Window glass with optical filter

Abstract

To provide a glass window which can be switched between a black surface from the outdoors and a peep hole or a mirror surface from the indoors. [Solution] Incident light 4 transmitted through the liquid crystal shutter 3 travels back and forth through the λ / 4 retardation plate 2 before and after being reflected by the half mirror 1, and the reflected light 6 is blocked by the liquid crystal shutter 3. Switching between the observation window and the mirror surface indoors is done by opening and closing the liquid crystal shutter 3.

Description

[Technical field]

[0001] This invention relates to a window glass (transparent substrate) that uses an optical filter that uses a half mirror (magic mirror) and a liquid crystal shutter. [Background technology]

[0002] Half mirrors are used as one-way mirrors. To explain how they work, the bright side of the one-way mirror functions as a pure mirror when the light coming from the dark side can be ignored, and the dark side functions as a semi-transparent window, allowing you to observe the outside if the light from the bright side is large enough.

[0003] For example, consider the case where a half mirror is used in the window of a building. The illuminance outside is about 100,000 lx on a sunny day, about 30,000 lx on a cloudy day, and about 0.2 lx at night with the light of a full moon. On the other hand, indoors, the normal illuminance is about 100 to 1000 lx when lighting is used. Therefore, during the day, the half mirror functions as a mirror from the outside, and functions as a normal window indoors, allowing the outside light to enter and allowing the outside to be observed. On the other hand, at night, it functions as a mirror indoors, but functions as a normal window from the outside, allowing the inside of the building to be seen, and does not provide any privacy. The above information can be summarized as shown in Table 1.

[0004] [Table 1]

[0005] In Table 1, the window appears to be a mirror when viewed from outside during the day, but there is concern that direct sunlight may be reflected and cause glare, which may be a nuisance to those around.

[0006] Patent documents 1 and 2 are known examples of providing a physical shutter on the outdoor side of a half-mirror glass, and using the half-mirror as a viewing window or a mirror surface by opening and closing the shutter. Because it is a physical shutter, the device is large-scale.

[0007] There seems to be no publicly known example of window glass that replaces a physical shutter with a liquid crystal shutter, but if we think of the backlight as external light, a similar publicly known example is Patent Document 3, in which the display switches between a normal display and a mirror by turning the backlight on and off. Specifically, a half-mirror film is attached to the surface of a mobile phone display to add a mirror function.

[0008] Table 2 shows how the window glass with a half-mirror layer attached to a liquid crystal shutter looks when the shutter is open or closed, relative to the brightness inside and outside the window.

[0009] [Table 2]

[0010] As shown in Table 2, when it is daytime outside, opening and closing the shutter indoors switches between the peephole and the mirror surface perfectly, but when opening and closing the shutter from outdoors, the window glass changes between the mirror surface and the black surface, making the operating status visible. At night, the shutter should be closed and the window should be used as a mirror indoors. Also, when looking outside at night, the shutter should be open and the indoor lights should be turned off.

[0011] In the case of the window glass having a half-mirror layer arranged on the liquid crystal shutter described above, it is not desirable for the operating status of the window glass to be visible from outdoors during the daytime, and it is therefore preferable for the window glass to have a uniform black surface from the outdoors in order to eliminate glare caused by regular reflection of direct sunlight.

[0012] Patents 4 and 5 are known examples of linearly polarized reflected light in a display being rotated 90 degrees to linearly polarized light by making it go back and forth through a λ / 4 retardation plate, and then blocked by a polarizing plate that passes just before the λ / 4 retardation plate. The reflection in Patent 5 occurs at a half mirror, and is almost the same as the situation assumed by this invention, except that Patent 5 is related to displays. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Publication No. 01-102392 [Patent Document 2] Japanese Patent Application Publication No. 04-261990 [Patent Document 3] JP 2004-241794 A [Patent Document 4] JP 2002-116435 A [Patent Document 5] JP 2011-133734 A Summary of the Invention [Problem to be solved by the invention]

[0014] If a half mirror (magic mirror) is used as the window glass, it is not possible to switch between a peephole and a mirror. Simple shutter methods, including liquid crystal shutters, are not desirable because the operating status of the window glass can be easily determined from outside. Also, if the window glass is in a mirror state from the outside, the reflection of direct sunlight is not desirable. [Means for solving the problem]

[0015] Fig. 1 shows an embodiment of the present invention. A liquid crystal shutter 3, a λ / 4 phase difference plate 2, and a half mirror 1 are arranged in this order to form a window, with the half mirror 1 side facing indoors (the user side). Effect of the Invention

[0016] Incident light 4 is generally unpolarized, but when liquid crystal shutter 3 is opened, polarized light with a polarization direction like 8 is transmitted through it and passes through λ / 4 phase difference plate 2, becoming circularly polarized at the position of half mirror 1, and is split into transmitted light 5 and reflected light 6. Reflected light 6 in a circularly polarized state passes through λ / 4 phase difference plate 2 again, achieving the effect of having passed through a total λ / 2 phase difference plate, and has its polarization direction 9 rotated by 90°, and is blocked by liquid crystal shutter 3. As a result, the reflection from half mirror 1 is eliminated.

[0017] At this time, the maximum reflected component of the incident light 4 is the reflected light 7 at the interface between the air and the filter, which is about a few percent of the incident light, and depending on the reflectance of the half mirror 2, can be reduced to about 1 / 10.

[0018] When the liquid crystal shutter 3 is closed, the window is simply darkened from the outdoors and functions as a mirror from the indoors.

[0019] As described above, the appearance of the window glass of the present invention depending on the indoor and outdoor brightness and the opening and closing of the liquid crystal shutter 3 is summarized in Table 3.

[0020] [Table 3]

[0021] As shown in Table 3, when it is daytime outside, the window always appears black when viewed from outside, and the operating status of the window glass cannot be seen from outside, providing excellent concealment for the interior. From inside, the window glass functions as a peephole and a mirror when the liquid crystal shutter 3 is opened and closed.

[0022] When it is nighttime outside, the liquid crystal shutter 3 is closed and used as a mirror indoors. When looking outside at night, the liquid crystal shutter 3 must be opened and the indoor lights must be turned off. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 shows an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Basically, the embodiment is as shown in Fig. 1. Regarding the crystal axis of the λ / 4 retardation plate 2, the polarization axis of the liquid crystal shutter 3 on the λ / 4 retardation plate 2 side is aligned with the midway direction between the fast axis (advance axis) and the slow axis (slow axis). Also, since the three optical elements in Fig. 1 may be in the form of a film, it is common for one of them to be supported by a transparent substrate such as glass. Also, other optical components such as an ultraviolet ray cut filter or an infrared ray cut filter may be additionally disposed as necessary.

[0025] When it is daytime outside, the incident light 4 from the outside passes through the liquid crystal shutter 3 with a polarization direction 8. The linearly polarized light passes through the λ / 4 retardation plate 2 and is split into transmitted light 5 and reflected light 6 by the half mirror 1, but is converted into circularly polarized light by the effect of the λ / 4 retardation plate 2. The reflector 6 passes through the retardation plate 2 again and becomes linearly polarized light, but for the incident light 4, it is equivalent to passing through a λ / 2 retardation plate, the polarization direction is rotated by 90 degrees, and the liquid crystal shutter 3 is blocked without passing through, and the reflection from the half mirror 1 is erased. Therefore, the maximum reflected component of the incident light 4 is the reflected light 7 from the liquid crystal shutter 3, and its intensity is at most a few percent of the incident light 4. Although it depends on the reflectance of the half mirror 1, if the reflectance is set to 50% as the name suggests, the reflected light can be suppressed to about 1 / 10. In this way, it is possible to avoid situations where the glare caused by the regular reflection of direct sunlight causes inconvenience to those around you.

[0026] To estimate the reflected light intensity from indoors, let us assume that the reflectance of the half mirror 1 is R, and the transmittance is (1-R). If the transmitted light 5 is totally reflected by a white object, the light intensity seen from outside is

[0027]

number

[0028] TIFF0003250192000006.tif10166 has a reflectivity of about 4-5%, so its ability to conceal the interior from the outside is inferior to that of a simple half mirror.

[0029] Methods for improving the hiding power include increasing the reflectance R of the half mirror 1, or intentionally shifting the axial alignment between the λ / 4 retardation plate 2 and the liquid crystal shutter 3 from the ideal state to allow some of the regular reflection component of the half mirror to pass through the liquid crystal shutter 3. In actual products, both methods are combined to achieve a balance between eliminating external light reflections, hiding performance, and external light transmittance. Also, if the increase in cost is ignored, there is a method of additionally placing a low-reflection mirror on the polarizing plate 3.

[0030] When the present invention is used indoors, for example as a partition wall in a room, the difference in brightness between the two sides of the window glass is small, and the contribution of the lighting on the user's side must also be taken into consideration, making the above adjustment difficult. [Explanation of symbols]

[0031] 1 Half mirror (magic mirror) 2 λ / 4 retardation plate 3 Liquid crystal shutter 4 Incident light 5 Transmitted light 6. Reflected light from half mirror 1 7 Reflected light from liquid crystal shutter 3 8 Polarization direction immediately after passing through the liquid crystal shutter 3 9 Polarization direction after going back and forth through the λ / 4 retardation plate

Claims

[Claim 1] A window glass comprising an optical filter including a liquid crystal shutter, a λ / 4 phase difference plate, and a half mirror arranged in this order.

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