GB2420902A - Printing of retroreflective sign - Google Patents

Printing of retroreflective sign Download PDF

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Publication number
GB2420902A
GB2420902A GB0425784A GB0425784A GB2420902A GB 2420902 A GB2420902 A GB 2420902A GB 0425784 A GB0425784 A GB 0425784A GB 0425784 A GB0425784 A GB 0425784A GB 2420902 A GB2420902 A GB 2420902A
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GB
United Kingdom
Prior art keywords
retroreflective
sign
sheet
heat
retroreflective surface
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
GB0425784A
Other versions
GB0425784D0 (en
Inventor
Jeremy James Curtis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tennants UK Ltd
Original Assignee
Tennants UK Ltd
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 Tennants UK Ltd filed Critical Tennants UK Ltd
Priority to GB0425784A priority Critical patent/GB2420902A/en
Publication of GB0425784D0 publication Critical patent/GB0425784D0/en
Publication of GB2420902A publication Critical patent/GB2420902A/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R13/00—Elements for body-finishing, identifying, or decorating; Arrangements or adaptations for advertising purposes
    • B60R13/10—Registration, licensing, or like devices
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F13/00—Illuminated signs; Luminous advertising
    • G09F13/16—Signs formed of or incorporating reflecting elements or surfaces, e.g. warning signs having triangular or other geometrical shape

Abstract

A method of manufacturing a retroreflective sign, and a retroreflective sign manufactured using such a method, are disclosed. The method comprises printing coloured indicia onto a retroreflective surface using a laser printer. The sign is typically a vehicle registration plate or a road sign.

Description

I
Title - Improvements relating to Retroreflectjve Signs This invention relates to retroreflective signs, and in particular to an improved method of manufacturing retroreflective signs.
Retroreflective signs convey information to the viewer, and reflect light along its path of incidence regardless of the angle of incidence. Such signs are of particular use as vehicle registration plates and road signs, and generally include indicia such as letters, numerals, words, phrases, symbols or images that convey the necessary information. In order to be effective, the indicia need to have sufficient contrast with their background, and be sufficiently well defined, to be clear to a viewer at a large distance from the sign.
Conventionally, vehicle registration plates and road signs are manufactured using a thermal transfer printer that prints directly onto a retroreflective surface of a retroreflective sheet. Thermal printers typically use a print head and a ribbon to transfer a mixture of colorant and binder onto the sheets of retroreflective material. The binder is generally either wax or resin, and acts to bind the colorant to the retroreflective surface.
Methods of manufacturing retroreflective signs using thermal printing suffer from numerous disadvantages. In particular, thermal printers that utilise wax or resin binders are a specialised form of printer and are therefore expensive to purchase and maintain. In addition, the printing action of a print head and a ribbon is slow because the print head acts on only a small area of the retroreflective surface at any one time, and hence must travel over the entire extent of the surface being printed.
Thermal printers generally comprise a single ribbon that is acted upon, in use, by a single print head, and are therefore able to print only one colour at a time.
Printing more than one colour onto a retroreflective sheet using such printers normally requires the ribbon to be changed and the retroreflective sheet reprinted for each additional colour. Thermal printers comprising a plurality of print heads, each having a ribbon with a different colorant, are available, but such printers tend to be very expensive.
Retroreflective sheets generally include exposed retroreflective beads and/or encapsulated retroreflective beads that are visible through the retroreflective surface. Those retroreflective sheets that include exposed retroreflective beads generally have an uneven surface that is difficult to print on using a print head and ribbon. In this case, the print head and ribbon tend to deteriorate rapidly due to the uneven nature of the surface on which they are printing and the elevated temperatures necessary to ensure effective adherence between the binder and the retroreflective surface. Those retroreflective sheets that include encapsulated retroreflective beads typically include a thin layer of transparent material that covers the beads. In this case, the print head and ribbon are liable to damage the covering layer.
There has now been devised an improved retroreflective sign and an improved method of manufacturing a retroreflective sign which overcome or substantially mitigate the above-mentioned and/or other disadvantages associated with the
prior art.
According to a first aspect of the invention, there is provided a method of manufacturing a retroreflective sign comprising printing coloured indicia onto a retroreflective surface using a laser printer.
According to a further aspect of the invention, there is provided a retroreflective sign comprising a retroreflective surface carrying coloured indicia, the coloured indicia having been printed using a laser printer.
The method and retroreflective sign according to the invention are advantageous principally because laser printers are in widespread use and hence are much less expensive than conventional machines for forming retroreflective signs. In addition, since laser printers do not require a movable printer head, the printing process is much quicker than conventional methods and the printer components will not deteriorate as quickly as those of thermal printers.
By "laser printer" is meant a printer that utilises one or more lasers to define the electrostatic charge distribution on a surface that in turn determines the distribution of print material applied to a substrate, such as a retroreflective surface.
By "coloured indicia" is meant indicia at least a part of which has a colour other than black or grey. Since retroreflective signs are typically required to convey information to the viewer, the indicia generally take the form of letters, numerals, words, phrases, symbols, and/or images that convey the necessary information.
The retroreflective sign is typically a vehicle registration plate, or a road sign for pedestrians or road users. However, other retroreflective signs could be manufactured using the method according to the invention.
The retroreflective sign preferably comprises a retroreflective sheet that has at least one retroreflective surface. The retroreflective sheet is preferably flexible in form, and hence is preferably suitable for travelling along a non-linear path within the laser printer. The retroreflective sign is preferably laminated, and preferably includes at least one relatively rigid layer such that the retroreflective sign maintains its shape during normal use. The relatively rigid layer may be a sheet of transparent plastics material that overlies the retroreflective surface of the retroreflective sheet.
The retroreflective sheet typically includes retroreflective beads, for example glass beads, that are either exposed at the retroreflective surface, or are encapsulated within the retroreflective surface but are visible therethrough.
The rear surface of the beads may be coated with a reflective substance, such as metallic paint, so as to enhance the reflectivity of the beads.
The laser printer may have the general form of a conventional laser printer that is capable of printing in colour. The laser printer will therefore typically include a plurality of toners for applying print material to the retroreflective surface.
Each toner will typically include a rotatable drum, means for applying an electrostatic charge to the surface of the drum, one or more lasers able to selectively discharge parts of the surface of the drum, and a bath of print material. Most preferably, the print material has the form of a dry powder.
In particularly preferred embodiments, the laser printer comprises a plurality of Light Emitting Diode (LED) lasers, and is therefore a socalled LED printer. In this case, the printer preferably includes a series of LED lasers adjacent to each drum for selectively discharging parts of the drum according to the image to be formed.
Each toner preferably applies its particular print material to the retroreflective surface, and then the printer preferably applies heat and pressure to the retroreflective surface to permanently adhere the print material to the retroreflective surface. Typically, the LED printer will comprise four toners that apply black, yellow, blue and red colour print material respectively.
Heat and pressure are preferably applied to the retroreflective surface by means of at least one heated roller. In order to ensure that a sufficient amount of print material adheres to the retroreflective surface, the heat that is applied to the retroreflective surface is preferably greater than that applied during conventional laser printing, onto paper for example. Most preferably, the temperature at which heat is applied to the retroreflective surface is greater than for conventional laser printing, and/or the speed of the retroreflective surface relative to the heated roller is less than for conventional laser printing.
In particular, the temperature at which heat is applied to the retroreflective surface is preferably greater than 180 C, more preferably greater than 190 C, and most preferably greater than 200 C. This compares to typical temperatures of 176 C for conventional monochrome printing and 168 C for conventional colour laser printing.
The retroreflective surface is preferably coated with a thermoplastic material, such as an acrylic resin and/or an aminoplast resin, so as to form a surface coating on the retroreflective surface. The thermoplastic material preferably softens on application of heat and pressure within the laser printer, and at least a proportion of the print material carried by the retroreflective surface is preferably urged into, and encapsulated by, the thermoplastic material during this process. The thermoplastic material of the surface coating therefore improves the adherence between the print material and the retroreflective surface. In order to improve the durability of the printing and hence the reflective sign, the thermoplastic material may be a thermosefting material.
The surface coating preferably also includes roughening and antistatic agents that act to minimise static build up on the retroreflective surface caused by the action of each toner, and hence improve the quality of the printing.
The invention will now be described in greater detail, by way of illustration only, with reference to the following example Manufacture of Vehicle Number Plates Firstly, a computer is used to prepare a design for each vehicle registration plate in the batch that is to be manufactured. Where the designs of the vehicle registration plates are substantially identical save for different registration numbers, a computer program is used to automatically prepare a design for each vehicle registration plate from a list of registration numbers. The computer is connected to an LED printer that is described in more detail below.
A flexible retroreflective sheet is firstly prepared for use in the LED printer. The retroreflective sheet includes encapsulated glass beads that are visible on one side of the sheet, that side of the sheet therefore forming the retroreflective surface. Suitable retroreflective sheets are manufactured by LG Chem, LG Twin Towers, 20 Yoido-dong, Youngdungpo-gu, Seoul 150-721, Korea.
The retroreflective surface is coated so as to improve the adherence of the print material of the printer to the retroreflective surface, and hence improve the quality of the printing. In particular, the retroreflective surface is coated with a thermoplastic surface coating comprising a styrene acrylic resin emulsion, aminoplast resins, roughening agents, and antistatic agents.
Suitably-shaped blanks on which to print the vehicle registration plate, which shape will most commonly be generally rectangular with rounded corners, are cut from the sheet of material. Such a blank may then be fed manually into the LED printer.
Once the retroreflective sheets have been prepared, a stack of retroreflective sheets are loaded into a cartridge of the LED printer.
The LED printer comprises four toners that each include a rotatable drum, a charge roller, and a bath of dry plastic toner powder including a colorant. The LED printer further comprises four series of LEDs, each series of LEDs being arranged adjacent to a drum of a toner such that the series of LEDs are able to illuminate the surface of its associated drum.
The toners each contain a differently coloured toner powder, which forms the print material, so that application of the four toner powders to the retroreflective surface can create any desired colour. In particular, the four toners contain black, yellow, blue and red toner powders, respectively. The toners are arranged in a series such that the retroreflective sheet is fed through the series of toners in a single movement. Such a printer is usually referred to as a single-pass printer.
The drum of each toner is rotatably coupled, with a frictional engagement, to the charge roller such that charge is transferred from the charge roller to the surface of the drum on contact. The LEDs then expose parts of the charged surface of the drum to laser light, which causes those parts of the drum to be discharged, according to the particular vehicle registration plate design being printed. The surface of the drum then passes through the bath of toner powder such that the charged parts of the surface of the drum electrostatically attract and collect toner powder. The drum then deposits the collected toner powder onto the retroreflective surface of the retroreflective sheet as it passes through the toner.
In this way, the action of the LEDs determines the distribution of print material applied to the retroreflective surface. The roughening and antistatic agents of the surface coating act to minimise static build up on the retroreflective surface caused by the action of each toner, and hence improve the quality of the printing.
Once the retroreflective sheet has passed through all four toners, it passes through a pair of finishing rollers that apply heat and pressure to the toner powder and retroreflective surface so as to permanently fix the toner powder to the retroreflective surface. The heat applied by the finishing rollers to the toner powder and retroreflective surface is at an increased temperature relative to the temperature conventionally used in laser printers, and is typically at a temperature of about 200 C or greater. In addition, the speed of the retroreflective surface relative to the finishing rollers is less than for conventional laser printing.
In addition, the thermoplastic resin of the surface coating is softened by the heat of the finishing rollers such that at least a proportion of the toner powder is urged into, and becomes encapsulated within, the surface coating of the retroreflective surface. The surface coating therefore acts to increase the adherence between the toner powder and the retroreflective surface.
Once the sheets of retroreflective material have been printed with the relevant vehicle registration plate designs, the cut-out retroreflective sheet is laminated under pressure to an adhesive coated surface of a sheet of relatively rigid, transparent plastics material, eg acrylic, such that the sheet of transparent plastics material overlies the retroreflective surface, thereby forming a vehicle registration plate.

Claims (38)

  1. Claims 1. A method of manufacturing a retroreflective sign comprising
    printing coloured indicia onto a retroreflectjve surface using a laser printer.
  2. 2. A method as claimed in Claim 1, wherein the indicia take the form of letters, numerals, words, phrases, symbols, and/or images, such that the reflective sign conveys information to a viewer.
  3. 3. A method as claimed in Claim I or Claim 2, wherein the retroreflective sign comprises a retroreflective sheet that has at least one retroreflective surface.
  4. 4. A method as claimed in Claim 3, wherein the retroreflective sheet is flexible in form, and is suitable for travelling along a non-linear path within the laser printer.
  5. 5. A method as claimed in Claim 3 or Claim 4, wherein the retroreflective sheet includes retroreflective beads that are either exposed at the retroreflective surface, or are encapsulated within the retroreflective surface but are visible therethrough.
  6. 6. A method as claimed in Claim 5, wherein the rear surface of the beads is coated with a reflective substance so as to enhance the reflectivity of the beads.
  7. 7. A method as claimed in any preceding claim, wherein the retroreflective sign is laminated.
  8. 8. A method as claimed in Claim 7, wherein the retroreflective sign includes at least one relatively rigid layer such that the retroreflective sign maintains its shape during normal use.
  9. 9. A method as claimed in Claim 8, wherein the relatively rigid layer is a sheet of transparent plastics material that overlies the retroreflective surface of the retroreflective sheet.
  10. 10. A method as claimed in any preceding claim, wherein the laser printer includes a plurality of toners for applying print material to the retroreflective surface.
  11. 11. A method as claimed in Claim 10, wherein each toner includes a rotatable drum, means for applying an electrostatic charge to the surface of the drum, one or more lasers able to selectively discharge parts of the surface of the drum, and a bath of print material.
  12. 12. A method as claimed in Claim 11, wherein the print material has the form of a dry powder.
  13. 13. A method as claimed in Claim 11 or Claim 12, wherein the laser printer comprises a plurality of Light Emitting Diode (LED) lasers.
  14. 14. A method as claimed in Claim 13, wherein the printer includes a series of LED lasers adjacent to each drum for selectively discharging parts of the drum according to the image to be formed.
  15. 15. A method as claimed in any one of Claims 11 to 14, wherein each toner applies its particular print material to the retroreflective surface, and then the printer applies heat and pressure to the retroreflective surface to permanently adhere the print material to the retroreflective surface.
  16. 16. A method as claimed in Claim 15, wherein heat and pressure are applied to the retroreflective surface by means of at least one heated roller.
  17. 17. A method as claimed in Claim 15 or Claim 16, wherein the heat that is applied to the retroreflective surface is greater than that applied during conventional laser printing.
  18. 18. A method as claimed in Claim 17, wherein the temperature at which heat is applied to the retroreflective surface is greater than for conventional laser printing, and/or the speed of the retroreflective surface relative to the heated roller is less than for conventional laser printing.
  19. 19. A method as claimed in Claim 18, wherein the temperature at which heat is applied to the retroreflective surface is greater than 180 C.
  20. 20. A method as claimed in Claim 19, wherein the temperature at which heat is applied to the retroreflective surface is greater than 190 C.
  21. 21. A method as claimed in Claim 20, wherein the temperature at which heat is applied to the retroreflective surface is greater than 200 C.
  22. 22. A method as claimed in any preceding claim, wherein the retroreflective surface is coated with a thermoplastic material.
  23. 23. A method as claimed in Claim 22, wherein the thermoplastic material softens on application of heat and pressure within the laser printer, and at least a proportion of the print material carried by the retroreflective surface is urged into, and encapsulated by, the thermoplastic material during this process.
  24. 24. A method as claimed in Claim 23, wherein the thermoplastic material is a thermosetting material.
  25. 25. A method as claimed in any one of Claims 22 to 24, wherein the surface coating includes roughening and antistatic agents.
  26. 26. A ret roreflective sign comprising a retroreflective surface carrying coloured indicia, the coloured indicia having been printed using a laser printer.
  27. 27. A retroreflective sign as claimed in Claim 26, wherein the indicia take the form of letters, numerals, words, phrases, symbols, and/or images, such that the reflective sign conveys information to a viewer.
  28. 28. A retroreflective sign as claimed in Claim 26 or Claim 27, wherein the retroreflective sign comprises a retroreflective sheet that has at least one retroreflective surface.
  29. 29. A retroreflect,ve sign as claimed in Claim 28, wherein the retroreflective sheet includes retroreflective beads that are either exposed at the retroreflective surface, or are encapsulated within the retroreflective surface but are visible therethrough.
  30. 30. A retroreflective sign as claimed in Claim 29, wherein the rear surface of the beads is coated with a reflective substance so as to enhance the reflectivity of the beads.
  31. 31. A retroreflective sign as claimed in any preceding claim, wherein the retroreflective sign is laminated.
  32. 32. A retroreflective sign as claimed in Claim 31, wherein the retroreflective sign includes at least one relatively rigid layer such that the retroreflective sign maintains its shape during normal use.
  33. 33. A retroreflective sign as claimed in Claim 32, wherein the relatively rigid layer is a sheet of transparent plastics material that overlies the retroreflective surface of the retroreflective sheet.
  34. 34. A retroreflective sign as claimed in any one of Claims 26 to 33, wherein the retroreflective surface is coated with a thermoplastic material.
  35. 35. A retroreflective sign as claimed in Claim 34, wherein the thermoplastic material is a thermosetting material.
  36. 36. A retroreflective sign as claimed in Claim 34 or Claim 35, wherein the surface coating includes roughening and antistatic agents.
  37. 37. A method of manufacturing a retroreflective sign as hereinbefore described and as illustrated by the example.
  38. 38. A retroreflect,ve sign as hereinbefore described and as illustrated by the
    example.
GB0425784A 2004-11-24 2004-11-24 Printing of retroreflective sign Withdrawn GB2420902A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0425784A GB2420902A (en) 2004-11-24 2004-11-24 Printing of retroreflective sign

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0425784A GB2420902A (en) 2004-11-24 2004-11-24 Printing of retroreflective sign

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GB0425784D0 GB0425784D0 (en) 2004-12-22
GB2420902A true GB2420902A (en) 2006-06-07

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5378575A (en) * 1990-05-15 1995-01-03 Minnesota Mining And Manufacturing Company Printing of reflective sheeting
US5897738A (en) * 1995-08-31 1999-04-27 Minnesota Mining And Manufacturing Company Process for manufacturing a sign
US20040073798A1 (en) * 2002-06-13 2004-04-15 Look Thomas F. System of controlled certificate production and management
WO2005056275A1 (en) * 2003-12-15 2005-06-23 Multi Sign A/S System and method for the manufacture of a film comprising a retro reflective pattern

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5378575A (en) * 1990-05-15 1995-01-03 Minnesota Mining And Manufacturing Company Printing of reflective sheeting
US5897738A (en) * 1995-08-31 1999-04-27 Minnesota Mining And Manufacturing Company Process for manufacturing a sign
US20040073798A1 (en) * 2002-06-13 2004-04-15 Look Thomas F. System of controlled certificate production and management
WO2005056275A1 (en) * 2003-12-15 2005-06-23 Multi Sign A/S System and method for the manufacture of a film comprising a retro reflective pattern

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Publication number Publication date
GB0425784D0 (en) 2004-12-22

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