JP7779119B2 - Half mirror - Google Patents

Description

The present invention relates to a half mirror, and in particular to one with a selective reflection film for circularly polarized light and a wave plate attached to its back surface.

Patent Documents 1 and 2 disclose a light-reflecting and transmitting component that is a type of half-silvered mirror. This light-reflecting and transmitting component comprises a support and an optical thin film laminated on the back surface of the support. The optical thin film reflects a portion of the light and transmits the remaining portion. The optical thin film transmits image light irradiated from the back side. Therefore, the light-reflecting and transmitting component exhibits display properties. The optical thin film reflects external light irradiated from the front. Therefore, the light-reflecting and transmitting component exhibits mirror properties.

A selectively reflective film is further laminated on top of the optical thin film. The selectively reflective film selectively transmits either left- or right-handed circularly polarized light and reflects the other. For example, left-handed circularly polarized image light is incident on the back surface of the light-reflecting/transmitting component, i.e., the selectively reflective film. The selectively reflective film transmits left-handed circularly polarized light and reflects right-handed circularly polarized light. The left-handed circularly polarized light that passes through the selectively reflective film is reflected multiple times between the optical thin film and the selectively reflective film. During this process, the image light changes its rotation direction with each reflection. The transmittance of left-handed circularly polarized light through the optical thin film is higher than the transmittance of right-handed circularly polarized light through the selectively reflective film. As a result, the image light is preferentially emitted from the optical thin film side after repeated multiple reflections. Therefore, the selectively reflective film brightens the image displayed on the light-reflecting/transmitting component.

By appropriately designing the optical structure, which combines an optical thin film and a selective reflection film, the sum of the transmittance of image light and the reflectance of external light exceeds 100% when viewed from the front by an observer.

A quarter-wave plate is further laminated on the back surface of the light-reflecting and transmitting component to generate circularly polarized light from linearly polarized light. When linearly polarized light with its polarization axis tilted 45° relative to the fast and slow axes of the quarter-wave plate is incident, it is converted into left-handed or right-handed circularly polarized light. This circularly polarized light is reflected multiple times between the optical thin film and the selective reflection film, and is preferentially emitted from the front of the light-reflecting and transmitting component.

Patent Documents 3 and 4 disclose a mirror and a half mirror with an image display function that are equipped with a circularly polarized light reflective layer.

International Publication No. 2017/126624 Japanese Patent Application Laid-Open No. 2019-137085 JP 2017-122776 A Japanese Patent Application Laid-Open No. 2017-198961

In the optical structure described above, a selective reflection film for circularly polarized light is laminated on the back surface of the half mirror, and a quarter-wave plate is further laminated on top of it. This optical structure promotes the transmission of linearly polarized light, but does not promote the transmission of unpolarized light. The object of the present invention is to provide a means to make it easier for unpolarized light to pass through such an optical structure.

<1> A support; a partially reflective film laminated on the back surface of the support;
a selective reflection film laminated on the back surface of the partially reflective film;
a quarter-wave plate laminated on the back surface of the selective reflection film, in this order;
Further provided on the rear surface of the selective reflection film are a first region where the quarter-wave plate is laminated and a second region where the quarter-wave plate is not laminated;
further comprising an anti-reflection film laminated to the rear surface of the second region;
The anti-reflection film has an anti-reflection layer on its back surface and has a transmittance for unpolarized light that is higher than the transmittance of the quarter-wave plate.
Half mirror.
<2> The antireflection film has a retardation smaller than that of the quarter-wave plate.
The half mirror according to <1>.
<3> The antireflection film includes a substrate film and the antireflection layer laminated on a back surface of the substrate film,
The substrate film has a birefringence smaller than that of the quarter-wave plate.
The half mirror according to <2>.
<4> The antireflection film has a transmittance for unpolarized light that is higher than the transmittance of the quarter-wave plate over the entire wavelength band of visible light.
<3> The half mirror according to any one of <1> to <3>.
<5> The anti-reflection film is laminated on the back surface of the quarter-wave plate,
the anti-reflection film covers the boundary between the first region and the second region,
The center of the rear surface of the quarter-wave plate is exposed on the rear surface side of the half mirror.
<4> The half mirror according to any one of <1> to <4>.
<6> The anti-reflection film is laminated on the center of the back surface of the quarter-wave plate,
The anti-reflection film further covers the center of the first region.
<4> The half mirror according to any one of <1> to <4>.
<7> The selective reflection film transmits one of left-handed circularly polarized light and right-handed circularly polarized light (hereinafter referred to as F-polarized light) more than the other (hereinafter referred to as R-polarized light) throughout the entire visible light band, and reflects R-polarized light more than F-polarized light,
the reflectance of the selective reflection film for R-polarized light is higher than the reflectance of the partially reflection film for F-polarized light over the entire visible light band;
When linearly polarized light having a polarization axis tilted 45 degrees with respect to the fast axis and slow axis of the quarter-wave plate is incident on the rear surface of the quarter-wave plate, the quarter-wave plate converts the linearly polarized light into F-polarized light,
The partially reflective film reflects F-polarized light toward the selectively reflective film and converts the F-polarized light into R-polarized light, and the selectively reflective film further reflects R-polarized light toward the partially reflective film and converts the R-polarized light into F-polarized light. Through this process repeated, F-polarized light is preferentially emitted from the front surface of the support.
<6> The half mirror according to any one of <1> to <6>.
<8> A half mirror according to any one of <1> to <7>, a display, and lighting,
a display surface of the display facing a rear surface of the quarter-wave plate in the first region;
the image light incident on the quarter-wave plate from the display surface is linearly polarized light having a polarization axis inclined at 45 degrees with respect to the fast axis and the slow axis of the quarter-wave plate,
the illumination faces the rear surface of the anti-reflection film in the second region;
The illumination light incident on the anti-reflection film from the lighting is unpolarized.
Multi-function mirror.
<9> A method for producing a half mirror according to any one of <1> to <7>,
a quarter-wave plate is laminated on the back surface of the support on which the partial reflection film and the selective reflection film are laminated, on the first region and the second region of the back surface of the selective reflection film;
removing the quarter wave plate on a second region while leaving the quarter wave plate on a first region;
laminating the antireflection film on the selective reflection film in the second region;
method.
<10> In laminating the quarter-wave plate, the back surface of the selective reflection film and the front surface of the quarter-wave plate are joined with a transparent adhesive layer, and the transparent adhesive layer is more strongly bonded to the selective reflection film than to the quarter-wave plate,
In removing the quarter-wave plate, the quarter-wave plate is cut on a boundary between the first region and the second region, and then the quarter-wave plate on the second region is peeled off from the selective reflection film;
In laminating the antireflection film, the back surface of the selective reflection film and the front surface of the antireflection film are bonded together with the transparent adhesive layer remaining on the second region.
The method according to <9>.

The present invention provides a means to make it easier for unpolarized light to pass through optical structures.

FIG. 3 is a cross-sectional view of a half mirror when viewed from above. Diagram of the multi-function mirror. FIG. 3 is an enlarged cross-sectional view of the half mirror when viewed from above. Rear view of the half mirror. FIG. 1 is a plan view of a half mirror under fabrication. FIG. 3 is an enlarged cross-sectional view of the half mirror when viewed from above. Rear view of the half mirror. Schematic diagram of half mirror testing.

<Half Mirror>

Figure 1 shows a cross section of the half mirror 10 when viewed from above. The half mirror 10 comprises a support 11, a selective reflection film 15, and other components. For ease of explanation, the side of the support 11 will be referred to as the front of the half mirror 10, and the side of the selective reflection film 15 will be referred to as the back of the half mirror 10. The front and back are defined uniformly for the components within the half mirror 10 and the elements combined with them. An observer Ob observes the half mirror 10 from the front.

In one embodiment shown in Figure 1, the half mirror 10 comprises a support 11, a partial reflection film 13, a selective reflection film 15, and a quarter-wave plate 17a, in this order. The partial reflection film 13 is laminated on the back surface of the support 11. The selective reflection film 15 is laminated on the back surface of the partial reflection film 13. The quarter-wave plate 17a is laminated on the back surface of the selective reflection film 15.

In one embodiment shown in FIG. 1, the half mirror 10 has a first region and a second region on the back surface of the selective reflection film 15. One embodiment of the first region is region 21a located in the vertical center of the half mirror 10. The number of first regions may be two or more. One embodiment of the second region is region 22a and region 22b located on the vertical outer edges of the half mirror. A quarter-wave plate 17a is laminated in region 21a. No quarter-wave plate 17a is laminated in regions 22a and 22b. The number of second regions may be one, three or more.

In one embodiment shown in Figure 1, light ray Lp is incident on the back surface of quarter-wave plate 17a. Light ray Lp has a polarization axis tilted 45 degrees relative to the fast and slow axes of quarter-wave plate 17a. Quarter-wave plate 17a converts linearly polarized light into one of left-handed circularly polarized light and right-handed circularly polarized light. Multiple reflections of circularly polarized light occur due to the selective reflection film 15 and the partially reflection film 13; details of multiple reflections will be discussed later.

In one embodiment shown in Figure 1, the half mirror 10 further includes AR (anti-reflective) films 19a and 19b. In one embodiment, unpolarized light rays Up are incident on the back surfaces of the AR films 19a and 19b. In another embodiment, a reflective layer is provided on the back surface of the emission point of the unpolarized light rays or in an area adjacent to the emission point. The reflective layer converts the circularly polarized light reflected by the selective reflection film when unpolarized light rays incident on the selective reflection film into an optical rotation direction that transmits through the selective reflection film and reflects it.

<Support>

In one embodiment shown in FIG. 1, the support 11 is entirely transparent. In another embodiment, the support 11 has transparent regions and opaque regions. Circularly polarized light passes through the transparent regions. In one embodiment, the support 11 is flat. In another embodiment, the support 11 is curved. In one embodiment, at least one of the front and back surfaces of the support 11 is flat. In another embodiment, at least one of the front and back surfaces of the support 11 is curved.

In one embodiment shown in Figure 1, the support 11 is a plate made of a transparent substrate. The substrate has a transmittance of 20% or more and 100% or less across the entire visible light range. In optical materials, light is reflected at their surfaces, or so-called interfaces. Therefore, the transmittance of the optical material itself is sometimes referred to as internal transmittance. The overall transmittance, including interfaces, is sometimes referred to as external transmittance. In this embodiment, transmittance refers to external transmittance unless otherwise specified. The same interpretation applies to transmittance in other elements made of a transparent substrate in this specification.

In one embodiment shown in Figure 1, the transmittance of the support 11 is 30% or more and less than 100%. In one embodiment, the transmittance is any of 30, 40, 50, 60, 70, 80, and 90%. The substrate is colorless or colored. The surface of the substrate is smooth.

In one embodiment, the substrate is made of inorganic glass. In one embodiment, the inorganic glass is alkali-free glass. In one embodiment, the inorganic glass is soda-lime glass with a low Fe content. Alkali-free glass has better rigidity than soda-lime glass. In one embodiment, the inorganic glass is laminated glass. In another embodiment, the substrate is made of plastic. In one embodiment, the plastic is either acrylic or polycarbonate. In another embodiment, the support 11 is made of inorganic glass and another member. In this embodiment, light transmits through the region made of inorganic glass. In one embodiment, the other member is plastic. In one embodiment, the plastic is acrylic, polycarbonate, or another plastic.

<Partial reflective film>

The partially reflective film 13 shown in FIG. 1 partially transmits light. The partially reflective film 13 partially reflects light. In one embodiment, the partially reflective film 13 is made of metal, metal oxide, and other dielectrics. In one embodiment, the partially reflective film 13 is a metal. In one embodiment, the metal is aluminum. In one embodiment, circularly polarized light is metallically reflected at the interface of the partially reflective film 13 made of a metal. In another embodiment, the partially reflective film 13 is a dielectric multilayer film. The ratio of reflectance to transmittance of a dielectric multilayer film is easier to adjust than for other thin films. In one embodiment, circularly polarized light is Bragg-reflected inside the partially reflective film 13 made of a dielectric multilayer film.

In another embodiment shown in FIG. 1, the partially reflective film 13 is a thin metal film. In one embodiment, a transparent protective film is formed on top of the thin metal film to protect it. In another embodiment, the transparent protective film is an organic thin film. The thickness of the thin metal film may be appropriately designed depending on the desired transmittance. When a touch panel is installed on the support 11, the thin metal film provided on the partially reflective film 13 may be used as a sensor electrode or part of the sensor electrode.

In one embodiment shown in Figure 1, the partially reflective film 13 is formed directly on the back surface of the support 11. In another embodiment, a thin film is formed on another transparent substrate and then attached to the support 11 to form the partially reflective film 13. In an embodiment different from the embodiment shown in the figure, a transparent adhesive layer is used for attachment.

In one embodiment shown in Figure 1, the optical properties of a basic half-mirror structure 12 consisting of a support 11 and a partially reflective film 13 are considered. In one embodiment, the optical properties of the half-mirror structure 12 are evaluated with other elements such as the selectively reflective film 15 and the quarter-wave plate 17a removed.

In one embodiment shown in FIG. 1, the reflectance of the half-mirror structure 12 for light with a wavelength of 550 nm is higher than the transmittance. This reflectance is for light incident on the front surface of the half-mirror structure 12. In one embodiment, the half-mirror structure 12 has a reflectance of 30% or more and less than 100% for light with a wavelength of 550 nm. In one embodiment, the reflectance is any of 35, 40, 45, 50, 52, 54, 56, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 75, 80, 85, 90, and 95%. In a preferred embodiment, the reflectance of the half-mirror structure 12 for light across the entire visible light band is higher than the transmittance.

In another embodiment shown in Figure 1, the transmittance of the half-mirror structure 12 for light with a wavelength of 550 nm is higher than the reflectance. In another embodiment, the reflectance of the half-mirror structure 12 is equal to the transmittance across the entire visible light range. In another embodiment, the reflectance of the half-mirror structure 12 for light with a wavelength of 550 nm is equal to the transmittance. Note that in this specification, the terms "half mirror" and "half-mirror structure" are not limited to those in which the transmittance and reflectance are equal.

<Selective Reflection Film>

Figure 2 shows the optical path of light passing through the half mirror 10, with the half mirror 10 viewed from above. The selective reflection film 15 is particularly located at its center. The selective reflection film 15 transmits one of left-handed and right-handed circularly polarized light, hereinafter referred to as F-polarized light, more than the other, hereinafter referred to as R-polarized light, throughout the visible light range. The selective reflection film 15 also reflects R-polarized light more than F-polarized light. In one embodiment, this reflection is Bragg reflection.

In Figure 2, left-handed circularly polarized light is represented as F-polarized light, and right-handed circularly polarized light is represented as R-polarized light. Furthermore, the reflectance of the selective reflection film 15 for R-polarized light is higher than the reflectance of the partially reflection film 13 for F-polarized light across the entire visible light band.

In one embodiment shown in FIG. 2, the selective reflection film 15 is made of a material that is selective for circularly polarized light. In one embodiment, the selective reflection film 15 is made of either a nematic liquid crystal or a smectic liquid crystal. In one embodiment, these liquid crystals are made of a phase that has chirality. In one embodiment, the phase is made of liquid crystal molecules to which a chiral dopant has been added. In another embodiment, the phase is made of liquid crystal molecules that have chirality. In one embodiment, the selective reflection film 15 is made of a cholesteric liquid crystal.

In one embodiment, the selective reflection film is a laminate of multiple films with different helical pitches. In one embodiment, these are laminated in order of increasing helical pitch. The films with different helical pitches have different selective reflection bands. The bandwidth W of such a multi-layer selective reflection film is larger than that of a single-layer film. In one embodiment, the bandwidth W is broadband. In another embodiment, the bandwidth W is the entire visible light band.

In another embodiment, the selective reflection film is a single-layer film. The size of the helical pitch changes continuously within the single-layer film. Alternatively, the orientation of the helical axis changes continuously within the single-layer film. In another embodiment, the selective reflection film is a laminate of multiple sheets of the above single-layer film.

Returning to Figure 1, in one embodiment shown in Figure 1, the quarter-wave plate 17a is made of a resin having birefringence. An example of the quarter-wave plate 17a that can be used is the Zeonor Film ZD series provided by Zeon Corporation.

<AR film>

In one embodiment shown in Figure 1, AR film 19a is laminated on the back surface of region 22a. AR film 19b is laminated on the back surface of region 22b. These AR films consist of a substrate film and an anti-reflection layer 20a or 20b. The back surface of AR film 19a consists of anti-reflection layer 20a. The back surface of AR film 19b consists of anti-reflection layer 20b. Both anti-reflection layer 20a and anti-reflection layer 20b are represented by thick dashed lines.

The anti-reflection layers 20a and 20b shown in Figure 1 are formed as follows. In one embodiment, an inorganic derivative is laminated onto the substrate film by vapor deposition or sputtering. In another embodiment, an organic material is applied onto the substrate film. The thickness of the AR film including these anti-reflection layers can be 10 μm to 500 μm. The thickness of the AR film including these anti-reflection layers can be any of 25, 40, 50, 80, 100, 125, and 200 μm.

In one embodiment, the substrate film is made of a resin. In one embodiment, the resin is either TAC (triacetyl cellulose) or PET (polyethylene terephthalate). Many TACs have a lower birefringence than PET. Many PETs have excellent heat resistance and dimensional stability. Another embodiment of the AR film is a low reflection film. In one embodiment, the LR film is a substrate film coated with a material with a low refractive index.

In one embodiment, the reflectance of the AR film is greater than 0% and less than 2%. In one embodiment, the reflectance of the AR film is any of 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1.

The AR films 19a and 19b shown in FIG. 1 have smaller retardation than the quarter-wave plate 17a. In one embodiment, retardation represents phase difference. In one embodiment, the substrate films of these AR films have smaller birefringence than the quarter-wave plate 17a. In one embodiment, the AR films have substantially no birefringence. In one embodiment, the AR films do not substantially convert unpolarized light into polarized light. The technical meaning of the AR films 19a and 19b having these optical properties will be described later.

In one embodiment, the birefringence Δn is expressed as follows:

In the formula, n ₀ is the refractive index for ordinary rays, and _{n e} is the refractive index for extraordinary rays. In one embodiment, unpolarized light has both ordinary and extraordinary rays. In one embodiment, linearly polarized light has either ordinary or extraordinary rays.

Retardation δ is expressed as follows:

In the formula, t is the thickness of the base film of the AR film.

In one embodiment shown in FIG. 1, AR films 19a and 19b have a higher transmittance for unpolarized light than quarter-wave plate 17a. In one embodiment, these AR films have a higher transmittance for unpolarized light than quarter-wave plate 17a across the entire wavelength band of visible light. In one embodiment, the entire wavelength band of visible light is 400 to 750 nm. In another embodiment, the lower limit of the wavelength of visible light is 360 to 400 nm, and the upper limit is 760 to 830 nm.

<Connecting elements>

In one embodiment shown in Figure 1, a transparent adhesive layer is used to bond each element together. In one embodiment, the transparent adhesive layer is made of OCA (Optical Clear Adhesive). In one embodiment, OCA is a film-like adhesive sheet that is used to bond films together. Hereinafter, unless otherwise specified, the term "transparent adhesive layer" refers to the same transparent adhesive layer.

In one embodiment shown in FIG. 1, the back surface of the partial reflection film 13 and the front surface of the selective reflection film 15 are bonded together with a transparent adhesive layer 14. In one embodiment, the transparent adhesive layer 14 has a refractive index smaller than the refractive indexes of the partial reflection film 13 and the selective reflection film 15. In one embodiment, the back surface of the selective reflection film 15 and the front surface of the quarter-wave plate 17a are bonded together with a transparent adhesive layer 16. In one embodiment, the back surface of the selective reflection film 15 and the front surfaces of the AR films 19a and 19b are bonded together with a transparent adhesive layer 16. In one embodiment, the transparent adhesive layer 16 has a refractive index smaller than the refractive indexes of the selective reflection film 15, the quarter-wave plate 17a, and the AR films 19a and 19b.

<Layering in each area>

In one embodiment shown in FIG. 1, the boundary between region 21a and region 22a is referred to as boundary 25a. The boundary between region 21a and region 22b is referred to as boundary 25b. In one embodiment, region 22a and region 22b are located on the outer edge of selective reflection film 15.

Figure 3 shows an enlarged view of one embodiment near boundaries 25a and 25b shown in Figure 1. Elements located in front of the selective reflection film 15 are omitted. Region 26a is the region on region 22a near boundary 25a. AR film 19a covers region 26a. In one embodiment, AR film 19a also covers boundary 25a. In another embodiment not shown, AR film 19a does not cover region 26a. In one embodiment, AR film 19a is laminated in the center of region 22a and is not laminated on the outer edge of region 22a.

In one embodiment shown in FIG. 3, region 26b is a region on region 22b near boundary 25b. AR film 19b covers region 26b. AR film 19b also covers boundary 25b. In another embodiment not shown, AR film 19b does not cover region 26b. In one embodiment, AR film 19b is laminated in the center of region 22b and not laminated to the outer edge of region 22b.

In one embodiment shown in FIG. 3, AR films 19a and 19b are further laminated to the back surface of quarter-wave plate 17a. AR films 19a and 19b further cover outer edges 27a and 27b of region 21a. In one embodiment, AR films 19a and 19b cover quarter-wave plate 17a.

In one embodiment shown in FIG. 3, AR films 19a and 19b are not laminated between the selective reflection film 15 and the quarter-wave plate 17a. In another embodiment, AR films 19a and 19b are not laminated between the selective reflection film 15 and the center of the quarter-wave plate 17a.

Figure 4 shows one embodiment of the half mirror 10 viewed from the rear. AR film 19a tightly covers area 26a. AR film 19b tightly covers area 26b. The cross section indicated by III-III in the figure is shown in Figure 3. The center of the rear surface of the quarter-wave plate 17a is located between AR films 19a and 19b and is exposed on the rear side of the half mirror 10.

<Making a half mirror>

Figure 5 shows a plan view of one embodiment of the fabrication of a half mirror. The laminate 35 is formed by laminating a partially reflective film 13, a transparent adhesive layer 14, and a selectively reflective film 15, in that order, on the back surface of the support 11. In one embodiment, a quarter-wave plate 17z is laminated on the back surface of the laminate 35. In one embodiment, the quarter-wave plate 17z is laminated on the selectively reflective film 15 via a transparent adhesive layer 16. In one embodiment, the transparent adhesive layer 16 is made of an adhesive that bonds more strongly to the selectively reflective film 15 than the quarter-wave plate 17z. Lamination is performed on region 21a and regions 22a and 22b.

In one embodiment shown in Figure 5, the quarter-wave plate 17z in regions 22a and 22b is removed. Meanwhile, the quarter-wave plate 17z in region 21a is left as the quarter-wave plate 17a. At this time, the quarter-wave plate 17z is first cut along boundaries 25a and 25b. In one embodiment, the selective reflection film 15 is not cut. In one embodiment, the transparent adhesive layer 16 is not cut.

In one embodiment shown in Figure 5, the quarter-wave plate 17z is then peeled off from the selective reflection film 15 on regions 22a and 22b. In one embodiment, the quarter-wave plate 17z is peeled off from the selective reflection film 15 only in the central portions of regions 22a and 22b. Furthermore, as shown in Figures 1 and 3, AR films 19a and 19b are laminated on the selective reflection film 15 on regions 22a and 22b via a transparent adhesive layer 16.

<Optical properties of half mirrors>

Returning to Figure 2, in one embodiment, when observer Ob observes half mirror 10 from the front, its reflectance is greater than 50% and less than 100%. This reflectance is for light incident on the front of half mirror 10. This reflectance takes into account each element within half mirror 10. In one embodiment, the reflectance is any of 52, 54, 56, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 75, 80, 85, 90, and 95%. In one embodiment, the reflectance is for unpolarized light of 550 nm.

In one embodiment shown in Figure 2, the reflectance of the front surface of the half mirror 10 in region 21a is greater than the reflectance of the front surface of the half mirror 10 in either or both of regions 22a and 22b.

In one embodiment of region 21a shown in Figure 2, the transmittance of light ray Lp traveling from the back surface to the front surface is greater than 50% and less than 100%. In one embodiment, the transmittance is any of 52, 54, 56, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 75, 80, 85, 90, and 95%. In one embodiment, the transmittance is the maximum value for linearly polarized light at 550 nm.

Now, let's assume the presence of linearly polarized light rays traveling from the back to the front of regions 22a and 22b shown in Figure 2. The maximum transmittance of linearly polarized light rays, i.e., light ray Lp, in region 21a is greater than the transmittance of unpolarized light rays in regions 22a and 22b.

In one embodiment of either of regions 22a and 22b shown in Figure 2, the transmittance of light ray Up directed from the back surface to the front surface is greater than 20% and less than 100%. In one embodiment, the transmittance is any of 21, 22, 23, 24, 25, 30, 35, 40, 50, 60, 70, 80, and 90%. In one embodiment, the transmittance of regions 22a and 22b is equal. In one embodiment, the transmittance is for unpolarized light at 550 nm.

Here, let's assume the presence of an unpolarized ray of light traveling from the back of area 21a shown in Figure 2 to the front. The transmittance of the unpolarized ray, i.e., ray Up, in areas 22a and 22b is greater than the transmittance of the unpolarized ray in area 21a.

<Multi-function mirror>

One aspect of utilizing the optical path shown in Figure 2 is the provision of a multi-function mirror 30. The multi-function mirror 30 is a transmissive display mirror or mirror display in region 21a. The multi-function mirror 30 is also a mirror with transmissive illumination in regions 22a and 22b.

In one embodiment shown in FIG. 2, a display panel with a display surface 27 and illumination 28a and 28b are added to the rear side of the half mirror 10. The display surface 27 faces the rear surface of the quarter-wave plate 17a in region 21a. In one embodiment, the display surface 27 is not located in regions 22a and 22b.

In one embodiment shown in Figure 2, image light consisting of linearly polarized light beam Lp is emitted from display surface 27. Light beam Lp is incident on the rear surface of quarter-wave plate 17a. Light beam Lp has a polarization axis tilted 45 degrees with respect to the fast and slow axes of quarter-wave plate 17a.

In one embodiment shown in FIG. 2, light 28a faces the rear surface of AR film 19a in region 22a. Light 28b faces the rear surface of AR film 19b in region 22b. In one embodiment, light 28a and 28b are not located on region 21a. The illumination light emitted from light 28a and 28b consists of unpolarized light rays Up. Light rays Up are incident on the rear surfaces of AR films 19a and 19b.

<Optical paths of each light>

Referring to Figure 2, the optical paths of image light, illumination light, and external light will be described in more detail. First, the image light will be described. The transmission of image light is promoted by the multiple reflections of circularly polarized light mentioned above. In one embodiment, multiple reflections of circularly polarized light occur due to the partially reflective film 13 and the selectively reflective film 15. This multiple reflection is the same as that described in Patent Documents 1 and 2. In one embodiment, to cause this multiple reflection, linearly polarized light is converted to circularly polarized light by a quarter-wave plate 17a.

In one embodiment shown in Figure 2, light ray Lp is incident on the back surface of quarter-wave plate 17a. As mentioned above, light ray Lp is linearly polarized light with its polarization axis tilted 45 degrees relative to the fast and slow axes of quarter-wave plate 17a. Quarter-wave plate 17a converts light ray Lp into F-polarized light.

In one embodiment shown in Figure 2, the partially reflective film 13 reflects F-polarized light toward the selectively reflective film 15. The partially reflective film 13 then converts the F-polarized light to R-polarized light. In one embodiment, the phase of the F-polarized light is reversed inside or at the interface of the partially reflective film 13, resulting in R-polarized light. The selectively reflective film 15 then reflects the R-polarized light toward the partially reflective film 13 and converts it to F-polarized light. In one embodiment, the phase of the R-polarized light is reversed inside or at the interface of the selectively reflective film 15, resulting in F-polarized light. Through these repeated reflections, the half mirror 10 preferentially emits F-polarized light from the front surface of the support 11. Therefore, the image light observed by the observer Ob through the half mirror 10 is bright.

Next, we will explain the illumination light. In one embodiment shown in Figure 2, there are no quarter-wave plates in areas 22a and 22b. As mentioned earlier, the light ray Up that enters these areas is unpolarized. The light ray Up passes through the AR films 19a and 19b, the selective reflection film 15, the partial reflection film 13, and the support 11. The light ray Up exits from the front of the support 11. The light ray Up illuminates the observer Ob as transmitted illumination. The AR films 19a and 19b have a higher transmittance for the unpolarized light ray Up than the quarter-wave plate 17a. Therefore, the transmitted illumination created by the light ray Up is bright.

Returning to Figure 1, the base film that constitutes each AR film, such as AR films 19a and 19b, has a smaller refractive index than the quarter-wave plate 17a. The difference in refractive index between the base film of each AR film and the transparent adhesive layer 16 is smaller than the difference in refractive index between the quarter-wave plate 17a and the transparent adhesive layer 16. Therefore, the transmission loss at the bonding interface between the base film and the transparent adhesive layer 16 that constitute each AR film is small.

In one embodiment shown in Figure 2, there is an interface between the partially reflective film 13 and the support 11. The interface reflects external light Ex incident on the front surface of the support 11. In one embodiment, the interior of the partially reflective film 13 reflects external light Ex incident on the front surface of the support 11. The interface and the interior of the partially reflective film 13 present a mirror image on the front side of the support 11. An observer Ob observes the mirror image from the front side of the support 11. In one embodiment, the interface and the interior of the partially reflective film 13 reflect external light Ex evenly across the entire visible light band.

<Uses of multi-function mirrors>

In one embodiment shown in FIG. 2, the multi-function mirror 30 is a mirror that reflects the image of the observer Ob. The observer Ob uses their eyes to observe their own mirror image reflected in front of the multi-function mirror 30. The observer Ob uses their eyes to observe an image superimposed on the mirror image. In one embodiment, the mirror is any one of a dressing table, a full-length mirror, a wall mirror, and a tabletop mirror. In one embodiment, the multi-function mirror 30 is used by customers to view their appearance when trying on clothing or cosmetics. In one embodiment, illumination light provided by the lights 28a and 22b illuminates the observer Ob. Therefore, the mirror image of the observer Ob reflected in front of the multi-function mirror 30 is bright.

In one embodiment shown in FIG. 2, the multi-function mirror 30 displays an image that is superimposed on the mirror image and is brighter than the mirror image. In one embodiment, the image is a sales or other advertisement. In one embodiment, the displayed image is a design. In another embodiment, the image is symbolic. In one embodiment, the image is a QR code (trademark) or other matrix code or barcode. In one embodiment, the multi-function mirror 30 darkens the image, thereby recovering the mirror image that was hidden in the image.

In one embodiment shown in FIG. 2, the multifunction mirror 30 includes a camera 31. The camera 31 captures an image of the observer Ob. In one embodiment, the multifunction mirror 30 further includes a computer 33. In another embodiment, the multifunction mirror 30 is connected to the computer 33 via a network. The computer 33 converts the image of the observer Ob into a mirror image. The multifunction mirror 30 sends the converted image to the computer 33. The computer 33 sends the image to a display panel including a display surface 27. The display surface 27 displays the image of the observer Ob. In one embodiment, the multifunction mirror 30 functions as such a digital mirror. In one embodiment, illumination light provided by the lights 28a and 28b illuminates the observer Ob. Therefore, the image of the observer Ob reflected in front of the multifunction mirror 30 is bright.

In one embodiment shown in FIG. 2, the computer 33 adds an image of makeup to the image of the observer Ob. In one embodiment, the image of makeup is an image that shows the appearance when the cosmetics are used. In one embodiment, the observer Ob specifies the cosmetics. In one embodiment, the multifunction mirror 30 functions as such a virtual makeup room. In another embodiment, the image of clothing is an image that shows the appearance when the clothing is worn. In one embodiment, the observer Ob specifies the clothing. In one embodiment, the multifunction mirror 30 functions as such a virtual changing room.

In another embodiment shown in FIG. 2, a computer 33 analyzes the image. In one embodiment, the combination of camera 31 and computer 33 is a motion sensor. In an embodiment different from the embodiment shown in FIG. 2, camera 31 is hidden behind a half mirror 10. In one embodiment, camera 31 is hidden behind areas 22a and 22b. Camera 31 photographs observer Ob through the half mirror 10. It is preferable that the multi-function mirror 30 facing camera 31 has an optical configuration similar to areas 22a and 22b, as this increases the amount of light entering camera 31 through the mirror 30.

In one embodiment shown in FIG. 2, the multifunction mirror 30 further includes a sensor (not shown). In one embodiment, the sensor detects the position of the observer Ob's hand. In one embodiment, the sensor is a touch panel disposed on the support 11. In one embodiment, the sensor is a capacitance sensor disposed on the support 11.

In another embodiment, the sensor reads a tag attached to the item. In one embodiment, the tag is a QR code (trademark) or other matrix code or barcode. In another embodiment, the tag is an RFID or other hard tag. In one embodiment, the multi-function mirror 30 displays an image of the item's information superimposed on the mirror image.

<Other aspects of AR film>

Figure 6 shows a half mirror 40, which is a different embodiment from the half mirror 10 shown in the previous figure, in a cross-sectional view similar to Figure 3. Elements located in front of the selective reflection film 15 are omitted. Figure 7 shows one embodiment of the half mirror 40 as viewed from the rear. The cross section indicated by VI-VI in the figure is shown in Figure 6.

The half mirror 40 shown in Figures 6 and 7 has the same configuration as the half mirror 10 shown in Figure 3, with the following exceptions: The half mirror 40 has region 21b instead of region 21a, region 22c instead of regions 22a and 22b, AR film 19c instead of AR films 19a and 19b, and quarter-wave plate 17b instead of quarter-wave plate 17a.

In one embodiment shown in Figures 6 and 7, region 22c surrounds region 21b. The boundary between region 21b and region 22c is boundary 25c. Quarter-wave plate 17b is located on region 21b. Boundary 25c surrounds quarter-wave plate 17b.

In one embodiment shown in Figures 6 and 7, the AR film 19c covers region 22c. In one embodiment, the AR film 19c also covers boundary 25c. In one embodiment, the AR film 19c covers the back surface of the quarter-wave plate 17b. In one embodiment, the AR film 19c covers the center of region 21b. In one embodiment, the AR film 19c covers the entire back surface of the quarter-wave plate 17b. In one embodiment, the AR film 19c is a single film that covers the entire selective reflection film 15.

In one embodiment shown in Figures 6 and 7, the composition and optical characteristics of the AR film 19c as an AR film are similar to those of the AR films 19a and 19b shown in Figure 3. The AR film 19c has an anti-reflection layer 20c on its back surface. The composition and optical characteristics of the quarter-wave plate 17b as a wave plate are similar to those of the quarter-wave plate 17a shown in Figure 3.

In a configuration different from that shown in Figures 6 and 7, a window is opened in the center of the AR film 19c. The AR film 19c does not cover the center of the region 21b. The center of the back surface of the quarter-wave plate 17b is exposed to the back side of the half mirror 40 through the window in the AR film 19c.

Returning to Figure 4, in an embodiment different from that shown in Figure 4, a single AR film similar to the AR film 19c shown in Figures 6 and 7 covers region 21a and regions 22a and 22b collectively. In one embodiment, a single AR film covers the entire surface of the quarter-wave plate 17a. In another embodiment, the AR film covers the entire selective reflection film 15.

<Checking the effectiveness of AR film>

Figure 8 shows a schematic of the half mirrors prepared for testing. The top row shows half mirror Z, the middle row shows half mirror A, and the bottom row shows half mirror B. First, a partially reflective film 13 was laminated on the back surface of a support 11 made of a glass plate to obtain half mirror Z. The back surface of the partially reflective film 13 is in contact with air.

As shown in the upper part of Figure 8, the reflectance of external light Ex incident from the front of half mirror Z was 63%. In the figure, external light Ex is reflected at the front interface of support 11, but this is a schematic representation. The same applies below. Some of the external light Ex is also reflected at the interface between support 11 and partially reflective film 13, as well as inside and on the back surface of partially reflective film 13. The transmittance of unpolarized light Up incident from the back surface of half mirror Z was 36%.

As shown in the upper part of Figure 8, a selective reflection film 15 was bonded to the back surface of half mirror Z via a 25 μm thick transparent adhesive layer 14. A quarter-wave plate 17z was bonded to the back surface of selective reflection film 15 via a 25 μm thick transparent adhesive layer 16. The back surface of quarter-wave plate 17z was in contact with air. In this way, half mirror A was obtained.

In Figure 8, the reflectance for external light Ex incident from the front of half mirror A was 64%. Note that some of the external light Ex is also reflected by elements located behind the partially reflective film 13. The transmittance for unpolarized light Up incident from the back of half mirror A was 23%. The maximum transmittance for linearly polarized light Lp incident from the back of half mirror A was 63%.

In Figure 8, the quarter-wave plate 17z was peeled off from the back surface of half mirror A. Next, an AR film 19z was bonded to the back surface of the selective reflection film 15 via a transparent adhesive layer 16. The AR film 19z is a TAC film with an anti-reflection layer 20z on its back surface. This completes the half mirror B. The anti-reflection layer 20z is in contact with air.

In Figure 8, the reflectance of external light Ex incident from the front of half mirror B was 61%. Note that some of the external light Ex is also reflected by elements located behind the partially reflective film 13. As far as the mirror images are concerned, there was no difference in the color tone of the reflected external light Ex between half mirror A and half mirror B. The transmittance of unpolarized light Up incident from the back of half mirror A was 39%.

The above suggests that by replacing the quarter-wave plate with an AR film in a portion of the rear surface of half mirror A, the transmittance of unpolarized light in that portion can be increased. It also suggests that the reflectance of external light in that portion does not decrease significantly. An embodiment that achieves this effect has been described in detail using Figures 1 to 7.

The present invention is not limited to the above-described embodiment, and modifications can be made as appropriate without departing from the spirit of the invention.

10 Half mirror, 11 Support, 12 Half mirror structure, 13 Partially reflective film, 14 Transparent adhesive layer, 15 Selectively reflective film, 16 Transparent adhesive layer, 17a-b Quarter wave plate, 19a-c,z AR film, 20a-c,z Anti-reflection layer, 21a-b Region, 22a-c Region, 25a-c Boundary, 26a-b Region, 27a-b Outer edge, 27 Display surface, 28a-b Lighting, 30 Multi-function mirror, 31 Camera, 33 Computer, 35 Laminate, 40 Half mirror, A Half mirror, B Half mirror, Ex External light, Lp Linearly polarized light, Ob Observer, Up Unpolarized light, Z Half mirror

Claims (10)

A support ;
a partially reflective film laminated on the rear surface of the support;
a selective reflection film laminated on the back surface of the partially reflective film;
a quarter-wave plate laminated on the back surface of the selective reflection film, in this order;
Further provided on the rear surface of the selective reflection film are a first region where the quarter-wave plate is laminated and a second region where the quarter-wave plate is not laminated;
further comprising an anti-reflection film laminated to the rear surface of the second region;
the partially reflective film comprises a metal, metal oxide, or other dielectric material and partially transmits and partially reflects light;
The selective reflection film is made of a material that has selectivity for circularly polarized light, and when one of left-handed circularly polarized light and right-handed circularly polarized light is called F-polarized light and the other is called R-polarized light, the selective reflection film transmits F-polarized light more than R-polarized light and reflects R-polarized light more than F-polarized light throughout the entire visible light band,
The anti-reflection film has an anti-reflection layer on its back surface and has a transmittance for unpolarized light that is higher than the transmittance of the quarter-wave plate.
Half mirror. The anti-reflection film has a smaller retardation than the quarter wave plate.
The half mirror according to claim 1 . the anti-reflection film includes a substrate film and the anti-reflection layer laminated on the back surface of the substrate film,
The substrate film has a birefringence smaller than that of the quarter-wave plate.
The half mirror according to claim 2 . The anti-reflection film has a transmittance for unpolarized light that is higher than the transmittance of the quarter-wave plate over the entire wavelength band of visible light.
The half mirror according to any one of claims 1 to 3. Furthermore, the anti-reflection film is laminated on the back surface of the quarter-wave plate,
the anti-reflection film covers the boundary between the first region and the second region,
The center of the rear surface of the quarter-wave plate is exposed on the rear surface side of the half mirror.
The half mirror according to any one of claims 1 to 4. Furthermore, the anti-reflection film is laminated at the center of the back surface of the quarter-wave plate,
The anti-reflection film further covers the center of the first region.
The half mirror according to any one of claims 1 to 4. the reflectance of the selective reflection film for R-polarized light is higher than the reflectance of the partially reflection film for F-polarized light over the entire visible light band;
When linearly polarized light having a polarization axis tilted 45 degrees with respect to the fast axis and slow axis of the quarter-wave plate is incident on the rear surface of the quarter-wave plate, the quarter-wave plate converts the linearly polarized light into F-polarized light,
The partially reflective film reflects F-polarized light toward the selectively reflective film and converts the F-polarized light into R-polarized light, and the selectively reflective film further reflects R-polarized light toward the partially reflective film and converts the R-polarized light into F-polarized light. Through this process repeated, F-polarized light is preferentially emitted from the front surface of the support.
The half mirror according to any one of claims 1 to 6. A half mirror according to any one of claims 1 to 7, a display, and lighting,
a display surface of the display facing a rear surface of the quarter-wave plate in the first region;
the image light incident on the quarter-wave plate from the display surface is linearly polarized light having a polarization axis inclined at 45 degrees with respect to the fast axis and the slow axis of the quarter-wave plate,
the illumination faces the rear surface of the anti-reflection film in the second region;
The illumination light incident on the anti-reflection film from the lighting is unpolarized.
Multi-function mirror. A method for producing the half mirror according to any one of claims 1 to 7, comprising the steps of:
The quarter -wave plate is laminated on the back surface of the support on which the partially reflective film and the selectively reflective film are laminated, on the first region and the second region of the back surface of the selectively reflective film;
removing the quarter wave plate on the second region while leaving the quarter wave plate on the first region;
laminating the antireflection film on the selective reflection film in the second region;
method. In laminating the quarter-wave plate, the back surface of the selective reflection film and the front surface of the quarter-wave plate are bonded with a transparent adhesive layer, and the transparent adhesive layer is bonded more strongly to the selective reflection film than to the quarter-wave plate;
In removing the quarter-wave plate, the quarter-wave plate is cut on a boundary between the first region and the second region, and then the quarter-wave plate on the second region is peeled off from the selective reflection film;
In laminating the antireflection film, the back surface of the selective reflection film and the front surface of the antireflection film are bonded together with the transparent adhesive layer remaining on the second region.
10. The method of claim 9.