Glass

A windshield glass, comprising:

• a glass having an inner surface, an outer surface, a first area used by a head-up display installed inside a vehicle, a second area adjacent to the first area, and a wedge angle δ at each point in a partial area of the second area including the edge on the boundary side in the second area such that the second area is not used by the head-up display, an edge on the boundary side in the first area represents an area closest to a boundary between the first area and the second area in the first area, and an edge on the boundary side in the second area represents an area, closest to the boundary in the second area,
• wherein the glass is configured to be installed on the vehicle in a position with respect to the head-up display such that the glass has a local incident angle φ of a ray of light emitted in an X-direction designating a front-and rear direction of the vehicle from a light source outside the vehicle to the eyes of a driver in the vehicle and incident on the outer surface of the glass, and that the glass has the wedge angle δ determined by Formula (1),
• δ
• =
• t
• R
• ⁢
• sin
• ⁢
• ⁢
• φcosφ
• n
• 2
• -
• sin
• 2
• ⁢
• φ
• -
• η
• ⁢
• cos
• ⁢
• ⁢
• φ
• 2
• ⁢
• n
• 2
• -
• sin
• 2
• ⁢
• φ
• (
• 1
• )
• where the wedge angle δ is formed by the inner surface and the outer surface and excludes a case of a uniform wedge angle δ, t represents a thickness of the glass, R represents a local curvature radius of the glass, n represents a refractive index of the glass, and when ηh is determined by Formula (2),
• η
• h
• =
• 2
• ⁢
• t
• R
• ⁢
• sin
• ⁢
• ⁢
• φ
• n
• 2
• -
• sin
• 2
• ⁢
• φ
• -
• 2
• ⁢
• δ
• h
• ⁢
• n
• 2
• -
• sin
• 2
• ⁢
• φ
• cos
• ⁢
• ⁢
• φ
• (
• 2
• )
• where ηh is an angle of perspective double images generated by the light from the light source and observed by the driver inside the vehicle at the edge on the boundary side in the first area, δh represents a wedge δ angle at the edge on the boundary side in the first area, η is an arbitrary value having a same sign as a sign of ηh and satisfies conditions of being less than or equal to a smaller one of 2|ηh| and 9 if |ηh|≤9 and being less than or equal to |ηh| if |ηh|>9, η is not 0 at all points in the part of the area, and 0<|η| is satisfied at the edge on the boundary side in the second area.