WO2010122458A1

WO2010122458A1 - Light-emitting electronic textile having light-spreading layer with increased optical transmittance

Info

Publication number: WO2010122458A1
Application number: PCT/IB2010/051640
Authority: WO
Inventors: Maarten M. J. W. Van Herpen; Liesbeth Van Pieterson; Hugo J. Cornelissen
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2009-04-20
Filing date: 2010-04-15
Publication date: 2010-10-28

Abstract

A light-emitting electronic textile for arrangement under a covering textile (5) for providing light-output through the covering textile (5), the light-emitting electronic textile comprising a flexible component carrier (2) having a plurality of light-sources (3) arranged thereon; and a flexible light-spreading layer (4) arranged on the flexible component carrier (2) for distancing the light-sources (3) from the covering textile (5) and for allowing light emitted by the light-sources (3) to spread before hitting the covering textile (5). The light- spreading layer (4) comprises a first flexible sheet (8) of a first material having a first optical transmittance, and a plurality of cavities (9a-c; 11) formed in the first flexible sheet (8), wherein each of the cavities (9a-c; 11) is empty, or contains a second material (12) having a second optical transmittance being higher than the first optical transmittance. Hereby, the textile-like mechanical properties of the light-emitting electronic textile can be improved, while enabling a reduction of the loss of light due to absorption in the light-spreading layer.

Description

Light-emitting electronic textile having light-spreading layer with increased optical transmittance

FIELD OF THE INVENTION

The present invention relates to a light-emitting electronic textile and to a method for manufacturing such a light-emitting electronic textile.

BACKGROUND OF THE INVENTION

By integrating light-sources, such as light-emitting diodes (LEDs), into textile applications and thereby creating light-emitting electronic textiles, attractive visual effects can be achieved.

Existing light-emitting electronic textiles, such as the device disclosed in US 2008/0218369, are often provided with a textile diffuser arranged on top of the light- sources to achieve a more uniform output of light from the light-emitting electronic textile. Although providing the desired improved uniformity of the output light, the textile diffusers used so far tend to absorb a substantial proportion of the light emitted by the light-sources and/or to suffer from increasing absorption over time. Furthermore, there is room for improving the mechanical properties of existing light-emitting electronic textiles.

SUMMARY OF THE INVENTION

In view of the above-mentioned and other drawbacks of the prior art, a general object of the present invention is to provide an improved light-emitting electronic textile and in particular an electronic textile enabling efficient output of light while maintaining textile- like mechanical properties.

According to a first aspect of the present invention there is provided a light- emitting electronic textile for arrangement under a covering textile for providing light-output through the covering textile, the light-emitting electronic textile comprising: a flexible component carrier having a plurality of light-sources arranged thereon; and a flexible light- spreading layer arranged on the flexible component carrier for distancing the light-sources from the covering textile and for allowing light emitted by the light-sources to spread before hitting the covering textile, wherein the light-spreading layer comprises a first sheet of a first material having a first optical transmittance, and a plurality of cavities formed in the first sheet, wherein each of the cavities is empty, or contains a second material having a second optical transmittance being higher than the first optical transmittance.

By "textile" should, in the context of the present application, be understood a material or product that is wholly or partly made of textile fibers. The textile may, for example, be manufactured by means of weaving, braiding, knitting, crocheting, quilting, or felting. In particular, a textile may be woven or non-woven. Non-woven textiles include, for example, felt, and foam.

Furthermore, the light-spreading here referred to should be understood as the spatial spreading of light that may, for example, result from divergent emission of light over a certain distance, scattering, refraction, or from light guiding in optical light guides such as fibers or ribbons and subsequent light extraction from these light guides.

Moreover, the flexible component carrier may, for example, comprise a flexible printed circuit board or a textile substrate comprising conductor lines. Such a textile substrate may, for example, be formed using interwoven conductive and non-conductive yarns.

The present invention is based on the realization that a light-emitting electronic textile exhibiting output of uniform light as well as textile-like mechanical properties can be achieved by providing a flexible light-spreading layer comprising a sheet having a plurality of cavities formed therein, wherein each cavity contains a material having a higher optical transmittance than the material of the textile sheet in which the cavities are formed, or is empty.

Hereby, the textile-like mechanical properties of the light-emitting electronic textile can be improved, while enabling a reduction of the loss of light due to absorption in the light-spreading layer.

Moreover, the present invention enables a reduction of the change (increase) in absorption over time, since the material contained in the cavities may be selected from a group of materials less sensitive to light (in particular UV light) than the material of the sheet comprised in the flexible light-spreading layer. It should be noted that the light-emitting electronic textile according to the present invention may advantageously be substantially sheet-shaped, which means that the lateral dimensions of the light-emitting electronic textile (in two dimensions) are substantially larger than the thickness thereof. For example, the thickness of the light- emitting electronic textile may be less than one tenth of the smallest lateral dimension (length/width) thereof.

Furthermore, the first sheet comprised in the flexible light-spreading layer may advantageously be a textile sheet. Mainly depending on considerations related to the desired mechanical properties of the light-emitting electronic textile, the cavities may be evenly distributed throughout the light-spreading layer, or be concentrated to locations in the vicinity of the light-sources. Combinations of these configurations are also considered.

According to various embodiments, a plurality of the cavities formed in the first sheet may be arranged in a portion of the light-spreading layer illuminated by an associated one of the light-sources, when in operation, to promote transmission of light emitted by the light-source.

By providing a plurality of cavities in the light-spreading layer over a given light-source, the light emitted by that light-source can be efficiently diffused while increasing the total transmittance of the light-spreading layer at least locally over the light-source.

The lateral dimension of these cavities may advantageously range between 50 micron and 2 mm, preferably between 50 micron and 500 micron.

Furthermore, the cavities may advantageously be arranged substantially periodically, whereby output of uniform light is enabled. Furthermore, an substantially periodical arrangement of the cavities ensures the structural integrity of the light-spreading layer, since the amount of material remaining between the cavities can be precisely controlled.

To reduce the risk of glare resulting from a direct view of one or several light- sources through the light-spreading layer, at least one of the cavities may be oriented in a direction deviating from the normal of the light-spreading layer.

According to one example, several cavities may have substantially the same orientation deviating from the normal of the light-spreading layer, which allows for a relatively simple formation of the cavities as well as a reduction in the risk of glare in a viewing direction normal to the light-emitting electronic device. The difference between the orientation of the cavities and the normal of the light-spreading layer depends on the size of the aperture and the thickness of the light-spreading layer. The angle is preferably chosen such that there is no line-of- sight from the light emitting electronic device to the cover layer.

According to another example, each of the cavities may be oriented to prevent direct view of the light-source through the cavity. This may, for example, be achieved by forming the cavities in such a way that their respective orientations are directed towards a common focal point, which lies outside the underlying light-source. As will be understood by the skilled person, other orientations may equally well serve to achieve the desired effect. For example, each cavity may be oriented towards a common focal point (or several focal points) located on the side of the light-spreading layer facing away from the light-sources.

Moreover, the at least one cavity comprised in the first sheet may advantageously be a hole formed in the first sheet. The hole may be a blind hole or a through- going hole, where the latter may allow for a simpler manufacturing process.

The holes may have any shape, such as having circular or rectangular cross- sections. Furthermore, the holes may be provided as slits, that is, having an oblong cross- section. The formation of holes in the form of slits facilitates the manufacturing of the light- spreading layer.

According to various embodiments of the present invention, the flexible light- spreading layer may further comprise a second sheet of a third material having a third optical transmittance, and at least one cavity formed in the second sheet, the at least one cavity being empty or containing a fourth material having a fourth optical transmittance being lower than the third optical transmittance.

Through the provision of a second (or further) sheet, which may advantageously be a textile sheet, having at least one cavity formed therein, additional design parameters are made available for combining a high light-output efficiency with a low risk of glare.

In particular, the at least one cavity formed in the second sheet may at least partly overlap the at least one cavity formed in the first sheet, whereby a direct view of the light-sources can be prevented while still achieving the desired improved output efficiency of uniform light. According to one embodiment, the at least one cavity in the first sheet may be centered over an associated light-source, and the at least one cavity in the second sheet may be provided around a remaining material portion arranged to shield the light-source from direct view. For example, the at least one cavity in the second sheet may be provided in the form of a hole substantially surrounding a central section, which may be held in place by thin structures connecting the central section with the surrounding part of the second sheet.

It should be noted that the first and third materials may or may not be identical, and that the second and fourth materials may or may not be identical.

Moreover, in analogy with what has been said above for the first sheet, the at least one cavity formed in the second sheet may be a hole, which may or may not be through- going. Furthermore, a plurality of the cavities formed in the second sheet may be arranged in a portion of the light-spreading layer illuminated by an associated one of the light-sources, when in operation, to promote transmission of light emitted by the light-source.

In various embodiments of the present invention, the first (and, when applicable, the second) sheet may advantageously be made of a light-diffusing non- woven textile material, such as a needle felt material or a foam material.

To achieve the desired spreading of the emitted by the light-sources, the light- spreading layer may advantageously be at least 1 mm thick, such as at least 3 mm thick.

The material contained in the cavities may be any material having a higher optical transmittance than the material in the sheet in which the cavities are formed. In various embodiments, the cavities may contain air, but other materials, such as less dense non-woven textiles, etc may also advantageously be contained in the cavities. The advantage of air is that the light transmittance is optimal. The advantage of a less dense textile- like material is that the apertures are structurally stronger (i.e. the covering textile cannot sink into the cavities).

In various embodiments of the light-emitting electronic textile, the light- spreading layer may be attached to the flexible component carrier using an adhesive. This may be particularly advantageous when the alignment between the cavities in the light- spreading layer and the light-sources arranged on the flexible component carrier are of importance. The adhesive may be provided substantially uniformly or spot-wise, where the latter configuration promotes the flexibility of the light-emitting electronic textile.

Furthermore, the light-emitting electronic textile according to the various embodiments of the present invention may advantageously be included in a light-emitting electronic arrangement, further comprising a covering textile arranged on top of the light- emitting electronic textile, such that light emitted by the light-sources is output through the covering textile.

The covering textile may advantageously be a diffractive textile, which is typically a textile material with a very tight weave, due to which the spacing between individual yarns becomes very small. To achieve the desired, visually attractive, diffractive effect, there should be a sufficiently large distance between the light-sources and the diffractive textile, and the light emitted by the light-sources should not be spread too much before hitting the covering textile. Therefore, embodiments including a diffractive textile as a covering textile would, in particular, benefit from a light-spreading layer configuration in which a single, relatively large, cavity is centered over each light-source, whereby practically unhindered passage of light from the light-sources to the diffractive textile is enabled, while achieving the desired spacing between the light-sources and the diffractive textile. According to a second aspect of the present invention, there is provided a method of manufacturing a light-emitting electronic textile for arrangement under a covering textile for providing light- output through the covering textile, the method comprising the steps of providing a light- spreading textile layer comprising a first textile sheet of a first material having a first optical transmittance; forming a plurality of cavities in the first textile sheet; providing a flexible component carrier having a plurality of light-sources arranged thereon; and arranging the light-spreading textile layer on top of the flexible component carrier. The cavities, which may be blind and/or through-going holes may be formed using any means for forming cavities, including, for example, punching, stamping, laser cutting, water-jet cutting etc etc.

Further embodiments and effects associated with this second aspect of the invention are largely analogous to those provided above for the first aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention, wherein:

Fig. 1 is a schematic perspective view of an exemplary light-emitting electronic textile arrangement;

Figs. 2a-c schematically illustrates a portion of the light-emitting electronic textile arrangement in Fig. 1 with different exemplary configurations where the light- spreading layer comprises several cavities associated with each light-source;

Figs. 3a-b schematically illustrates a portion of the light-emitting electronic textile arrangement in Fig. 1 with different exemplary configurations where the light- spreading layer comprises a single cavity associated with each light-source;

Fig. 4 schematically illustrates a portion of the light-emitting electronic textile arrangement in Fig. 1 with an exemplary configuration where the light-spreading layer comprises two textile sheets, each having cavities formed therein; and

Fig. 5 is a flow-chart schematically illustrating a manufacturing method according to an embodiment of the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, the present invention is described with reference to a light-emitting electronic textile in which the cavities formed in the textile sheet(s) are provided in the form of through-going holes with circular or square cross-sections. It should be noted that this by no means limits the scope of the invention, which is equally applicable to other light-emitting electronic textiles in which the cavities have other shapes. For example, the cavities may be provided in the form of slits and/or may be blind holes that only partly penetrate the textile sheet(s).

Fig. 1 schematically illustrates a light-emitting electronic textile arrangement 1, comprising a flexible component carrier 2 having a plurality of light-sources 3 (for the sake of clarity of drawing, only one of the light-sources is indicated by a reference numeral) arranged thereon, a light-spreading textile layer 4 arranged on top of the flexible component carrier 2, and a covering textile 5 arranged at the top. The light-sources 3 may advantageously be light-emitting diodes (LEDs). The light-spreading layer 4 spaces the covering textile 5 apart from the light- sources 3 to ensure that the light emitted by the light-sources is spread out over a larger area. This effect is schematically indicated by the circles drawn on top of the covering textile 5 in Fig. 1. In some applications, the light-spreading layer 4 may also act as a shock-absorbing layer to prevent damage to the light-sources 3 resulting from external forces. In the following, various examples of configurations of the light-spreading layer 4 for improving the performance of the light-emitting electronic textile arrangement in Fig. 1 will be described with reference to Figs. 2a-c, 3a-b and 4.

First, with reference to Figs. 2a-c, various embodiments will be described, in which the light-spreading layer 4 comprises a first textile sheet 8, and a plurality of cavities 9a-c (only three of the cavities are indicated with reference numerals for the sake of clarity of drawing) arranged in a portion of the light-spreading layer 4 which is illuminated by the light-source 3, when the light-source 3 is in operation.

In Fig. 2a, the cavities 9a-c are provided in the form of periodically arranged through-going holes having substantially square cross-sections. Obviously, some or all of the holes may instead have another cross-section, such as a circular cross-section. Such holes are production-friendly and can advantageously be formed using various well-known hole- forming processes, such as laser cutting. In addition to providing for a reduced loss of the light emitted by the light-source 3, the hole configuration shown in Fig. 2a reduces the stiffness of the light-spreading layer 4, whereby the textile-specific mechanical properties, such as the pliability (simultaneous flexibility in several directions) of the light-emitting electronic textile arrangement can be improved.

With the hole configuration in Fig. 2a, there is a possibility that the viewer may receive light travelling directly from the light-sources 3 through the holes 9a-c, especially in embodiments lacking the covering layer 5. To reduce the risk of direct view of the light-sources, the hole configuration may be modified by orienting the cavities/holes to prevent direct view of the light-sources from a preferred viewing direction.

One such exemplary configuration is schematically illustrated in Fig. 2b, where the holes 9a-c are oriented at a non-zero angle with respect to the normal of the light- spreading layer 4. As is illustrated in Fig. 2b, the angle may advantageously be at least 30° relative to the normal of the light-spreading layer 4. The provision of the covering textile 5 will, of course, further reduce the risk of direct viewing of the light-sources 3.

As is schematically illustrated in Fig. 2c, the risk of direct view of the light- sources 3 may be even further reduced by arranging the cavities/holes 9a-c in such a way that all of them are oriented to prevent direct view of the light-source 3. In the example of Fig. 2c, all of the cavities 9a-c are oriented towards a common focal point P located outside the light- source 3.

Alternatively, the cavities may be arranged in such a way that the common focal point coincides with the light-source 3, which provides for a high transmission of light in many possible viewing directions.

As an alternative to the hole configurations described above with reference to Figs. 2a-c, the light-spreading layer 4 may comprise a single cavity 11 formed in the first textile sheet 8 at a location corresponding to an associated one of the light-sources 3. Various examples of this configuration will now be described with reference to Figs. 3a-b. Turning first to Fig. 3a, a portion of the light-emitting textile arrangement 1 in

Fig. 1 is shown, in which a single hole is provided in the first textile sheet 8. The cavity 11, which is here provided in the form of a through-going hole formed in the first textile sheet 8, is air- filled, whereby the light emitted by the light-source 3 is allowed to spread before hitting the covering textile 5, where the light is diffused. To enhance the diffusing effect, as well as to increase the structural strength of the cavity, the cavity/hole 11 may be filled with a diffusing material having a higher optical transmittance than the material in the first textile sheet. This is schematically illustrated in Fig. 3b, where the cavity 11 is filled with a plug 12 of a material having a higher optical transmittance than the material of the first textile layer 8. The material contained in the cavity 11 may, for example, be a textile material that is less dense than the material of the first textile layer 8.

In various embodiments, the light-spreading layer 4 may additionally comprise a second or further textile sheets, which each may or may not comprise cavities formed therein. Below, with reference to Fig. 4, one exemplary embodiment will be described in which the light-spreading layer comprises two perforated textile sheets.

In Fig. 4, the light-spreading layer 4 comprises a first textile sheet 8, having a single cavity 11 formed therein, and a second textile sheet 13 having a single cavity 14 formed therein. The second textile sheet 13 overlies the first textile sheet 8 in such a way that there is substantially no overlap between the cavities 11, 14 formed in the respective textile sheets 8, 13. Through this configuration, an improved uniformity in the emitted light can be achieved, while practically eliminating the risk of direct view of the light-source and any glare that may be associated therewith.

An embodiment of a method for manufacturing a light-emitting electronic textile according to embodiments of the present invention will now be described with reference to the flow chart in Fig. 5.

In a first step 501, a textile sheet 8 is provided. Subsequently, in step 502, holes 9a-c are formed in the textile sheet using any suitable hole-making process, such as laser cutting. Thereafter, in step 503, a flexible component carrier 2 having a plurality of light-sources 3 mounted thereon is provided. Finally, in step 504, the textile sheet 8 having the holes 9a-c formed therein is arranged on top of the flexible component carrier 2.

Claims

CLAIMS:

1. A light-emitting electronic textile for arrangement under a covering textile (5) for providing light-output through said covering textile (5), said light-emitting electronic textile comprising: a flexible component carrier (2) having a plurality of light-sources (3) arranged thereon; and a flexible light-spreading layer (4) arranged on said flexible component carrier (2) for distancing said light-sources (3) from said covering textile (5) and for allowing light emitted by said light-sources (3) to spread before hitting said covering textile (5), wherein said light-spreading layer (4) comprises a first flexible sheet (8) of a first material having a first optical transmittance, and a plurality of cavities (9a-c; 11) formed in said first flexible sheet (8), wherein each of said cavities (9a-c; 11) is empty, or contains a second material (12) having a second optical transmittance being higher than said first optical transmittance.

2. The light-emitting electronic textile according to claim 1, wherein at least one of said cavities (9a-c; 11) is arranged to allow transmission of light emitted by an associated one of said light-sources (3).

3. The light-emitting electronic textile according to claim 2, wherein a plurality of said cavities (9a-c) are arranged in a portion of said light-spreading layer (4) illuminated by an associated one of said light-sources (3), when in operation, to promote transmission of light emitted by said light-source (3).

4. The light-emitting electronic textile according to claim 2 or 3, wherein at least one of said cavities (9a-c) is oriented in a direction deviating from the normal of said light- spreading layer (4).

5. The light-emitting electronic textile according to claim 4, wherein each of said cavities (9a-c) is oriented to prevent direct view of said light-source (3) through said cavity.

6. The light-emitting electronic textile according to any one of the preceding claims, wherein said at least one cavity (9a-c; 11) is a through-going hole formed in said first flexible sheet (8).

7. The light-emitting electronic textile according to any one of the preceding claims, wherein said light-spreading layer (4) further comprises a second flexible sheet (13) of a third material having a third optical transmittance, and at least one cavity (14) formed in said second flexible sheet (13), said at least one cavity (14) being empty, or containing a fourth material having a fourth optical transmittance being lower than said third optical transmittance.

8. The light-emitting electronic textile according to claim 7, wherein said at least one cavity (14) formed in the second flexible sheet (13) at least partly overlaps said at least one cavity (9a-c; 11) formed in the first flexible sheet (8).

9. The light-emitting electronic textile according to any one of the preceding claims, wherein said first material is a diffusive textile material, such as a non-woven material, a foam or a felt.

10. A light-emitting electronic textile arrangement (1) comprising: the light-emitting electronic textile according to any one of the preceding claims; and an at least partly transparent covering textile (5) arranged on top of said light- emitting electronic textile, such that light emitted by said light-sources (3) is output through said covering textile (5).

11. The light-emitting electronic textile (1) arrangement according to claim 10, wherein said covering textile (5) is a diffractive textile.

12. A method of manufacturing a light-emitting electronic textile for arrangement under a covering textile (5) for providing light-output through said covering textile (5), the method comprising the steps of: providing (501) a flexible light-spreading layer (4) comprising a first flexible sheet (8); forming (502) a plurality of cavities (9a-c; 11) in said first flexible sheet (8); providing (503) a flexible component carrier (2) having a plurality of light- sources (3) arranged thereon; and arranging (504) said flexible light-spreading layer (4) on top of said flexible component carrier (2).

13. The method according to claim 12, wherein said step of arranging (504) comprises the steps of: aligning the light-spreading layer in respect of the light-sources comprised in the flexible component carrier; and attaching the light-spreading layer to the flexible component carrier.