Robust connections in a multi- layer woven fabric

FIELD OF THE INVENTION

The present invention relates to textiles for photonic and/or electronic applications. In particular, the present invention relates to via-connections made in a multilayer woven fabric to connect two electrically conductive yarns.

BACKGROUND OF THE INVENTION

Many types of textiles are already in use in our every day life, and new application fields for these textiles have emerged as electronics is now integrated into these textiles. For instance, photonic textiles such as fabrics comprising light emitting diodes (LED) open up a wide range of new interior and apparel applications, ranging from illumination to atmosphere creation to messaging. Very compact, low-power LED packages, available as so-called surface mounted devices, can be attached to the textile by e.g. gluing, snap button connection or stitching. This advantageously provides new types of e.g. foldable and flexible displays. The fabric substrate of such displays is usually made of interwoven or embroidered electrically conductive and non-conductive yarns to build an electronic circuit to which electronic components are connected. As an example, document WO2006/ 129272 discloses a multilayer woven fabric display in which the fabric comprises non- insulated conductive yarns in a top layer and a bottom layer to carry electrical current to electronic components (LEDs) connected to the fabric, each of the electronic component corresponding to a pixel of the display. The use of a multilayer woven fabric is advantageous since optoelectronic devices may be connected to either one of or both faces of the fabric. However, the realization of electrical connections (called via-connections) between the top and bottom layers of the fabric, i.e. from one face of the textile to another, is sensitive, in particular for foldable displays since loose connections may cause malfunctioning of the textile display.

Thus, there is a need for providing improved textiles which would overcome some of these problems.

SUMMARY OF THE INVENTION

An object of the present invention is to wholly or partly overcome the above disadvantages and drawbacks of the prior art and to provide improved multilayer textiles.

The present invention provides a multilayer textile for photonic and/or electronic applications such as a foldable and flexible display.

By increasing the tightness of the interweaving between electrically conductive yarns establishing via-connections and the other yarns of the textile, the via- connections become robust and little sensitive to mechanical deformation such as e.g. wrinkling of the textile. In addition, the specific structure of the yarns at the via connections provides robust via connections and thereby reliable fabrics (textiles).

Hence, according to a first aspect of the present invention, a textile formed of interwoven electrically conductive and insulating yarns (or fibres, threads or strikes) arranged along a warp direction and a weft direction is provided. The textile includes a multilayer structure comprising a first layer of electrically insulating yarns and at least one electrically conductive yarn, a second layer of electrically insulating yarns, and a third layer of electrically insulating yarns arranged between the first and the second layers. The weft yarns of the first, second and third layers are arranged along the weft direction. The textile includes also a warp comprising at least one electrically conductive warp yarn arranged along the warp direction. The at least one electrically conductive warp yarn establishes an electrical connection with at least one electrically conductive weft yarn of the first layer by means of a loop arranged around the at least one electrically conductive weft yarn. The at least one electrically conductive warp yarn engages with (or interlaces) also the two weft yarns most adjacent to the loop in either one of the second and third layers.

The present invention is based on an insight that a tight interweaving between an electrically warp yarn and an electrically conductive weft yarn of the first layer increases the robustness of the via-connection realized between these two yarns. A tight interweaving is obtained by maximizing the contact area, and thereby the contact pressure, between the electrically conductive weft yarn of the first layer and the electrically conductive warp yarn. A robust via-connection is obtained by means of an electrically conductive warp yarn forming a loop around an electrically conductive weft yarn, wherein a first section of the electrically conductive warp yarn going into the loop is substantially parallel to a second section of the electrically conductive warp yarn going out of the loop. In other words, the course of the electrically conductive warp yarn before and after the via-connection (or loop) is substantially parallel.

Further, the electrically conductive warp yarn is significantly bended around each of the two adjacent weft yarns in order to form stable fixation points, thereby ensuring a robust via contact.

In particular, the bending of the electrically conductive warp yarn around the electrically conductive weft yarn may cause the two sections to be directed towards each other. In an alternative embodiment, the two sections of the electrically conductive warp yarn may touch each other.

The angle formed by the electrically conductive warp yarn before and after the via-connection, i.e. between the first and the second sections, may vary from e.g. 100 to 270° but even more preferable 150-210°, and most preferable 180°. In other words, a robust via- connection is obtained with an electrically conductive warp yarn interlacing an electrically conductive weft yarn by means of a loop interlacing also the most adjacent weft yarns of either one of the second and third layers.

An advantage of the present invention is that robust via-connections are provided in the textile, thereby increasing the mechanical stability and functional life time of the electronic textile. Similarly, any device such as a display made of such a textile has an increased mechanical stability and life time while still providing flexibility.

Other electrically conductive weft and warp yarns may also be used in combination with via connections in the textile to realize electrical connection zones at one of the faces of the textile, which faces are defined by the first and second layers. However, it is not necessary that these zones are arranged in the first and second layer. These electrical connection zones may then be used as addressing lines, or to connect electronic components such as sensors, actuators, integrated circuits or optoelectronic devices. As an example, a plurality of light emitting diodes may be connected to the textile and arranged in the form of an array or matrix in order to form a display.

According to an embodiment, the weft yarns of the first, second and third layers may be arranged essentially parallel along the weft direction.

According to an embodiment, the weft yarns of the first, second and third layers may be shifted from one to another along the warp direction. According to an embodiment, the second layer of the textile further comprises at least one electrically conductive yarn in either one of the warp and weft directions.

According to an embodiment, the third layer of the textile further comprises at least one electrically conductive yarn in either one of the warp and weft directions.

According to an embodiment, the yarn density in the weft direction for a region of the textile is in a range of 20-70 strikes per cm. Normally, using a yarn fineness of 110 dtex for the electrically insulating (non-conductive) yarns, a yarn density of 44 to 48 strikes/cm may be achieved. The density of the weft yarns may be increased by reducing the yarn fineness. As an example, a yarn fineness of 78 dtex would result in a yarn density of 55- 60 strikes/cm.

More generally, using a yarn fineness A (unit dtex) and a yarn density D (unit strikes/cm), the product P = D*VA is limited to the range 440 < P < 525 for the present multilayer (3-layer) fabric. The reduction of the yarn fineness, i.e. the increase of the yarn density, decreases the efficiency of the production process. Normally, the yarn density in the weft direction may range from 20 to 70 strikes/cm.

The yarn density in the warp direction, however, is defined by the weaving apparatus, such as a jacqardmachine, and is set in accordance with various standards. The following standards are available: 32-34 threads/cm for fabric quality, 55-60 threads/cm for label quality taft, 70-72 threads/cm for fabric quality, and 120 threads/cm for label quality satin.

More specifically, the maximum density in warp and weft direction is depending on the yarn diameter and there is a coherence between the two densities, i.e. if the yarn density in the warp direction is increased, the yarn density in the weft direction is decreased.

The diameter of a thread, in its turn, depends on the fineness, the material (such as polyester, polyamid or cotton for instance), the specific density and the packaging density of the yarn (i.e. monofil or multifil).

The combinations of yarn fineness values and yarn density values cited above are, for a region of the textile where a via connection is established, advantageous since this further increases the robustness of the via-connection.

This range of yarn density provides both a flexible textile and robust via- connections. Higher yarn densities would provide a stiff textile which would reduce the drape-able properties of the textile while lower yarn densities would provide loose via- connections which may cause malfunctioning of eventual electronic components arranged on the textile.

According to an embodiment, the interweaving of the warp and the weft yarns in a region of the textile forms a Leno structure in which two warp yarns adjacent to each other are twisted around consecutive weft yarns to form a spiral pair. The use of a Leno

structure effectively "locks" each weft at a predetermined place in the textile. The Leno structure or the combination of the Leno structure with a plain weave structure is advantageous in that it improves the stability of the textile (or fabric), in particular for low yarn density. Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional objectives, features and advantages of the present invention, will be better understood through the following detailed description and illustrative drawings, on which: Fig. 1 shows a cross-sectional view of a textile illustrating the interweaving of an electrically conductive warp yarn in a multilayer structure according to an embodiment of the present invention; and

Fig. 2 shows a top view of a schematic representation of a textile according to another embodiment of the present invention, wherein the weaving structure is a Leno weave structure.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Fig. 1, a first embodiment of the present invention will be described. Fig. 1 shows a cross-sectional view of a textile 100 illustrating the interweaving of an electrically conductive warp yarn 141 in a multilayer structure 105. The multilayer structure 105 of the textile (or fabric) 100 comprises a first layer 110, a second layer 120 and a third layer 130 arranged between the first layer 110 and the second layer 120. The weft yarns of the first, second and third layers 110, 120 and 130 are shifted from one to another along a warp direction. The first layer 110 comprises at least one electrically conductive weft yarn 111 and electrically insulating weft yarns 112. The second and third layers 120 and 130 comprise electrically insulating weft yarns 122 and 132, respectively.

The textile 100 also comprises a warp comprising the electrically conductive warp yarn 141 which is interwoven within the yarns of the multilayer structure 105 and

crosses the first layer 110 by means of a loop 145 arranged around the electrically conductive weft yarn 111 of the first layer 110 in order to establish an electrical connection (also called via-connection or via-connection point). The course of the electrically conductive warp yarn 141 is arranged in such a manner that it also interlaces or engages with an adjacent weft yarn 122a of the second layer 120 on one side of the loop 145 and an adjacent weft yarn 132a of the third layer 130 on the other side of the loop 145, which provides a tight interweaving, thereby resulting in a robust via-connection.

In particular, a first section 141a of the electrically conductive warp yarn 141 going into the loop 145 is directed towards a second section 141b of the electrically conductive warp yarn 141 going out of the loop 145.

According to an embodiment, the two sections 141a and 141b touch each other.

In the present embodiment, the first section 141a of the electrically conductive warp yarn 141 before the loop 145 (or going into the loop 145) forms an angle about 180° with the second section 141b of the electrically conductive warp yarn 141 after the loop 145 (or going out of the loop 145). In the present case, the course of the electrically conductive warp yarn 141 may be considered to go from left to right with respect to Fig. 1. However, the same reasoning would be applied if the course of the electrically conductive warp yarn 141 was considered to go from right to left. It is to be noted that the weft and warp directions along which the yarns are arranged are different from each other. As an example, the weft and warp directions may be orthogonal to each other. However, any angle may be formed between these two directions.

It is also noted that the first, second and third layers each comprises yarns along both the weft and warp directions. For matter of simplicity, however, only the weft yarns of the first, second and third layers arranged along the weft direction are represented in the drawings.

According to an embodiment, the warp comprises more than one electrically conductive warp yarn which are electrically separated from each other by at least one insulating weft yarn (not shown in the figures), thereby enabling different types of connections in the textile.

Similarly, the fabric or textile may also comprise more than one electrically conductive weft yarn which are electrically separated from each other by at least one insulating weft yarn.

With reference to Fig. 2, another embodiment of the present invention will be described.

Fig. 2 shows a top view of a schematic representation of a textile 300 according to an embodiment of the present invention, wherein the weaving structure formed by the weft yarns 311 and 312 and the warp yarns 341 is a Leno weave structure. The Leno weave structure may be used for the entire fabric or may be combined with a plain weave structure. In particular, the leno structure is provided at the via-contact (intersection point) with the conductive weft yarn. At other locations, where there is no via contact, the crossing conductive weft and warp yarns in the multi-layer structure needs to pass at different layers. Figure 2 shows the first layer 310 of the multilayer structure of the textile 300.

In the present embodiment, two adjacent warp yarns 341a and 341b of the warp are interwoven within the weft yarns of the multilayer structure. The two adjacent warp yarns 341a and 341b of the warp are twisted around consecutive weft yarns 311 and 312 to form a spiral pair. The two adjacent warp yarns 341a and 341b may be two electrically conductive warp yarns or may be of different types, one being electrically conductive and the other one being electrically insulating.

Similarly, two consecutive weft yarns of the first layer may be of the same type or of different types. In the embodiment shown in Figure 2, a first warp yarn 341a is electrically conductive and a second warp yarn 341b is electrically insulating, the two warp yarns being twisted around electrically insulating weft yarns 312 and an electrically conductive weft yarn 311, thereby establishing an electrical connection between the first warp yarn 341a and the electrically conductive weft yarn 311. The electrically conductive weft yarns 341a and 341b may be interwoven in the multilayer structure in a similar manner as that described with reference to Fig. 1, thereby establishing a via-connection in the textile.

The use of a Leno structure is particularly advantageous for a textile having a low yarn density (low fibre count). It is to be noted that in the embodiments described above more than one electrically conductive yarn may be arranged adjacent to each other within the first layer and electrically separated from other electrically conductive yarns by at least one electrically insulating yarn. In other words, an electrically conductive yarn may be made of one or more electrically conductive yarns.

It is to be noted that the electrically conductive fabric (or weft) described in the embodiments above may be made of one or more electrically conductive yarns.

It is also to be understood that the number of insulating warp yarns electrically separating two adjacent electrically conductive warp yarns in the first layer may vary and various combinations are possible.

It is also to be understood that the multilayer structure may be made of more than three layers. In particular, the third layer (130) may be made of two or more physical layers arranged between the first (110) and the second (120) layers, thereby forming a multilayer structure having four or more layers. It is also to be noted that the warp and weft directions may be interchanged, thereby forming a textile comprising a multilayer structure having three or more layers and a weft comprising electrically conductive and insulating yarns interwoven within the yarns of the multilayer structure.

The present invention is applicable for all types of electronic and/or photonic multilayer textiles. In particular, the textile of the present invention may be used for dynamic interior lighting systems at home or on the move (e.g. furniture upholsteries, curtains or carpets), wearable communication displays (e.g. in a bag or jacket) and photonic therapy devices such as a baby jaundice sleeping bag and an acne treating t-shirt.

Although the invention above has been described in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the scope of the invention as defined by the following claims.