Pilkington Brothers P.l.c.

Pilkington Plc

Pilkington Glass Limited

Raymond Peter Cross

Gordon T Simpkin

Timothy Jenkinson

Steven John Reilly

Derek Edward Thomas

A mirror assembly comprising a glass substrate, a low transmissivity reflecting coating on the substrate and an opacifying member which is assembled adjacent to the glass substrate for a front surface mirror or the reflecting coating for a back surface mirror. The present invention also provides a method of producing a mirror assembly comprising depositing onto a hot ribbon of glass during the production process a low transmissivity reflecting coating and assembling an opacifying member adjacent to the glass substrate or the reflecting coating of the mirror so formed.

Coatings on glass

Glass is heated to a temperature above its strain point and is thermally toughened by chilling with a quiescent gas-filuidized particulate material which has gas-generating properties and a mean particle size in the range 30 .mu.m to 120 .mu.m, a particle size distribution in the range 1.15 to 2.78, a flowability in the range 69.5 to 92, and a thermal capacity per unit volume at minimum fluidization in the range 0.7 to 1.59 MJ/m.sup.3 K. The invention is particularly suitable for thermally toughening glass sheets for vehicle windscreens.

Method of thermal toughening of glass in a fluidized bed

The thermal treatment of glass is effected by contacting the glass, when it is hot, with a gas-fluidized mixture of particulate materials, at least one of which is selected to have gas-generating properties when heated by the hot glass. The materials are mixed in selected pre-determined proportions which impart to the mixture a thermal capacity and flowability which are such that a required thermal treatment is achieved. The method is particularly suitable for the thermal toughening of glass sheets for vehicle windscreens.

Thermal treatment of glass

A fluidized bed for the thermal treatment of glass articles is maintained in a quiescent uniformly expanded state of particulate fluidization by establishing a high pressure drop across a porous membrane through which fluidizing gas is supplied to the bed, of at least 60% of the pressure at which the fluidizing gas is supplied to a plenum chamber beneath the membrane.

Method of heat treating glass in a fluidized bed and apparatus therefore

Glass is thermally treated by contacting the glass with a gas-fluidized particulate material of non-compacted particle structure which is such that the apparent density of the particles is less than the actual density of the material forming the particles. The buoyant particles constitute a gas-fluidized bed in a quiescent uniformly expanded state of particular fluidization, and the material of the particles and the temperature of the bed are selected so that the heat transfer coefficient of the bed is sufficient to produce a desired thermal treatment, for example thermal toughening of hot glass.

Method of thermal treatment of glass in a fluidized bed

The thermal treatment of glass is effected by heat transfer between the glass and a gas-fluidized particulate material which is in a quiescent uniformly expanded state of particulate fluidization. Glass sheets are thermally toughened by immersing each glass sheet, which is at a temperature above its strain point, in the gas-fluidized bed prior to the immersion of the glass in the bed.

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Preston, United Kingdom

Raymond Peter Cross