GB2416179A - Fabric for a blackout blind - Google Patents

Abstract

A fabric for a blackout blind comprises a planar substrate comprising a plurality of parallel elongate elements bound to a sheet of blackout material. The elongate elements are formed from wood, bamboo, grasses, jute, paper, cardboard, synthetic imitations of these materials, plastic strips or mixtures thereof. The blackout material may be a plastics material. The substrate may be bound to the blackout material by lamination. The elongate elements may be arranged parallel and adjacent to one another and may be connected by transverse binding elements. The elongate elements may be woven with the transverse elements which may be provided by other of the elongate elements. The invention also extends to a method of forming such a fabric by laminating a plastics material to a planar blind substrate and to a blind made using such a fabric.

Description

BLIND FABRIC

The present invention relates to an improved fabric for use in a window blind and a method of manufacturing the fabric. Further, the present invention relates to a window blind comprising the fabric.

The term 'window' is used herein as a convenient reference with the understanding that the invention may also be used as a covering for doors or other architectural openings.

It is often desirable to use a woven natural effect product as a window covering. Blinds manufactured for example from wood weave, bamboo slats, papers, cardboards, woven grasses, jute, synthetic imitations of these materials, or plastics strips are often chosen for their aesthetic properties, in particular in outdoor and conservatory settings. However, the nature of the substrates used causes the weave to be more open than conventional woven or other textile fabrics, allowing greater light and heat transmission. This can be undesirable as it can lead to a blind with poor solar properties, and a difficulty in blocking out light entering the building. In addition there can be a user perception that there is a lack of privacy in the living or working space.

The present invention attempts to overcome this problem by providing a blind fabric with the aesthetic, tactile, and commercial properties of woven natural effect products, but with reduced heat and light transmission and an improved opacity.

In accordance with a first aspect of the invention, there is provided a woven natural effect product for use in window blind systems, the fabric comprising a substantially planar blind substrate comprising a plurality of parallel elongate elements wherein the elongate elements are formed from wood, bamboo, grasses, jute, paper, cardboard, synthetic imitations of these materials and/or plastics strips; and wherein the blind substrate is bound to a sheet of blackout material.

This combination of a natural weave substrate with a blackout backing provides an aesthetically pleasing fabric, with enhanced light transmission and solar properties and improved privacy.

Window coverings comprising woven and non-woven fabrics with blackout backings are known. However, these do not provide the desirable natural aesthetic, tactile and commercial properties of woven natural effect products which is often preferred.

The elongate elements may be arranged such that there are two sets of elongate elements wherein the first set forms the warp strands of the natural weave IS substrate and the second set is woven with the first set of elongate elements such that they form the weft strands of the fabric. The weft strands will typically be substantially perpendicular to the warp strands.

Alternatively, the elongate elements may be arranged parallel and adjacent to the neighbouring elongate element and connected by at least one transverse binding element. They may preferably be substantially parallel in use. It is possible that the elongate elements will form the warp strands, and the binding elements the weft strands of the blind, however, preferably, the elongate elements will form the weft strands and the transverse binding elements the warp strands. The transverse binding elements will preferably be substantially perpendicular to the elongate elements.

The elongate elements may be formed from any suitable natural or synthetic material, in particular, wood, bamboo, grasses, jute, paper, cardboard, synthetic imitations of these materials, plastics strips or mixtures thereof.

In addition, the elongate elements may be formed from two or more of the above substrates. Preferably the elongate elements will be formed from wood, paper, a synthetic imitation of wood or paper, or mixtures thereof. Most preferably, the elongate elements will be formed from wood.

Where used, the synthetic imitation of these materials will include, but not be limited to, plastics materials which have been treated to mimic the appearance of a natural fibre. The treatment may, for example, be crimping or twisting of the synthetic fibres. The synthetic fibre may be any plastics fibre commonly used in the fabrics industry, although typically the fibres will be acrylic or polyester.

T he blind substrate is bound to a blackout material. In the present invention the term 'blackout' is used to refer to any material through which the transmission of light, heat and other radiation is substantially impaired. More specifically, a blackout material can preferably be quantitatively defined as a material which has an optical transmission in the visible wavelengths of 15% or less, preferably 10% or less, more preferably 5% or less, even more preferably less than 4%, less than 3%, less than 2%, less than 1%, less than 0.1%, less than 0.01%, less than 0.001% and less than 0.0001%. Most preferably no or substantially no light will be transmitted through the blackout material and the blackout material will pass the visual assessment test for blackout materials

outlined on in the specification.

Materials considered to be suitable for use as the blackout material of the invention include woven and non-woven synthetic and natural fabrics, for example, knitted, spun bonded or melt bonded materials; plastics materials, flexible metal sheets, paper and mixtures thereof.

The blackout material may be, as appropriate, coloured or non-coloured and/or resistant to fading. Further the blackout material may be coated with stain resistant or flame retardant finishes.

The blackout material may be bound to the blind substrate by stitching, adhesive, lamination or a combination of these methods.

Preferably, the blackout material is a plastics material; more preferably, the blind substrate is bound to the sheet of blackout plastics material by lamination; conveniently it may be heat laminated. Most preferably, substantially all of the blind substrate is bound by lamination to the blackout material.

In particular with blackout materials which are plastics materials, it has been found that some materials do not provide acceptable bonding to the blind substrate, or that bubbling of the plastics material may occur. Further, even when a satisfactory degree of bonding could be achieved, the resultant fabrics produced were undesirably stiff and inflexible or did not provide sufficient light blockage.

When the blackout material is a plastics material, plastics materials for use in the present invention may comprise one layer of plastic only. The preferred plastics material comprises at least two layers of plastics film. Most preferably there are three layers of plastics fihn, however as many as six plastics layers may preferably be used in the plastics material of the invention. Typically, but not exclusively, the plastics layers will be joined by lamination, in particular by flat-bed lamination. It is also possible that the 'plastics material' may include one or more layers of a non-plastics material, for example a metallic inner, outer or internal layer to reflect radiation away from the blind.

In a particularly preferred embodiment, the blackout material is a three layer laminated material which can be heat laminated to the blind substrate. For consistency of terminology herein, in any multilayer blackout material referred to, the 'inner' layer will be that closest to or directly bound to the blind substrate, whilst the 'outer' layer will be that furthest from the blind substrate, typically facing outwards and away from the blind substrate. For the avoidance of doubt, the 'internal' layer or layers, where present, will be disposed between the inner and the outer layer.

Any different layers of the blackout material may each be the same colour or different colours. Further, the inner layer and the outer layer of the blackout material may be coloured to match the blind substrate, or to contrast with the blind substrate. It is preferred that at least one of the layers is black; most preferably one of the internal layers (e.g. the middle layer in a three layer material) is black, and provides the blind with the maximum possible blackout performance. It is preferred that the inner layer is white. It is also preferred that the outer layer is white. The one or more internal layers may be coloured to match the inner or outer layers, however, it is preferred that at least one of the internal layers is black. Where the internal layer or layers is black, the sheet of blackout material may act to prevent substantially all the light passing through the blind.

In a further preferred embodiment the blackout material is a three layer laminated material having a middle layer which is black, the inner layer being attachable to the blind substrate by heat lamination and comprising an inner layer which has a lower melting point than the outer layer.

It is generally preferred that the inner layer is a low melting plastics material which becomes tacky around it's melting point. Preferably the inner layer has a melting point (Kofler bank test) in the range 60 C - I 50 C, more preferably in the range 70 C - 140 C, most preferably in the range 70 C - 130 C.

The inner layer may comprise Acrylic Polymers (e.g. Ethylene Ethyl Acrylate (EEA), Ethylene Methyl Acrylate (EMA), Ethylene Butyl Acrylate (EBA)), Ethylene Vinyl Acetate (EVA), Polyurethane (PU), Thermoplastic Polyurethane (TPU), Copolyester (CoPES), Copolyamide (CoPA), graft Polyolefin (graft PO) and their blends/mechanical compounds, more preferably the inner layer will comprise Acrylic Polymers, EVA, graft Polyolefin and their blends, most preferably the inner layer will comprise graft Polyolefn and/or blends with EVA and Acrylic Polymers.

The outer layer of any laminate blackout material may conveniently be a plastics layer that melts at a higher temperature than the inner layer. In addition, the outer layer will typically comprise a plastics material layer which does not become tacky on heating, especially at the temperature which may be used to bind the inner layer of the laminate to the binding substrate.

Alternatively, additives may be present to prevent the outer layer from becoming tacky at or around it's melting point in a manner known to those skilled in the art. Preferably the outer layer has a melting point (Kofler bank test) of at least 130 C, more preferably in the range 130 C - 210 C, most preferably in the range 130 C - 180 C.

Preferably, the outer layer comprises Polyurethane (Cross-linked, Thermoplastics (e.g. TPU)), Polyesters (e.g. PET, PBT, Copolymers of Polyesters), Polyamide (Polyamide 6 (PA 6), Polyamide 6,6 (PA 6,6) and Copolymers of Polyamides), Polypropylenes (PP) such as Omo-PP and CoPP and blends of the above polymers. More preferably the outer layer comprises Thermoplastic Polyurethane, CoPolyesters (e.g. CoPBT), Polypropylene, blends of Thermoplastic Polyurethane and CoPBT, most preferably the outer layer comprises thermoplastic Polyurethane and/or Polypropylene.

The internal layer or layers may comprise a plastic or plastics with a melting point (Kofler bank test) of at least 130 C, more preferably in the range 130 C - 210 C, most preferably in the range 130 C - 180 C. Preferably, the internal layer or layers comprises plastics materials based on Polyurethane (Crosslinked, Thermoplastics (e.g. TPI1)), Polyesters (PET, PBT, Copolymers of Polyesters), Polyamide (PA 6, PA 6,6 and Copolymers of Polyamides), Polypropylene (Omo-PP and CoPP) and blends of the above polymers, more preferably the internal layer or layers comprises Thermoplastic Polyurethane, CoPolyesters (e.g. CoPBT), Polypropylene, blends of 1PU and CoPBT, most preferably l hermoplastic Polyurethane and/or Polypropylene. Even more preferably, there is one internal layer. ] O

Most preferably, the plastics material will comprise three layers wherein the inner layer is a graft Polyolefin or EVA containing layer with a melting point in the range 70 C - I 10 C, the internal layer is black polypropylene and has a melting point in the range 130 C - 170 C, and the outer layer is white polypropylene and has a melting point in the range 130 C - 170 C.

The lamination of this three-layer plastics material to a woven natural effect blind substrate produces a fabric which does not fray, is easy to cut and shape as required, has excellent solar properties, prevents substantially all light transmission, has good flexibility and is aesthetically pleasing.

If the blind substrate and the blackout material are to be bound together by lamination, they will preferably be laminated using a flat bed laminator.

The laminator comprises a first set of heaters, and these will be heated to a temperature in the range 80 C - 200 C, more preferably in the range 120 C C, most preferably in the range 135 C - 145 C. In addition to the first set of heaters, the laminator will comprise a second set of heaters heated preferably to a temperature in the range 80 C - 200 C, preferably in the range 130 C - 170 C, most preferably in the range 145 C - 155 C. If the laminator is a Cat bed laminator, the first set of heaters will be the top heaters, and the second set of heaters will be the base or 'bottom' heaters.

Preferably the roller pressure of the laminator is in the range 1 N/cm2, more preferably in the range 2 - 8 N/cm2, even more preferably 4 6 N/cm2.

In a preferred method of manufacture, a flat bed laminator is used. In this method the laminator is loaded so that a layer of cushioning nonwoven substrate is between the laminator and the plastics material. This non-woven substrate both cushions the fabric, and assists in the control and even distribution of the heat. This method of lamination may also be used in non- flat bed laminating machines.

In accordance with second aspect of the invention, there is provided a window blind including the fabric of the present invention. The fabric may be used in any fabric window blind assembly including, but not limited to, Roman blinds, roller blinds, panel blinds, pleated blinds and vertical louver blinds. The construction and operation of blinds of this type would be well known to the person skilled in the art of blind manufacture.

It is particularly envisaged that the fabric is used in Roman blinds or roller blinds.

EXAMPLES

One flat bed laminator which may be used to produce the fabric is a Meyer_ RPS-K1800. Where a Meyer_ RPS-K1800 is used, the belt system will be a glassware coated PTFE belt system.

The fabric may be produced by loading the machine with the blind substrate directly onto the laminator belt. In this example, the blind substrate comprises a plurality of parallel wooden elongate elements bound together with transverse cord bindings at approximately 20mm intervals along the length of the elongate element. The elongate elements have a cross-section of 5mm x 2mm.

A three layer film is loaded above the blind, the composition of a three layer film falling within the scope of the invention is as follows: Layer Colour Melting point Composition Inner white 70 C - I 10 C EVA graft MAH Middle blackout 130 C- 170 C Polypropylene Outer white 130 C- 170 C Polypropylene EVA = ethylene vinyl acetate MAH = maleica acrylic Alternative film compositions were investigated, and it was found that many films did not adhere to the blind substrate sufficiently. A comparative example of a film which does not fall within the scope of the invention is as follows: Layer Colour Melting point Composition Inner white 100 C - 1 10 C Polyethylene Middle blackout 90 C- 100 C Polyethylene Outer white 150 C - 160 C Polypropylene This film represents a particularly common multi-layer laminate film which is well known in the art. However, when used as outlined above delamination is observed between the outer and middle layers, and the blackout effect is not observed as the middle layer melts during the lamination process. Further, binding to the blind substrate is poor.

A cushioning non-woven substrate base layer is loaded on top of the threelayer film to assist in heat control and to cushion the composite during lamination.

The machine parameters of the Meyer_ RPS-K 1800 are as follows: Top heaters 140 C Base heaters 150 C Roller pressure 5.0 N/cm2 Roller height + 1.4 mm Nip height - 0.5 mm Belt speed + 4.0 m/min Determination of whether a material is a 'blackout material' The function of the blackout material is to conceal, or obfuscate one side from the other. Assuming that on one side of the material there is a source of light (natural or artificial) the aim of the material is to prevent the source of light being seen on the other side. The blackout effect can be partial or total. The same material can have a total or partial blackout effect, depending on the intensity of the source of light.

Two tests are used to determine whether a material is a 'blackout material'.

Visual Assessment: pass or fail test A 9000 lux light source is shone through a circular fabric sample of area 3 l4 cm2 (radius ot' 10 cm). The light source emanates from a box with a perspex upper surface on which the fabric sample is placed. The fabric is visually assessed in a darkened room for light transmission, pin holes of light, or a halo effect. If any of these features are observed, the fabric fails the blackout test.

Spectrophotometry: quantitative measurement of 'blackout' A Lambda 900 W/Vis/NIR spectrophotometer is used to determine the solar and optical properties of the fabric in the wavelength range 200 - 2500 nm.

The solar reflectance, optical transmittance and thermal emittance of the fabric can be determined as follows.

The solar reflectance, Ps, of a sample is determined as follows. The inner wall of the 60 mm diameter integrating sphere of the spectrophotometer is coated with a white highly diffusing barium sulphate coating and the sphere is calibrated using an NPL traceable reflectance standard (CP85). A photomultiplier is used as a detector for measurements made in the ultraviolet and visible regions of the electromagnetic spectrum and a lead sulphide detector for measurements in the near infrared. The detector switching wavelength is 850 nm ( 1 rim = 1 Ohm).

The spectral reflectance curve for the sample is measured over the wavelength range 300 non - 2300 nm (0.3 lam - 2.3 rim). The measured monochromatic reflectance, p;, may be read directly from the spectral reflectance curve or obtained as a digital readout from the spectrophotometer display.

The solar reflectance, Ps, may be calculated from the expression: |PA GA dA P = 300 ( I) IG] do where IG;dA is the solar irradiance evaluated using air mass 2 data of Parry Moon ( 1).

Equation (1) is evaluated using a selected ordinate method of integration (2).

The area under the G curve is divided into 20 equal energy bands. An average wavelength, Hi, is selected for each band. The solar reflectance, Ps, is then computed as the average of the sum of the ps values at the i wavelengths, i.e. 1 l-20 PS 20 PA (2) The optical transmittance, To, of a sample is evaluated by reprocessing the data obtained for the solar transmittance measurement. The values of monochromatic transmittance are weighted according to the response of the human eye at the wavelength using a weighting factor, wf,.

rAO = 14'fAr; where rho is the optically-weighted monochromatic transmittance. The values of p were obtained from Kurt Nassau (Ref. 3). The value of optical transmittance is then taken as the mean of the values of r;O. The optical reflectance is calculated from the measured data in a similar manner.

The broad band thermal emittance is determined from reflectance measurements made using a differential thermopile which employs two silvered and two blackened detector elements. The infrared source temperature is 82 C corresponding to a black body distribution peaking at 8163 nm. The differential thermopile detects infrared radiation reflected frotn the sample surface. The detector output voltage correlates linearly with sample emittance and is measured using a high impedance digital voltmeter having 0.001 mV resolution. Calibration of the thermopile against surfaces of known thermal emittance enables the thermal emittance for the sample to be deduced. The standard samples used, calibrated by NPL, were ref. Nos. 8/85 and 9/SS.

For the purposes of the subject invention a fabric is regarded as a blackout material where the optical transmittance is 15 % or less at visible wavelengths.

Claims (8)

1. A fabric for use in window blind systems, the fabric comprising a substantially planar blind substrate comprising a plurality of parallel elongate elements wherein the elongate elements are formed from wood, bamboo, grasses, jute, paper, cardboard, synthetic imitations of these materials, plastics strips or mixtures thereof; and wherein the blind substrate is bound to a sheet of blackout material.

2. A fabric according to claim 1 wherein the blackout material is a plastics material.

3. A fabric according to claim 2 wherein the blind substrate is bound to the sheet of plastics material by lamination.

4. A fabric according to any preceding claim wherein substantially all of the blind substrate is bound to the sheet of plastics material.

5. A fabric according to any preceding claim, wherein the plurality of elongate elements are arranged parallel and adjacent to the neighbouring elongate element, and are connected by at least one transverse binding elements.

6. A fabric according to claim 5 wherein the binding elements are woven with the elongate elements such that the elongate elements form the weft strands and the binding elements form the warp strands of the blind substrate.

7. A fabric according to any one of claims 1 to 4 wherein the plurality of elongate elements are arranged such that they are woven with other

7. A fabric according to any one of claims l to 4 wherein the plurality of elongate elements are arranged such that they are woven with other elongate elements such that the elongate elements form both the warp strands and the weft strands of the blind substrate.

8. A fabric according to any preceding claim wherein the elongate elements arc formed from two or more of wood, bamboo, grasses, jute, paper, cardboard, synthetic imitations of these materials and/or plastics strips.

9. A fabric according to any preceding claim wherein the elongate elements are wooden strips.

10. A fabric according to any preceding claim wherein the sheet of plastics material comprises a laminate of at least two layers of plastics film.

A fabric according to claim 10 wherein one of the layers of the laminate is black.

12. A fabric according to claim 10 or claim 1 1 wherein the laminate comprises an inner, internal and outer layer of plastics film.

13. A fabric according to claim 12 wherein the sheet of plastics material comprises an internal layer of plastics film which is black.

14. A fabric according to claim 12 or claim 13 wherein the inner layer has a melting point in the range 70 C - 140 C.

15. A fabric according to any one of claims 12 to 14 wherein the inner layer is selected from graft polyolefin (graft PO) ethylene vinyl acetate (EVA) and/or acrylic polymers.

16. A fabric according to any one of claims 12 to 15 wherein the internal layer is selected from Thermoplastic polyurethane (TPU) and/or polypropylene.

5l 7. A fabric according to any one of claims l 2 to 16 wherein the outer layer has a melting point of at least 130 C.

l

8. A fabric according to any one of claims 12 to 17 wherein the outer layer is coloured to match the substantially planar blind substrate.

19. A fabric according to any one of claims 12 to 17 where the outer layer is white.

20. A fabric according to any one of claims 12 to 19 wherein the inner layer 15is white.

21. A fabric according to any one of claims 12 to 20 wherein the outer layer is selected from Thennoplastic polyurethane (TPU) and/or polypropylene.

2022. A fabric according to any preceding claim wherein the blackout material has an optical transmission of 5% or less at visible wavelengths.

23. A method of Conning the fabric of any preceding claim the method comprising the steps of: providing a substantially planar blind substrate 25and a plastics material, laminating the plastics material to the blind substrate under conditions of heat and pressure.

24. A method according to claim 23 wherein lamination occurs on a flat bed laminator.

25. A method according to claim 23 or claim 24 wherein the laminator comprises a first set of heaters at a temperature in the range 120 C 160 C.

26. A method according to any one of claims 23 to 25 wherein the laminator comprises a second set of heaters at a temperature in the range 130 C C.

27. A method according to any one of claims 23 to 26 wherein the laminator includes rollers and the roller pressure is in the range l - 10 N/cm2.

28. A method according to any one of claims 23 to 27 wherein the laminator is loaded with a non-woven cushioning substrate adjacent to the second set of heaters, the sheet of plastics material adjacent to the non- woven substrate and the blind substrate adjacent to the first set of heaters.

29. A window blind made using the fabric of any of claims 1 to 22.

30. A window blind according to claim 29 wherein the blind is one of a Roman blind, roller blind, panel blind, pleated blind or vertical louver blind.

31. A window blind substantially as herein described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows 1. A fabric for use in window blind systems, the fabric comprising a substantially planar blind substrate comprising a plurality of parallel elongate elements wherein the elongate elements are formed from wood, bamboo, grasses, jute, paper, cardboard, synthetic imitations of these materials or mixtures thereof, and wherein the blind substrate is bound to a sheet of blackout material.

2. A fabric according to claim 1 wherein the blackout material is a plastics material.

3. A fabric according to claim 2 wherein the blind substrate is bound to the sheet of plastics;naterial by lamination. lj

4. A fabric according to claim 2 or 3 wherein substantially ail of the blind substrate is bound to the sheet of plastics material.

5. A fabric according to any preceding claim, wherein the plurality of elongate elements are arranged parallel and adjacent to the neighbouring elongate element, and are connected by at least one transverse binding elements.

6. A fabric according to claim S wherein the binding elements are woven with the elongate elements such that the elongate elements form the weft strands and the binding elements form the warp strands of the blind substrate.