SE1930282A1 - Switchable sunglasses with reflective lenses - Google Patents

Abstract

The present invention relates to switchable sunglasses with reflective lenses, and more specifically to the design of a reflective optical lens comprising at least one liquid crystal element 10 placed in-between two absorptive linear polarizers 11, 12. The invention is based on the insight that by using an additional reflective linear polarizer 13 placed in close proximity to said first absorptive linear polarizer 11, then a lens suitable for sunglasses can be developed that possesses high reflective characteristics for light incident on the front surface, but which simultaneously possesses a low reflectance for light that is incident on the back surface. This enables switchable sunglasses to be developed that appear to be highly reflective when observed from the front thereby providing for good aesthetic characteristics (i.e. mirror sunglasses), but which simultaneously prevents light coming from behind and being reflected back into the user’s eye thereby reducing the occurrence of glare. Furthermore, the overall transmission of said reflective optical lens according to the disclosed invention is higher than that for other technologies based on the prior-art.

Description

Crystal Vision Sweden ABOur ref: 1936-5 SWITCHABLE SUNGLASSES WITH REFLECTIVE LENSES Field of Invention The present invention relates to switchable sunglasses with reflective lenses, andmore specifically to the design of a reflective optical lens comprising at least one liquidcrystal element and which possesses a high level of optical reflectance when viewed fromthe front in order to provide for good aesthetic Characteristics, but which alsosimultaneously possesses a low level of optical reflectance for light incident on the backsurface in order to prevent light from being reflected back into the user”s eye and thusreducing glare. Additionally, the disclosed optical lens possesses a higher level of opticaltransmission when switched to the highest transmissive state as compared to other technologies based on the prior-art.

Background art Switchable sunglasses have been commercially available for many years. Onetechnology known to the art and described for example in European patent no.EP0341519A2 with priority date May 11th, 1988 and entitled “Electronic sunglasses”uses at least one liquid crystal element comprising of Twisted Nematic (TN) liquidcrystal materials. Here, said twisted nematic liquid crystal materials are bound in-betweentwo mutually parallel substrates with the inner-surfaces of said substrates each beingcoated with a transparent conducting electrode. Furthermore, said electrodes mayadditionally be typically coated with an alignment layer, such as uniaXially rubbedpolyimide or otherwise according to the prior-art.

The alignment layer results in the molecular aXes for said twisted nematic liquidcrystal materials located in close proXimity to the surfaces of said substrates beingaligned in a predetermined orientation. Application of suitable voltage-signals to saidelectrodes results in said twisted nematic liquid crystal materials being switch betweenthe homogeneous and homeotropic textures. The homogeneous teXture is characterizedby the molecular aXes for said twisted nematic liquid crystal materials being aligned predorninantly parallel with the surfaces of said substrates, whereas the homeotropic Page 1/12 Crystal Vision Sweden ABOur ref: 1936-5 texture is characterized by said molecular aXes instead being aligned predominantlyperpendicular to the surfaces of said substrates thereof.

Furthermore, said liquid crystal element is commonly placed in-between a firstand second absorptive linear polarizer and typically arranged such that the transmissionaXes for said first and second absorptive linear polarizers are predominantly alignedmutually perpendicular. In such case, when said twisted nematic liquid crystal materialsare switched to said homogeneous teXture, then said liquid crystal element can bearranged to be in a first optical state possessing a high level of optical transmission.Moreover, when said twisted nematic liquid crystal materials are instead switched to saidhomeotropic teXture, then in this case said liquid crystal element can be arranged to be ina second optical state possessing a low level of optical transmission thereof. Therefore,said liquid crystal element can be switched between a first and second optical state viaapplication of suitable voltage-signals, hence said liquid crystal element is suitable foruse as an optical lens for switchable sunglasses according to the state-of-the-art.

However, said liquid crystal element according to the aforementioned prior-arttechnology will typically be neutral-grey in coloration and also possess a relatively lowlevel of optical reflection when viewed from both the front and back surfaces. Moreover,for the application of sunglasses and other related products it is often desirable for theoptical lens to instead appear highly reflective when viewed from the front in order toprovide good aesthetic characteristics (i.e. rnirror sunglasses or alternatively “pilotsunglasses”). Furthermore, it will be known to one skilled-in-the-art that this may beachieved by adding a serni-reflective coating (typically referred to as a mirror coating oralternatively a flash coating) to the front surface of said liquid crystal element thereof.Such coatings provide a high level of reflectance with a typical value of 50%, but theyalso decrease the overall optical transmission through the lens by a similar correspondingfactor of 50%. Typical eXemplary semi-reflective coatings may or may not comprise ofthin metallic layers such as titanium, nickel or chrorr1ium, or alternatively of dielectriclayers such as chromium oxide, silicon dioxide or titanium dioxide (i.e. metallic oxides)according to the state-of-the-art.

Moreover, since said liquid crystal element is typically already placed in-between two absorptive linear polarizers, then it will be understood by one skilled-in-the-art that Page 2/12 Crystal Vision Sweden ABOur ref: 1936-5 the overall maximum theoretical optical transmission through said liquid crystal elementin the absence of an additional semi-reflective coating will only be 50% due to theoccurrence of light absorption by said absorptive linear polarizers thereof. Furthermore,should an additional serni-reflective coating also be added to the front surface of saidliquid crystal element in order to obtain the desired aesthetic Characteristics, then in thiscase the overall maximum theoretical optical transmission will be reduce to only 50% x50% = 25%. Moreover, in practice this value may typically drop further to below 20%due to the presence of other optical losses within the system, thereby severely lirniting themaximum optical transmission that can be achieved by said liquid crystal element thereofaccording to the state-of-the-art.

In order to increase the maximum theoretical transmission of said liquid crystalelement according to the prior-art, it will be known to one skilled-in-the-art that Guest-Host (GH) liquid crystal materials can alternatively be utilized. This is described forexample in US patent no. 5,943, l04 with priority date March 25th, 1997 and entitled“Liquid crystal eyewear with two identical Guest-Host subcells and tilted homeotropicalignment”.

Here, dichroic-dye material (often referred to as the “Guest”) is added to saidnematic liquid crystal materials (often referred to as the “Host”) in a typical concentrationof between 0.l% and 5.0% by weight. The dichroic-dye material only absorbscomponents of light that possess an electrical-field vector that is aligned parallel with themolecular axis for said dichroic-dye material thereof. Moreover, when said nematic liquidcrystal materials are switched to said homogeneous texture, then in this case saiddichroic-dye material can be arranged to weakly absorb the light passing through saidliquid crystal element, whereas when said nematic liquid crystal materials are insteadswitched to said homeotropic texture then the light will pass through said liquid crystalelement without there being any significant level of optical attenuation. Therefore, saidGuest-Host liquid crystal materials are capable of being switched between a first opticalstate possessing a high level of optical transmission (i.e. homeotropic texture) and asecond optical state possessing a lower level of optical transmission (i.e. homogeneoustexture) without the necessity of utilizing additional absorptive linear polarizers according to the prior-art.

Page 3/12 Crystal Vision Sweden ABOur ref: 1936-5 This therefore allows Guest-Host liquid crystal materials to be used forapplications such as switchable sunglasses where a higher level of optical transmission isprovided as compared to that for when twisted nematic liquid crystal materials are usedtogether with absorptive linear polarizers. Furthermore, it will be known to one skilled-in-the-art that the maximum theoretical optical transmission for said Guest-Host liquidcrystal materials when placed together with a semi-reflective coating on the front surfacein order to provide the desired aesthetic characteristics will in this case be 50% accordingto the prior-art. However, it will also be known to one skilled-in-the-art that the opticalcontrast generated by said Guest-Host liquid crystal materials will in general be relativelylow and not suitable for use in switchable sunglasses that are required to provide a highlevel of protection from bright sunlight when switched to the darkest available optical state.

Summary of Invention An object of the present invention is to provide switchable sunglasses withreflective lenses. A further object of the present invention is to provide switchablesunglasses that offer both a high level of optical contrast as well as a high level of opticaltransmission when said lenses are switched to their highest transmissive state.

The invention is based on the insight that by placing a liquid crystal elementcomprising of twisted nematic liquid crystal materials in-between a first and secondabsorptive linear polarizer and with there also being an additional reflective linearpolarizer placed in close proXimity to said first absorptive linear polarizer with saidreflective linear polarizer and said first absorptive linear polarizer being aligned mutuallyparallel, then said liquid crystal element according to the present invention can bearranged to possess both a high level of reflectance when viewed from the front in orderto provide the desirable aesthetic characteristics, as well as a low level of reflectance forlight incident on the back surface in order to reduce the occurrence of glare. In addition tothis, said liquid crystal element according to the present invention will possess both ahigh level of optical contrast as well as having a high level of optical transmission when said liquid crystal element is switched to the highest transmissive state.

Page 4/12 Crystal Vision Sweden ABOur ref: 1936-5 This enables sWitchable sunglasses to be developed that possess a highlyreflective lens When vieWed from the front, but that also simultaneously reduces theoccurrence of glare arising due to the reflection of light from the back surface of said lensthereof. Additionally, said sunglasses according to the present invention Will also possessboth a high level of protection When sWitched to the darkest available state as Well ashaving a higher level of optical transmission When sWitched to the highest transmissive state as compared to sunglasses based on other prior-art technologies.

Brief description of the draWingsThe present invention may be better understood and its objectives and advantagesWill become apparent to one skilled-in-the-art by reference to the accompanying draWings, Wherein like reference numerals refer to like elements in several of the figures.

FIG. l: Typical design of sWitchable sunglasses according to the prior-art.

FIG. 2: Typical design of an electronic optical lens according to the prior-art.

FIG. 3: Reflective optical lens according to a first embodiment of the present invention.FIG. 4: Reflective optical lens according to a second embodiment of the present invention.

Description of the embodiments Fig. l shows the typical design of sWitchable sunglasses according to the prior-art.SWitchable sunglasses are defined as being electronically sWitchable sunglasses that canchange their optical transmission in response to the ambient illumination conditions.Here, there is provided a first and second electronic optical lens l, 2 held in position by afront-fascia 3. There is also provided a left-temple 4 and a right-temple 5 mechanicallyconnected to said front-fascia via first and second hinge elements 6, 7 thereof.Additionally, there is also provided a controlling electronics 8 together With a light-sensor9 and said controlling electronics is arranged to provide suitable voltage-signals (not shown) to said electronic optical lenses in response to the ambient illumination levels Page 5/12 Crystal Vision Sweden ABOur ref: 1936-5 measured by said light-sensor thereof in order to switch said electronic optical lenses tothe required optical state according to the prior-art.

Further details for said electronic optical lenses 1, 2 are shown in fig. 2 accordingto the state-of-the-art. Here, each of said electronic optical lenses comprises a liquidcrystal element 10 placed in-between a first absorptive linear polarizer 11 and a secondabsorptive linear polarizer 12.

Absorptive linear polarizers are known-to-the-art and typically comprise of thinplastic sheets of material containing absorptive chemicals that are arranged to absorbspecific components of linear polarization for light passing through said material. Thisresults in the transrr1itted light becoming devoid of said specific absorbed linearpolarization components, thus said transmitted light becomes linearly polarized.Moreover, the aXis of the electrical-field Vector for the linear polarization state of saidtransmitted light is defined as being the transmission aXis for said absorptive linearpolarizer thereof. Suitable absorptive chemicals typically comprise of either iodine-typechemicals or alternatively dye-type chemicals according to the state-of-the-art.

Furthermore, the liquid crystal element 10 composing each of said electronicoptical lenses 1, 2 typically comprises of twisted nematic liquid crystal materials (notshown) bound in-between two mutually parallel substrates (not shown). Furthermore, theinner-surfaces of each of said substrates may additionally be coated with a transparentconducting electrode (not shown) such as indium-doped tin oXide (ITO) or otherwise.The surfaces of each of said electrodes may additionally be coated with an alignmentlayer (not shown) such as uniaXially rubbed polyimide or otherwise according to theprior-art.

It will also be known to one skilled-in-the-art that said twisted nematic liquidcrystal materials may be switched between the homeotropic and homogeneous texturesVia application of suitable Voltage-signals to said transparent conducting electrodesthereof. Furthermore, said liquid crystal elements can for example be arranged to be in afirst optical state possessing a high level of transmission when said twisted nematic liquidcrystal materials are switched to said homogeneous teXture, and a second optical statepossessing a low level of optical transmission when said twisted nematic liquid crystal materials are instead switched to said homeotropic teXture thereof.

Page 6/12 Crystal Vision Sweden ABOur ref: 1936-5 However, although the aforementioned technology according to the prior-artprovides an electronic optical lens that can be switched between at least two differentoptical states via application of suitable voltage-signals, it will be understood by oneskilled-in-the-art that said electronic optical lens will be neutral- grey in coloration andalso possess a low level of optical reflectance when viewed from both the front and backsurfaces.

However, when designing switchable sunglasses and other similar products it isoften desirable for the optical lenses to instead appear highly reflective when viewedfrom the front in order to provide the required aesthetic characteristics (i.e. mirrorsunglasses). Moreover, it will be known to one skilled-in-the-art that this may beachieved by adding an additional serr1i-reflective coating to the front surface of saidoptical lens thereof according to the prior-art. However, although this will significantlyincrease the reflectance from the front surface, it will also result in there being acorresponding reduction in the overall optical transmission of said optical lens, therebylirniting the maximum optical transmission through said lens thereof. Additionally, it willalso be understood by one skilled-in-the-art that the presence of said serni-reflectivecoating will also increase the quantity of light being reflected from the back surfacetowards the user”s eyes, thereby resulting in an unwanted increase in the amount of glare.Optical glare occurs when light coming from behind the user”s head is reflected by theback surface of the optical lens into the user”s eye and results in there being anundesirable reduction of visual clarity.

Fig. 3 shows the design of a reflective optical lens according to a firstembodiment of the present invention that possesses both a high level of reflectance whenviewed from the front in order to provide for good aesthetic characteristics (i.e. reflectivelenses), as well as a low level of reflectance from the back surface thereby reducing theoccurrence of glare. Furthermore, said reflective optical lens according to the presentinvention will possess both a high level of optical contrast as well as having a higherlevel of optical transmission when switched to the highest transmissive state as comparedto that for other prior-art technologies.

Here, a liquid crystal element 10 comprising of twisted nematic liquid crystal materials (not shown) is placed in-between a first absorptive linear polarizer ll located Page 7/12 Crystal Vision Sweden ABOur ref: 1936-5 on the front surface and a second absorptive linear polarizer 12 located on the backsurface. Moreover, in a first preferred embodiment of the present invention thetransmission axes for said first and second absorptive linear polarizers 11, 12 arearranged to be predominantly mutually perpendicular. There is also provided a reflectivelinear polarizer 13 located in close proXimity to said first absorptive linear polarizer 11and arranged such that the transmission aXes for said reflective linear polarizer and saidfirst absorptive linear polarizer are predorninantly aligned mutually parallel.

Reflective linear polarizers are knoWn-to-the-art and are typically designed toreflect a first component of linear polarization Whilst simultaneously transmitting asecond component of linear polarization, Wherein said first and second linear polarizationcomponents are predorninantly mutually orthogonal. Furthermore, the axis of theelectrical-field Vector for said second component of linear polarization transmitted bysaid reflective linear polarizer is defined as being the transmission aXis for said reflectivelinear polarizer thereof. Typical reflective linear polarizers may or may not comprise of aWire-Grid-Polarizer (WGP) or alternatively a stack of multi-layer birefringent coatingsaccording to the prior-art.

It Will be understood by one skilled-in-the-art that When unpolarized light (i.e.randomly polarized light) is incident on the front surface of said reflective optical lensaccording to the present invention Wherein said front surface is defined as being thesurface Where said reflective linear polarizer 13 is located, then approximately 50% of theincident light Will be reflected and the remaining 50% of said incident light Will betransrr1itted through said reflective linear polarizer thereof. This therefore provides ahighly reflective optical lens With desirable aesthetic characteristics When Viewed fromthe front in accordance With the objectives of the present invention.

Furthermore, since the transmission aXes for both said reflective linear polarizer13 and said first absorptive linear polarizer 11 are mutually aligned predominantlyparallel in accordance With the teachings of the present invention, then it Will beunderstood by one skilled-in-the-art that the light transmitted through said reflectivelinear polarizer 13 Will thereafter also pass through said first absorptive linear polarizer 11 Without there being any further significant optical attenuation (i.e. light absorption).

Page 8/12 Crystal Vision Sweden ABOur ref: 1936-5 Thereafter, said light will pass through said liquid crystal element 10 comprisingof twisted nematic liquid crystal materials (not shown). Moreover, when said twistednematic liquid crystal materials are switched to said homogeneous teXture, then saidtwisted nematic liquid crystal materials can be arranged to rotate the linear polarizationstate of light passing through said liquid crystal element thereof. In this case, it will beunderstood by one skilled-in-the-art that the light reaching said second absorptive linearpolarizer 12 may be arranged to be linearly polarized with its electrical-field vectoraligned parallel with the transmission aXis for said second absorptive linear polarizerthereof. Furthermore, in this case said light will then pass through said second absorptivelinear polarizer 12 without there being any further significant optical attenuation.Consequently, said reflective optical lens according to the present invention will thuspossess a high level of optical transmission when said twisted nematic liquid crystalmaterials are switched to said homogeneous teXture thereof.

However, if instead said twisted nematic liquid crystal materials are switched tosaid homeotropic teXture, then in this case the linear polarization state of light passingthrough said liquid crystal element 10 will no longer be rotated. Therefore, upon reachingsaid second absorptive linear polarizer 12 said light will still be linearly polarized with itselectrical-field vector aligned perpendicular to the transmission aXis for said secondabsorptive linear polarizer thereof. This will result in said light being strongly attenuatedby said second absorptive linear polarizer, hence said reflective optical lens according tothe present invention will in this case possess a low level of optical transmission whensaid twisted nematic liquid crystal materials are switched to said homeotropic teXture.

Furthermore, when light is incident on the back surface of said reflective opticallens wherein said back surface is defined as being the surface where said secondabsorptive linear polarizer 12 is located, then it will be understood by one skilled-in-the-art that said reflective optical lens as disclosed herein will possess a low level ofreflectance when said twisted nematic liquid crystal materials are switched to either oneof said homogeneous or homeotropic textures thereof. Therefore, said reflective opticallens according to the present invention will possess a low level of reflectance from theback surface at all times irrespective of the teXture of said twisted nematic liquid crystal materials, thereby reducing the occurrence of glare.

Page 9/12 Crystal Vision Sweden ABOur ref: 1936-5 It will also be understood by one skilled-in-the-art that should said first absorptivelinear polarizer 11 be removed, then said reflective optical lens would in this specific casepossess a high level of optical reflectance for light incident on the back surface when saidtwisted nematic liquid crystal materials are switched to said homeotropic texture thereof,hence said reflective lens would in this case generate a correspondingly high level ofunwanted glare. On the other hand, should said reflective linear polarizer 13 be removed,then in this specific case said reflective optical lens would no longer possess a high levelof reflectance for light incident on the front surface of said reflective optical lens thereof,hence said reflective optical lens would in this case not provide the required aestheticcharacteristics.

Therefore, the presence of both said reflective linear polarizer 13 and said firstabsorptive linear polarizer 11 are essential features of the invention as disclosed herein.Furthermore, said first absorptive linear polarizer 11 is mandated to be located in-between said reflective linear polarizer 13 and said liquid crystal element 10 in order toachieve the objectives of the present invention. Additionally, the transmission aXes forsaid reflective linear polarizer 13 and said first absorptive linear polarizer 11 shouldpreferably be aligned predominantly mutually parallel in order to ensure that both a highlevel of optical transmission is maintained when said reflective optical lens is switched tothe highest transmissive state, as well as there being a low level of reflection from theback surface thereby reducing the occurrence of glare. However, in practice it will beunderstood by one skilled-in-the-art that both a satisfactory level of optical transmissionas well as a satisfactory low level of glare can be achieved as long as the angle betweenthe transmission aXes for said reflective linear polarizer 13 and said first absorptive linearpolarizer 11 is arranged to be in the interval between 0 degrees and 30 degrees, and morepreferably in the interval between 0 degrees and 10 degrees respectively.

Although the transmission aXes for said first and second absorptive linearpolarizers 11, 12 should preferably be aligned predominantly mutually perpendicular inorder to maXimize the level of darkness (i.e. contrast) when said reflective optical lens isswitched to the darkest optical state according to the first preferred embodiment of thepresent invention, it will be understood that in other embodiments the angle between the transmission aXes for said first and second absorptive linear polarizers may alternatively Page 10/12 Crystal Vision Sweden ABOur ref: 1936-5 be arranged to be in the interval between 60 degrees and 90 degrees respectively in orderto provide satisfactory performance that is suitable for a commercial product.

Fig. 4 shows a second preferred embodiment of the present invention. Here, thetransmission aXes for said first absorptive linear polarizer 11 located on the front surfaceand said second absorptive linear polarizer 12 located on the back surface are arranged tobe predorninantly mutually parallel. Furthermore, there is also provided a reflective linearpolarizer 13 placed in close proXimity to said first absorptive linear polarizer 11 andarranged such that the transmission axes for said reflective linear polarizer and said firstabsorptive linear polarizer are predominantly aligned mutually parallel. There is alsoprovided a liquid crystal element 10 comprising of twisted nematic liquid crystalmaterials (not shown) and arranged to rotate the linear polarization state of light passingthrough said liquid crystal element when said twisted nematic liquid crystal materials areswitched to said homogeneous teXture thereof.

It will be understood by one skilled-in-the-art that said reflective optical lensaccording to the second preferred embodiment of the present invention will possess botha high level of reflectance when viewed from the front thereby providing for goodaesthetic characteristics, whilst also simultaneously possessing a low level of reflectancefor light incident on the back surface thereby reducing the level of glare in accordancewith the objectives of the present invention.

Furthermore, although the transmission axes for said first absorptive linearpolarizer 11 and said second absorptive linear polarizer 12 should preferably be alignedpredorninantly mutually parallel in order to maximize the level of optical contrastaccording to the second preferred embodiment of the present invention, it will beunderstood by one skilled-in-the-art that in other embodiments the angle between thetransmission axes for said first and second absorptive linear polarizers 11, 12 mayalternatively be arranged to be in the interval between 0 degrees and 30 degreesrespectively in order to provide the desired level of darkness when said reflective opticallens is switched to the darkest optical state.

Additionally, although the transmission axes for said reflective linear polarizer 13and said first absorptive linear polarizer 11 should preferably be aligned mutually parallel according to the second preferred embodiment of the present invention, it will be Page 11/12 Crystal Vision Sweden ABOur ref: 1936-5 understood by one skilled-in-the-art that in other embodiments the angle between thetransmission aXes for said reflective linear polarizer and said first absorptive linearpolarizer may be in the interval between 0 degrees and 30 degrees, and more preferablyin the interVal between 0 degrees and 10 degrees respectively.

A further embodiment of the present invention is that at least one of said first andsecond absorptive linear polarizers 11, 12 is bonded to the surface of said liquid crystalelement 10 using an adhesive material. Additionally, it is further disclosed that in anotherembodiment said reflective linear polarizer 13 is bonded to the surface of said firstabsorptive linear polarizer 11 using an adhesive material.

Whilst preferred embodiments of the present invention have been shown anddescribed herein, Various modifications may be made thereto without departing from theinVentiVe ideas of the present invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

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Claims (11)

Crystal Vision Sweden ABOur ref: 1936-5 Claims I/we claim:

1. Switchable sunglasses comprising at least one liquid crystal element 10 that can beswitched between at least a first and second optical state Via application of an electrical-signal, and with said liquid crystal element being configured to rotate the plane of linearpolarization when said liquid crystal element is switched to at least one of said first andsecond optical states, and with there being a first absorptive linear polarizer 11 located inclose proXimity to a first surface of said liquid crystal element and a second absorptivelinear polarizer 12 being located in close proXimity to a second surface of said liquidcrystal element with said first and second surfaces being on mutually opposite sides ofsaid liquid crystal element thereof, and with there also being a reflective linear polarizer13 placed in close proXimity to said first absorptive linear polarizer and with said firstabsorptive linear polarizer being located in-between said reflective linear polarizer andsaid liquid crystal element, wherein said first absorptive linear polarizer and saidreflective linear polarizer are mutually aligned such that the angle between thetransmission-axis for said first absorptive linear polarizer and the transmission-axis for said reflective linear polarizer is in the interval between 0 degrees and 30 degrees.

2. Switchable sunglasses according to claim 1 wherein the angle between thetransmission-axis for said first absorptive linear polarizer and the transmission-axis for said reflective linear polarizer is in the interVal between 0 degrees and 10 degrees.

3. Switchable sunglasses according to claim 2 wherein the transmission-axis for said firstabsorptive linear polarizer and the transmission-axis for said reflective linear polarizer are mutually aligned predominantly parallel.

4. Switchable sunglasses according to claim 1 wherein the angle between the transmission-axis for said first absorptive linear polarizer and the transmission-axis for Page 1/3 Crystal Vision Sweden ABOur ref: 1936-5 said second absorptive linear polarizer is in the interVal between 0 degrees and 30 degrees.

5. Switchable sunglasses according to claim 4 wherein the transrnission-axis for said firstabsorptive linear polarizer and the transrnission-axis for said second absorptive linear polarizer are predominantly aligned mutually parallel.

6. Switchable sunglasses according to claim 1 wherein the angle between thetransmission-axis for said first absorptive linear polarizer and the transrnission-axis forsaid second absorptive linear polarizer is in the interval between 60 degrees and 90 degrees.

7. Switchable sunglasses according to claim 6 wherein the transrnission-axis for said firstabsorptive linear polarizer and the transrnission-axis for said second absorptive linear polarizer are predominantly aligned mutually perpendicular.

8. Switchable sunglasses according to claim 1 wherein said reflective linear polarizercomprises at least one of a wire-grid polarizer and a stack of multi-layer birefringent coatings.

9. Switchable sunglasses according to claim 1 wherein said first absorptive linearpolarizer comprises at least one of an iodine-type linear polarizer and a dye-type linear polarizer.

10. Switchable sunglasses according to claim 1 wherein at least one of said first andsecond absorptive linear polarizers is bonded using an adhesive to at least one of said surfaces of said liquid crystal element. Page 2/3 Crystal Vision Sweden ABOur ref: 1936-5

11. Switchable sunglasses according to claim 1 Wherein said reflective linear polarizer is bonded using an adhesive to the surface of said first absorptive linear polarizer. Page 3/3