Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B19/00—Indicating the time by visual means
  • G04B19/06—Dials
  • G04B19/12—Selection of materials for dials or graduations markings
• • 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
  • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
  • C23D5/00—Coating with enamels or vitreous layers
  • C23D5/06—Coating with enamels or vitreous layers producing designs or letters

Definitions

• the present invention relates to an enamel dial for a watch, as well as to a method for manufacturing an enamel dial.
• Enamel dials have been known for a very long time in the field of watches and clocks. Such dials have been used more particularly for pendants, clocks and for pocket watches. All these dials are round in shape and the enamel is generally deposited on a copper substrate, flat or curved.
• the enamel dials of non-circular shape pose problems of adhesion and difference in coefficient of expansion between the substrate and the white enamel.
• a finishing flux which is a layer of transparent enamel
• cracks can occur in the finishing flux, especially in curved areas of the dial shape, due to the too low hardness of the white enamel which behaves like a moving element.
• the fondant layer does not adhere to white enamel.
• the painted coating deposited on the white enamel layer also poses a problem of deformation of the painted lines. This distortion problem is particularly apparent when letters or numbers are painted, especially when it comes to Roman numerals, made up of straight lines.
• the clock dials are closer to the enameling of sheets in the household appliance sector than to the manufacture of dials for watches for which the tolerances are of the order of hundredths of a mm, or even a few hundredths of a mm at most to allow fitting without play or stresses likely to crack the enamel.
• the object of the present invention is to solve the above-mentioned problems with a view to being able to remedy the defects observed on enamel dials of non-circular shape for watches, more particularly for wristwatches.
• the present invention firstly relates to an enamel dial for a watch according to claim 1.
• the substrate used in these examples is mild steel with a very low carbon content, less than 0.08% and preferably 0.004%. These are cold-rolled sheets for glazing enameling.
• the steels used are designated DC03ED or DC04ED according to European standard EN 10027-1.
• the thickness of the substrate is between 0.30 and 0.80 mm and is preferably around 0.45 mm. These steel sheets must be treated before enamelling to obtain, on the one hand a perfectly degreased surface, on the other hand a homogeneous surface structure. It is indeed necessary to eliminate the products which cover the rolled sheets, made up of a mixture of drawing greases and anticorrosive oil.
• Degreasing can be done either by burning, by treatment with hydrocarbons, or by alkaline degreasing, followed by several rinses. This operation is followed by pickling with dilute sulfuric acid (60 to 90g of concentrated acid with a density of 1.84 / 1 of water), for ten minutes at a temperature above 70 ° C, immediately followed by neutralization in a slightly alkaline bath at 0.3-0.5% Na 2 0 at 65-80 ° C, then drying with hot air.
• the substrate thus prepared is then ready to receive a layer of mass enamel which constitutes on the one hand an adhesion agent between the support and the covering of white enamel which will be deposited later, on the other hand makes it possible to balance the expansions between the substrate and the white enamel cover. This mass enamel layer also makes it possible to absorb the gases which emanate from the sheet during cooking.
• the mass enamel used in the following examples has the following composition, expressed in g:
• the enamel slip prepared using this composition is ground until the desired fineness and density are obtained, determined experimentally, it being understood that too great a fineness increases the surface tension of the enamel and can cause removal. Then it is passed through a magnetic separator to remove the ferrous particles.
• the layer of mass enamel is deposited over the entire substrate (front, back and edge) using a spray gun, followed by drying intended to remove the water before cooking the mass enamel. All the usual drying methods can be used, in the open air, in an oven or by radiation. Then the mass enamel is fired in an electric box oven heated between 760 ° and 860 ° C so as to obtain a uniform coating.
• the preparation of white enamel is made from commercial products available in powder form or in pieces. In either case, this product must be ground to obtain a fine powder with regular grains, the size of which is around 10 to 15 ⁇ m.
• the grinding is preferably carried out in an agate grinder. Distilled water is added to the powder and the grinding is interspersed with several washes to remove the impurities and the silt formed by the finest particles of enamel which remain in suspension in the water. Grinding from pieces is obviously longer than from more or less coarse powder. On the other hand, this one contains much more impurities coming from the sieves, the magnetic filters and the coatings of the crushers.
• the enamel obtained is then acidified using nitric acid diluted to 40% (60% acid in 40% water) to dissolve the non-assimilated metallic elements within the enamel, the various salts derived enamel during grinding (silt) and to dissolve organic matter which may be in suspension in water.
• Another effect of the acidification of the enamel is to harden it. This hardening is directly linked to the proportion of acid introduced into the enamel slip, which makes it possible to adjust the hardness of the enamel layer, as will be explained below.
• the good hardness of the white enamel is the condition so that the finishing fondant layer does not crack, in particular at the level of the curve.
• the tests carried out have shown that the hardness of the white enamel must be between 5 and 6, preferably around 5.5, on the Mohs scale, used to measure the hardness of mineral materials.
• the good hardness of the white enamel is the condition so that the lines painted on its surface do not deform.
• the enamel Once the enamel has been ground to the desired particle size and acidified, it is stored in airtight containers. Part of the enamel is wetted with distilled water, the other part is dried. The wet enamel is applied with a brush and then dried before being baked between 700 ° and 790 ° in an oven box. It is then slowly cooled and then degreased with industrial alcohol.
• a second layer of dried enamel is then applied, using a very fine sieve, and a second firing is carried out. Finally, apply a new layer of dried enamel followed by firing. When the enamel is cold, it is degreased and ironed in the oven to even out the three layers.
• the enamel is then stoned with 15 ⁇ - 9 ⁇ sandpaper and water to avoid overheating, until a regular desired thickness is obtained over the entire surface of the dial.
• the final equalization is carried out after a further degreasing with alcohol, by ironing the dial in the oven between 700 ° and 790 ° C.
• the frosted enamel during stoning becomes vitrified and tightened. This can be repeated if necessary.
• the thickness of the dial is at most 1.1 mm, including the thickness of the substrate, that of the mass enamel covering the two faces of the substrate and that of the white enamel.
• the next step is to deposit the paint.
• This painting includes numbers and characters to indicate the hours, minutes and various indicators. relating in particular to the brand.
• This paint can also be decorative and include several colors, using the usual vitrifiable paints sold for enamel and which generally consist of metallic oxide pigments which are mixed with a fatty essence or another suitable dispersion medium. , in a proportion depending on the desired consistency.
• vitrifiable colors are ground very finely and are applied with a brush to the white enamel, then they are fired between 750 ° C and 830 ° C, which has the effect of vitrifying the colors and embedding them in the white enamel.
• the last coating operation is to apply the finishing flux.
• This fondant is prepared by alternating grinding and washing as for white enamel without the addition of nitric acid, for approximately 35 minutes. The purpose of this operation is to improve the transparency of the finishing fondant. When sufficiently ground and washed, the finishing fondant is dried.
• the total thickness of the finishing fondant layer is of the order of 0.1 mm.
• any enamelling technique consisting in depositing a liquid product in the form of successive layers, the thickness of the enamel at the edge of the substrate intended to form the dial is necessarily different than on the rest of this substrate.
• the edge of the dial which must press against the bezel, hence the importance of having a determined thickness and not a random thickness, like that of the peripheral zone of the enamelled plate. This is the reason why, this peripheral zone of the dial is cut out to keep only the part in which the thickness of the enamel can be controlled with sufficient precision and is thus practically constant, which is not the case. case of clock faces in particular.
• Cutting must be performed by a technique capable of not damaging the edge of the enamel layer.
• the possible cutting techniques one can cite cutting with ultrasound, water jet, masking and chemical attack, in particular.

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• Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Organic Chemistry (AREA)
• Glass Compositions (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Magnetic Heads (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Physical Vapour Deposition (AREA)

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• 2002
  • 2002-10-22 EP EP02405902A patent/EP1413649A1/de not_active Withdrawn
• 2003
  • 2003-10-17 EP EP03750226A patent/EP1554415B1/de not_active Expired - Lifetime
  • 2003-10-17 WO PCT/CH2003/000678 patent/WO2004038066A2/fr active IP Right Grant
  • 2003-10-17 DE DE60323117T patent/DE60323117D1/de not_active Expired - Lifetime
  • 2003-10-17 AT AT03750226T patent/ATE405691T1/de not_active IP Right Cessation
  • 2003-10-17 AU AU2003269661A patent/AU2003269661A1/en not_active Abandoned
• 2005
  • 2005-07-26 HK HK05106355.1A patent/HK1074062A1/xx not_active IP Right Cessation

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