Hair detangling device

Abstract

A detangling hair brush 1 comprising an array of bristles 5, wherein a first set of bristles 7 comprise a relatively wide base 7a with an elongate or oval cross section which extends to a relatively n

Description

Technical Field of the Invention The present invention relates to devices for detangling hair. In particular, but not exclusively, the present invention relates to hair brushes. Background to the Invention Many types of devices for styling and / or detangling hair are known in the art. Common examples of these are hair brushes, brush attachments for hair dryers and hot air styling devices with integrated brush heads. There are many types of hair brush known in the art, including various hair brushes having different properties in order to achieve certain effects. GB2447692 discloses a detangling brush having a plurality of bristles each extending from a base to a free end, wherein the bristles have two lengths. All bristles have a circular cross-section, and the longer bristles are arranged such that they bend in the region of the free ends of the shorter bristles. The bristles are arranged in an array such that, for bristles in the centre of the array, each long bristle is placed in the centre of a square defined by four short bristles, and vice versa. The brush according to this patent, assigned to the applicant, has been extremely commercially successful, has spawned numerous copycats, and has been refined, with variants for fine and fragile hair, and thick and curly hair, a compact version and a particularly effective version incorporating a handle, sold under the trade mark “The Ultimate Detangler”. Comparative testing has shown that the ‘Ultimate Detangler’ provides the best detangling performance of the brushes according to GB2447692. Despite the success of the original brushes according to GB2447692 and the refinements thereto, the inventors aim to produce an improved detangling brush capable of improved detangling, less breakage, imparting greater shine to hair, and / or other benefits. Apart from detangling brushes, the applicant has developed hair styling devices for other purposes, for example the brush shown in GB2528574 is designed for use in blow-styling. In this hair brush, each bristle extends from a base to a free end and has a relatively wide first portion towards the base and a relatively narrow second portion towards the free end. The bristles are arranged in offset rows and centre lines of the rows are spaced apart such that part of the base of bristles in one row extends between bristles in an adjacent row and, when viewed perpendicular to the rows, the width of the base of the bristles in one row is such that it partially occludes the space between bristles in an adjacent row. The relatively wide portions have an elongate cross-section with the longitudinal axis parallel to the longitudinal axis of the brush, and in use, the second portion of the bristles penetrate and divide the hair, whilst the first portion enable tension to be applied when it flows between the bristles. These brushes are not intended for detangling hair and do not perform anywhere near as well as the brushes of GB2447692 in detangling hair. Another brush developed by the applicant is disclosed in WO2018 / 069697, which discloses a backcombing brush, specifically designed for use in backcombing. The backcombing brush includes an elongate array of bristles, each bristle extending from a base to a free end where two lengths of bristle are provided. The shorter bristles and the bottom of longer bristles ruck the hair at the base to provide volume, whilst the longer bristles act as a guide to keep the brush head held within the hair section that is being backcombed. The long bristles have a relatively wide first portion, towards the base of the bristle with an elongate cross-section, and a relatively narrow second portion, towards the free end of the bristle. The bristles are arranged such that bristles in one row neither extend between adjacent bristles in an adjacent row nor partially occlude the space between bristles in an adjacent row and with the longitudinal axis of the long bristles perpendicular to the longitudinal axis of the array. Again, this brush, whilst excellent at its purpose (backcombing) is very poor at detangling, trapping and pulling tangled hair. It is an object of the present invention to provide an improved device for detangling hair. Summary of the Invention According to the present invention, there is provided a device according to the appended claims. In a broad sense, the present invention relates to a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end. The bristles may be flexible. At least some of the bristles may have a crosssection having at least three curved sides between the base and free end. The curved sides may be convex. At least some of the bristles may have a cross-section having at least four sides. The at least four sides may be curved. The cross-section may have rounded vertices. At least one side may have a length which is not equal to the length of at least one other side. At least some of the bristles may have a cross-section having three rounded vertices between the base and free end. At least some of the bristles may have a cross-section having only three rounded vertices between the base and free end. At least some of the bristles may comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end. The device may comprise both bristles which comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end and some bristles which have a cross-section having at least three sides and / or at least three (or only three) rounded vertices between the base and free end. The bristles may be arranged in one or more rows, which rows may be arranged along a longitudinal axis of the device. A plurality of bristles may comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end. A plurality of bristles may not comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end(which may not have an elongate cross-section and / or may have a polygonal (optionally rounded polygonal) cross-section, such as a cross-section having three or at least three curved sides and / or at least three or only three (optionally rounded) vertices). Within each row the bristles may alternate between bristles comprising first and second portions and bristles not having a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end. At least some of the bristles comprising a first, relatively wide, elongate portion which extends from the base and a second, relatively narrow, portion which extends from the first portion to the free end may be oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions. At least some of the bristles comprising first and section portions may be oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle to the longitudinal axis of the hair care device. In a first aspect of the present invention, there is provided a device for detangling hair comprising an array of flexible bristles, each flexible bristle extending from a base to a free end; wherein at least some of the flexible bristles have a crosssection having at least three convex curved sides and / or only three rounded vertices between the base and free end. Provision of flexible bristles having at least three curved sides and / or only three rounded vertices between the base and free end allow for separation and division of the hair whilst minimising the force applied thereto (thus minimising the breakage of the hair) as it moves across the surface of the device between the bristles. The curved sides and / or rounded vertices ensure sufficient contact between the bristle and hair to impart a shine upon the hair as it passes the bristles, whilst flexibility allows the bristles to bend and release hair to avoid pulling. In a second aspect of the present invention, there is provided a device for detangling hair comprising an array of flexible bristles, each flexible bristle extending from a base to a free end; wherein at least some of the flexible bristles have a crosssection having at least four sides (optionally being curved sides and the cross-section optionally having rounded vertices); wherein at least one side has a length which is not equal to the length of at least one other side. Provision of flexible bristles with a cross-section having at least four, optionally curved, sides in which at least one side has a length which is not equal to the length of at least one other side provides a novel shape of bristle capable of interacting with hair in a different manner from known bristles. In particular, the requirement that at least one side has a length which is unequal to at least one other side results in a bristle crosssection which acts differently upon hair depending upon which side or corner of the bristle meets the hair. In a third aspect of the present invention, there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein at least some of the bristles comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end, and at least some of the bristles have a cross-section having at least three sides and / or at least three rounded vertices between the base and free end. Provision of bristles with first and second portions enables the second portions to penetrate and divide hair between the bristles when the brush is introduced into the hair (i.e. penetration and division in the direction generally parallel with the direction in which the bristles extend from the device), and the transition of the bristle from the relatively narrow second portion to the wider first portions enables better separation of the hair, by simultaneously moving hair both in the axis in which the bristles extend and in the axis in which the bristle widens. The reduction in cross-sectional area away from the base also leads to bristles which become more flexible away from the base; consequently, the first portions are relatively stiff, particularly at their base whilst the second portions are relatively flexible. Thus, the first portions act as a support allowing for the long bristles to reach deep into the hair. The relatively stiff support means that the bristles bend more closer to the free end, this bending means that they do not get stuck in the hair. Provision of shorter bristles having at least three curved sides and / or at least three rounded vertices between the base and free end allows for additional separation and division of the hair whilst minimising the force applied thereto (thus minimising the breakage of the hair) yet ensuring sufficient contact between the bristle and hair to impart a shine upon the hair as it passes the bristles, and in combination with the wide first portion of the other bristles at the base additionally improves glossiness of hair at the surface. In a fourth aspect of the present invention, there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, wherein: a plurality of bristles comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles do not have a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and within each row the bristles alternate between bristles comprising first and second portions and bristles not having first and second portions. For brevity, this specification uses the expression bristles comprising / having / which have first and second portions to refer to bristles comprising / having / which have first and second portions as defined, i.e. which comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end. Likewise, this specification uses the expression bristles not comprising / having / which do not have first and second portions to refer to bristles which don not comprise first and second portions as defined, i.e. which do not comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end. Provision of bristles which alternate between bristles having a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end and bristles which do not have a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end allows for the hair to interact with both types of bristle, when the device is moved through the hair in use (i.e. at an angle to the longitudinal axis of the device). This ensures all hair being brushed interacts with each type of bristle, maximising the interaction between each type of bristle and the hair. Additionally, the provision of bristles having a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion in addition to bristles which do not have a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end allows for a greater density of bristles in the proximity of the first portions (i.e. near the base). This enables hair to interact more with the bristles in this region, and less towards the second portions where the density of bristles is lower. This reduces the chances of tangles snagging within the brush, whilst allowing maximising the interaction between the hair and bristles near the base (so as to impart a shine upon the hair as it passes the bristles). In a fifth aspect of the present invention, there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein at least some of the bristles comprise a first, relatively wide, elongate portion which extends from the base and a second, relatively narrow, portion which extends from the first portion to the free end wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions. Provision of bristles which have non-alignment between the elongate portions thereof allows for the elongate first portions to differently interact depending on their orientation. Notably, due to the different angles of the base of the elongate first portions can form arrow / funnel type arrangements and separate the hair in different directions whilst the bristles are in contact the hair, whilst the upper part of the elongate first portions and the narrower second portions bend as required (thereby not causing breakage of the hair). In particular, the nature of the elongate first portions means that the bristles with first and second portions preferentially bend along their short axis (i.e. not in the elongate direction), so the non-alignment between the elongate portions enables the bending of the bristles having first and second portions in different directions, further allowing the hair to be spread and dispersed when the bristles are pulled through the hair. In particular in embodiments where the narrower second portions are not elongate, as the bristles are bent over by the hair, the different parts of the bristles will bend at different angles - to be specific, non-elongate second portions will bend in the direction of the force applied by the hair, whereas the elongate portions will bend preferentially along their short axis. As such, the spreading and dispersion of the hair by the elongate parts will be done gently, tempered by the non-elongate second portions bending in the direction of the force applied by the hair. In a sixth aspect of the present invention, there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein the device for detangling hair has a longitudinal axis; at least some of the bristles comprise a first, relatively wide, elongate portion which extends from the base and a second, relatively narrow, portion which extends from the first portion to the free end; and at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle to the longitudinal axis of the hair care device. Provision of bristles with elongate portions arranged at an oblique angle to the longitudinal axis of the device allows for the elongate first portions to interact with the hair differently from the manner in which the relatively narrow second portions interact with the hair. In particular, the elongate first portions will preferentially bend along their short axis, and thereby bend at an oblique angle with respect to the longitudinal axis of the brush. The second narrower portions, on the other hand, may bend at a different angle, as directed by the force of the hair through the bristles. Thus, in particular when the hair care device is pulled through hair perpendicular to the longitudinal axis, the different portions of the bristles may bend in different directions, allowing the hair to be moved sideways when the bristles are pulled through the hair. In particular in embodiments where the narrower second portions are not elongate, as the bristles are bent over by the hair, the different parts of the bristles will bend at different angles - to be specific, non-elongate second portions will bend in the direction of the force applied by the hair, whereas the elongate portions will bend preferentially along their short axis. As such, the sideways movement of the hair by the elongate parts will be done gently, tempered by the non-elongate second portions bending in the direction of the force applied by the hair. Those skilled in the art will appreciate that the expression "relatively" above means relative to the other part described and is not used as a colloquial synonym to "quite". Likewise, when referring to the cross-section of a bristle, those skilled in the art will understand that the cross-section of a bristle is the cross-section when viewed in a plane perpendicular to the length of the bristle, i.e. the transverse cross-section. The expression rounded polygonal when used herein refers to a polygon with rounded vertices and straight sides; a polygon with curved sides, but pointed vertices, or a polygon with both curved sides and rounded vertices. The invention may comprise any combination of the six aspects outlined above. The optional features set out below apply equally to each of the six aspects of the invention - any aspect of the invention may comprise any of the optional features outlined below as required or as desired without necessarily including the features of the specific aspect described beforehand, unless that is incompatible. Devices incorporating any / all of the six aspects of the invention can be used in a method of detangling hair. ‘At least some’ bristles may be a plurality of bristles, approximately or at least one quarter of the bristles, approximately or at least half of the bristles, approximately or at least three quarters of the bristles, or where appropriate and not incompatible, all of the bristles on the device. According to the first aspect of the invention, there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end wherein at least some of the bristles have a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end. The bristles with a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end may be arranged in rows. The rows may be offset. There may be two or more rows of such bristles. The rows may align with a longitudinal axis of the device. The rows may extend along a longitudinal axis of the device. The rows may be parallel to a longitudinal axis of the device. Each bristle may have a rounded tip, to prevent scratching the scalp or hair in use. At least some of the bristles may have a cross-section having only three curved sides and / or only three rounded vertices between the base and free end. In a particular embodiment, at least some of the bristles have a cross-section having only three curved sides and only three rounded vertices between the base and the free end. In another particular embodiment, at least some of the bristles have a crosssection having at least four curved sides. In another particular embodiment, at least some of the bristles have a crosssection having only four curved sides. In another particular embodiment, at least some of the bristles have a crosssection having only four curved sides and only four rounded vertices between the base and the free end. In a particular embodiment, at least some of the bristles have a cross-section having only three convex, curved sides and only three rounded vertices therebetween. In one embodiment at least some of the bristles have a Reuleaux triangle shaped cross-section. The bristles which have a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a taper (optionally a uniform taper) between the base and free end. The bristles with a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a crosssection having at least three convex curved sides and / or only three rounded vertices half-way between the base and free end. Additionally or alternatively, the bristles with a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a cross-section having at least three convex curved sides and / or only three rounded vertices one quarter of the way from the base to the free end. Additionally or alternatively, the bristles with a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a cross-section having at least three convex curved sides and / or only three rounded vertices three quarters of the way from the base to the free end. The bristles with a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a uniformly shaped cross-section between the base and free end. The cross-section of the bristles which have a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may not be elongate. In a particular embodiment, the cross-section of said bristles is generally triangular. The cross-section may be generally that of an equilateral triangle (i.e. the distance between each vertex may be of the same length). Each curved side may be the same length. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices may be oriented such that one of said rounded vertices points in a direction perpendicular to the row of which said bristle forms a part. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices may be oriented in alignment with other bristles which have a cross-section having only three rounded vertices in the same row. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices may be oriented in alignment with other bristles which have a cross-section having only three rounded vertices in an adjacent row. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices may be oriented in opposition to other bristles which have a cross-section having only three rounded vertices in an adjacent row, i.e. so that the vertices of bristles in one row point in the opposite direction to those in an adjacent row. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices may be oriented in alignment with other bristles which have a cross-section having only three rounded vertices in one adjacent row and in opposition to other bristles which have a cross-section having only three rounded vertices in another adjacent row. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices may be oriented in alignment with other bristles which have a cross-section having only three rounded vertices in the same row. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices such that one of said rounded vertices points in a direction perpendicular to the row of which said bristle forms a part. At least some (and optionally all) bristles which have a cross-section having only three rounded vertices may be oriented such that one of said rounded vertices points in a direction perpendicular to a longitudinal axis of the device. At least some bristles which have a cross-section having only three rounded vertices may be oriented such that one of said rounded vertices points towards the rounded vertex of an adjacent bristle having only three rounded vertices. Each bristle having only three rounded vertices other than a bristle having only three rounded vertices which is arranged at the periphery of the array of bristles may be oriented such that one of said rounded vertices points towards the rounded vertex of an adjacent bristle having only three rounded vertices. This arrangement, in which rounded vertices face each other mean that the vertices face in multiple directions. For example, where the bristles have the shape of a generally equilateral triangle, with vertices at 60 degrees from one another, arranging them such that adjacent vertices point towards one another ensures that there are vertices pointing in six directions, each 60 degrees apart. As such, regardless of the direction of brushing, it is highly likely that a rounded vertex will come into contact with a tangle of hair during brushing, splitting the tangle either side of the vertex and thereby detangling. Where the bristles not only have rounded vertices, but also convex curved sides, the hair which is split by the rounded vertex will rub against the curved side, adding shine, compared to a bristle with a rounded vertex but straight sides. The bristles with a cross-section having only three rounded vertices between the base and free end may form rows perpendicular to the longitudinal axis. For example, the bristles with a cross-section having only three rounded vertices between the base and free end may be arranged in a grid and as such each form part of both a longitudinal row (parallel with the longitudinal axis) and a lateral row (perpendicular to the longitudinal axis). Along one or more, or each, lateral row, the alignment of one or more, some, or each bristle having a cross-section having only three rounded vertices between the base and free end may alternate. The bristles with a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in one row may be offset with respect to bristles having a crosssection having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in an adjacent row. As such, the bristles with a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in one longitudinal row may be staggered with respect to a bristles with a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in another row, for example an adjacent row, or each adjacent row. For example, the bristles with a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in one row may be offset such that a bristle which has a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in one row is aligned with the midpoint of two adjacent bristles which have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in an adjacent row. The bristles which have a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a maximum width (excluding any chamfer at the base) of no more than 2mm, no more than 1.5mm, no more than 1.2 or no more than 1mm, for example about 0.8mm. The bristles which have a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a height of at least 5mm, at least 6mm or at least 7mm. As such, the bristles are narrow - substantially thinner than they are long (e.g. at least 4, at least 5, at least 6, or at least 7 times as long as they are wide), leading to flexibility along their length. The device may further comprise at least some bristles comprising a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end, and at least some of the bristles have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end. As such, the device of the first aspect of the invention may be a device of the third aspect of the invention. According to the second aspect of the invention, there is provided a device for detangling hair comprising an array of flexible bristles, each bristle extending from a base to a free end wherein at least some of the bristles have a cross-section having at least four sides; wherein at least one side has a length which is not equal to the length of at least one other side. The sides (or at least one side, or a plurality of sides) may be curved. The vertices of the cross-section (or at least one vertex, or a plurality of vertices) may be rounded. The cross-section having at least four sides may have five, six, seven, eight, nine or ten sides. Preferably the cross-section having at least four sides has only four sides, i.e. the cross-section is preferably a quadrilateral (optionally one with curved sides and / or rounded vertices). Amongst the quadrilaterals with at least one side which has a length which is not equal to the length of at least one other side, the cross-section may have an oblong shape (i.e. a rectangular shape that is not a square). Preferably the cross-section has at least one angle of less than 90 degrees. The quadrilateral may be a parallelogram. The quadrilateral may be a trapezium (UK-English), known as a trapezoid in US-English. The quadrilateral may be an isosceles (UK-English), known as an isosceles trapezoid in US-English. The quadrilateral may be an irregular quadrilateral (UK-English) known as a trapezium in US English. The quadrilateral may be an Apollonius quadrilateral (in which the products of opposite sides are equal). Preferably the quadrilateral is a kite. On a hierarchical definition a kite includes a rhombus, but on a partitional definition (meaning each quadrilateral is only in one class) a kite does not include a rhombus. Since the quadrilateral of the second aspect of the invention has at least one side with a length which is not equal to the length of at least one other side, evidently as defined herein a kite does not include a rhombus. A kite is a quadrilateral with reflection symmetry across one of its diagonals. Equivalently, it is a quadrilateral whose four sides can be grouped into two pairs of adjacent equal-length sides. Preferably the kite is a convex kite. The kite may be a right kite (i.e. with two opposite right angles). The kite may be an equidiagonal kite (i.e. in which the two diagonals between opposite corners are equal). The equidiagonal kite may have curved edges, but cannot take the form of a Reuleaux triangle because, as defined herein a Reuleaux triangle is not a kite shape. This is because each of the three curved sides of a Reuleaux triangle has an equal radius, thus there are only three vertices. Preferably the kite is a non-equidiagonal kite, i.e. it is preferably a kite with unequal diagonals, i.e. a longer diagonal and a shorter diagonal. The longer diagonal may be at least 5% longer than the shorter diagonal. The longer diagonal may be at least 10% longer than the shorter diagonal. The longer diagonal may be at least 15% longer than the shorter diagonal. The longer diagonal may be at least 20% longer than the shorter diagonal. The longer diagonal may be at least 25% longer than the shorter diagonal. The longer diagonal may be no more than 50% longer than the shorter diagonal. The longer diagonal may be no more than 30% longer than the shorter diagonal. The longer diagonal may be no more than 20% longer than the shorter diagonal. The longer diagonal may be no more than 15% longer than the shorter diagonal. The longer diagonal may be no more than 10% longer than the shorter diagonal. For example, the longer diagonal may be between 10% and 15% longer than the shorter diagonal, such as 11%-12% longer. Preferably the kite is a convex kite with curved sides and rounded corners. Preferably the kite is a non-equidiagonal convex kite with curved sides and rounded corners. A kite shape in particular may be advantageous over a square or diamond (rhombus) shape in terms of producing a particularly “directional” quadrilateral bristle. Approaching the corners of a square, all four corners have the same angle and same length sides, as such, hair will be treated the same by each corner. A diamond has more directionality, because two corners are sharper than others, so approached in one direction, hair is split by sharper corners and moves round a smaller width than if it approaches the other two corners. By contrast, with a kite, each of the four corners present a different combination of angle and side-length. At the “top” of the kite the angle of the corner is relatively large and the sides are relatively short. At the “bottom” of the kite, the angle of the corner is relatively small, and the sides are relatively long. Each side offers a corner of equal size, and a pair of different length sides, but their arrangement is opposite depending on whether they are approached from the right or the left. A kite shape may also be advantageous over a triangular shape. A triangular bristle is particularly advantageous in terms of the way that one of its vertices can be arranged (as discussed above) to face in a particular direction. In the same way as a triangular bristle, a kite can be arranged with its sharpest (optionally rounded) vertex pointing in a particular direction, i.e. to separate and divide hair. However, because a kite has an additional vertex opposite to the sharpest vertex, a kite based upon a corresponding triangle, but with the “added” fourth vertex has a larger footprint at the base of the bristle making it harder to deform than a triangle and increasing bristle life. The additional vertex can also improve stability of the bristle compared to a corresponding triangular bristle and the extra vertex can improve the movement through the hair. One or more or each side of the bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be convexly curved. The bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be arranged in rows. The rows may be offset. There may be two or more rows of such bristles. The rows may align with a longitudinal axis of the device. The rows may extend along a longitudinal axis of the device. The rows may be parallel to a longitudinal axis of the device. Each bristle may have a rounded tip, to prevent scratching the scalp or hair in use. The bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may have a taper (optionally a uniform taper) between the base and free end (preferably from the base to the free end). The bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may have a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side half-way between the base and free end. Additionally or alternatively, the bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may have a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side one quarter of the way from the base to the free end. Additionally or alternatively, the bristles having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may have a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side three quarters of the way from the base to the free end. The bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may have a uniformly shaped cross-section between the base and free end (i.e. the shape may be the same from the base to the free end (whilst the dimensions may change on account of the taper). At least some (and optionally all) bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be oriented such that one of the (optionally rounded) vertices points in a direction perpendicular to the row of which said bristle forms a part. At least some (and optionally all) bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be oriented such that the sharpest (optionally rounded) vertex (i.e. the vertex with the smallest angle between the (optionally curved) sides) points in a direction perpendicular to the row of which said bristle forms a part. At least some (and optionally all) bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be oriented in alignment with other bristles which have a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side, in the same row. At least some (and optionally all) bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side, may be oriented in alignment with other bristles with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side, in an adjacent row. At least some (and optionally all) bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be oriented in opposition to other bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in an adjacent row, i.e. so that the sharpest (optionally rounded) vertices of bristles in one row point in the opposite direction to those in an adjacent row. At least some (and optionally all) bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be oriented in alignment with other bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in one adjacent row and in opposition to other bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in another adjacent row. At least some (and optionally all) bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be oriented such that one of its (optionally rounded) vertices (optionally the sharpest vertex) points in a direction perpendicular to a longitudinal axis of the device. With this arrangement, provided that the brush is pulled through the hair perpendicularly to the longitudinal axis, the sharpest vertices will spread and disperse the hair. At least some bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may be oriented such that one of its (optionally rounded) vertices (optionally its sharpest vertex) points towards a vertex (optionally the sharpest vertex) of an adjacent bristle with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side. The bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may form rows perpendicular to the longitudinal axis. For example, the bristles with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side between the base and free end may be arranged in a grid and as such each form part of both a longitudinal row (parallel with the longitudinal axis) and a lateral row (perpendicular to the longitudinal axis). Along one or more, or each, lateral row, the alignment of one or more, some, or each bristle with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may alternate. The bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in one row may be offset with respect to bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in an adjacent row. As such, the bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in one longitudinal row may be staggered with respect to bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in another row, for example an adjacent row, or each adjacent row. For example, the bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in one row may be offset such that with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in one row is aligned with the midpoint of two adjacent bristles with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in an adjacent row. The bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side may have a maximum width (excluding any chamfer at the base) of no more than 2mm, no more than 1.5mm, no more than 1.2 or no more than 1mm, for example about 0.9mm. The bristles which have a cross-section having at least three (optionally curved) sides and / or only three rounded vertices between the base and free end may have a height of at least 5mm, at least 6mm or at least 7mm. As such, the bristles are preferably narrow -substantially thinner than they are long (e.g. at least 4, at least 5, at least 6, or at least 7 times as long as they are wide), leading to flexibility along their length. The device may further comprise at least some bristles comprising a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end, and at least some of the bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side. As such, the device of the first aspect of the invention may be a device of the third aspect of the invention. Turning to the third aspect of the present invention, it will be recalled that there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein at least some of the bristles comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end, and at least some of the bristles have a cross-section having at least three sides and / or at least three rounded vertices between the base and free end. The bristles which comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end may not have a cross-section having at least three sides and / or at least three vertices between the base and the free end. Similarly, the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end may not comprise first and second portions. The at least three sides of the bristles which have a cross-section having at least three sides and / or at least three (optionally only three) vertices between the base and free end may be curved. The at least three (optionally curved) sides of the bristles which have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three) vertices between the base and free end may be convex. The at least three vertices of the bristles which have a cross-section having at least three (optionally curved) sides and / or at least (optionally only three) three vertices between the base and free end may be rounded. The at least three (optionally only three, optionally rounded) vertices of the bristles may be only three vertices. In embodiments where the bristles are arranged in rows, each row of bristles may comprise both bristles comprising a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and bristles having a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and the free end. In embodiments where the bristles are arranged in rows, when viewed parallel to and / or perpendicular to the rows, the bristles which have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and the free end may be occluded, or partially occluded, by the bristles comprising first and second portions. The bristles may be arranged in one or more rows along a longitudinal axis of the device, wherein: a plurality of bristles comprise a first, relatively wide portion which tapers form the base and a second, relatively narrow, portion which extends from the first portion to the free end, wherein a plurality of bristles do not have a first, relatively wide portion which tapers form the base and a second, relatively narrow, portion which extends from the first portion to the free end, and wherein within each row the bristles alternate between bristles comprising first and second portions and bristles not having first and second portions. As such, the device of the third aspect of the invention may be a device of the fourth aspect of the invention. Turning to the fourth aspect of the invention, it will be recalled that there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, wherein: a plurality of bristles comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles do not have a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and within each row the bristles alternate between bristles comprising first and second portions and bristles not having first and second portions. The bristles not having not having first and second portions may of course be bristles of the first or second aspects of the invention, optionally including any optional feature described in relation thereto. The first portion of the bristles comprising first and second portions may have an elongate cross-section over all or part of the length of the first section. The elongate cross-section may be oval. The plurality of bristles which do not have first and second portions may not have an elongate cross-section and / or may have a polygonal (optionally rounded polygonal) cross-section. In particular they may have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end. This particular combination of types of bristles has been found particularly effective at detangling and rendering the hair glossy, as a result of the different actions of the different types of bristle. The plurality of bristles having a polygonal (optionally rounded polygonal) cross-section may have a cross-section having at least four sides; wherein at least one side has a length which is not equal to the length of at least one other side. This too can be particularly effective at detangling and rendering the hair glossy, as a result of the different actions of the different types of bristle. In a particular embodiment, the bristles may additionally alternate between bristles comprising first and second portions and bristles not having first and second portions in a direction that is perpendicular to the longitudinal axis of the device. In said particular embodiment, the bristles may not alternate in a direction that is at a 45° angle to the longitudinal axis of the row. In other words, this particular embodiment has a chequerboard arrangement, where bristles adjacent to each other differ in type, and are the same type as bristles that are ‘adjacent plus one’. When viewed either parallel to or perpendicular to the rows, the bristles which do not have first and second portions may be occluded, or partially occluded, by the bristles comprising first and second portions. The first portion of the bristles comprising first and second portions may, along any part of its length, be at least as wide as the bristles which do not have first and second portions. That is to say, at any given height of the bristles which do not have first and second portions, the bristles comprising first and second portions may be at least as wide as the bristles which do not have first and second portions. The second portion of the bristles comprising first and second portions may have a non-elongate cross-section, for example a circular cross-section. This arrangement is particularly beneficial, since a different bending is achieved as between the first and second portions - the second, non-elongate, preferably circular, portion will bend in the direction that the hair pulls it, thus allowing knots to pull through the bristles rather than getting stuck in them, whilst the first, elongate portion bends preferentially along its short axis, which can spread the hair, moving it in the direction of the short axis. At least some of the bristles comprising first and section portions wherein the first portion has an elongate cross-section may be oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions. As such, the device of the fourth aspect of the invention may be the device of the fifth aspect of the invention. It will be recalled that according to the fifth aspect of the present invention, there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein at least some of the bristles comprise a first, relatively wide, elongate portion which extends from the base and a second, relatively narrow, portion which extends from the first portion to the free end wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions. The elongate portion of said at least some bristles comprising first and second portions may be oriented at an angle of at least 5°, at least 10°, at least 20°, at least 30°, at least 40°, at least 50°, at least 60°, at least 70°, at least 80°, or at least 85° to the elongate portion of at least some adjacent bristles comprising first and second portions. The elongate portion of said at least some bristles comprising first and second portions may be oriented at an angle of less than 175°, less than 170°, less than 160°, less than 150°, less than 140°, less than 130°, less than 120°, less than 110°, less than 100°, or less than 95° to the elongate portion of at least some adjacent bristles comprising first and second portions. For example, the elongate portion of at least some bristles comprising first and second portions may be oriented at an angle of between 60° and 120°, or between 80° and 100°, and most preferably at 90° to the elongate portion of at least some adjacent bristles comprising first and second portions. This arrangement at an angle enables the bristles comprising first and second portions to bend in different directions from adjacent bristles, whilst the most preferable arrangement enables the bristles comprising first and second portions to bend in a direction that is perpendicular to the direction of bend of adjacent bristles comprising first and second portions, which enables hair contacting said bristles to be evenly dispersed through the array of bristles. Where such bristles are arranged in rows, the elongate portion of at least some (and optionally all) bristles comprising first and second portions may be oriented such that the elongate portion is not aligned with the row of which the or each bristle forms a part. In particular, the elongate portion of at least some bristles comprising first and second portions may be oriented at an oblique angle of at least 5°, at least 10°, at least 20°, at least 30°, or at least 40° to the row of which the or each bristle forms a part. The elongate portion of at least some bristles comprising first and second portions may be oriented at an oblique angle of less than 85°, less than 80°, less than 70°, less than 60°, or less than 50° to the row of which the or each bristle forms a part. For example, the elongate portion of at least some bristles comprising first and second portions may be oriented at an oblique angle of between 30°, and 60°, or between 40° and 50°, and most preferably at 45° to the row of which the or each bristle forms a part. This enables the portion of the bristles with an elongate cross-section to bend partially in the direction of the rows and in the direction perpendicular to the rows, providing enough resistance to disperse hair along the rows, and to bend perpendicularly to the rows enough to avoid getting caught in the hair. The device for detangling hair may have a longitudinal axis; and at least some of the bristles comprising first and section portions may be oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle to the longitudinal axis of the hair care device. As such, the device of the fifth aspect of the invention may be a device according to the sixth aspect of the invention. It will be recalled that in the sixth aspect of the present invention, there is provided a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein the device for detangling hair has a longitudinal axis; at least some of the bristles comprise a first, relatively wide, elongate portion which extends from the base and a second, relatively narrow, portion which extends from the first portion to the free end; and at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle to the longitudinal axis of the hair care device. Preferably at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of at least 5°, at least 10°, at least 20°, at least 30°, or at least 40° to the longitudinal axis of the hair care device. Preferably at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of less than 85°, less than 80°, less than 70°, less than 60°, or less than 50° to the longitudinal axis of the hair care device Most preferably at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of between 30° and 60°, such as between 40° and 50°, for example at 45° to the longitudinal axis of the hair care device. Preferably the majority of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of at least 5°, at least 10°, at least 20°, at least 30°, or at least 40° to the longitudinal axis of the hair care device. Preferably the majority of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of less than 85°, less than 80°, less than 70°, less than 60°, or less than 50° to the longitudinal axis of the hair care device Most preferably the majority of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of between 30° and 60°, such as between 40° and 50°, for example at 45° to the longitudinal axis of the hair care device. As noted above, the device may comprise any or all of the features of the first to sixth aspects. The below statements and optional features apply to the invention generally and may apply equally to any of the six aspects of the present invention outlined above, as desired or as required. The bristles may be flexible. The bristles may be resilient (i.e. they may resile to their original shape when bent). The bristles may be resiliently flexible. The bristles may be formed of plastics material. The bristles may be formed form resiliently flexible plastics material. The device may be a brush, in particular a hairbrush (i.e. suitable and intended for brushing the hair that extends from a person’s scalp). The device may be a brush attachment for a hair dryer. The device may be a hot air styling device comprising an integrated brush head. The device may be a round brush. The device may be a paddle brush. The device may comprise an air mover portion. The device may be configured to be attachable to an air mover portion. The device may comprise a handle portion (which may have no bristles formed thereon). The handle portion may be less than 50mm wide e.g. less than 40mm wide, for example 30-35mm wide. The handle portion may increase in width along its length towards its free end, at which it may be gently rounded. The device may comprise a head portion on which the bristles are formed. The head portion may be longer than it is wide. For example, it may be less than 100mm wide, for example less than 80mm wide, e.g. less than 70mm, such as about 60 to 65mm wide. The head portion may be at least 40mm wide, for example at least 50mm wide, such as about 60 to 65mm wide. The head portion may be at least 70mm long, at least 80mm long, or at least 100mm long. It may be less than 200mm long, for example less than 150mm long, e.g. less than 125mm long such as about 100mm to 110mm long. The device may have a longitudinal axis extending from the end of the handle portion to the end of the head portion. The device may have a lateral axis perpendicular to the longitudinal axis. Both the lateral and longitudinal axes may be perpendicular to the direction in which the bristles extend. The array of bristles may have a longitudinal axis and a lateral axis perpendicular to the longitudinal axis. Both the lateral and longitudinal axes may be perpendicular to the direction in which the bristles extend. The longitudinal axis of the array may be parallel with the longitudinal axis of the device and the lateral axis of the array may be parallel with the lateral axis of the device. The array of bristles may be arranged such that the tips of the bristles in one or more rows in the longitudinal direction define a concave shape. Alternatively, the tips of the bristles in one or more rows in the longitudinal direction may define a straight line. The tips of the bristles perpendicular to the longitudinal direction may define a convex shape. Alternatively, the tips of the bristles perpendicular to the longitudinal direction may define a straight line. Each bristle may comprise a chamfer, or interface region, at its base. This may for example be less than a fifth, a tenth or a twentieth of the total height of the bristle. Any properties of the bristles discussed above and below are referred to independently of any such chamfer / interface region unless otherwise stated. The bristles which have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end may all be substantially the same length. For example, they may differ in length by no more than 20%, 10%, 5%, 3%, 2% or 1%. At least some (and optionally all) of the bristles which have a cross-section having at least three (optionally at least four, optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end may be tapered, or substantially the same thickness along substantially their entire length, from the base to the free end. The taper may be uniform between the base and free end. The taper of such bristles between the base and the free end may be less than 10°, less than 5°, or less than 3°. In a particular embodiment, the taper of the bristles which have a cross-section having at least three (optionally at least four, optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and the free end is 2°. In a particular embodiment, the bristles which have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end may be in the form of a Reuleaux triangle preferably a Reuleaux triangle having rounded vertices. The Reuleaux triangle may have a radius between 0.5 and 1 mm (in that each side of the triangle may be between 0.5 and 1mm away from the opposing corner). The Reuleaux triangle may have a radius between 0.6 and 0.9 mm. The rounding of each vertex of a bristle with rounded vertices, such as any such rounded Reuleaux triangle may have a radius of between 0.05 and 0.35mm. This extent of rounding is understood to be sufficient that the vertices are not sharp and will therefore not damage the hair or strip it of sebum. In line with the tapering, the radii of said Reuleaux triangle (both the Reuleaux triangle’s radius and radius of the rounded vertices thereof) may decrease from the base to the free end. The ratios of the radii of the Reuleaux triangle and rounded vertices may be between 20:1 and 2.5:1. Preferably, the ratios of the radii of the Reuleaux triangle and rounded vertices may be between 5:1 and 3:1. This ratio may stay substantially constant from the base to the free end. Alternatively, the ratio may change between the base and the free end. In particular, whilst the radius of the Reuleaux triangle may decrease owing to the tapering of the bristles, the radii of the rounded vertices may remain constant (or substantially constant) between the base and free end. The bristles comprising first and second portions may all be substantially the same length. For example, they may differ in length by no more than 20%, 10%, 5%, 3%, 2% or 1%. The array of bristles may include bristles of at least two lengths, bristles of a first length being shorter than bristles of a second length. At least some (and optionally all) of the bristles of a first length may be bristles according to the first aspect of the invention (optionally including any optional feature described in relation thereto. At least some (and optionally all) of the bristles of a first length may be bristles according to the second aspect of the invention (optionally including any optional feature described in relation thereto. In a particular embodiment, all bristles of the first length are bristles according to the first aspect of the invention (optionally including any optional feature described in relation thereto). In another particular embodiment, all bristles of the first length are bristles according to the second aspect of the invention (optionally including any optional feature described in relation thereto). At least some (and optionally all) of the bristles of a first length may be bristles which have a cross-section having at least three (optionally at least four, optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end. In a particular embodiment, all bristles of the first length are bristles which have a cross-section having only three curved sides and only three rounded vertices therebetween. In another particular embodiment, all bristles of the first length are bristles which have a cross-section having at least four sides (optionally being curved sides and the cross-section optionally having rounded vertices); wherein at least one side has a length which is not equal to the length of at least one other side. At least some (and optionally all) of the bristles of a second length may be bristles according to the third, fifth or sixth aspect of the invention (optionally including any optional features described in relation thereto). In a particular embodiment, all bristles of the second length bristles according to the third, fifth or sixth aspect of the invention (optionally including any optional features described in relation thereto). At least some (and optionally all) of the bristles of a second length may be bristles which comprise a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end. In a particular embodiment, all bristles of the second length comprise a first, relatively wide elongate portion which tapers from the base and a second, relatively narrow, nonelongate portion which extends from the base to the free end. At least some of the bristles of a first length may not comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end. In a particular embodiment, all bristles of the first length do not comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end. At least some of the bristles of the second length may not be bristles which have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end. Alternatively / additionally, at least some of the bristles of the second length may not be bristles which have a cross-section having at least four sides (optionally being curved sides and the cross-section optionally having rounded vertices); wherein at least one side has a length which is not equal to the length of at least one other side. In a particular embodiment, none of the bristles of the second length are bristles which have a crosssection having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end. In a particular embodiment, none of the bristles of the second length are bristles which have a crosssection having at least four sides (optionally being curved sides and the cross-section optionally having rounded vertices); wherein at least one side has a length which is not equal to the length of at least one other side At least some of the bristles of a first length may be only slightly tapered, or substantially the same thickness along substantially their entire length, from the base to the free end. The taper of the bristles of the first length between the base and the free end may be less than 5°. In a particular embodiment, the taper of the bristles of the first length between the base and the free end is 2°. Any lengths of bristle referred to below includes, where provided, any chamfer / interface region of said bristle. The bristles of the first length may be no more than 15mm long, preferably no more than 10mm, 9mm or 8mm long, e.g. 7mm. The bristles of the first length may be at least 3mm, at least 5mm, or at least 6mm long. The bristles of the second length may be at least 15mm long, preferably at least 20mm or at least 21 mm long, e.g. 22mm long. The bristles of the second length may be no more than 30mm, 25mm or 23mm long. The bristles of the first length may be more than one sixth of the length of the bristles of the second length. The bristles of the first length may be no more than one half of the length of the bristles of the second length. The bristles of the first length may be between one quarter and one half of the length of the bristles of the second length. The bristles of the first length may be approximately one third of the length of the bristles of the second length. The first portion of the bristles comprising first and second portions may be longer than the bristles which have a cross-section having at least three (optionally at least four, optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end. The second portion of the bristles comprising first and second portions may be longer than the bristles which have a cross-section having at least three (optionally at least four, optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end. The bristles of the second length may be at least 10mm longer than the bristles of the first length. The bristles of the second length may be approximately 15mm longer than the bristles of the first length. The first and / or second portion of the bristles having a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion may be flexible. The first and / or second portion of the bristles having a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion may be resiliently flexible. The second portion of bristles having first and second portions may be more flexible than the first portion. The first portion of the bristles having a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion may have a larger transverse cross-sectional area than the second portion. All, substantially all, or a substantial proportion (such as at least half), of the bristles in the array, or of the brush, may be bristles of either the first length or bristles of the second length. All bristles of the first length may be the same length (i.e. substantially the same length, for example within 1mm difference in length) and all the bristles of the second length may be the same length (i.e. substantially the same length, for example within 1mm difference in length). Alternatively, the bristles of the first length may not all be the same length, and the bristles of the second length may not all be the same length. For example, a substantial portion (such as at least half) of the bristles of the first length may be the same length and a substantial portion of the bristles of the second length may be the same length, but some bristles of the first and / or second length, e.g. less than 30%, less than 20%), or less than 10% may be of a different length. For example, some of the bristles of the first and / or second length, e.g. less than 30%, less than 20%, or less than 10% may be shorter than the others. The second portions of bristles of the second length having first and second portions may all be of the same length, regardless of the overall length of the bristles of the second length. Thus, for example, the head of the brush may be convex, with bristles nearest the middle shorter, to account for a bulging of the brush in that region, but the contour of the tips of the bristles may be straight and the second portions may be equally long. Likewise, all, substantially all, or a substantial portion (such as at least half) of the bristles of a first length may be uniformly (i.e. substantially uniformly) shorter than all, substantially all, or a substantial portion (such as at least half) of the bristles of a second length. When viewed in the same direction, the width of the widest part of the first portion of the bristles having first and second portions may be at least twice the width of any part of the second portion or the second portion at or near to its free end. When viewed in the same direction, the width of the widest part of the first portion of the bristles having first and second portions may be no more than four times the width of the bristle at any part of the second portion or at or near its free end. For example, the width of the widest part of the first portion may be about 2.85mm and the width of the second portion near to its free end may be about 0.8mm. The width of the narrowest part of the first portion of the bristles having first and second portions at their widest part may be at least one quarter of the width of the widest part of the first portion. The width of the narrowest part of the first portion of the bristles having first and second portions at their widest part may be no more than three quarters of the width of the widest part of the first portion. For example, the width of the narrowest part of the first portion may be about 1.90mm. The widest part of the cross-section of the first portion of the bristles comprising first and second portions may be at least 1.25 times larger than the narrowest part of the same cross-section. The widest part of the cross-section of the first portion of the bristles comprising first and second portions may be no more than 2 times larger than the narrowest part of the same cross-section. When viewed in the same direction, the width of the widest part of the first portion of the bristles having first and second portions may be at least three times the width of any part of the first bristle. When viewed in the same direction, the width of the widest part of the first portion of the bristles having first and second portions may be no more than four times the width of any part of the first bristle. For example, the width of the widest part of the first portion may be about 2.85mm and the width of the first bristle may be about 0.65mm. The width of the narrowest part of the first portion of the bristles having first and second portions at their widest may be at least twice the width of the first bristles. The width of the narrowest part of the first portion of the bristles having first and second portions at their widest may be no more than three times of the width of the narrowest part of the first portion. For example, the width of the narrowest part of the first portion at its widest may be about 1.90mm. The length of each of the bristles of a second length having first and second portions may be no greater than ten times its maximum width. The length of each of the bristles of a second length having first and second portions may be no less than five times its maximum width. A longitudinal gap may be provided between adjacent bristles (whether in the same row or otherwise). The longitudinal gap may be the gap in the direction parallel (or substantially parallel) to the longitudinal axis. The longitudinal gap between adjacent bristles at the height of the free ends of the first bristles may be no more than 5mm, for example 4mm. The longitudinal gap between adjacent bristles, at their bases may be no more than 3mm. A lateral gap may be provided between adjacent bristles (whether in the same row or otherwise). The lateral gap may be the gap in the direction parallel (or substantially parallel) to the lateral axis. The lateral gap between adjacent bristles at the height of the free ends of the first bristles may be no more than 5mm, for example 4mm. The lateral gap between adjacent bristles, at their bases may be no more than 3mm. The longitudinal gap between centre points of at least some adjacent second bristles may be no less than 2mm and / or no greater than 6mm, for example no less than 3mm and / or no greater than 5mm, e.g. 4mm. The lateral gap between centre points of adjacent second bristles may be no less than 2mm and / or no greater than 6mm, for example no less than 3mm and / or no greater than 5mm, e.g. 4mm. The longitudinal gap between centre points of at least some consecutive first bristles in the same longitudinal row may be no less than 4mm and / or no greater than 12mm, for example no less than 6mm and / or no greater than 10mm, e.g. 8mm. The lateral gap between centre points of at least some consecutive first bristles in the same lateral row may be no less than 4mm and / or no greater than 12mm, for example no less than 6mm and / or no greater than 10mm, e.g. 8mm. The longitudinal gap between centre points of at least some consecutive second bristles in the same longitudinal row may be no less than 4mm and / or no greater than 12mm, for example no less than 6mm and / or no greater than 10mm, e.g. 8mm. The lateral gap between centre points of at least some consecutive second bristles in the same lateral row may be no less than 4mm and / or no greater than 12mm, for example no less than 6mm and / or no greater than 10mm, e.g. 8mm. The various ranges and sizes mentioned above have been found to provide a satisfactory balance between the performance of the bristles of first and second lengths. The width of the bristles having first and second portions may vary continuously or discontinuously between their base and free ends. Along part of their length, and preferably within the first portion of the bristles, the width of the bristles may taper at an angle greater than the angle of taper of a uniformly tapered bristle (i.e. a bristle tapering in a straight line) having the same length and variation in width. This allows there to be significantly more space between the second portion of the bristles in the array than the first portion, as compared to uniformly tapered bristles. This enables the two portions of the bristles to perform their different functions without being unduly long. Two opposed edges of the first portion of those bristles comprising first and second portions may taper towards each other with a minimum average angle of at least 5 degrees between the opposed edges over the length of the first portion. Opposite sides of the second portion may taper towards each other with a maximum average angle of 3 degrees between opposed edges over the length of the second portion, for example 2 degrees. Two opposed edges of the first portion may taper towards each other with a minimum average angle of at least 8 degrees or at least 10 degrees. The angle between the opposed edges of the first portion may increase from the base of the first portion to the end of the first portion. The opposed edges of the first portion may be curved. All opposed edges of the first portion may taper towards each other with a minimum average angle of at least 2 degrees between the opposed edges over the length of the first portion. At least some of the bristles, or at least some of the bristles having first and second portions or at least some of the first portions of bristles having first and second portions may have a non-circular transverse cross-section over at least part or substantially all of their length. The cross-section may be elongate in shape and may be oval, i.e. substantially ovular. At least some of the bristles, or at least some of the bristles having first and second portions or at least some of the second portions of bristles having first and second portions may have a circular transverse cross-section over at least part or substantially all of their length. The first portion of at least some of the bristles having first and second portions may have a non-circular cross-section at its base which gradually transitions to a substantially circular cross-section at the point where it meets the second portion. The first portion of those bristles with first and second portions may terminate where the second portion begins. The bristles may consist only of the first and second portions. The bristles may consist only of the first portions, second portions and chamfers / interface regions (where these are provided). The length of the chamfers / interface regions may be less than 1mm. The chamfers / interface regions may be steeply tapered, e.g. by about 45 degrees. The first portion of the bristles comprising first and second portions may comprise a transition portion. The transition portion may be a sub-section of the first portion of each bristle having first and section portions. The transition portion may be the part of the first portion where the cross-section transitions from the wider, optionally non-circular, transverse cross-section (which is optionally elongate, and optionally oval) of the lower part of the first portion to narrower, optionally non-elongate (and optionally circular) cross-section of the second portion. In particular, the region of each bristle having first and second portions above and below the transition portion may each have a cross-section that is uniformly shaped. That is to say, the first portion may, in the region below the transition portion, have a uniformly shaped cross-section from the base to the transition portion. The uniformly shaped cross-section from the base to the transition portion may be non-circular. The uniformly shaped cross-section from the base to the transition portion may be elongate. The uniformly shaped cross-section from the base to the transition portion may be oval. Likewise, the second portion, which is in the region above the transition portion, may have a uniformly shaped cross-section from the transition portion of the first portion to the free end. The uniformly shaped cross-section from the transition portion to the free end may be non-elongate. The uniformly shaped cross-section from the transition portion to the free end may be circular. The shape of the cross-section of the transition portion at its uppermost and lowermost point may be different. The cross-section of transition portion at its lowermost point (where it meets the first portion) may be non-circular. The crosssection of transition portion at its lowermost point may be elongate. The cross-section of transition portion at its lowermost point may be oval. The cross-section of transition portion at its uppermost point (where it meets the second portion) may be non-elongate. The cross-section of transition portion at its uppermost point may be circular. The transition portion may comprise a significant narrowing of the bristles between it lowermost and uppermost points. The transition portion may smoothly and continuously narrow across its extent. The transition portion may taper. The transition portion may taper at a greater angle than the first and / or second portions. The taper of the transition portion may be the same as the taper of the first and / or second portion at the point at which the transition portion meets the first and / or second portion. The taper of the transition portion may be non-uniform, i.e. curved. On the other hand, the taper of the second portion, and / or the taper of the remainder of the first portion other than the transition portion, may be uniform, i.e. straight. In such embodiments, the transition portion being narrower than lower region of the first portion renders it more flexible than said lower region. As such, the transition portion is the most flexible region of the first portion. Similarly, as any such transition portion is wider than the second portion, it is less flexible than the second portions. The transition portion thus provides a ‘middle ground’ region of the bristles which is somewhat flexible, but not overly flexible. Where the transition portion has an at least partially elongate cross-section, it will tend to bend preferentially along the short axis; where the transition section has a non-elongate, e.g. circular cross-section, it will bend in the direction it is pulled. As such, when hair pulls the second section, creating a force on the transition portion, it will bend in a curved manner, with the more elongate part bending more along its short axis, and the less elongate (narrower) part bending more in the direction it is pulled; this can create a gentle detangling action, especially where the bristles include transition portions with elongate portions which are differently aligned to one another. Where the width of the second bristles tapers at an angle greater than the angle of taper of a uniformly tapered bristle (i.e. a bristle tapering in a straight line) having the same length and variation in width, it may, in particular, be the transition portion which tapers at a greater angle than a uniformly tapered bristle. Where at least part of the first portion has an ovular cross-section, edges of the first portion lying on a long axis of its oval cross-section may approach each other in a curved path over the length of the first portion. Edges of the first portion lying on a short axis of its oval cross-section may approach each other in a straight (i.e. substantially straight) path over the length of the first portion. The second portion may have a circular (i.e. substantially circular) cross-section over all or substantially all of its length. All opposed edges of the second portion may taper towards each other with a maximum average angle of 2 degrees between the opposed edges over the length of the second portion. The length of the second portion of bristles having first and second portions may be at least one quarter of the length of the first portion. For example, the length of the second portion may be about 8.75mm and the length of the first portion may be about 13.25mm. The length of the first portion may be at least half of, or three quarters of, the second portion. At least some bristles of the second length, comprising first and second portions, may comprise a first portion that is at least half the length of the bristles of the first length. The second portion may be no more than three times as long as the bristles of the first length, for example no more than twice as long as the bristles of the first length. For example, the first portion of bristles of a second length may be 13mm and the bristles of a first length may be 7mm. These dimensions / ratios lead to the second bristles being fairly rigid, but still flexible, up to and beyond the height at which they are adjacent to first bristles, but even more flexible higher still, in the region of the second portions. By nature of their dimensions, the bristles of the first length are flexible along their entire length. The spacing of the bristles of the first length performs detangling of any hair which reaches said bristles without being detangled (for example those which have bent over the second portions of the second bristles and become free). The bristles of the first length also assist in smoothing / shining of hair, by virtue of the at least three (optionally at least four, optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices. The bristles of the first length being flexible, allows them to bend and ‘release’ any tangles which are particularly tough - this reduces the likelihood of hair being broken or pulled out by said bristles. The bristles may all be spaced apart from one another (i.e. each arranged singly, as opposed to being arranged in bunches). This reduces the risk of hair binding to the brush. Each row of bristles may be straight (i.e. substantially straight) or may be curved. The rows may be parallel (i.e. generally parallel). The bristles in each row, or at least a number of adjacent rows, may all be evenly spaced apart by the same distance (i.e. substantially the same distance). This distance may be between 1 and 10 mm. This distance may be between 3 and 5 mm. In a specific embodiment, this distance is approximately 4mm. Each row of bristles may contain both bristles comprising a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and bristles having a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and the free end. Each row of bristles may contain both bristles of a first length and bristles of a second length. Bristles in adjacent rows may be offset relative to each other so that the centre of each bristle in a row is aligned (i.e. substantially aligned) with the midpoint between bristles of the same type in an adjacent row. The relative offset of the rows (and hence the spacing apart of the bristles therein) may be such that, when viewed perpendicular to the rows, no part of a bristle which has a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in one row occludes or overlaps any part of any bristles which have a cross-section having at least three (optionally curved) sides and / or at least three (optionally only three, optionally rounded) vertices between the base and free end in an adjacent row. The relative offset of the rows (and hence the spacing apart of the bristles therein) may be such that, when viewed perpendicular to the rows, no part of a bristle comprising first and second portions in one row occludes or overlaps any part of any bristles comprising first and second portions in an adjacent row. There may be at least three, at least four or at least five rows of at least three, four or five bristles. There may be no more than 35, no more than 30, no more than 25, no more than 20, no more than 15, no more than ten, no more than eight, no more than six, or no more than five rows of at least five bristles. For example, there may be five rows of at least five bristles, such as five rows of at least ten bristles, such as two rows of at least ten (e.g. 20) second bristles and three rows of at least ten (e.g. nineteen) first bristles. There may be no more than 500, no more than 200, no more than 150, or no more than 100 bristles. There may be no more than 200, no more than 100, or no more than 50 bristles of a first length. There may be no more than 200, no more than 100, or no more than 50 bristles of a second length. There may be at least 50, at least 75, or at least 90 bristles. For example, there may be about 100. The bristles may be moulded and may be moulded from a plastics material, particularly a resiliently flexible plastics material. Bristles of a first length and bristles of a second length may have a dissimilar width and / or shape when viewed along the longitudinal axis. Bristles of a second length may have a width which is at least twice as wide as the bristles of a first length. Bristles of a first length may be flexible (i.e. substantially flexible) and at least a portion of the bristles of the second length higher than the height of the free end of the bristles of a first length may also be flexible (i.e. substantially flexible). The elongate array of bristles may be at least twice as long as it is wide, at least three times as long as it is wide, at least four times as long as it is wide, at least five or even at least six or more times as long as it is wide. The length of the array (measured across its width from the outside of one bristle to the outside of the bristle on the opposite side) may be at least 75mm, at least 80mm, at least 90 mm, at least 100mm or at least 110mm, for example, about 115mm, (e.g. 118mm). The width of the array (measured from the outside of the outermost bristle at one end to the outside of the outermost bristle at the other end) may be at least 50mm, at least 60mm, for example, about 65mm, (e.g. 68mm). Another aspect of the invention extends to a method of detangling hair using a device according to the any aspect of the invention as described above (optionally including any of the optional features). One specific method comprises detangling hair using a device comprising an array of bristles, each bristle extending from a base to a free end, wherein at least some of the bristles have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end; wherein the bristles separate and divide the hair whilst minimising the force applied thereto (thus minimising the breakage of the hair) as it moves across the surface of the device between the bristles. Preferably the curved sides and / or rounded vertices of the bristles ensure sufficient contact between the bristle and hair to impart a shine upon the hair as it passes the bristles. A second specific method comprises detangling hair using a device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end wherein at least some of the bristles have a cross-section having at least four sides; wherein at least one side has a length which is not equal to the length of at least one other side, wherein the wherein the bristles separate and divide the hair whilst minimising the force applied thereto (thus minimising the breakage of the hair) as it moves across the surface of the device between the bristles. Preferably the bristles comprise curved sides and / or rounded vertices of the bristles which ensure sufficient contact between the bristle and hair to impart a shine upon the hair as it passes the bristles. A third specific method comprises detangling hair using a device comprising an array of bristles, each bristle extending from a base to a free end, wherein at least some bristles comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and at least some bristles have a cross-section having at least three sides and / or at least three vertices between the base and the free end; wherein the second portions of the bristles having first and second portions penetrate and divide hair between the bristles when the brush is introduced into the hair and the transition of the bristle from the relatively narrow second portion to the wider first portions separates the hair, by simultaneously moving hair both in the axis in which the bristles extend and in the axis in which the bristle widens. The reduction in cross-sectional area away from the base also leads to bristles which become more flexible away from the base; consequently, the first portions are relatively stiff, particularly at their base whilst the second portions are relatively flexible. Thus, in the method, the first portions preferably act as a support allowing for the long bristles to reach deep into the hair. Preferably, in the method of detangling, the bristles bend more (i.e. to a greater extent) closer to the free end, such that they do not get stuck in the hair. Preferably in the method of detangling, the shorter bristles having at least three curved sides and / or at least three rounded vertices between the base and free end separate and divide the hair whilst minimising the force applied thereto (thus minimising the breakage of the hair) yet ensuring sufficient contact between the bristle and hair to impart a shine upon the hair as it passes the bristles, and in combination with the wide first portion of the other bristles at the base improve glossiness of hair at the surface. A fourth specific method comprises detangling hair using a device comprising an array of bristles, each bristle extending from a base to a free end, the bristles being arranged in one or more rows along a longitudinal axis of the device wherein a plurality of bristles comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles do not have a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and within each row the bristles alternate between bristles comprising first and second portions and bristles not have a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end; wherein the hair interacts with both types of bristle, when the device is moved through the hair at an angle to the longitudinal axis of the device. Preferably all hair being brushed interacts with each type of bristle, maximising the interaction between each type of bristle and the hair. Preferably in the detangling method hair interacts more with the bristles in the proximity of the first portions (i.e. near the base) where there is a greater density of bristles and less towards the second portions where the density of bristles is lower, whereby the chance of tangles snagging within the brush is reduced and the interaction between the hair and bristles near the base is maximised so as to impart a shine upon the hair as it passes the bristles. A fifth specific method comprises detangling hair using a device comprising an array of bristles, each bristle extending from a base to a free end wherein at least some bristles comprise a first, relatively wide, elongate portion, which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, wherein at least some bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions; wherein the elongate first portions interact differently with the hair depending on their orientation. Preferably during brushing according to the method, the elongate first portions can form arrow / funnel type arrangements and separate the hair in different directions whilst the bristles are in contact the hair, whilst the upper part of the elongate first portions and the narrower second portions bend (thereby reducing breakage of the hair). In particular, the method preferably comprises brushing the hair such that the bristles with first and second portions preferentially bend along their short axis (i.e. not in the elongate direction), wherein non-alignment between the elongate portions results in the bending of the bristles having first and second portions in different directions, further spreading and dispersing hair when the bristles are pulled through the hair. A sixth specific method comprises detangling hair using a device comprising an array of bristles, each bristle extending from a base to a free end; wherein the device for detangling hair has a longitudinal axis; at least some of the bristles comprise a first, relatively wide, elongate portion which extends from the base and a second, relatively narrow, portion which extends from the first portion to the free end; and at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle to the longitudinal axis of the hair care device; wherein the elongate first portions interact with the hair differently from the manner in which the relatively narrow second portions interact with the hair. In particular, the elongate first portions may preferentially bend along their short axis, and thereby bend at an oblique angle with respect to the longitudinal axis of the brush, whilst the second narrower portions may bend at a different angle, as directed by the force of the hair through the bristles. Thus, in particular when the hair care device is pulled through hair perpendicular to the longitudinal axis, the different portions of the bristles may bend in different directions, allowing the hair to be moved sideways when the bristles are pulled through the hair. Another aspect of the invention extends to a method of manufacturing a device according to any aspect of the invention as described above (optionally including any of the optional features); the method comprising moulding an array of bristles as defined in of the invention as described above (optionally including any of the optional features) from resiliently flexible plastics material. The method may comprise moulding the array of bristles as a bristle pad and incorporating the bristle pad into a device for detangling hair. The method may comprise moulding the array of bristles integrally with the body of a device for detangling hair. The method may comprise moulding the array of bristles integrally with the body and handle of a device for detangling hair. Detailed Description of the Invention In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a plan view of a first embodiment of a device for detangling hair; Figure 2 is an end view of the device of figure 1; Figure 3 is a side view of the device of figure 1; Figure 4 is a partial plan view of the device of figure 1; Figure 5 is an enlarged side view of part of an array of bristles of the device of figure 1; Figure 6 is a perspective view of the device of figure 1; Figure 7 shows a chart showing the force of each stroke through the hair as a percentage of the force of the first stroke through the hair; Figure 8 is a plan view of a second embodiment of a device for detangling hair; Figure 9 is an end view of the device of figure 8; Figure 10 is a side view of the device of figure 8; Figure 11 is a partial plan view of the device of figure 8; Figure 12 is a perspective view of the device of figure 8; Figure 13 is an enlarged side view of part of an array of bristles of the device of figure 8; Figure 14 is a magnified plan view of the device of figure 8; Figure 15 is a plan view of a first (generally kite-shaped) bristle of the device of figure 8; Figures 16a to 16f are plan views of generally triangular and generally kiteshaped bristles. In the following, the terms front, back, top, bottom and like terms refer to the articles in the orientation in which they are illustrated but should not be taken as otherwise limiting. Referring to the drawings, figures 1 to 4 and 6 show a device for detangling hair, specifically a brush 1 of a first embodiment. Figure 5 shows an enlarged part of the brush 1. The brush comprises a body including a head portion 2 moulded in one piece with a handle 3 which extends generally perpendicularly from the approximate mid-point of one of the ends of the head portion 2. The head portion 2 and handle 3 extend in generally the same plane, and together define a longitudinal axis A. The underside of the brush 1 has a generally flat surface formed of a planar surface of the head portion 2 which merges into a planar surface of the handle 3. The upper side of the head portion 2 has a surface 4 which is generally flat and straight in the longitudinal direction and blends into the handle 3, which extends from the approximate mid-point of one of the ends of the head portion 2 and is narrower than the head portion 2. Along the lateral plane (i.e. between the long sides of the head, perpendicular to the longitudinal axis), the surface 4 of the upper side of the body is generally slightly convex. Of course, it will be understood that the exact nature of the body, head portion 2 and handle 3 can be varied as desired and appropriate. Other shapes of device are also possible. The head portion 2 comprises, or supports, moulded bristles 5 which project generally perpendicularly from the surface 4. The bristles 5 extend parallel to one another, and generally perpendicular from the plane of the brush (i.e. perpendicular to both the longitudinal axis and lateral plane as defined above). Each bristle 5 is spaced apart from each other bristle 5. The centre of each bristle 5 is 4mm away from each adjacent bristle 5. All of the bristles 5 are moulded together in one piece, together with a base (which may form all or part of the surface 4 of the brush) from a resiliently flexible plastics material. Suitable materials are thermoplastic elastomers, such as copolyesters and aliphatic polyamides (nylons). Elastomers with hardnesses from 45 to 82 Shore D are particularly suitable, especially grades in the range of 45 to 72 Shore D. In particular, the copolyester sold under the trade mark Hytrel by E. I. du Pont de Nemours and Company. For example, grades of Hytrel such as Hytrel 6356 and Hytrel 7246 are suitable. Other suitable elastomers include those sold under the trade mark Bexloy by Celanese. Grades of Bexloy such as Bexloy GPV45B5, GPV55B5 NC010, GPV63B5 NC010 and Bexloy GPV72B5 NC010 are examples of suitable elastomers. Also suitable are elastomers sold under the trade marks Pebax and Rnew by Arkema, in particular Pebax Rnew 55r53sp01, Pebax Rnew 63r53sp01 and Pebax Rnew 72r53sp01, and elastomers sold under the trade mark Triel by Samyang Corporation, in particular Triel 5550 NA, Triel 5590 NA and Triel 5720 NA. Each bristle 5 comprises a chamfer region around the bristle 5 where the bristles extends from the surface 4. Each chamfer extends at approximately 45° to both the bristle 5 which it surrounds and the surface 4. Each chamfer has minimal height (e.g. typically less than 1mm). In the below, the widths of any bristle 5 are given ignoring the chamfer, whilst the heights of any given bristle 5 include said chamfer. The tip of each bristle 5 (i.e. the free end) is rounded, with a diameter of 0.8mm. As seen in the figures, two types of bristle 5 are provided; first bristles 6 which are shorter than second bristles 7. Each first bristle 6 has a generally triangular cross-section. For the sake of clarity, throughout this description, the cross-section of a bristle is the cross-section when viewed in a plane perpendicular to the length of the bristle. In particular, the generally triangular cross-section is in the form of a Reuleaux triangle having rounded vertices - being a triangle, there are three, and only three, rounded vertices and being a Reuleaux triangle, each of the three (and only three) sides is curved. Adjacent the base / surface 4 and chamfer region of each first bristle 6, the triangle has a radius of 0.65mm (in that each side of the triangle is 0.65mm away from the opposing corner). Each vertex is rounded, with a radius of 0.2 mm. At the free end of each first bristle 6, the triangle has a radius of 0.6mm (in that each side of the triangle is 0.6mm away from the opposing corner). Each first bristle has a uniform taper of approximately 2° between the base and free end. The cross-section of each first bristle 6 is uniformly shaped between the base and free end (ignoring the chamfer region and rounded tip of the bristle). The ratios of the radii (of the curved sides) of the Reuleaux triangle and rounded vertices thereof is substantially constant along the length of the bristles, and is approximately 3:1. All of the first bristles 6 are of the same length, and have the dimensions discussed above. Each first bristle 6 is identical (or substantially identical) to every other first bristle 6 in terms of dimensions (as set out below, the arrangement / orientation of the first bristles 6 differs). In the illustrated embodiment each of the first bristles 6 extends about 7mm from the base to the tip. Each second bristle 7 has a base with a distinctly oval cross-section, having a long axis and a much shorter perpendicular short axis. As the second bristle 7 extends away from the base it tapers. Over a first portion 7a of the length of the second bristle 7, the second bristle 7 tapers such that its cross-sectional shape changes from oval to substantially circular. In particular, each second bristle 7 comprises a transition portion. The transition portion is a sub-section of the first portion7a of each second bristle 7 and is the portion of said second bristle 5 where the cross-section transitions from the oval cross-section of the lower part of the first portion 7a (i.e. the region of the first portion 7a closest to the base) to the circular cross-section of the second portion 7b. In particular, the portions of each second bristle 7 above and below the transition portion each have cross-sections that are uniformly shaped (i.e. which have the same geometrical shape along their length, albeit the size changes as a result of the taper). In contrast, the cross-section of the transition portion at its uppermost and lowermost planes are different. Moreover, whilst the taper of the second portion 7b is uniform, and the taper of the first portion 7a below the transition portion is uniform, the taper of the transition portion is non-uniform, thus when viewed perpendicular to the elongate axis of the bristle, the taper of the transition portion gradually becomes steeper, then less steep (in a less exaggerated S-shape) to blend into the adjacent second portion and the remainder of the first portion. The edges of the second bristles 7 through which the long axis extends approach each other as each second bristle 7 extends away from the base. The opposite edges of said second bristles 7 approach each other in a curved path, which then flattens out towards a straighter taper as the second bristle 7 approaches the free end. The edges of the second bristle 7 through which the short axis extends approach each other at a substantially constant angle, and the edges of these second bristles 7 are therefore substantially straight. At the end of the first portion 7a of each second bristle 7 its cross-section is substantially circular. At this point a second portion 7b of the second bristle 7 begins. Over the second portion 7b of each second bristle 7 the cross-section of said bristle 7 remains substantially circular and the second bristle 7 tapers towards a free end, with a domed surface. The degree of taper (approximately 2°) of the second bristle 7 over the second portion 7b of the bristle 7 is less than over the first portion 7a. The degree of taper of the second portion 7b of the second bristle 7 is, in effect, the minimum consistent with being able to reliably remove the second bristle 7 from a mould tool. As far as the function of the second portion 7b of the second bristle 7 is concerned it could have a substantially constant diameter, and the same is true for the first bristles 6. In the illustrated embodiment the first portion 7a of the second bristles 7 extends about 13.25mm from the base, and the second portion 7b of the second bristles 7 extends about a further 8.75mm from the end of the first portion 7a to the end of the bristle 7. As such, the total length of the second bristles is about 22mm from the base to the free end. The widest part of the first portion 7a of each second bristle 7, measured above the chamfer, along the long axis of its oval cross-section, has a width of about 2.85mm. The narrowest part of the first portion 7a of each second bristle 7, above the chamfer, measured along the short axis of its oval cross-section, has a width of about 1.90mm. The sides of each second bristle 7 along its short axis approach each other at an angle of about 2 degrees. The sides of each second bristle 7 along its long axis approach each other with a gradually increasing angle and then gradually decreasing angle, forming a smooth curve which eventually transitions smoothly into the second portion 7b of the bristle 7. The average angle of taper between the two sides of each first portion 7a of each second bristle 7 along its long axis is 6.2°, i.e. approximately 6°, that is to say the angle of taper that would be required if the sides were straight rather than curved. At the end of the first portion 7a of each second bristle 7 it has a substantially circular cross-section with a diameter of about 1.4mm. The sides of each second bristle 7 approach each other over the second portion 7b of its length with an angle of about 2°, resulting in a diameter of about 0.8mm at the free end of each second bristle 7, not including the rounded tip (though this also has a diameter of 0.8mm). Other dimensions are possible, as discussed elsewhere. All of the second bristles 7 are of the same length, and have the dimensions discussed above. Each second bristle 7 is identical (or substantially identical) to every other second bristle 7 in terms of dimensions (as set out below, the arrangement / orientation of the second bristles 7 differs). The array of bristles 5 has a longitudinal axis parallel with the longitudinal axis of the brush 1 and is intended to be moved through hair in a direction generally perpendicular to said longitudinal axis, though it is noted that brushes (in particular those with handles) are rarely moved through the hair strictly perpendicular to the longitudinal axis, and in practice may be moved through the hair at various angles predominantly between 45 degrees and 135 degrees with respect to the longitudinal axis. For this reason, the brush of the present invention is intended to perform well at various angles in this range, not just when strictly perpendicular or close to perpendicular to the longitudinal axis. Each bristle 5 in the array forms a part of a “longitudinal row” of bristles 5 (i.e. a row that extends along the length of the brush 1) and a “lateral row” of bristles 5 which extends perpendicularly to the longitudinal row (across the width of the brush ll- Each of the longitudinal rows are straight (but could be slightly curved), substantially parallel and substantially evenly spaced apart. In each longitudinal row the bristles 5 are substantially evenly spaced apart, with the bristles 5 alternating between first bristles 6 and second bristles 7. The bristles in the longitudinal rows are offset relative to one another so that the centre of the cross-section of the first bristles 6 in one row lies mid-way between adjacent first bristles 6 in the adjacent row and likewise the centre of the cross-section of the second bristles 7 in one row lies mid-way between adjacent second bristles 7 in the adjacent row. Owing to the alternation of the bristles 5 within each row, this means that the bristles 5 also alternate in type within the lateral rows, in addition to the longitudinal rows. The generally triangular first bristles 6 are arranged such that one of the rounded vertices of the cross-section thereof points in a direction that is perpendicular to the longitudinal row of which any given first bristle 6 forms a part. In other words, one of the rounded vertices of the cross-section thereof points in a direction parallel to the lateral row of which the first bristles 6 forms a part. This enables any hair introduced into the brush 1 in a direction perpendicular to the longitudinal axis of the brush 1 to be separated smoothly by the rounded vertex aligned with the lateral row, which helps detangle hair without breaking said hair (by virtue of the vertex being rounded). The first bristles 6 are also arranged that, when taking any pair of consecutive first bristles 6 in a lateral row (ignoring any second bristles 7 therebetween), the rounded vertex of each of said first bristles 6 that is perpendicular to the longitudinal row of which each said first bristle 6 forms a part is arranged to be in the opposite direction to that of the other first bristle 6 in the pair. The first bristles 6 in any given longitudinal row are all arranged such that they have the same orientation. This means that regardless of the direction in which the brush is moved perpendicularly through the hair, half of the first bristles 6 will have a vertex pointing towards them. Specifically, the alternation of the orientation of the first bristles 6 means that there are, across the array of bristles 5, rounded vertices of the first bristles 6 pointing in six directions. This means that, regardless of which direction the brush 1 is moved through the hair, that a rounded vertex will still be substantially aligned with the direction in which the hair moves, enabling the vertex to separate the hair. The long axis of each second bristle 7 is arranged such that each second bristle 7 is at an oblique angle, which in the illustrated embodiment is a 45° angle to the longitudinal axis of the brush 1, and as such also at a 45° to the direction of the row of which the bristle 7 forms a part. The long axis of any given second bristle 7 is also arranged such that said long axis is at a 90° angle to the long axis of any adjacent second bristles 7. In the illustrated first embodiment the array comprises fifteen longitudinal rows; each row having anywhere between seven and twenty-eight bristles 5. The lateral rows defined by said array contain anywhere between three and fifteen bristles 5. The majority of the bristles 5 are contained within a rectangular section of the array having eleven longitudinal rows (i.e. eleven bristles 5 wide) and twenty-two lateral rows (i.e. twenty-two bristles 5 long), with the remaining bristles being arranged so as to extend to the edges of the surface 4. Of course, the number of rows and number of bristles 5 in each row can be varied as desired and appropriate. Other shapes of array are also possible. Although the bristles 5 are moulded in a single piece from the same material, owing to their different cross-section and shape, the first portions 7a are stiffer than the second portions 7b, though the first portions 7a are still flexible. In use, the first portions 7a are somewhat flexible, whereas the second portions 7b are highly flexible. The second portions 7b can be easily bent completely back on themselves (such that the tip points back towards the surface 4). On the other hand, a relatively high level of force is required to bend the first portions 7a even to 90 degrees along their short axis, and it requires an even higher level of force difficult to bend the first portions 7 a to 90 degrees by hand when bending along their long axis. This has the effect that, when combined with the fact that the long axes of the second bristles 7 are arranged at 45° angles to the longitudinal row and longitudinal axis of the brush, that the first portions 7a of the second bristles 7 preferentially bend in a direction that is at 45° to said longitudinal row and axis. This has the consequence that hair interacting with said bristles is dispersed across the row via the directional bending of the first portions 7 a of the second bristles 7, with the flexing of the second portions 7b of the second bristles 7 ensuring any tangles within the hair are not caught by said bristles 7. The first bristles 6 and the second bristles 7 are arranged in the array such that each shorter first bristles 6 is located at the centre of four longer second bristles 7, and vice versa (of course with the exception of any bristles 5 on the edge of the array). The alternation of the orientation of the long axes of the second bristles 7 means that, for any first bristle 6, the two pairs of the second bristles 7 on opposing sides of said first bristle 6 will both have long axes parallel to one another. In use, a user grips the handle of the brush 1, and inserts the bristles 5 into the hair to be detangled. Owing to the position and configuration of the handle 3, the user will introduce bristles 5 into the hair (introducing them parallel with the direction that they extend from the surface 4 of the head 2) such that the hair is roughly perpendicular to the longitudinal axis of the device, i.e. substantially parallel to the lateral axis of the brush 1. In introducing and moving the brush 1 through the hair, the second portion 7b of longer second bristles 7 will penetrate and divide the hair. As the brush 1 is inserted deeper into the hair, the first portion 7a of the second bristles 7 seek to further separate each strand of hair, by virtue of their widening cross-section. As the brush 1 is moved yet deeper into the hair, the first bristles 6 also help to separate hair not yet separated by the second bristles 7 as well as hair released from the second bristles if they are bent over by a tangle. Once the brush 1 is inserted into the hair, the brush 1 being drawn through the hair enables the first bristles 6 to divide the hair smoothly, without tearing or damaging the hair (by virtue of their rounded vertices), and also to impart a shine or glossiness upon the hair as it moves past the bristles (by virtue of the curved sides). Meanwhile, any tangles present at a height where the second portions 7b reside will either be teased apart through the motion of the second portion 7b through the hair, or will not be teased apart, and the second portion 7b will flex accordingly, in the direction which the hair is being moved through the brush 1. This provides detangling action, whilst also minimise the brush ‘catching within any knots or tangles’, which can result in hair breakage and even the hair being pulled out entirely, owing to the increased force required to pull the brush through the hair. The arrangement of the elongate first portions 7a of the second bristles 7 causes the flexion of the first portion 7a of the second bristles 7 to occur in a direction at substantially 45° to the motion of the hair. This enables the flexion of the second bristles 7 to aid in dispersing hair across the array of bristles 5, ensuring maximal interaction between the hair and bristles 5, whilst the second portions 7b will bend in the direction that they are pulled, more easily bending over sideways and releasing knotted hair. Table 1 below shows a table of data obtained in a comparative test between an array of bristles as described herein and the applicant’s ‘Ultimate Detangler’ as discussed above (which represents the best detangling brush in the applicant’s range). The comparative test comprised running each array of bristles through 12 identical tresses of dry, uniformly tangled hair (each of the same composition, the hair being curly, multi-ethnic hair so as to provide a representative sample of many hair types) 12 times and measuring the force applied to the hair throughout. The test was performed in line with the method first proposed by Garcia and Diaz ((JSCC, 27, (1976) 379-398 - Combability Measurements on Hair). The 12 tresses each weighed 3.0g and were 8in in length. The tresses were treated at 40°C with a controlled flow rate of 1.0 GPM. All tresses were cleansed with non-conditioning shampoo and left overnight to dry and equilibrate overnight in a controlled temperature and humidity room (60% RH). Dry combing measurements were performed the next morning using an Instron 3343 single column tensile tester equipped with a 50 N load cell to evaluate product performance, specifically the force (in gram-force units, denoted gf) throughout each stroke was recorded, and the mean maximum force for each stroke was calculated. For readability, the data in the table has been rounded to the nearest gram-force, and the mean calculated to 2 significant figures. As will be understood by the skilled person, a successful detangling brush will detangle hair faster, which will reduce the force required to pull the brush through the hair for any subsequent strokes. In other words, a quicker reduction in the force required to pull the brush through hair on a stroke by stroke basis is indicative of a better detangling performance, as more tangles will be removed by the first stroke than the second, and by the second stroke than in the third, and so forth. To be commercially successful, a detangling device must also detangle the hair gently, so in addition to a quick reduction in the force, a relatively low average force across all brush strokes is desirable. Figure 7 shows a chart plotting the data from table 1, in particular showing the force of each stroke 2-12 through the hair as a percentage of the force of the first stroke through the hair. It can be seen that an array according to the present invention plateaus between 15-20% of the first stroke for stokes 4 through 12, which indicates that the hair is tangle free, and this force that remains is merely friction / the static force of the hair. As can be seen from Figure 7, the device as described herein provides a significant reduction in relative force (as compared to the first stroke through the hair) than the ‘Ultimate Detangler’ for the second and third strokes and is still lower for the fourth stroke. The significantly lower relative force (relative to the first stroke of each brush through the hair) of the present invention compared with the Ultimate Detangler for stokes 2 and 3 indicates that there are fewer tangles within the hair for these strokes when compared with the Ultimate Detangler. Moreover, for virtually every stroke, the mean maximum force of the brush of the present invention is lower than the corresponding stroke of the Ultimate Detangler, indicating that detangling not only happens faster, but more gently. Brush Type Brush Stroke # Tress Number Mean Maximum Force (gf) 1 2 3 4 5 6 7 8 9 10 11 12 The Present Invention 1 162 326 309 321 202 1071 337 325 146 389 2680 421 557.31 2 101 188 98 147 194 146 150 189 128 209 115 215 156.62 3 111 138 135 114 101 76 154 82 79 266 126 187 130.77 4 68 121 79 96 62 125 54 106 75 85 82 126 89.98 5 144 112 113 59 106 83 57 88 99 193 89 169 109.24 6 146 103 75 118 91 72 58 83 80 237 102 132 108.06 7 92 122 109 74 67 50 77 69 74 70 108 211 93.60 8 65 186 84 154 71 78 47 70 56 157 222 155 112.11 9 109 124 83 193 69 81 39 88 53 106 105 104 95.99 10 224 83 54 54 54 129 54 47 88 145 92 135 96.48 11 90 87 94 83 74 87 23 76 55 155 141 150 92.90 12 68 116 164 56 95 120 30 67 88 134 73 133 95.28 The Ultimate Detangler 1 703 891 1010 239 128 1508 162 582 1286 376 901 281 672.34 2 181 251 151 205 129 147 148 426 1144 174 205 195 279.53 3 181 210 113 98 109 85 178 100 917 158 205 166 210.03 4 222 131 83 140 96 75 181 51 108 136 122 150 124.61 5 100 198 55 150 55 105 181 79 92 132 169 125 119.98 6 104 168 75 96 45 95 107 66 76 96 123 189 103.30 7 108 176 65 105 52 48 146 124 83 68 94 138 100.62 8 76 122 64 122 53 65 140 113 107 120 1241 143 197.38 9 112 155 44 89 47 51 114 192 84 120 1707 100 234.72 10 69 77 55 54 56 69 115 73 287 105 97 99 96.43 11 76 212 44 183 81 68 152 72 76 149 125 129 113.87 12 111 113 45 80 44 52 84 70 143 72 221 108 95.38 Table 1 Referring to the drawings, figures 8 to 14 show a device for detangling hair, specifically a brush 11 of a second embodiment. Figures 11 and 13 show enlarged parts of the brush 11, whilst figure 14 shows a magnified portion of the brush. The brush 11 5 comprises a body including a head portion 12 moulded in one piece with a handle 13 which extends generally perpendicularly from the approximate mid-point of one of the ends of the head portion 12. The head portion 12 and handle 13 extend in generally the same plane, and together define a longitudinal axis A. The underside of the brush 11 has a generally flat surface formed of a planar surface of the head portion 12 which merges into a planar surface of the handle 13. The upper side of the head portion 12 has a surface 14 which is generally flat and straight in the longitudinal direction and blends into the handle 13, which extends from the approximate mid-point of one of the ends of the head portion 12 and is narrower than the head portion 12. Along the lateral plane (i.e. between the long sides of the head, perpendicular to the longitudinal axis), the surface 14 of the upper side of the body is generally slightly convex. Of course, it will be understood that the exact nature of the body, head portion 12 and handle 13 can be varied as desired and appropriate. Other shapes of device are also possible. The head portion 12 comprises, or supports, moulded bristles 15 which project generally perpendicularly from the surface 14. The bristles 15 extend parallel to one another, and generally perpendicular from the plane of the brush (i.e. perpendicular to both the longitudinal axis and lateral plane as defined above). Each bristle 15 is spaced apart from each other bristle 15. The centre of each bristle 15 is a distance “a” away from each adjacent bristle 15. In this embodiment, the distance “a” is 4mm, but of course in light of this description, those skilled in the art will envisage alternative suitable distances. All of the bristles 15 are moulded together in one piece, together with a base (which may form all or part of the surface 14 of the brush) from a resiliently flexible plastics material. Suitable materials are thermoplastic elastomers, such as copolyesters and aliphatic polyamides (nylons). Elastomers with hardnesses from 45 to 82 Shore D are particularly suitable, especially grades in the range of 45 to 72 Shore D. In particular, the copolyester sold under the trade mark Hytrel by E. I. du Pont de Nemours and Company. For example, grades of Hytrel such as Hytrel 6356 and Hytrel 7246 are suitable. Other suitable elastomers include those sold under the trade mark Bexloy by Celanese. Grades of Bexloy such as Bexloy GPV45B5, GPV55B5 NC010, GPV63B5 NC010 and Bexloy GPV72B5 NC010 are examples of suitable elastomers. Also suitable are elastomers sold under the trade marks Pebax and Rnew by Arkema, in particular Pebax Rnew 55r53sp01, Pebax Rnew 63r53sp01 and Pebax Rnew 72r53sp01, and elastomers sold under the trade mark Triel by Samyang Corporation, in particular Triel 5550 NA, Triel 5590 NA and Triel 5720 NA. As best seen in figure 14, each bristle 15 comprises a chamfer region 18 around the bristle 15 where the bristles extend from the surface 14. Each chamfer in this embodiment extends at approximately 45° to both the bristle 15 which it surrounds and the surface 14. Each chamfer 18 has minimal height (e.g. typically less than 1mm). In the discussion below, the widths of any bristle 15 are given ignoring the chamfer 18, whilst the heights of any given bristle 15 include said chamfer 18. As seen in the figures, two types of bristle 15 are provided; first bristles 16 and second bristles 17, of which the first bristles 16 are shorter than second bristles 17. Each first bristle 16 has a cross-section with four sides, at least one of the sides having a length which is different from at least one other side. For the sake of clarity, throughout this description, the cross-section of a bristle is the cross-section when viewed in a plane perpendicular to the length of the bristle. In particular, the cross-section of each first bristle of the second embodiment of the invention is in the form of a non-equidiagonal kite having curved sides and rounded vertices. As such, as best seen in figure 15, each first bristle has a cross-section including a two shorter curved sides 16a which meet each other at a first rounded vertex 16c (which may be equated to the “top” corner of a kite, with reference to the orientation that a conventional kite is flown), and two longer curved sides 16b, which meet each other at a second rounded vertex 16d (which may be equated to the “bottom” corner of a kite, with reference to the orientation that a conventional kite is flown. Each shorter curved side 16a meets an adjacent longer curved side at one of two opposite third rounded vertices 16e. In this particular embodiment, at the end, where the bristle meets its domed tip (to avoid scratching the scalp), the longer diagonal between the first rounded vertex 16c and the second rounded vertex 16d is a distance “c”, which in this embodiment is 0.9mm, whilst the shorter diagonal (between the third vertices 16e) is the same as distance “b” above, i.e. 0.8mm. Each of the curved sides 16a, 16b has a radius of curvature “d” of 0.6mm. Of course, these dimensions are illustrative and those skilled in the art will be able to modify them as required / desired. In this embodiment, the angle of the first rounded vertex 16c (as calculated based on the tangents to the shorter curved sides 16a which meet at the first rounded vertex 16c) is largest; the angle of the second rounded vertex 16d (as calculated based on the tangents to the longer curved sides 16b which meet at the second rounded vertex 16d) is smallest; and the other two vertices 16e (as calculated based on the tangents to adjacent shorter sides 16a and longer curved sides 16b) are in between. Thus the kiteshaped cross-section is directional, with a sharp (albeit rounded) “bottom” corner. The radius of each rounded vertex may be 0.2 mm, i.e. the same as in the first embodiment. Likewise, each first bristle of the second embodiment has the same uniform taper as the first bristles 6 of the first embodiment, i.e. approximately 2° between the base and free end. The cross-section of each first bristle 16 is uniformly shaped between the base and free end (ignoring the chamfer region and rounded tip of the bristle). All of the first bristles 16 are of the same length, and have the dimensions discussed above. Each first bristle 16 is identical (or substantially identical) to every other first bristle 16 in terms of dimensions (as set out below, the arrangement / orientation of the first bristles 16 differs). In the illustrated embodiment each of the first bristles 16 extends about 7mm from the base to the tip. Each second bristle 17 has a base with a distinctly oval cross-section, having a long axis and a much shorter perpendicular short axis. As the second bristle 17 extends away from the base it tapers. Over a first portion 17a of the length of the second bristle 17, the second bristle 17 tapers such that its cross-sectional shape changes from oval to substantially circular. In particular, each second bristle 17 comprises a transition portion. The transition portion is a sub-section of the first portion 17a of each second bristle 17 and is the portion of said second bristle 17 where the cross-section transitions from the oval cross-section of the lower part of the first portion 17a (i.e. the region of the first portion 17a closest to the base) to the circular cross-section of the second portion 17b. In particular, the portions of each second bristle 17 above and below the transition portion each have cross-sections that are uniformly shaped (i.e. which have the same geometrical shape along their length, albeit the size changes as a result of the taper). In contrast, the cross-section of the transition portion at its uppermost and lowermost planes are different. Moreover, whilst the taper of the second portion 17b is uniform, and the taper of the first portion 17a below the transition portion is uniform, the taper of the transition portion is non-uniform, thus when viewed perpendicular to the elongate axis of the bristle, the taper of the transition portion gradually becomes steeper, then less steep (in a less exaggerated S-shape) to blend into the adjacent second portion and the remainder of the first portion. The edges of the second bristles 17 through which the long axis extends approach each other as each second bristle 17 extends away from the base. The opposite edges of said second bristles 17 approach each other in a curved path, which then flattens out towards a straighter taper as the second bristle 17 approaches the free end. The edges of the second bristle 17 through which the short axis extends approach each other at a substantially constant angle, and the edges of these second bristles 17 are therefore substantially straight. At the end of the first portion 17a of each second bristle 17 its cross-section is substantially circular. At this point a second portion 17b of the second bristle 17 begins. Over the second portion 17b of each second bristle 17 the cross-section of said bristle 17 remains substantially circular and the second bristle 17 tapers towards a free end, with a domed surface. The degree of taper (approximately 2°) of the second bristle 17 over the second portion 17b of the bristle 17 is less than over the first portion 17a. The degree of taper of the second portion 17b of the second bristle 17 is, in effect, the minimum consistent with being able to reliably remove the second bristle 17 from a mould tool. As far as the function of the second portion 17b of the second bristle 17 is concerned it could have a substantially constant diameter, and the same is true for the first bristles 16. In the illustrated embodiment the first portion 17a of the second bristles 17 extends about 13.25mm from the base, and the second portion 17b of the second bristles 17 extends about a further 8.75mm from the end of the first portion 17a to the end of the bristle 17. As such, the total length of the second bristles is about 22mm from the base to the free end. The widest part of the first portion 17a of each second bristle 17, measured above the chamfer, along the long axis of its oval cross-section, has a width of about 2.85mm. The narrowest part of the first portion 17a of each second bristle 17, above the chamfer, measured along the short axis of its oval cross-section, has a width of about 1.90mm. The sides of each second bristle 17 along its short axis approach each other at an angle of about 2 degrees. The sides of each second bristle 17 along its long axis approach each other with a gradually increasing angle and then gradually decreasing angle, forming a smooth curve which eventually transitions smoothly into the second portion 17b of the bristle 17. The average angle of taper between the two sides of each first portion 17a of each second bristle 17 along its long axis is 6.2°, i.e. approximately 6°, that is to say the angle of taper that would be required if the sides were straight rather than curved. At the end of the first portion 17a of each second bristle 17 it has a substantially circular cross-section with a diameter of about 1.4mm. The sides of each second bristle 7 approach each other over the second portion 7b of its length with an angle of about 2°, resulting in a diameter of about 0.8mm at the free end of each second bristle 7, not including the domed tip (which of course has a corresponding diameter of 0.8mm at its base). Other dimensions are possible, as discussed elsewhere. All of the second bristles 17 are of the same length, and have the dimensions discussed above. Each second bristle 17 is identical (or substantially identical) to every other second bristle 17 in terms of dimensions (as set out below, the arrangement / orientation of the second bristles 7 differs). The array of bristles 15 has a longitudinal axis parallel with the longitudinal axis of the brush 11 and is intended to be moved through hair in a direction generally perpendicular to said longitudinal axis, though it is noted that brushes (in particular those with handles) are rarely moved through the hair strictly perpendicular to the longitudinal axis, and in practice may be moved through the hair at various angles predominantly between 45 degrees and 135 degrees with respect to the longitudinal axis. For this reason, the brush of the present invention is intended to perform well at various angles in this range, not just when strictly perpendicular or close to perpendicular to the longitudinal axis. Each bristle 15 in the array forms a part of a “longitudinal row” of bristles 15 (i.e. a row that extends along the length of the brush 11) and a “lateral row” of bristles 15 which extends perpendicularly to the longitudinal row (across the width of the brush 11). Each of the longitudinal rows is straight (but could be slightly curved), substantially parallel and substantially evenly spaced apart. In each longitudinal row the bristles 15 are substantially evenly spaced apart, with the bristles 15 alternating between first bristles 16 and second bristles 17. The bristles in the longitudinal rows are offset relative to one another so that the centre of the cross-section of the first bristles 16 in one row lies mid-way between adjacent first bristles 16 in the adjacent row and likewise the centre of the cross-section of the second bristles 17 in one row lies mid-way between adjacent second bristles 17 in the adjacent row. Owing to the alternation of the bristles 15 within each row, this means that the bristles 15 also alternate in type within the lateral rows, in addition to the longitudinal rows. The generally kite-shaped first bristles 16 are arranged such that the sharpest rounded vertex 16d of the cross-section thereof points in a direction that is perpendicular to the longitudinal row of which any given first bristle 16 forms a part. In other words, the second rounded vertex 16d of the cross-section thereof points in a direction parallel to the lateral row of which the first bristle 16 forms a part. This enables any hair introduced into the brush 1 in a direction perpendicular to the longitudinal axis of the brush 1 to be separated smoothly by the second rounded vertex 16d aligned with the lateral row, which helps detangle hair without breaking said hair (by virtue of the vertex being rounded). The first bristles 16 are also arranged that, when taking any pair of consecutive first bristles 16 in a lateral row (ignoring any second bristles 17 therebetween), the second, sharpest rounded vertex 16d of each of said first bristles 16 that is perpendicular to the longitudinal row of which each said first bristle 16 forms a part is arranged to be in the opposite direction to that of the other first bristle 16 in the pair. The first bristles 16 in any given longitudinal row are all arranged such that they have the same orientation. This means that regardless of the direction in which the brush is moved perpendicularly through the hair, half of the first bristles 16 will have a sharp vertex pointing towards the hair to smoothly separate it. The generally kite-shaped cross-section also means that, the alternation of the orientation of the first bristles 16 means that there are, across the array of bristles 15, two further rounded vertices at the “sides” of the kite-shape which point diagonally with respect to the longitudinal / lateral rows in another four directions, so that all-in-all, like the rounded triangular bristles of the first embodiment, the vertices of the first bristles 16 are pointing in six directions. This means that, regardless of which direction the brush 11 is moved through the hair, that a rounded vertex will still be substantially aligned with the direction in which the hair moves, enabling the vertex to separate the hair. Potentially advantageously compared to the rounded triangular bristles of the first embodiment, hair moving perpendicular to the longitudinal rows may also be separated to a greater degree by the relatively blunt “top” first vertex 16c. Moreover, this additional vertex can result in a more stable bristle, and potentially add to the longevity of the bristles. The long axis of each second bristle 17 is arranged such that each second bristle 17 is at an oblique angle, which in the illustrated embodiment is a 45° angle to the longitudinal axis of the brush 11, and as such also at a 45° to the direction of the row of which the bristle 17 forms a part. The long axis of any given second bristle 17 is also arranged such that said long axis is at a 90° angle to the long axis of any adjacent second bristles 17. In the illustrated second embodiment the array comprises seventeen longitudinal rows; each row having anywhere between seven (at the lateral edges) and thirty bristles 15 (towards the centre). The lateral rows defined by said array contain anywhere between three (at the upper and lower edges) and seventeen bristles 15 (towards the centre). The majority of the bristles 15 are contained within a rectangular section of the array having twelve longitudinal rows (i.e. twelve bristles 15 wide) and twenty-three lateral rows (i.e. twenty-three bristles 15 long), with the remaining bristles 15 being arranged so as to extend to the edges of the surface 14. In the second embodiment, the surface 14 is asymmetric, so the arrangement of remaining bristles is correspondingly unequal. Of course, the number of rows and number of bristles 15 in each row can be varied as desired and appropriate. Other shapes of array are also possible. Although the bristles 15 are moulded in a single piece from the same material, owing to their different cross-section and shape, the first portions 17a are stiffer than the second portions 17b, though the first portions 17a are still flexible. In use, the first portions 17a are somewhat flexible, whereas the second portions 17b are highly flexible. The second portions 17b can be easily bent completely back on themselves (such that the tip points back towards the surface 14). On the other hand, a relatively high level of force is required to bend the first portions 17a even to 90 degrees along their short axis, and it requires an even higher level of force difficult to bend the first portions 7a to 90 degrees by hand when bending along their long axis. This has the effect that, when combined with the fact that the long axes of the second bristles 17 are arranged at oblique angles of 45° angles to the longitudinal row and longitudinal axis of the brush, the first portions 17a of the second bristles 17 preferentially bend at an oblique angle (specifically in this embodiment a direction that is at 45°) to said longitudinal row and axis. This has the consequence that hair interacting with said bristles is dispersed across the row via the directional bending of the first portions 17a of the second bristles 17, with the flexing of the second portions 17b of the second bristles 17 ensuring any tangles within the hair are not caught by said bristles 17. The first bristles 16 and the second bristles 17 are arranged in the array such that each shorter first bristles 16 is located at the centre of four longer second bristles 17, and vice versa (of course with the exception of any bristles 15 on the edge of the array). The alternation of the orientation of the long axes of the second bristles 17 means that, for any first bristle 16, the two pairs of the second bristles 17 on opposing sides of said first bristle 16 will both have long axes parallel to one another. In use, a user grips the handle of the brush 11, and inserts the bristles 15 into the hair to be detangled. Owing to the position and configuration of the handle 13, the user will introduce bristles 15 into the hair (introducing them parallel with the direction that they extend from the surface 14 of the head 12) such that the hair is roughly perpendicular to the longitudinal axis of the device, i.e. substantially parallel to the lateral axis of the brush 11. In introducing and moving the brush 11 through the hair, the second portion 17b of longer second bristles 17 will penetrate and divide the hair. As the brush 11 is inserted deeper into the hair, the first portion 17a of the second bristles 17 seek to further separate each strand of hair, by virtue of their widening crosssection. As the brush 11 is moved yet deeper into the hair, the first bristles 16 also help to separate hair not yet separated by the second bristles 17 as well as hair released from the second bristles 17 if they are bent over by a tangle. Once the brush 11 is inserted into the hair, the brush 11 being drawn through the hair enables the first bristles 16 to divide the hair smoothly, without tearing or damaging the hair (by virtue of their rounded vertices), and also to impart a shine or glossiness upon the hair as it moves past the bristles (by virtue of the curved sides). Meanwhile, any tangles present at a height where the second portions 17b reside will either be teased apart through the motion of the second portion 17b through the hair, or will not be teased apart, and the second portion 17b will flex accordingly, in the direction which the hair is being moved through the brush 11. This provides detangling action, whilst also minimise the brush ‘catching within any knots or tangles’, which can result in hair breakage and even strands of the hair being pulled out entirely, owing to the increased force required to pull the brush through the hair. The arrangement of the elongate first portions 17a of the second bristles 17 causes the flexion of the first portion 17a of the second bristles 17 to occur in a direction at an oblique angle (in this case substantially 45°) to the motion of the hair. This enables the flexion of the second bristles 17 to aid in dispersing hair across the array of bristles 15, ensuring maximal interaction between the hair and bristles 15, whilst the second portions 17b will bend in the direction that they are pulled, more easily bending over sideways and releasing knotted hair. With reference to figures 16 a-f, certain alternative options for bristle shapes which may replace the kite shaped bristles in the second embodiment are shown. For context figure 16a shows a plan view of a triangular bristle 6, with three convex curved sides 6a and three rounded vertices 6b. Figure 16b, shows a bristle with an equidiagonal kite shape, in which (in transverse cross-section) the distance between the two vertices 16e where a long side 16b meets a short side 16a is equal to the distance from the vertex 16c where the two short sides 16a meet each other to the vertex 16d where the long sides 16b meet each other. Clearly in the embodiment of figure 16b, the rounding of the vertex 16c between two short sides is different from the radius of curvature of the two short sides 16a, in order that the cross-section is generally kite-shaped, rather than triangular. Figure 16c shows a bristle with a non-equidiagonal kite shape. Here, (in transverse cross-section) the distance between the two vertices 16e where a long side 16b meets a short side 16a is not equal to the distance from the vertex 16c where the two short sides 16a meet each other to the vertex 16d where the long sides 16b meet each other. In this embodiment the difference in those diagonals is relatively small, a ratio of 0.8 : 0.85. Figure 16d is also provided for context and shows a kite shaped bristle 16 with the dimensions as set out in the description of the second embodiment and therefore a ratio of 0.8 : 0.9 between the short diagonal (or “width”) and the long diagonal (or “length”) of the kite-shape. Figure 16e shows a bristle with a generally kite-shaped cross-section with curved sides and rounded vertices, in which there is a ratio of 0.8 : 0.95 between the short diagonal (or “width”) and the long diagonal (or “length”) of the kite-shape. Finally, the kite shaped bristle shown in figure 16f is elongated still further, such that there is a ratio of 0.8 : 0.95 between the short diagonal (or “width”) and the long diagonal (or “length”) of the curved-sided, rounded-verticed kite-shaped cross-section. Of course, both triangular and kite-shaped bristles have their advantages and it is considered that the advantages of the kite-shaped bristles may extend to other quadrilaterals with at least one side which is not equal in length to at least one other side. One particular advantage that a kite shape is considered to have over triangular bristles is that in the “pull” direction of the brush, assuming it is pulled back and forth along the longer diagonal of the kite, the base of the bristle has a longer footprint than for a corresponding triangle of the same width (equal to the shorter diagonal). This makes the kite shape harder to deform and increases bristle life. In addition the “spine” at the “top” of the bristle adds stability compared to the flatter edge of a triangle. Finally the extra “spine” can divide hair better than the flatter edge of a curved triangular crosssection. As compared to quadrilaterals with equal sides, such as squares and diamonds the kite is more directional - with a square, whichever way hair approaches the square, it has the same length sides and the same angles (90 degrees). A diamond offers two alternatives in terms of angles at least, and because there are two different angles, the bristle is wider in one direction than the other. A kite, however, is a further improvement - approaching any of the four vertices of the kite, the hair sees a different combination of angle and length of side - two short, two long, or one short and one long (the latter either with the long face on the left, or on the right, from the point of view of approaching hair). This makes it more “directional” than these other quadrilaterals. The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims. Certain definitions of the invention are also set out in the following numbered clauses: CLAUSE SET 1 1. A device for detangling hair comprising an array of flexible bristles, each bristle extending from a base to a free end wherein at least some of the bristles have a cross-section having at least four sides; wherein at least one side has a length which is not equal to the length of at least one other side. 2. A device according to clause 1 wherein the sides are curved. 3. A device according to clause 1 or 2 wherein the vertices of the cross-section are rounded. 4. A device according to any of clauses 1 to 3 wherein the cross-section having at least four sides has only four sides. 5. A device according to any preceding clause wherein the cross-section has at least one angle of less than 90 degrees. 6. A device according to any preceding clause wherein the cross-section is a kite. 7. A device according to clause 6 wherein the kite is a convex kite. 8. A device according to clause 7 wherein the kite is a right kite. 9. A device according to any of clauses 6 to 8 wherein the kite is a non- equidiagonal kite. 10. A device according to clause 9 wherein the longer diagonal is between 10% and 15% longer than the shorter diagonal. 11. A device according to any of clauses 6 to 10 wherein the kite is a convex kite with curved sides and rounded corners. 12. A device according to clause 11 wherein the kite is a non-equidiagonal convex kite with curved sides and rounded corners. 13. A device according to clause 11 or 12 wherein any preceding clause, wherein one or more or each side of the bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side is convexly curved. 14. A device according to any preceding clause wherein the bristles with a crosssection having at least four sides; wherein at least one side has a length which is not equal to the length of at least one other side are arranged in rows two or more rows which are parallel to a longitudinal axis of the device. 15. A device according to clause 14 wherein at least some bristles with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side are oriented such that one of the vertices points in a direction perpendicular to the row of which said bristle forms a part. 16. A device according to clause 14 when directly or indirectly dependent on clause 5 or 6 wherein at least some bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side are oriented such that the sharpest vertex points in a direction perpendicular to the row of which said bristle forms a part. 17. A device according to any of clauses 14 to 16 wherein at least some bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side are oriented in alignment with other bristles which have a cross-section having with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side, in the same row. 18. A device according to clause 17 wherein at least some bristles with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side are oriented in opposition to other bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side in an adjacent row. 19. A device according to any of clauses 14 to 18 wherein at least some bristles with a cross-section having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side are oriented such that one of its vertices points in a direction perpendicular to a longitudinal axis of the device. 20. A device according to any preceding clause wherein the bristles with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side have a taper from the base to the free end. 21. A device according to any preceding clause wherein the bristles with a crosssection having at least four sides wherein at least one side has a length which is not equal to the length of at least one other side have a uniformly shaped crosssection between the base and free end. 22. A device according to any preceding clause wherein the bristles are formed from a resiliently flexible plastics material. 23. A device according to any preceding clause further comprising at least some bristles comprising a first, relatively wide portion which tapers from the base and a second, relatively narrow, portion which extends from the base to the free end. 24. A device according to any preceding clause wherein the device is a brush, preferably a hair brush. 25. A device according to any preceding clauses wherein the bristles are all spaced apart from one another. CLAUSE SET 2 1. A device for detangling hair comprising an array of flexible bristles, each bristle extending from a base to a free end, wherein: at least some of the bristles have a cross-section having: at least three convex curved sides; and / or only three rounded vertices; between the base and free end. 2. A device according to clause 1 wherein at least some of the bristles have a crosssection having only three curved sides and / or only three rounded vertices between the base and free end. 3. A device according to either clause 1 or 2 wherein at least some of the bristles have a cross-section having only three curved sides and only three rounded vertices between the base and free end. 4. A device according to any preceding clause wherein the bristles are arranged in two or more rows. 5. A device according to clause 4 wherein at least some bristles which have a cross-section having only three rounded vertices are oriented such that one of said rounded vertices points in a direction perpendicular to the row of which said bristle forms a part. 6. A device according to clause 5 comprising bristles which have a cross-section having only three rounded vertices, said bristles being oriented such that one of said rounded vertices points towards the rounded vertex of an adjacent bristle having only three rounded vertices. 7. A device according to any of clauses 4 to 6 wherein the bristles which have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end in one row are offset such that a bristle which has a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end in one row is aligned with the midpoint of two adjacent bristles which each have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end in an adjacent row. 8. A device according any of clauses 4 to 7 wherein the rows extend along a longitudinal axis of the device. 9. A device according to any of clauses 4 to 8 wherein the bristles are spaced apart such that, when viewed perpendicular to the rows, no part of a bristle which has a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end in one row occludes or overlaps any part of any bristles which have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end in an adjacent row. 10. A device according to any preceding clause wherein at least some of the bristles have a cross-section having at least three convex curved sides and / or only three rounded vertices half way between the base and free end. 11. A device according to any preceding clause wherein at least some of the bristles have a uniformly shaped cross-section from the base to the free end. 12. A device according to any preceding clause wherein the cross-section of the bristles which have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end is not elongate. 13. A device according to any preceding clause wherein the bristles which have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end are all substantially the same length. 14. A device according to any preceding clause wherein the bristles which have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end have a length between 3mm and 10mm. 15. A device according to any preceding clause wherein the bristles which have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end are tapered between the base and the free end. 16. A device according to clause 15 wherein the taper is uniform. 17. A device according to any preceding clause wherein the radii of the rounded vertices of any bristles having rounded vertices remains constant between the base and free end. 18. A device according to any preceding clause further comprising at least some bristles which comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end. 19. A device according to any preceding clause wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, a plurality of bristles comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end, and within each row the bristles alternate between bristles comprising first and second portions and bristles which have a cross-section having at least three curved sides and / or only three rounded vertices between the base and free end. 20. A device according to any of clauses 1 to 19 wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, a plurality of bristles comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles have a cross-section having at least three sides and / or at least three vertices between the base and free end, and within each row the bristles alternate between bristles comprising first and second portions and bristles which have a cross-section having at least three sides and / or at least three vertices between the base and free end. 21. A device according to any of clauses 1 to 18 wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, a plurality of bristles comprise a first, relatively wide, elongate portion, thereby which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles have a cross-section having at least three sides and / or at least three vertices between the base and free end, and wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions, and within each row the bristles alternate between bristles comprising first and second portions and bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end. 22. A device according to any preceding clause wherein the bristles are formed of a resiliently flexible plastics material. 23. A device according to any preceding clause wherein the device is a brush, preferably a hair brush. 24. A device according to any preceding clause wherein the device comprises a handle. 25. A method of detangling hair using a device according to any preceding clause. CLAUSE SET 3 1. A device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end, wherein: at least some bristles comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and at least some bristles have a cross-section having at least three sides and / or at least three vertices between the base and the free end; wherein the sides are optionally curved and / or the vertices are optionally rounded. 2. A device according to clause 1 wherein the bristles which comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end do not have a cross-section having at least three sides and / or at least three vertices between the base and the free end. 3. A device according to any preceding clause wherein the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end do not comprise first and second portions. 4. A device according to any preceding clause wherein the at least three sides of the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end are curved. 5. A device according to clause 4 wherein the curved sides of the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end are convex. 6. A device according to any preceding clause wherein the three vertices of the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end are rounded. 7. A device according to any preceding clause wherein the bristles are arranged in rows. 8. A device according to clause 7 where the rows are aligned with a longitudinal axis of the array of bristles. 9. A device according to either clause 7 or 8 wherein each row of bristles comprises both bristles comprising a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and bristles having a cross-section having at least three sides and / or at least three vertices between the base and the free end. 10. A device according to any of clauses 7 to 9 wherein, when viewed either parallel to or perpendicular to the rows, the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end are occluded, or partially occluded, by the bristles comprising first and second portions. 11. A device according to any preceding clause wherein the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and free end have a length between 3mm and 10mm. 12. A device according to any preceding clause wherein the bristles which comprise first and second portions have a length between 15mm and 30mm. 13. A device according to any preceding clause wherein the first portion of the bristles comprising first and second portions are longer than the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and free end. 14. A device according to any preceding clause wherein the second portion of the bristles comprising first and second portions are longer than the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and free end. 15. A device according to any preceding clause wherein the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and free end are all substantially the same length. 16. A device according to any preceding clause wherein the bristles which comprise first and second portions are all substantially the same length. 17. A device according to any preceding clause wherein the bristles which have a cross-section having at least three sides and at least three vertices between the base and free end have a cross-section having: at least three curved sides; and / or only three rounded vertices; between the base and free end. 18. A device according to any preceding clause wherein the bristles which have a cross-section having at least three sides and at least three vertices between the base and free end have a cross-section having only three curved sides and only three rounded vertices therebetween. 19. A device according to any preceding clause wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, and within each row the bristles alternate between bristles comprising first and second portions and bristles which have a cross-section having at least three sides and / or three vertices between the base and the free end. 20. A device according to any of clause 1 to 18 wherein the first portion of the bristles comprising first and second portions has an elongate cross-section, and at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions. 21. A device according to any of clauses 1 to 18 wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, and within each row the bristles alternate between bristles comprising first and second portions and bristles have a cross-section having at least three sides and / or three vertices between the base and the free end, wherein the first portion of the bristles comprising first and second portions has an elongate cross-section, and at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions. 22. A device according to any of clauses 1 to 18 wherein the bristles are arranged in one or more rows along a longitudinal axis of the device, a plurality of bristles comprise a first, relatively wide, elongate portion, which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles have a cross-section having at least three curved sides and / or only three rounded vertices between the base and the free end, wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles comprising first and second portions is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions, and within each row the bristles alternate between bristles comprising first and second portions and bristles which have a cross-section having three curved sides and / or only three rounded vertices between the base and the free end. 23. A device according to any preceding clause wherein the device is a brush, preferably a hair brush. 24. A device according to any preceding clause wherein the device comprises a handle. 25. A method of detangling hair using a device according to any preceding clause. 1. A device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end, the bristles being arranged in one or more rows along a longitudinal axis of the device wherein: a plurality of bristles comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles do not have a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, and within each row the bristles alternate between bristles comprising first and second portions and bristles not having first and second portions. 2. A device according to any preceding clause wherein the bristles additionally alternate between bristles comprising first and second portions and bristles not having first and second portions in a direction that is perpendicular to the longitudinal axis of the device. 3. A device according to any preceding clause wherein the bristles do not alternate in a direction that is at a 45° angle to the longitudinal axis of the device. 4. A device according to any preceding clause wherein the first portion of the bristles comprising first and second portions has an elongate cross-section. 5. A device according to clause 4 wherein the elongate cross-section is oval. 6. A device according to any preceding clause wherein the first portion of the bristles comprising first and second portions is, along any part of its length, at least as wide as the bristles which do not have first and second portions. 7. A device according to any preceding clause wherein the second portion of the bristles comprising first and second portions has a circular cross-section. 8. A device according to any preceding clause wherein, when viewed either parallel to or perpendicular to the rows, the bristles which do not have first and second portions are occluded, or partially occluded, by the bristles comprising first and second portions. 9. A device according to any preceding clause wherein the bristles which do not have first and second portions have a length between 3mm and 10mm. 10. A device according to any preceding clause wherein the bristles which comprise first and second portions have a length between 15mm and 30mm. 11. A device according to any preceding clause wherein the bristles comprising first and second portions are longer than the bristles which do not have first and second portions. 12. A device according to clause 11 wherein the first portion of the bristles comprising first and second portions are longer than the bristles which do not have first and second portions. 13. A device according to clause 11 or 12 wherein the second portion of the bristles comprising first and second portions are longer than the bristles which do not have first and second portions. 14. A device according to any preceding clause wherein the bristles which do not have first and second portions are all substantially the same length. 15. A device according to any preceding clause wherein the bristles which comprise first and second portions are all substantially the same length. 16. A device according to any preceding clause wherein the bristles are formed from a resiliently flexible plastics material. 17. A device according to any preceding clause wherein the bristles which do not have first and second portions do not have an elongate cross-section. 18. A device according to any preceding clause wherein the bristles which do not have first and second portions have a cross-section having at least three sides and / or at least three vertices between the base and the free end. 19. A device according to any preceding clause wherein the bristles which do not have first and second portions have a cross-section having only three curved sides and only three rounded vertices therebetween; or wherein the bristles which do not have first and second portions have a cross-section having at least four sides; wherein at least one side has a length which is not equal to the length of at least one other side. 20. A device according to any of the preceding clauses wherein the first portion of the bristles comprising first and second portions has an elongate cross-section, and some or all of the bristles comprising first and second portions are oriented such that the elongate portion of said some or all bristles is not aligned with the elongate portion of some or all adjacent bristles comprising first and second portions. 21. A device according to any of the preceding clauses wherein the bristles which do not have first and second portions have a cross-section having at least three curved sides and / or only three rounded vertices between the base and the free end, and the first portion of the bristles comprising first and second portions has an elongate cross-section, and some or all of the bristles comprising first and second portions are oriented such that the elongate portion of said some or all bristles is not aligned with the elongate portion of some or all adjacent bristles comprising first and second portions. 22. A device according to any of the preceding clauses wherein the bristles which do not have first and second portions have a cross-section having at least three sides and / or at least three vertices between the base and the free end, and the first portion of the bristles comprising first and second portions has an elongate cross-section, and some or all of the bristles comprising first and second portions are oriented such that the elongate portion of said some or all bristles is not aligned with the elongate portion of some or all adjacent bristles comprising first and second portions. 23. A device according to any preceding clause wherein the device is a brush, preferably a hair brush. 24. A device according to any preceding clause wherein the device comprises a handle. 25. A method of detangling hair using a device according to any preceding clause. 1. A device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end wherein: at least some bristles comprise a first, relatively wide, elongate portion, which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, wherein at least some bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is not aligned with the elongate portion of at least some adjacent bristles comprising first and second portions. 2. A device according to clause 1 wherein the elongate portion of said at least some bristles comprising first and second portions is oriented at 90° to the elongate portion of at least some or all adjacent bristles comprising first and second portions. 3. A device according to any preceding clause wherein the bristles are arranged in two or more rows. 4. A device according to clause 3 wherein the rows are aligned with a longitudinal axis of the device. 5. A device according to either clause 3 or clause 4 wherein the elongate portion of at least some or all bristles comprising first and second portions is oriented such that the elongate portion is not aligned with the row of which the or each bristle forms a part. 6. A device according to clause 5 wherein the elongate portion of at least some bristles comprising first and second portions is oriented at 45 ° to the row of which the or each bristle forms a part. 7. A device according to any preceding clause wherein the elongate cross-section is oval. 8. A device according to any preceding clause wherein the widest part of the cross-section of the first portion of the bristles comprising first and second portions is at least 1.25 times larger than the narrowest part of the same crosssection. 9. A device according to any preceding clause wherein the widest part of the cross-section of the first portion of the bristles comprising first and second portions is no more than 2 times larger than the narrowest part of the same crosssection. 10. A device according to any preceding clause wherein the second portion of the bristles comprising first and second portions has a non-elongate cross-section. 11. A device according to any preceding clause wherein the second portion of the bristles comprising first and second portions has a circular cross-section. 12. A device according to any preceding clause wherein the bristles which comprise first and second portions have a length between 15mm and 30mm. 13. A device according to any preceding clause wherein the bristles which comprise first and second portions are all substantially the same length. 14. A device according to any preceding clause wherein the first portion of the bristles comprising first and second portions is longer than the second portion of said bristles. 15. A device according to any preceding clause wherein the bristles are formed of a resiliently flexible plastics material. 16. A device according to any preceding clause further comprising bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end. 17. A device according to clause 16 wherein the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end have a cross-section having only three curved sides and only three rounded vertices therebetween. 18. A device according to any of clauses 1 to 16 wherein the bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end have a cross-section having at least four sides; wherein at least one side has a length which is not equal to the length of at least one other side. 19. A device according to any of the preceding clauses the bristles being arranged in one or more rows along a longitudinal axis of the device wherein: a plurality of bristles comprise a first, relatively wide, portion which tapers from the base and a second, relatively narrow, portion which extends from the first portion to the free end, a plurality of bristles do not first and second portions, and within each row the bristles alternate between bristles comprising first and second portions and bristles not having first and second portions. 20. A device according to any of clauses 16 to 18, the bristles being arranged in one or more rows along a longitudinal axis of the device wherein: within each row the bristles alternate between bristles comprising first and second portions and bristles which have a cross-section having at least three sides and / or at least three vertices between the base and the free end. 21. A device according to any preceding clause wherein the device is a brush, preferably a hair brush. 22. A device according to any preceding clause wherein the device comprises a handle. 23. A method of detangling hair using a device according to any preceding clause.

Claims

1. A device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein the device for detangling hair has a longitudinal axis; at least some of the bristles comprise a first, relatively wide, 5 portion with an elongate cross-section which extends from the base and asecond, relatively narrow, portion which extends from the first portion to the free end; and at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle to the longitudinal axis of the hair care device.10 2. A device according to claim 1 wherein at least some of the bristles comprisingfirst and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of at least 5° to the longitudinal axis of the hair care device.

3. A device according to claim 2 wherein at least some of the bristles comprising 15 first and section portions are oriented such that the elongate portion of said atleast some bristles is arranged at an oblique angle of at least 30° to the longitudinal axis of the hair care device.

4. A device according to claim 3 wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at 20 least some bristles is arranged at an oblique angle of at least 40° to thelongitudinal axis of the hair care device.

5. A device according to any preceding claim wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of less than 85° to 25 the longitudinal axis of the hair care device.

6. A device according to any preceding claim wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of less than 60° to the longitudinal axis of the hair care device.30 7. A device according to any preceding claim wherein at least some of the bristlescomprising first and section portions are oriented such that the elongate portionof said at least some bristles is arranged at an oblique angle of less than 50° to the longitudinal axis of the hair care device.

8. A device according to claim 1 wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at 5 least some bristles is arranged at an oblique angle of between 30° and 60° to thelongitudinal axis of the hair care device.

9. A device according to claim 1 wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of between 40° and 50° to the 10 longitudinal axis of the hair care device.

10. A device according to claim 1 wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of 45° to the longitudinal axis of the hair care device.15 11. A device according to any preceding claim wherein the majority of the bristlescomprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of between 30° and 60° to the longitudinal axis of the hair care device.

12. A device according to any preceding claim wherein the majority of the bristles 20 comprising first and second portions are oriented such that the elongate portionof said at least some bristles is arranged at an oblique angle of between 40° and 50° to the longitudinal axis of the hair care device.

13. A device according to any preceding claim wherein the majority of the bristles comprising first and second portions are oriented such that the elongate portion 25 of said at least some bristles is arranged at an oblique angle of 45° to thelongitudinal axis of the hair care device.

14. A device according to any preceding claim wherein the bristles are formed froma resiliently flexible plastics material.

15. A device according to any preceding claim wherein the device is a brush17. A device according to any preceding claims wherein the bristles are all spaced apart from one another.26 11 2526 11 25CLAIMS1. A device for detangling hair comprising an array of bristles, each bristle extending from a base to a free end; wherein the device for detangling hair has a longitudinal axis; at least some of the bristles comprise a first, relatively wide, 5 portion with an elongate cross-section which extends from the base and asecond, relatively narrow, portion which extends from the first portion to the free end; and at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle to the longitudinal axis of the hair care device.10 2. A device according to claim 1 wherein at least some of the bristles comprisingfirst and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of at least 5° to the longitudinal axis of the hair care device.

3. A device according to claim 2 wherein at least some of the bristles comprising 15 first and section portions are oriented such that the elongate portion of said atleast some bristles is arranged at an oblique angle of at least 30° to the longitudinal axis of the hair care device.

4. A device according to claim 3 wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at 20 least some bristles is arranged at an oblique angle of at least 40° to thelongitudinal axis of the hair care device.

5. A device according to any preceding claim wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of less than 85° to 25 the longitudinal axis of the hair care device.

6. A device according to any preceding claim wherein at least some of the bristles comprising first and section portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of less than 60° to the longitudinal axis of the hair care device.30 7. A device according to any preceding claim wherein at least some of the bristlescomprising first and section portions are oriented such that the elongate portion26 11 25of said at least some bristles is arranged at an oblique angle of less than 50° to the longitudinal axis of the hair care device.

8. A device according to claim 1 wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at 5 least some bristles is arranged at an oblique angle of between 30° and 60° to thelongitudinal axis of the hair care device.

9. A device according to claim 1 wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of between 40° and 50° to the 10 longitudinal axis of the hair care device.

10. A device according to claim 1 wherein at least some of the bristles comprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of 45° to the longitudinal axis of the hair care device.15 11. A device according to any preceding claim wherein the majority of the bristlescomprising first and second portions are oriented such that the elongate portion of said at least some bristles is arranged at an oblique angle of between 30° and 60° to the longitudinal axis of the hair care device.

12. A device according to any preceding claim wherein the majority of the bristles 20 comprising first and second portions are oriented such that the elongate portionof said at least some bristles is arranged at an oblique angle of between 40° and 50° to the longitudinal axis of the hair care device.

13. A device according to any preceding claim wherein the majority of the bristles comprising first and second portions are oriented such that the elongate portion 25 of said at least some bristles is arranged at an oblique angle of 45° to thelongitudinal axis of the hair care device.

14. A device according to any preceding claim wherein the bristles are formed from a resiliently flexible plastics material.

15. A device according to any preceding claim wherein the device is a brush17. A device according to any preceding claims wherein the bristles are all spaced apart from one another.26 11 25

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