Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/22—Roughening, e.g. by etching
  • C23C18/24—Roughening, e.g. by etching using acid aqueous solutions
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/2006—Pretreatment of the material to be coated of organic surfaces, e.g. resins by other methods than those of C23C18/22 - C23C18/30

Definitions

• the invention relates to a method of providing a metal mirror on an article of which at least the surface on which the metal mirror is to be provided is manufactured from a synthetic resin.
• the treatment of an acrylic plastic with tannic acid known from the above-mentioned United States Patent Specification has the disadvantage that an adherent silver mirror cannot be obtained.
• the treatment with tannic acid known from the above-mentioned Netherlands Patent Application has the disadvantage that it can be applied only to a special synthetic resin, namely an acrylate synthetic resin which comprises an N-substituted pyrolidone compound, In the preparation of this special synthetic resin the pyrolidone compound is not completely copolymerized. The remaining pyrolidone molecules are volatile and in the course of time can adversely influence the quality of the provided metal mirror.
• this object is achieve achieved by means of a method of the type mentioned in the opening paragraph which is characterized in that the surface of a synthetic resin which comprises a carboxylic acid amide group is treated with tannic acid and is then provided with a metal mirror by means of an electroless metallization process, and that the surface of a synthetic resin which is a polyester, a polyolefine or a polyolefine containing halogen atom(s) or aromatic group(s) as substituents is subjected to an oxidising treatment, is then treated with tannic acid, and is furthermore provided with a metal mirror by means of an electroless metallization process.
• the invention is based on the recognition gained by Applicants that a pretreatment with tannic acid, in particular in combination with an oxidising pretreatment step, has a more universal character and can be applied to the above-mentioned types of synthetic resin, in which after metallisation, a very adherent metal mirror is obtained.
• the metal mirror also remains bonded to the synthetic resin surface after ageing tests, for example a cyclic moisture test.
• a surface of polyimide, polyamide, polyurethane or poly(urethane) acrylate which all comprise a carboxylic acid amide group is treated with tannic acid, which treatment may be preceded by an oxidising treatment and then provided with a metal mirror by using an electroless metallization process.
• a surface of polyethylene, polyvinyl chloride, polystyrene, polyethylene terephthalate, polyacrylate or polymethylmethacrylate is subjected to a corona discharge, is treated with tannic acid, and is provided with a metal mirror by means of an electroless metallization process.
• a corona discharge is a known process in which a high voltage is applied between the synthetic resin surface and an electrode.
• high-energy particles will be formed, for example atomic oxygen, electrons, ions and the like which impact against the synthetic resin surface, the composition of the synthetic resin at the surface varying and in particular oxygen being bound to the surface of the synthetic resin.
• the synthetic resin surface is oxidized and obtains a hydrophilic character.
• a surface of polyvinyl chloride or polycarbonate is treated with chromic acid, then with tannic acid, and is provided with a metal mirror by means of an electroless metallization process.
• the surface of a synthetic resin as recorded in column 1 of the Table below is subjected for a few seconds to a corona discharge by means of a HF generator having a sinusoidal alternating voltage of 12-18 kV and a frequency of 20-40 kHz which is connected to an electrode placed above the surface of the synthetic resin.
• the surface of the synthetic resin is then treated with an aqueous solution of tannic acid for at most one minute at a temperature of 25°C.
• concentration of tannic acid in the solution is not restricted to narrow limits and may be chosen, by way of example, between 0.1 and 10 g of tannic acid per litre.
• the solution may also comprise water-miscible organic solvents, for example, an organic acid, alcohol, ketone, either or ester.
• the synthetic resin surface may be dipped in the solution of tannic acid.
• a solution of tannic acid may also be sprayed or poured onto the surface to be treated.
• a metal mirror for example an Ag mirror
• the synthetic resin surface is treated with a sensitising solution.
• a sensitizing solution which comprises an aqueous, acid SnCl 2 solution.
• the concentration of SnCl 2 is not restricted to narrow limits and is preferably from 0.01 to 1 g of SnCl 2 per litre, such as 0.1 g per litre.
• the treatment may be carried out by means of, for example, a dipping process, a pouring process or a spraying process.
• the synthetic resin surface is then treated with the actual metal-plating solutions, hence with the aqueous metal salt solution, for example, an ammoniacal silver nitrate solution and an aqueous reducing agent solution.
• a suitable reducing agent is formaldehyde in combination with a sugar, for example, sodium gluconate.
• the metal-plating solutions are preferably provided according to the aerosol metal-plating process in which the solutions are simultaneously sprayed onto the synthetic resin surface. This process, as well as the metal salt solutions and reduction agent solutions used therein are described, for example, in the above-mentioned literature reference "Technical Proceedings etc.”.
• Various metal-plating chemicals are commercially available from, for example, Messrs. Ermax, London Laboratories Ltd. or Merck.
• the bonding of the silver layer thus plated on the underlying synthetic resin surface is tested according to the so-called diamond scratching test (DIN 53151).
• DIN 53151 diamond scratching test
• twelve scratches are provided in the surface of the metal layer so as to extend over the whole width of the metal layer.
• the pattern of scratches comprises 6 parallel scratches having a mutual distance of 1 mm which are crossed at right angles by likewise 6 parallel scratches having a mutual distance of 1 mm so that the pattern of scratches comprises 25 areas of 1 mm .
• An adhesive tape is pressed on the pattern of scratches and is then pulled off from the surface.
• the pretreatment with only tannic acid provides good results in synthetic resins having a carboxylic acid amide group, in this case polyimide, polyamide, polyurethane and poly (urethane)acrylate.
• a combined pretreatment is necessary in which an oxidising treatment, for example a corona discharge or a treatment with chromic acid, is succeeded by a treatment with tannic acid.
• the synthetic resins of the polyester type recorded in the Table are polyethylene terephthalate, polyacrylate, polymethyl methacrylate and polycarbonate.
• polystyrene polystyrene
• polypropylene polystyrene
• the polyolefine synthetic resins recorded in the Table which may be substituted with halogen atoms or with aromatic groups are polyethylene, polyvinyl chloride and polystyrene.
• Other representatives of the said types of synthetic resin, for example polypropylene, may also be used successfully in the method in accordance with the invention.
• the combined pretreatment of a corona discharge and tannic acid presents the advantage that the metal mirror can be provided very accurately on certain parts of the synthetic resin surface. This is because a corona discharge can be carried out very accurately in which there exists a sharp boundary between parts of the surface which have been subjected to a corona discharge and parts which have not been subjected to a corona discharge.
• the method according to the invention may be used in the metallization of all kinds of products of synthetic resin, in particular optical components, for example mirrors.
• the method according to the invention is suitable in particular for providing a metal mirror on a synthetic resin surface which has a finely detailed structure which may not or only slightly be attacked during the metallization.
• the areas have very small dimensions in which the difference in height is 0.1-0.2 / um and the length of the areas is between 0.3 and 3 fume
• the disc is known by the tradenames Laser Vision and Compact Disc.
• the disc is usually manufactured from an acrylate synthetic,resin, methacrylate synthetic resin or polycarbonate.
• a metal layer for example a silver layer.
• the silver layer must follow the contours of the information track very accurately and be firmly bonded to the synthetic resin substrate.
• the difference in level between the information areas must be maintained during and after providing the metal layer because this difference is decisive of the quality of the reproduction (reading) of the stored information.
• the provision of the metal layer must not cause cloudiness of the synthetic resin of the synthetic resin-metal interface.
• the synthetic resin surface to be copper-plated is sensitized with an acid SnCl2 solution.
• the sensitized surface is treated with an aqueous ammoniacal silver salt solution in which a redox reaction takes place at the surface according to the equation Sn 2+ +2Ag + ⁇ 2Ag + Sn 4+ .
• the resulting surface which comprises one or a few monolayers of Ag is then provided with a copper layer by using an ammoniacal cuprous salt solution and an acid.
• This type of copper plating is known per se, as the disproportioning process and is described inter alia in Technical Proceedings 51st Annular Convention of the American Electropiaters' Society, p. 147, right-hand column and in German Offenlegungsschrift 2,527,096.

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• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemically Coating (AREA)
• Treatments Of Macromolecular Shaped Articles (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=19842782

Family Applications (1)

Country Status (6)

Cited By (2)

Families Citing this family (2)

Family Cites Families (3)

• 1983
  • 1983-11-29 NL NL8304084A patent/NL8304084A/nl not_active Application Discontinuation
• 1984
  • 1984-11-20 DE DE8484201682T patent/DE3478863D1/de not_active Expired
  • 1984-11-20 EP EP84201682A patent/EP0149861B1/de not_active Expired
  • 1984-11-22 CA CA000468452A patent/CA1229265A/en not_active Expired
  • 1984-11-27 JP JP24883384A patent/JPS60131974A/ja active Pending
  • 1984-11-27 AU AU35901/84A patent/AU584068B2/en not_active Ceased

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