Kabushiki Kaisya Ohara

Kabushiki Kaisha Ohara Kogaku Garasu Seizosho

Mutsumi Miyazaki

Hisao Yatsuda

Toshiaki Yoshida

An apparatus for continuously forming a glass-ceramic which melts raw materials and forms melted glass to a predetermined shape without cutting the melted glass and thereafter continuously crystallizes the formed glass to the glass-ceramic is provided. The apparatus includes a melting device for melting raw materials, a flow tube for conveying the melted glass, a flow quantity control device connected to the flow tube for controlling the flow quantity of the melted glass, a pressing device for pressing the melted glass from the flow tube into a predetermined form, a glass preform checking device for measuring the weight or volume of the glass preform and feeding back a difference signal corresponding to a difference between the measured value of the weight or volume and a reference value to the flow quantity control device, the flow quantity control device controlling the quantity of the melted glass flowing through the flow tube in response to the difference signal to reduce the difference between the measured value and the reference value, and a crystallizing device for crystallizing the glass preform. The flow tube has an inner diameter which becomes smaller toward a melted glass outlet.

Apparatus for continuously forming and processing a glass-ceramic

According to one aspect of the invention, there is provided glass for a photomask consisting, in weight percent, of 45 to 62% SiO.sub.2, 3 to 15% B.sub.2 O.sub.3, 12 to 25% Al.sub.2 O.sub.3, 5 to 15% MgO, 0 to 5% CaO, 0 to 5% SrO, 0 to 5% BaO, 0 to 5% ZnO, 0.5 to 5% PbO, 0 to 20% La.sub.2 O.sub.3 +Gd.sub.2 O.sub.3 +Y.sub.2 O.sub.3, 0 to 1.5% Na.sub.2 O, 0 to 1.5% K.sub.2 O, 0 to 0.5% As.sub.2 O.sub.3 and 0 to 6% Sb.sub.2 O.sub.3. This glass is easy to melt and homogenize and has good resistivity to phase separation and excellent heat resisting and refractory properties, chemical durability, ultraviolet transmittance and metal vapor deposition property. According to another aspect of the invention, there is provided glass for a photomask consisting, in weight %, 45 to 60% SiO.sub.2, 0.5 to 12% B.sub.2 O.sub.3, 10 to 22% Al.sub.2 O.sub.3, 5 to 17% MgO, 0 to 5% CaO, 0 to 8% SrO, 1.5 to 15% BaO, 1.5 to 17% ZnO, 0.5 to 10% PbO, the total content of ZnO and PbO being at least 6%, 0 to 7% Ta.sub.2 O.sub.5 +Nb.sub.2 O.sub.5 +La.sub.2 O.sub.3 +Gd.sub.2 O.sub.3 +Y.sub.2 O.sub.3 +Bi.sub.2 O.sub.3 +WO.sub.3, 0 to 5% ZrO.sub.2 +TiO.sub.2, 0 to 2.5% Na.sub.2 O+K.sub.2 O+Li.sub.2 O, 0 to 0.5% As.sub.2 O.sub.3 and 0 to 0.5% Sb.sub.2 O.sub.3. This glass has the same excellent features as the first described glass and, in addition, has further improved melt properties.

Growing community of inventors

Sagamihara, Japan

Mutsumi Miyazaki