Kyocera Corporation

Kuniaki Mitsuda

Motohiro Umehara

Takashi Uto

Kazuyoshi Fujimoto

A composite substrate of the present disclosure includes a piezoelectric substrate having a first surface which is an element formation surface and a second surface which is a back surface of the first surface, a sapphire substrate having a third surface which is disposed opposing a second surface and a fourth surface which is a back surface of the third surface, a fifth surface opposing the second surface, and a sixth surface opposing the third surface. It includes an alumina layer bonding the second surface and the third surface, and an arithmetic mean roughness Ra of the third surface is 0.1 μm or more and 0.5 μm or less. The arithmetic mean roughness Ra of the fifth surface is 0.1 μm or less and is smaller than the arithmetic mean roughness Ra of the third surface.

Composite substrate, piezoelectric device, and method for manufacturing composite substrate

A composite substrate of the present disclosure is a composite substrate in which a piezoelectric substrate and a sapphire substrate are directly bonded, and a bonding surface of the sapphire substrate has a step bunch structure. A piezoelectric device of the present disclosure includes the composite substrate. A method for manufacturing a composite substrate includes the steps of: preparing a piezoelectric substrate and a sapphire substrate including a surface having a predetermined off-angle to a specific crystal plane, heat treating the sapphire substrate in an oxidizing atmosphere to form a step bunch on the surface of the sapphire substrate, and bonding the piezoelectric substrate and the surface of the sapphire substrate directly.

A composite substrate of the present disclosure is a composite substrate comprising a piezoelectric substrate and a sapphire substrate which are directly bonded, wherein the ratio of the number of oxygen atoms to the number of aluminum atoms in the bonding surface region including the bonding surface of the sapphire substrate bonded to the piezoelectric substrate is less than 1.5. The piezoelectric device of the present disclosure comprises the composite substrate. A method for manufacturing the composite substrate of the present disclosure comprises a step of preparing a piezoelectric substrate and a sapphire substrate, a step of heat-treating the sapphire substrate in a reducing atmosphere or in a vacuum, and a step of directly bonding the piezoelectric substrate to the sapphire substrate.

An electronic apparatus and a light-transmissive cover plate are disclosed. The electronic apparatus includes an image display device that includes an image display surface; a casing that houses at least a portion of periphery of the image display device; a light-transmissive cover plate that includes a first surface facing the image display surface, at least a peripheral edge region of the first surface is bonded to the casing; and a joining member that bonds the peripheral edge region of the first surface to the casing. The joining member has a Young's modulus smaller than that of the light-transmissive cover plate. The light-transmissive cover plate includes a gradual reduction area, and in this gradual reduction area, thickness is gradually reduced towards an outermost edge. At least a portion of the peripheral edge region of the first surface of the light-transmissive cover plate is included in the gradual reduction area.

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Omihachiman, Japan

Kuniaki Mitsuda