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WO1989006811A1 - Materiau reflechissant - Google Patents

Materiau reflechissant Download PDF

Info

Publication number
WO1989006811A1
WO1989006811A1 PCT/GB1989/000032 GB8900032W WO8906811A1 WO 1989006811 A1 WO1989006811 A1 WO 1989006811A1 GB 8900032 W GB8900032 W GB 8900032W WO 8906811 A1 WO8906811 A1 WO 8906811A1
Authority
WO
WIPO (PCT)
Prior art keywords
cube
recesses
corner
reflective
punch element
Prior art date
Application number
PCT/GB1989/000032
Other languages
English (en)
Inventor
William Nevil Heaton Johnson
Nicholas John Phillips
Original Assignee
Scientific Applied Research (S.A.R.) Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Scientific Applied Research (S.A.R.) Plc filed Critical Scientific Applied Research (S.A.R.) Plc
Priority to KR1019890701695A priority Critical patent/KR900700897A/ko
Publication of WO1989006811A1 publication Critical patent/WO1989006811A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
    • B29C33/3842—Manufacturing moulds, e.g. shaping the mould surface by machining
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/12—Reflex reflectors
    • G02B5/122—Reflex reflectors cube corner, trihedral or triple reflector type
    • G02B5/124—Reflex reflectors cube corner, trihedral or triple reflector type plural reflecting elements forming part of a unitary plate or sheet

Definitions

  • THIS INVENTION relates to a reflective material which is particularly, but not exclusively, useful for the production of such items as cinema projection screens, motorway signs, advertising signs, reflective vehicle number plates and the like.
  • the invention relates to the manufacture of a reflective sheet material having a light reflective surface which is formed with a plurality of cube- corner recesses, as herein defined, whereby light striking said material will be reflected back in the direction from whence it has come.
  • reflective sheet material Several forms of reflective sheet material are already known.
  • One class of such materials comprises a mass of transparent spheres embedded in a cement matrix applied as a coating to the surface which is intended to be reflective, such as a flexible film.
  • the retroreflectivity i.e. the efficiency of such a material, in terms of the percentage of the light striking the material which is reflected back along the path of incidence, is low, for the exposed portions of the spheres actually form a relatively small proportion of the total surface of the medium and only a part of the light entering each sphere is reflected back along its path of incidence.
  • Reflective materials are also known comprising a metallic or quasi-metallic reflective surface formed with a regular array of cube-corner recesses. Whilst materials of this character exhibit a substantially greater retro- reflectivity than materials of the first-mentioned class, it has, hitherto, been difficult to provide such materials in the form of relatively thin sheets, for if the material is in the form of a thin sheet, this implies that the individual reflective cube-corner recesses shall be of correspondingly small size and it has hitherto been difficult to provide accurately formed recesses of such small size economically.
  • One known material of this type is formed from a moulding or pressing operation using tools derived from a master formed by scoring a surface with three sets of parallel equally spaced grooves, the three sets being mutually at 120° with respect to each other, using a grinding wheel or other tool having a triangular-section edge such that the finished workpiece comprises a corres ⁇ ponding array of projections of cube-corner form.
  • a method of making a light reflective material comprising an array of cube-corner reflectors, as herein defined, comprising forming a master by indexing a body of deformable material, in a scanning mode, relative to a tool so that a surface of the deformable material is advanced in steps past said tool, said tool comprising a punch element having a cube corner head, as herein defined, of a hard material, such as diamond, capable of receiving an optically smooth surface finish, said punch element being mounted for movement towards and away from said surface, the punch element being connected with piezo-electric motor means whereby, at each indexing step, the punch element, more particularly said head of the punch element, can be propelled into said deformable material to form a respective cube corner recess, as herein defined, in said surface of the material, whereby in a succession of indexing steps and scans, an array of such cube-corner recesses is formed in said surface of the material, the material, bearing said array of reces
  • cube-corner recess as used herein is intended to denote a recess defined by three mutually perpendicular planar surfaces intersecting along three orthogonal axes meeting in a vertex of the recess.
  • the term "cube corner head” as used herein in relation to a punch element denotes a punch element head defined by three mutually perpendicular planar faces meeting in respective edges terminating in an apex or point.
  • a reflective material made by a method embodying the invention and comprising an array of such cube-corner reflectors forms a highly efficient reflector for use in situations where the material will be viewed in substantially the same direction as that in which light is directed to the material to illuminate the same, for example in motorway signs intended to be observed by the drivers of vehicles having headlamps illuminating the signs, or for reflective vehicle number plates or in relation to cinema projection screens.
  • a further application of such a material, particularly where the material comprises a dense array of relatively minute indentations, is in relation to certain optical and holographic and laser techniques utilising, for example, the fact that a plate of such material, because it effectively reverses each light ray falling thereon, can be utilised, in principle, to provide a simultaneous real image of an object, coincident with the object itself, or, if a semi- transparent/semi-reflective screen is utilised as a "beam splitter", located at a position spaced from the object.
  • a master in order to manufacture a retroreflective material, is first manufactured by indexing a sheet of deformable plastics material supported by an indexing table, in a scanning mode, step-by-step past a tool so that, relative to the plastics sheet, the tool effects a scanning movement above the surface of the plastics.
  • the tool comprises a punch element having a cube-corner head and motor means, in the form of a piezo-electric element, for propelling said punch, at each indexing step, into the deformable plastics material to form a respective cube corner recess in the surface of the material.
  • the punch element is mounted for movement towards and away from the exposed surface of the deformable material, for example by being directly secured to one end of the piezo electric motor element mounted by its opposite end in a suitable support, so that the elongation of the piezo electric element on the application of a voltage pulse thereto automatically moves the stylus or head towards and into the deformable material.
  • the punch element has the head thereof formed by a tip or stylus of diamond or like hard material capable of receiving an optically smooth surface finish, said tip or stylus being formed with three mutually perpendicular highly polished planar facets defining the cube corner, said facets being also equally inclined to the direction of movement of the punch element into and out of the deformable material.
  • the piezo electric motor element is energised periodically by electrical pulses at successive indexing steps whereby during an entire scan, the surface of deformable plastics material is formed with a close array of such right pyramidal recesses, each recess being formed, at a res ⁇ pective indexing step, in a respective single electrical pulse applied to the piezo-electric motor element.
  • the punch element is also mounted for rotation about an axis parallel with the last-noted direction of movement, relative to the table, whereby two interspersed sets of cube-corner recesses forming the array can be formed, one set being rotated through 180° relative to the other set (as seen looking down on the material), so that the recessed surface is formed entirely by said cube-corner recesses, without surface regions of finite width between adjacent said recesses which do not form part of the cube-corner surfaces.
  • the punch element may be rotated at every step, in alternate senses, so that in successive indenting steps each recess formed is oriented at 180° relative to that formed in the preceding step. It will be appreciated, however, that this arrangement also necessitates a slight displacement of the tool, or the indexing table, relative to the line scan direction, in one sense or the opposite sense, at each indexing step, and it will generally be preferable, in the first of every two successive scanning lines, to form a first row of similarly oriented cube-corner recesses, and in the second scanning line, after turning the punch element through 180° and advancing the indexing table appropriately perpendicularly to the scanning lines, to form a second row of oppositely oriented cube corner recesses each located between a respective pair of adjacent recesses in the first row, the apparatus being so controlled as to ensure that the necessary half-pitch displacement between two lines of intermeshed recesses is maintained.
  • the means provided for moving the indexing table in steps during each scanning line, and for moving the indexing table by the appropriate amount in a perpendicular direction between successive scanning lines, and also the piezo ⁇ electric motor means for the tool, and further means provided for rotating the punch about said axis, are all preferably controlled by microprocessor.
  • the depth of the recesses is determined principally by the voltage of the electrical pulse applied to the piezo-electric element at each indexing step, the appropriate voltage to produce recesses corresponding in size to the indexing steps being determined by experiment for the respective deformable material used.
  • the apparatus may comprise a sensor, possibly constituted by the piezo electric element itself, arranged to provide a signal when the corner-cube head touches the material, and the arrange ⁇ ment may be such that, at each indexing step, the electrical pulse applied comprises a relatively slowly rising voltage applied to the piezo electric element to bring the cube corner head into contact with the material, and a pre- determined voltage increment which is then added rapidly to the voltage applied to the element, to drive the head to a predetermined extent into the material.
  • a further motor means may be provided to effect approach of the tool to the material prior to contact and for retraction of the tool after indenting of the material.
  • a plastics material such as PVC (polyvinyl- chloride) or polyethylene or a polyester, which is mechanic ⁇ ally deformable but has minimal recovery or flow character- istics so that the impressions of the tool head will be retained therein without distortion.
  • the deformable material may be a deformable oxidation-resistant metal, such as aluminium, silver or gold.
  • the master formed by the above described treatment of the deformable material is used to provide, by an electro ⁇ type or other process, known per se, a relatively hard and durable mould or die part affording a complementary surface and which can be used, in a moulding or pressing operation, to provide a plastics sheet, for example of PVC having a surface configuration corresponding with that of the master.
  • This plastics sheet may then be provided, on its surface afforded by the cube-corner recesses, with a thin reflective metallic layer, for example by vacuum deposition of the metal over the recessed surface, the layer being very thin, for example 10 to 100 atoms thick, and conforming closely with the plastics surface.
  • the cube corner embossed, metallised sur ⁇ face is then coated with a layer of transparent plastics, such as clear PVC of a melting point lower than the base material, which fills the cube-corner recesses and affords an optically smooth flat surface, remote from the metallisation, which lies parallel with the notional surface in which lie the edges of the cube-corner recesses, and which is parallel with the flat surface of the embossed or moulded reflective sheet which is remote from the cube- corner recesses.
  • transparent plastics such as clear PVC of a melting point lower than the base material
  • This covering layer of transparent plastics not only protects the reflective cube corner recesses, for example by preventing foreign material from lodging in the recesses and protecting the metallisation from oxidation or other chemical attack, but also serves to refract any light ray, incident on the reflective sheet at an angle to the perpendicular, so that it enters the respective reflective recesses at an angle closer to the perpendicular to the reflective sheet than it would otherwise have done, whereby the range of angles of incidence over which the reflective material is fully effective is increased.
  • the microprocessor controlling the apparatus may be programmed to apply a limited random or pseudo-random variation to the recess size and/or spacing and/or the angular orientation of the recesses about axes perpendicular to the general plane of the deformable sheet material.
  • Such variation necessarily entails leaving a small proportion of the reflective surface of the finished product which is not part of any cube-corner recess and which may therefore reflect an incident ray in a direction other than that opposite to that in which it reached the material.
  • the randomisation referred to brings with it a degree of scatter which represents a trade-off against the reduction or elimination of diffraction effects.
  • the characteristic pattern of variation may be used to determine whether a given sample of the material emanates from a manufacturer using that specific pattern of variation, or was derived by "reverse engineering" from that manufacturer's product.
  • the pattern of variation from strict regularity may be used to serve a security function.
  • a cylindrical member having its surface provided by an appropriate deformable material may be rotated and traversed stepwise, past a deforming tool such as described above, with a view to producing, ultimately, a cylindrical roller which can be used in the production, on a continuous basis, of a continuous length of the reflective material, by passing an appropriate sheet plastics material, in strip form, through the nip between the cylindrical roller, (formed with surface projections complementary in form to the desired right pyramidal recesses), and a counter roller, to produce the indented sheet which is then metallised and coated as before.
  • each recess comprising an array of reflective cube corner recesses in which the size of the recesses is substantially smaller and the recess density, in terms of number of recesses per unit area, substantially greater, than has been possible hitherto.
  • the edge of each recess where the planes of the three mutually perpendicular planes defining the recess meet the notional plane containing the uppermost or outermost part of the surface defined by the recesses, has substantially the form of an equilateral triangle.
  • the length of each side of each such triangle in the preferred embodiment of the invention, may be from 30 to 100 microns, preferably in the range of from 30 to 50 microns.
  • Reflective material embodying the invention may also, for example, have applications in advertising.
  • the metallised reflect ⁇ ive material might, in effect, be overprinted with "ink” of differently coloured but transparent plastics, to afford a poster or the like of striking brightness.
  • the neutral transparent coating layer applied directly over the reflective recesses may be retained and the transparent coloured "inks" printed onto the coating layer.
  • the reflective material embodying the invention might be used as a backing for a photographic print material similar to that sold under the trade mark "CIBA-CHROME" in which light transmitting layers in the medium are overlaid on a highly reflective backing material, the use of material made in accordance with the invention in such an application providing prints, affording an even higher brightness with high contrast combined with a full range of tone gradations.
  • Material embodying the invention may also, for example, be manufactured in the form of an adhesive plastics tape, provided with a permanently tacky adhesive on the side thereof remote from the reflective side so that, for example, pieces of such tape might be applied to existing road signs to modify the same or might be applied directly to the road surface, to provide temporary road signs.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)

Abstract

Un matériau réfléchissant la lumière, qui comprend un réseau de réflecteurs d'angle de cube est fabriqué par moulage ou pressage d'une feuille de plastique au moyen d'un moule ou d'un outil de pressage de forme conçu pour produire, dans la surface de la feuille en plastique, un réseau d'évidements d'angle de cube. La surface de la feuille est ensuite métallisée, pour transformer les évidements en réflecteurs d'angle de cube, et une couche transparente remplissant l'évidement est appliquée sur la surface métallisée de la feuille en plastique. Le moule ou l'outil de pressage est obtenu par un procédé de galvanotypie, à partir d'un patron formé par indexage d'une feuille de plastique déformable selon un mode de balayage en passant par un poinçon d'endentement comprenant une pointe de diamant découpée en forme d'angle de cube. Le poinçon est porté par un élément piézo-électrique, lequel est soumis à une impulsion électrique à chaque étape d'indexage, de façon à permettre l'enfoncement de la pointe de diamant d'angle de cube dans le plastique déformable à chaque étape d'indexage, formant ainsi un évidement d'angle de cube correspondant.
PCT/GB1989/000032 1988-01-13 1989-01-13 Materiau reflechissant WO1989006811A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1019890701695A KR900700897A (ko) 1988-01-13 1989-01-13 반사재료

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888800710A GB8800710D0 (en) 1988-01-13 1988-01-13 Reflective material
GB8800710 1988-01-13

Publications (1)

Publication Number Publication Date
WO1989006811A1 true WO1989006811A1 (fr) 1989-07-27

Family

ID=10629884

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1989/000032 WO1989006811A1 (fr) 1988-01-13 1989-01-13 Materiau reflechissant

Country Status (4)

Country Link
KR (1) KR900700897A (fr)
AU (1) AU2931789A (fr)
GB (1) GB8800710D0 (fr)
WO (1) WO1989006811A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000042454A1 (fr) * 1999-01-11 2000-07-20 3M Innovative Properties Company Retroreflecteurs a cavites en angle droit et procedes de fabrication desdits retroreflecteurs
US6280822B1 (en) 1999-01-11 2001-08-28 3M Innovative Properties Company Cube corner cavity based retroeflectors with transparent fill material
US6843571B2 (en) 2002-06-11 2005-01-18 3M Innovative Properties Company Methods of making a master and replicas thereof
US6935756B2 (en) 2002-06-11 2005-08-30 3M Innovative Properties Company Retroreflective articles having moire-like pattern
EP1149317B1 (fr) * 1999-01-21 2007-06-06 Reflexite Corporation Construction prismatique a surfaces decouvertes, retroreflechissante, et durable
US20120117807A1 (en) * 2005-07-25 2012-05-17 Hakko, Co., Ltd. Ultrasonic piercing needle

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2440963A (en) * 1945-03-06 1948-05-04 Richard W Luce Method of making molds
US3069721A (en) * 1960-03-04 1962-12-25 Ciba Ltd Tools for making surface patterns
US4080280A (en) * 1975-11-26 1978-03-21 Ferro Corporation Pin for forming reflector
US4082414A (en) * 1976-03-03 1978-04-04 Pyreflex Corporation Heat recuperation
US4189209A (en) * 1978-10-13 1980-02-19 Ferro Corporation Retroreflector of integrated light reflecting units of varying configurations
US4478769A (en) * 1982-09-30 1984-10-23 Amerace Corporation Method for forming an embossing tool with an optically precise pattern
EP0171975A2 (fr) * 1984-08-10 1986-02-19 Amerace Corporation Procédé et appareil pour former un motif optique de précision par gaufrage dans une feuille ou un stratifié en matière plastique

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2440963A (en) * 1945-03-06 1948-05-04 Richard W Luce Method of making molds
US3069721A (en) * 1960-03-04 1962-12-25 Ciba Ltd Tools for making surface patterns
US4080280A (en) * 1975-11-26 1978-03-21 Ferro Corporation Pin for forming reflector
US4082414A (en) * 1976-03-03 1978-04-04 Pyreflex Corporation Heat recuperation
US4189209A (en) * 1978-10-13 1980-02-19 Ferro Corporation Retroreflector of integrated light reflecting units of varying configurations
US4478769A (en) * 1982-09-30 1984-10-23 Amerace Corporation Method for forming an embossing tool with an optically precise pattern
EP0171975A2 (fr) * 1984-08-10 1986-02-19 Amerace Corporation Procédé et appareil pour former un motif optique de précision par gaufrage dans une feuille ou un stratifié en matière plastique

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2000042454A1 (fr) * 1999-01-11 2000-07-20 3M Innovative Properties Company Retroreflecteurs a cavites en angle droit et procedes de fabrication desdits retroreflecteurs
US6280822B1 (en) 1999-01-11 2001-08-28 3M Innovative Properties Company Cube corner cavity based retroeflectors with transparent fill material
US6287670B1 (en) 1999-01-11 2001-09-11 3M Innovative Properties Company Cube corner cavity based retroreflectors and methods for making same
US6656571B2 (en) 1999-01-11 2003-12-02 3M Innovative Properties Company Cube corner cavity based retroreflectors and methods for making same
EP2261700A1 (fr) 1999-01-11 2010-12-15 3M Innovative Properties Company Rétro réflecteur à coins de cube dont les cavités sont remplies de matériau transparent
EP2267494A2 (fr) 1999-01-11 2010-12-29 3M Innovative Properties Company Rétroréflecteurs à cavités en angle droit et procédés de fabrication desdits rétroréflecteurs
EP2267495A2 (fr) 1999-01-11 2010-12-29 3M Innovative Properties Company Rétroréflecteurs à cavités en angle droit et procédés de fabrication desdits rétroréflecteurs
US8596799B2 (en) 1999-01-11 2013-12-03 3M Innovative Properties Company Cube corner cavity based retroreflectors with transparent fill material
EP1149317B1 (fr) * 1999-01-21 2007-06-06 Reflexite Corporation Construction prismatique a surfaces decouvertes, retroreflechissante, et durable
US6843571B2 (en) 2002-06-11 2005-01-18 3M Innovative Properties Company Methods of making a master and replicas thereof
US6935756B2 (en) 2002-06-11 2005-08-30 3M Innovative Properties Company Retroreflective articles having moire-like pattern
US20120117807A1 (en) * 2005-07-25 2012-05-17 Hakko, Co., Ltd. Ultrasonic piercing needle

Also Published As

Publication number Publication date
KR900700897A (ko) 1990-08-17
GB8800710D0 (en) 1988-02-10
AU2931789A (en) 1989-08-11

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