FR2537969A1 - METHOD FOR MANUFACTURING MIRRORS - Google Patents

Abstract

THE INVENTION CONCERNS THE MANUFACTURING OF MIRRORS INCLUDING A SHEET OF GLASS 1 COATED WITH A REFLECTING LAYER 2 AND WITH ONE OR MORE PROTECTIVE LAYERS 4 OF THE REFLECTING LAYER. A PROTECTIVE LAYER 4 IS FORMED ON THE MIRROR FROM A COMPOSITION POLYMERISABLE BY IRRADIATION BY ELECTRON BEAM, WHICH IS POLYMERIZED ON THE MIRROR FORMING AN ADHESIVE COATING. THE INVENTION IS PARTICULARLY APPLICABLE TO THE RAPID ONLINE MANUFACTURING OF MIRRORS.

Description

The present invention relates to a method of manufacturing a mirror

  including the application of a reflective layer on

  a back surface of a transparent glass sheet and cover it with

  of the reflective layer by means of one or more protective layer (s). In the most common mirror manufacturing processes, a transparent glass sheet is coated on its face

  back of a reflective layer usually made of silver.

  The silver layer is covered with a layer of copper and the copper layer is then painted or varnished. The paint layer serves to protect the underlying metal layers from corrosion and abrasion.

  A major disadvantage of such methods is that the

  It takes a long time for the paint protector to dry and it is therefore necessary to store the mirrors that have just been made in such a way that their rear faces are not touched while the paint is still fresh.

  online production and requires additional storage space

  important when mirrors are manufactured in large quantities.

  In the usual production processes used

  so far, the protective coating cures by solvent evaporation.

  This leads to the pollution of the production plant's atmosphere by solvent vapors, especially during mass production. Furthermore, drying is not fast enough unless

that we heat the mirrors.

  One of the objects of the present invention is to provide a

  mirror manufacturing method in which this disadvantage is avoided.

  The present invention provides a method of manufacturing a mirror comprising applying a reflective layer on

  a back surface of a transparent glass sheet and cover it with

  the reflective layer by means of one or more protective layers, characterized in that the said protective layer or layers are formed by applying to the rear surface coated with the sheet a coating of a polymerizable composition by electron beam irradiation and by polymerization thereof with one or more

  beam (x) of electrons to form an adherent protective coating.

  By use of the present invention, the resin layer can be polymerized in a few seconds so that the mirrors that have just been manufactured can be stacked as desired without having to take precautions against the deterioration of a layer. protective yet wet and online production is facilitated Similarly, the problem of solvent pollution can

to be uselessly eliminated.

  In addition, beam irradiation polymerization

  electrons has considerable advantages vis-à-vis

  photon radiation polymerization, Firstly, it is not necessary to use a photoinitiator in the composition of

  Then, the coating must not be transparent to the

  photon composition, so that the composition may comprise any desired pigment or filler, and the coating may be thicker than

  to provide better protection of the reflective layer.

  In fact, there has been a prejudice against electron beam polymerization of polymerizable compositions applied to a sheet of glass for any reason. This is because it is theoretically predictable that the irradiation of a glass sheet will have a marked detrimental effect on its optical properties. In fact, it has now been found that

  anticipated adverse effects are not as significant as expected.

  and that any change in the properties of the mirror is within

acceptable limits.

  It is therefore possible to use beam polymerization

  of electrons enjoying the benefits mentioned.

  Polymerization by bombardment - beam of electricity

  trons must take place in an inert atmosphere, for example in a nitrogen atmosphere, since the presence of oxygen at this stage is detrimental to the quality of the protective coating formed.

  inert can be very easily maintained even in a

  tinu, for example by carrying out the polymerization in a tunnel-shaped chamber fed continuously with inert gas at a pressure greater than atmospheric pressure. The use of nitrogen as gas

  inert is preferred for reasons of economy and convenience.

  The polymerizable composition preferably comprises by weight: at least one unsaturated monomer substance and / or oligomer as polymerizable base material 10-90% at least one monomeric and / or oligomeric substance and / or polymer as reactive diluent polymerizable with the base 0-90% plasticizer 0-40% pigment and / or filler 0-40% other additive (s) 0.5-10% The electron beam acts on the base material to effect polymerization Examples of suitable oligomers are of the following type: polyurethane acrylate, epoxy acrylate, acrylate

  polyester-polyol, polyether-polyol acrylates and polyene-polythiols.

  Reactive diluents are used, for example for

  reduce the viscosity of the base material

  mono-or multifunctional lates, especially to reduce the Z 0 viscosity of polyurethane acrylate and epoxy base materials reactive diluents combine with the base material

  activation of the latter by the electron beam.

  If desired, you can also use plasticisers, it-

  Conventionally, the polymerization is carried out by scanning the face of the coated sheet by means of one or more electron beam (s) in the form of a curtain. a method

  simple and suitable for carrying out the polymerization.

  Preferably, the radiation polymerizable coating

  This technique is advantageous for forming thin coatings.

  high quality and uniform thickness.

  Advantageously, said coating is applied and polymerized so as to form an adherent protective layer whose thickness is at least 20 μm, and is preferably comprised

between 30 um and 80 μm.

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  Coatings of the minimum thickness indicated

  provide excellent protection to the reflective layer, and the

  Such a preferred range of thickness helps to facilitate the polymerization and economy of the resin. Preferably, it is absorbed by the composition.

  polymerizable at a dose of 3 to 10 m rad to perform its polymeric

  Such an assay contributes to efficient and rapid polymerization.

  The present invention is particularly applicable to the continuous line production of mirrors in which several mirrors are successively conveyed through application stations of

  polymerizable and polymerization composition, as is preferred.

  The present invention includes a mirror manufactured by

  a process as described above and extends to an intermediate product.

  re intended for use in such a process.

  Therefore, the present invention also provides a

  intermediate product intended for the manufacture of a mirror by a

  assigned as described above, characterized in that the product comprises

  a transparent glass sheet whose back surface is covered with

  reflective material which is surmounted by a coating of a composition

  polymerization by electron beam irradiation and which

  forms by polymerization an adherent protective layer.

  Preferred embodiments of the invention are now described by way of example with reference to the accompanying schematic drawings in which: Figure 1 is a cross-section of a mirror made in accordance with the present invention, and Figure 2 is a view schematic of a part of a device for implementing the invention

  Figure 1 shows a mirror formed of a trans-

  parent of glass 1 carrying on its rear face (upper) a reflective layer 2 covered with an intermediate layer 3 and a layer

  protector 4 formed of a polymerized resin coating irra-

Electron beam diation.

  The reflective layer 2 and the intermediate layer 3,

  for example silver and copper respectively may be

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  by any conventional process The main role of the

  intermediate is the protection against oxidation of the reflective

  The present invention is characterized by the mode of application

  application of the protective layer 4.

  A device for applying the adhering protective layer 4 is illustrated in FIG. Z. In FIG. Z, transparent glass sheets 5 carrying reflective coatings (not

  represented) and optional intermediate coatings (not shown

  are conveyed by a conveyor 6 under a coating device

  7, preferably a curtain coating device, where an electron beam radiation polymerizable resin coating 8 is applied. The conveyor 6 transports the sheets thus

  coated through a tunnel-shaped enclosure 9 where the coating

  The applied electrode 8 is treated by an electron beam 10 emitted by an electron generator 11 of the curtain type. The tunnel-shaped enclosure is swept by an inert gas, such as nitrogen; The entrance 13 of the tunnel is as low as possible while leaving the passage to the coated sheets 5 and the exit of the tunnel 14 can be closed, as shown, by a flexible curtain 15 for facilitate the maintenance of a substantially inert atmosphere inside the tunnel 9 with low gas consumption from

of the tank 12.

  In a particular installation, mirror-coated layers of an electron-beam-polymerizable resin coating are deposited on the coated glass sheets by a curtain coating technique while being conveyed at a rate.

  20 m / min Two electron beam accelerators are available

  end-to-end, each being arranged to scan a sheet width of 1.7 m, to treat a 3.4 m wide sheet The accelerators are 175 Ke V accelerators from ESI, Geneva; one could also use accelerators of

  Ke V The polymerizable coating is applied in a thick

  60 jim corresponding to about 120 gr / m 2, which obviously depends on

  of the resin composition used The absorbed dose by

  the resin coating is 6 m rad (6 × 10 5 Gy).

  Polymerizable compositions used may have the following general composition (parts by weight) Electron bombardment polymerizable material containing unsaturated monomer or oligomer 10-90% Unsaturated polymerizable monomeric, oligomeric and / or polymeric component , as reactive diluent 90 O% Plasticizer 0-40% Pigment and / or filler 0-40%

Other additives 0.5-10%.

  Here are specific examples of polymerizable compositions intended to be applied and polymerized as well as

described above.

Example 1

  Plex 6628-0 (from Rohm) 60% by weight Plex 6670-0 (from Rohm) 14% acrylic resin polymerizable by electron beam irradiation Lead oxide 7% Titanium oxide 7% Calcium carbonate 10% VN 3 ( of Union Carbide) 2 viscosity reducing agent

Example Z

  As the electron beam irradiating base material, the reaction product of: tetrachlorophthalic anhydride, polypropylene glycol and glycidyl acrylate 55% by weight Diethylene glycol diacrylate 15% Pht-dioctylate 2% Lead oxide 7% Calcium carbonate 10% Barium sulphate 10% BYK-W 980 (from Mallinckrodt) 1% dispersing agent

Example 3

  Dow DER 661 epoxy resin reacted with acrylic acid to give a polymerizable epoxy-acrylate base material by electron beam irradiation 40% by weight

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  15% tetraethylene glycol diacrylate Mixed Ester (dimethylamino acrylate, 13% hexane diol propionate) Lead Oxide 5% Calcium Carbonate 7% Magnesium Carbonate 15% Iron Oxide 4% BYK-W 900 UP (V ' ailinckrodt) 1% dispersing agent The properties of lunar reflection and reflection

  such mirrors provided with the protective layer are

  essentially the same as those of a similar mirror that has not received a protective layer polymerized by electron beam irradiation. Plex 6628-0, Plex 6670-0, VN 3, BYK-W 980, DER 661

  and BYK-W 900 UP are trademarks.

25379 b 9

Claims (8)

  A method of manufacturing a mirror comprising the   plication of a reflective layer on a back surface of a   transparent glass sheet and the covering of the reflecting layer   with one or more protective layers, characterized in that the one or more protective layers are formed by application   on the back surface coated with the sheet, a coating of a   polymerizable position by electron beam irradiation and by polymerization thereof with one or more electron beam (s)   to form an adherent protective coating.   Process according to Claim 1, characterized in that the said composition comprises, by weight, at least one unsaturated and / or oligomeric monomeric substance as polymerizable base material 10-90%, at least one monomeric and / or oligomeric and / or polymeric substance. as polymerizable reactive diluent with the base material 0-90 o% plasticizer 0-40% o pigment and / or filler 0-40% other additive (s) 0.5-10%.   3. Method according to one of claims 1 or Z,   characterized in that said polymerization is effected by scanning the face of the coated sheet by means of one or more beams (x) of electrons in the form of a curtain.   4 Process according to one of claims 1 to 3, characterized   characterized in that the radiation-curable coating is applied   by a curtain coating technique.   Process according to one of Claims 1 to 4,   characterized in that said coating is applied and polymerized to form an adherent protective layer having a thickness of at least   , um and is preferably between 30 um and 80 μm.   Process according to one of claims 1 to 5,   in that the polymerizable composition is absorbed by   dose of 3 to 10 m rad to effect its polymerization.   Method according to one of claims 1 to 6, characterized   In this embodiment, several mirrors are successively conveyed through application stations of polymerizable composition and polymerization.   8 Mirror made by a process according to one of the   1 to 7. 9 Intermediate product for the manufacture of a   mirror according to one of claims 1 to 7, characterized   rised in that the product comprises a transparent glass sheet   whose back surface bears a reflective coating which is   mounted with a coating of a polymerizable composition by electron beam irradiation and which forms by polymerization a layer adherent protector.