A synthetic quartz glass lid for use in optical device packages is prepared by furnishing a synthetic quartz glass lid precursor comprising a synthetic quartz glass substrate (1) and a metal or metal compound film (2), and forming a metal base adhesive layer (3) on the metal or metal compound film (2). The metal or metal compound film contains Ag, Bi, and at least one element selected from P, Sb, Sn and In.

A synthetic quartz glass lid for use in optical device packages is prepared by furnishing a synthetic quartz glass lid precursor comprising a synthetic quartz glass substrate (1) and a metal or metal compound film (2), and forming a metal base adhesive layer (3) on the metal or metal compound film (2). The metal or metal compound film contains Ag, Bi, and at least one element selected from P, Sb, Sn and In.

A wavelength conversion element includes a wavelength conversion layer which has a first face on which an excitation light is incident and a second face facing the first face, a first layer which is provided facing the second face and contains a first inorganic oxide, a second layer which is provided facing the first layer and contains a first metal or a second inorganic oxide that is different from the first inorganic oxide, and a third layer which is provided facing the second layer, contains either silver or aluminum, and reflects the excitation light or a light obtained by wavelength conversion of the excitation light by the wavelength conversion layer.

A wavelength conversion element includes a wavelength conversion layer which has a first face on which an excitation light is incident and a second face facing the first face, a first layer which is provided facing the second face and contains a first inorganic oxide, a second layer which is provided facing the first layer and contains a first metal or a second inorganic oxide that is different from the first inorganic oxide, and a third layer which is provided facing the second layer, contains either silver or aluminum, and reflects the excitation light or a light obtained by wavelength conversion of the excitation light by the wavelength conversion layer.

A cover glass for a hermetic package includes a sealing material layer on one surface. The sealing material layer satisfies one of the following relationships (1) to (6) between its center line length (L.sub.CL) and average width (W.sub.A): (1) when L.sub.CL is 150 mm or more, W.sub.A is 0.20% or more of L.sub.CL; (2) when L.sub.CL is 100 mm or more and less than 150 mm, W.sub.A is 0.30% or more of L.sub.CL; (3) when L.sub.CL is 75 mm or more and less than 100 mm, W.sub.A is 0.35% or more of L.sub.CL; (4) when L.sub.CL is 50 mm or more and less than 75 mm, W.sub.A is 0.40% or more of L.sub.CL; (5) when L.sub.CL is 25 mm or more and less than 50 mm, W.sub.A is 0.60% or more of L.sub.CL; and (6) when L.sub.CL is less than 25 mm, W.sub.A is 0.90% or more of L.sub.CL.

A functional element according to an embodiment of the present disclosure includes: a first substrate; a second substrate disposed to face the first substrate; and a buffer layer provided between the first substrate and the second substrate. The buffer layer has, in a layer thereof, a distribution of concentration of a metallic element. The distribution changes in a film thickness direction.

Provided is an interlayer film for laminated glass that can improve bending rigidity and sound insulating properties of laminated glass and can inhibit the occurrence and growth of foam in the laminated glass. An interlayer film for laminated glass according to the present invention has a single-layer structure or a two or more-layer structure and includes a first layer containing a polyvinyl acetal resin and a plasticizer, in which a glass transition temperature of the first layer is 10 C. or lower, and an elastic modulus of the first layer at 30 C. is 285,000 Pa or greater.

Provided is an interlayer film for laminated glass that can improve bending rigidity and sound insulating properties of laminated glass and can inhibit the occurrence and growth of foam in the laminated glass. An interlayer film for laminated glass according to the present invention has a single-layer structure or a two or more-layer structure and includes a first layer containing a polyvinyl acetal resin and a plasticizer, in which a glass transition temperature of the first layer is 10 C. or lower, and an elastic modulus of the first layer at 30 C. is 285,000 Pa or greater.

An embodiment of the present disclosure provides a cover for a flexible display panel, including an organic film including a recessed portion, a reinforcing layer disposed in the recessed portion, and a first and second rigid structure adjacent to each other disposed on the organic film, the first rigid structure includes a first joint portion, and the second rigid structure includes a second joint portion, the first joint portion and the second joint portion being configured to be separated from each other when the reinforcing layer is bent, and to be joined to form a one-piece structure when the reinforcing layer is not bent. In an embodiment of the present disclosure, by providing on the organic film a reinforcing layer and rigid structures that can be joined and separated, the cover may exhibit enhanced surface hardness, impact resistance and user's feel while the bending of the cover can be realized.

The present invention provides a glass substrate in which in a heat treatment step of sticking a silicon substrate and a glass substrate to each other, an alkali ion is hardly diffused into the silicon substrate, and a residual strain generated in the silicon substrate is small. A glass substrate of the present invention has: an average thermal expansion coefficient .sub.50/100 at 50 C. to 100 C. of 2.70 ppm/ C. to 3.20 ppm/ C.; an average thermal expansion coefficient .sub.200/300 at 200 C. to 300 C. of 3.45 ppm/ C. to 3.95 ppm/ C.; a value .sub.200/300/.sub.50/100 obtained by dividing the average thermal expansion coefficient .sub.200/300 at 200 C. to 300 C. by the average thermal expansion coefficient .sub.50/100 at 50 C. to 100 C. of 1.20 to 1.30; and a content of an alkali metal oxide being 0% to 0.1% as expressed in terms of a molar percentage based on oxides.