WINDSHIELD
FIG5 is a side view showing one example of a manufacturing method of a glass plate  FIG6 is a cross-sectional view showing one example of glass plates and an interlayer
Here, a mold will be described in detail with reference to FIG5. FIG5 is a side view of furnaces through which the mold passes. As shown in FIG5, a mold 800 includes a mold main body having the shape of a frame that mostly matches the external forms of the glass plates 11 and 12. Since this mold main body 810 has the shape of a frame, there is an interior space that vertically penetrates the inner side of the mold main body. Peripheral portions of the glass plates 11 and 12 each having the shape of a flat plate are placed on an upper surface of the mold main body 810. Accordingly, heat is applied to the glass plates 11 and 12 via the interior space by a heater (not shown) that is arranged below the glass plates. When heat is applied, the glass plates 11 and 12 soften and curve downward under their own weight. In some cases, a shield plate for shielding the glass plates from heat is arranged on an inner periphery of the mold main body 810 to enable adjustment of heat applied to the glass plates 11 and 12. The heater can be arranged above the mold 800 as well as below the mold. After the above-described mask layer 2 is layered on the outer glass plate 11 and the inner glass plate 12 having the shape of a flat plate, the outer glass plate 11 and the inner glass plate 12 are superimposed and passed through a heating furnace 802 in a state of being supported by the above-described mold 800 as shown in FIG5. When the glass plates 11 and 12 are heated to around the softening point in the heating furnace 802, portions of the glass plates inward of peripheral portions curve downward under their own weight and thus the glass plates are molded into a curved shape. Subsequently, the glass plates 11 and 12 are conveyed from the heating furnace 802 to an annealing furnace 803 to be subjected to annealing treatment. Thereafter, the glass plates 11 and 12 are conveyed out of the annealing furnace 803 and cooled.  It is thought that a double image is mainly generated in any of the following cases or a combination thereof. First, as shown in FIG6, there is a case where almost no irregularities are formed in the outer glass plate 11 and the inner glass plate 12 but irregularities are formed in surfaces of the interlayer 13. In this case, when the glass plates 11 and 12 and the interlayer 13 are permanently bonded as described above, irregularities may also be formed in the glass plates 11 and 12 due to the irregularities in the interlayer 13.
cross-sectional view, side view
7
less. Aspect
5
up-down direction. Aspect aldehyde having
12
glass plates glass plate
810
mold main body
6
glass. Aspect OSLO Premium Edition Rev.
802
heating furnace
803
annealing furnace
['1. A windshield that has a display region onto which information is projected using light emitted from a head-up display device, the windshield comprising: an outer glass plate; an inner glass plate that is arranged opposite to the outer glass plate; and an interlayer that is arranged between the outer glass plate and the inner glass plate, wherein lattice points are defined at a pitch of no greater than 20 mm in the display region, and when wedge angles at the lattice points are measured using an interferometer with 240 × 240 pixels or more, a difference between the largest value and the smallest value of the wedge angles is no greater than 0.32 mrad.']