relatively flexible first substrate (1).

6. A method of manufacturing as claimed in claim 1 or 2, wherein the first alignment structures (21) are provided by an embossing technology.

7. A method of manufacturing as claimed in claim 1 or 2, wherein the first alignment structures (21) are protruding alignment structures and the second alignment structures (22) are indented alignment structures.

8. A method of manufacturing as claimed in claim 1 or 2, wherein the first alignment structures (21) are created by underfilling or overfilling the microcapsules (10) with the insulating fluid (11) comprising the charged electrophoretic particles (12).

9. A method of manufacturing as claimed in claim 1 or 2, wherein a characteristic dimension of the microcapsules (10) is between 5 and 50 μm, preferably between 5 and 20 μm.

10. An electrophoretic display device comprising a plurality of microcapsules

(10), each microcapsule encapsulating an insulating fluid (11) and a plurality of charged electrophoretic particles (12) dispersed in the insulating fluid (11), the plurality of microcapsules (10) being arranged on a relatively flexible first substrate (1) in a substantially regular two-dimensional manner, the relatively flexible first substrate (1) being provided with first alignment structures (21), the first alignment structures

(21) registering with the arrangement of the microcapsules (10), a plurality of pixel electrodes (15) being arranged on a relatively rigid second substrate (2) in a substantially similar regular two-dimensional manner, the relatively rigid second substrate (2) being provided with second alignment structures (22), the second alignment structures (22) registering with the arrangement of the pixel electrodes (15), the shape of the second alignment structures (22) being complementary with the shape of the first alignment structures (21).

11. An electrophoretic display device as claimed in claim 10, wherein the density of the first alignment structures (21) is higher in one direction than in a direction perpendicular to said one direction.

12. An electrophoretic display device as claimed in claim 10 or 11, wherein the second alignment structures (22) have an elongate shape, each second alignment structure

(22) engaging with more than one first alignment structure (21).

13. An electrophoretic display device as claimed in claim 10 or 11, wherein the relatively flexible first substrate (1) is provided with a common electrode (16) between the microcapsules (10) and the relatively flexible first substrate (1).

14. An electrophoretic display device as claimed in claim 10 or 11, wherein the first alignment structures (21) are protruding alignment structures and the second alignment structures (22) are indented alignment structures.

15. An electrophoretic display device as claimed in claim 10 or 11, wherein the first alignment structures (21) are provided by underfilling or overfilling the microcapsules (10) with the insulating fluid (11) comprising the charged electrophoretic particles (12).

16. An electrophoretic display device as claimed in claim 10 or 11, wherein a characteristic dimension of the microcapsules (10) is between 5 and 50 μm, preferably between 5 and 20 μm.