JP7510605B2 - Screens and Projection Systems - Google Patents

Description

The present invention relates to a screen and a projection system, and in particular to a screen onto which projection light emitted from a projection device is projected, and a projection system equipped with this screen.

Conventionally, so-called transparent screens have been known that are made of a material with high transmittance and low Bayes value as a screen onto which the projection light emitted from a projection device is projected.

Such a transparent screen is configured with a transparent base layer that transmits the projection light through a transparent film, and a diffusion layer that is attached to the base layer and diffuses the projection light incident from the front and transmits the light incident from the rear. With this configuration, the projection light incident from the front is diffused by the diffusion layer, making it possible to view the projected image from behind the screen, and since some of the light incident from the front or rear is transmitted through the diffusion layer, the opposite side of the screen can be viewed from the front and rear of the screen (i.e., the screen appears transparent). In this specification, such a transparent screen is referred to as a transmissive screen.

Also known is a configuration that includes a transparent base layer and a reflective diffusion layer that reflects a portion of the projection light from the front forward and transmits a portion of the light from the rear forward, as described in Patent Document 1, for example. With this configuration, the projection light incident from the front is reflected and diffused by the reflective diffusion layer, making it possible to view the projected image from the front of the screen, and since a portion of the light incident from the front or rear passes through the diffusion layer, the opposite side of the screen can be viewed from the front and rear of the screen (i.e., the screen appears transparent). In this specification, such a transparent screen is referred to as a reflective screen.

Patent No. 6578908

For the base layer of such a transparent screen, it is preferable to use a resin sheet to provide flexibility. However, if a resin sheet such as PET, which can be manufactured to a thickness suitable for a screen, is used for the base layer and a polarized projection light is irradiated from a projector, there is a problem that the resin sheet causes color unevenness, which deteriorates the viewer's visibility.
The present invention has been made in consideration of the above problems, and aims to provide a transparent screen that can improve the visibility of the projected light from a projection device when a resin sheet such as PET is used as a base layer.

The screen of the present invention has a base layer and a projection layer consisting of a diffuse reflection layer or a diffusion layer, and projection light emitted from a projection device passes through the base layer and is projected onto the projection layer. The screen is characterized by having a polarizing layer that converts the projection light from linearly polarized light to circularly polarized light or elliptically polarized light.

When a resin sheet such as PET is used for the base layer, color unevenness occurs.
In contrast, according to the present invention, by making projection light incident on a polarizing material layer, the projection light is converted into circularly polarized light or elliptically polarized light, and then diffused or diffusely reflected before reaching the observer. Therefore, even when a resin sheet such as PET is used as the base layer, the occurrence of color unevenness can be suppressed and visibility can be improved.

In the present invention, the base layer is preferably formed of PET.
According to the present invention having the above-mentioned configuration, there is no need to reinforce the base material with other materials, and the base material layer can be provided to a desired thickness using only PET at low cost.

In the present invention, the polarizing layer preferably includes a 1/4 λ sheet, a laminated sheet of a 1/2 λ sheet and a 1/4 λ sheet, or a reverse dispersion sheet.
The laminated sheet of the 1/4 λ sheet, the 1/2 λ sheet, and the 1/4 λ sheet, or the reverse dispersion sheet all have the function of converting linearly polarized light into circularly polarized light or elliptically polarized light. Therefore, according to the present invention having the above configuration, even if the base layer uses a resin sheet such as PET, the occurrence of color unevenness can be suppressed.

In the present invention, the polarizing layer is preferably adhered to one surface of the base layer with an adhesive.
According to the present invention having the above configuration, the polarizing layer only needs to be adhered to the base layer with an adhesive, and therefore the present invention can be applied to existing screens.

In the present invention, the projection layer is preferably a diffuse reflection layer, and the diffuse reflection layer preferably comprises a vacuum-deposited metal film.
The metal film formed by vacuum deposition is very thin, so that according to the present invention having the above configuration, in a screen for which a reduction in thickness is required, the diffuse reflection layer can be formed without significantly increasing the thickness.

In the present invention, the projection layer is preferably a diffuse reflection layer, and the cross section of the reflection surface of the diffuse reflection layer is sawtooth-shaped.
According to the present invention having the above-mentioned configuration, even if the projection device is disposed laterally, such as above or below, the projection light can be reliably reflected from the screen.

In the present invention, the sawtooth reflective surface of the diffuse reflective layer is preferably formed on the surface of the UV curable resin.
According to the present invention having the above configuration, by molding with a UV-curable resin, minute projections and recesses can be easily formed on the reflecting surface.

In the present invention, the screen preferably has a transmittance of 30% or more and a haze value of 20 or less.
According to the present invention having the above-mentioned configuration, the screen can function as a so-called transparent screen through which the background behind the screen can be sufficiently seen.

The projection system of the present invention includes a screen and a projection device that emits projection light onto the screen.

The present invention provides a transparent screen that can improve the visibility of the projected light from a projection device when a resin sheet such as PET is used as the base layer.

1 is a schematic perspective view of a projection system according to a first embodiment of the present invention when an observer is on the projection device side. FIG. 2 is a side cross-sectional view of a reflective screen in the projection system shown in FIG. 1 . FIG. 11 is a schematic perspective view of a projection system according to a second embodiment of the present invention when an observer is behind a screen. FIG. 4 is a side cross-sectional view of a rear projection screen in the projection system shown in FIG. 3 .

First Embodiment
Hereinafter, a screen and a projection system according to a first embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the direction of the projection device side and the front side of the screen will be referred to as the projection device side or front, and the direction opposite the projection device with respect to the screen will be referred to as the rear side or back of the screen.
Fig. 1 is a schematic perspective view of a projection system 1 according to a first embodiment of the present invention when an observer is on the projection device side. As shown in Fig. 1, the projection system 1 includes a reflective screen 2 and a projection device (projector) 4.

The reflective screen 2 is a rectangular, flat member that is installed so that the projection surface is vertical. The reflective screen 2 is a so-called reflective transparent screen that can diffusely reflect the projection light emitted from the projection device 4 on the projection surface to project an image, and can transmit horizontal light from the front and back to the opposite side.

Projection device 4 has a light source 6, and emits projection light from the light source 6 toward a predetermined range by an optical system (not shown) inside the device. The projection light projected from projection device 4 is linearly polarized. Projection device 4 is placed in front of screen 2, and emits linearly polarized projection light toward screen 2 within a predetermined horizontal angular range and a predetermined vertical angular range. Projection device 4 projects the projection light upward at an angle of 20 to 80 degrees from the horizontal direction.

In addition, in FIG. 1, the arrows indicate the path that the projection light emitted from the light source 6 in the projection device 4 takes to reach the observer's eyes. The projection light from the projection device 4 is projected diagonally upward toward the screen 2. The projected light is diffusely reflected by the reflective screen 2, and the observer on the projection device side can observe the projection light diffusely reflected by the reflective screen 2.

Next, the configuration of the reflective screen 2 will be described in detail with reference to FIG. 2. FIG. 2 is a side cross-sectional view of the reflective screen in the projection system shown in FIG. 1. The reflective screen 2 includes a base layer 8, a polarizing layer 10 provided in front of the base layer 8, and a diffuse reflection layer (projection layer) 12 provided behind the base layer 8. The polarizing layer 10 is bonded to the front surface of the base layer 8 with an adhesive, and the diffuse reflection layer 12 is bonded to the rear surface of the base layer 8 with an adhesive. As the adhesive, a UV-curable resin that is preferable for bonding at room temperature is used. Note that the method of bonding the polarizing layer 10 and the diffuse reflection layer 12 to the base layer 8 is not limited to this. In this embodiment, the base layer 8, the polarizing layer 10, and the diffuse reflection layer 12 are the same rectangular shape, but it is sufficient that the polarizing layer 10 and the diffuse reflection layer 12 are provided in the area where the projection light is to be projected. The reflective screen 2 has an overall transmittance of 30% or more and a haze value of 20 or less. It is preferable that the transmittance of the reflective screen 2 is 50% or more and the haze value is 10 or less.

The base layer 8 is a colorless, transparent, rectangular sheet made of PET. In this embodiment, the thickness of the base layer 8 is most preferably about 0.2 mm, but may be 0.1 mm to 0.5 mm. PET is preferred as the material for the base layer 8 because it can be molded to the desired thickness, but resins such as polycarbonate resin can also be used.

The polarizing layer 10 of this embodiment is made of a rectangular polarizing film. The polarizing film that constitutes the polarizing layer 10 converts the projection light incident from the front from linearly polarized light to circularly polarized light. In this embodiment, a 1/4 λ sheet is used as such a polarizing film, but this is not limited to this, and it may also be a laminated sheet of a 1/2 λ sheet and a 1/4 λ sheet, or a reverse dispersion sheet.

The diffuse reflection layer 12 has an incident layer 12A and a transmission layer 12B. The front surface of the diffuse reflection layer 12 contacts the base material layer 8, and the rear surface has an outer surface 22 that does not contact any surface. A reflection surface 14 having a sawtooth-shaped vertical cross section is formed on the front surface of the transmission layer 12B at the middle of the layer thickness direction in the diffuse reflection layer 12. In this embodiment, the reflection surface 14 is configured by alternating horizontal surfaces 15 and inclined surfaces 16 in the height direction. The horizontal surface 15 extends horizontally, and the inclined surface 16 is inclined so as to advance forward toward the top. The angle formed by the inclined surface 16 is an angle according to the angle of the projection light of the projection device 4, and reflects the projection light emitted from below the projection device 4 approximately horizontally. The surface of the incident layer 12A has minute irregularities formed thereon, and the reflection surface 14 is configured by coating a metal film 20 on the minute irregularities of the incident layer 12A. The angle of the inclined surface 16 of the reflecting surface 14 relative to the horizontal plane 15 is preferably aligned in a direction along the outer surface 22 between about 5 degrees and 35 degrees in order to efficiently reflect the projection light from the projection device 4. The incident layer 12A and the transmissive layer 12B are molded from the same UV-curable resin.

As described above, this embodiment describes a case where projection light is projected from below by the projection device 4, but the present invention can also be applied when projection is from above, in which case the reflective surfaces are arranged rotated symmetrically from top to bottom. Projection from the side is also possible. In order to accommodate projection from both below and above, instead of forming a horizontal surface 15, it is also possible to alternately form inclined surfaces that slope forward toward the top and inclined surfaces that slope backward toward the top.

The metal film 20 is a thin metal film formed by vacuum deposition, and is optically transparent. The metal film 20 may be any light-reflecting material such as silver, aluminum, or gold, and is coated on the reflective surface 14 to a thickness of about 1 to 100 nm. In particular, chromium is preferred, as it has excellent durability and a high light absorption rate.

Next, the path of the projection light until it reaches the observer's eye will be described with reference to FIG. 2. The arrows in FIG. 2 indicate the path of the projection light. As shown in FIG. 2, the projection light emitted from the light source 6 provided in the projection device 4 enters the polarizing material layer 10 of the screen 2, where the projection light is converted into circularly polarized light, passes through the base material layer 8, and reaches the reflection surface 14 of the diffuse reflection layer (projection layer) 12. The reflection surface 14 has minute irregularities formed thereon, and is further coated with a metal film 20 from above. A portion of the projection light that reaches the reflection surface 14 is reflected by the coated metal film 20 (reflection surface 14). The reflection rate of the projection light depends on the type of metal that is coated. In this way, the projection light reflected by the reflection surface 14 (hereinafter referred to as reflected light) is diffused by the irregularities, and the angle of the light reaches the observer 3 with the angle limited by the irregularities. In this embodiment, the diffusion angle of the reflected light when the reflected light is reflected toward the observer 3 is a maximum of about 15 degrees.

A portion of the light incident on the screen 2 from behind passes through the diffuse reflection layer 12, passes through the base material layer 8 and the polarizing material layer 10, and reaches the observer 3. A portion of the light incident on the screen 2 from the front passes through the diffuse reflection layer 12 and is transmitted to the rear. Note that a portion of the light incident on the screen 2 from the front is reflected by the diffuse reflection layer 12, but because it is reflected downward, the light reflected by the diffuse reflection layer 12 is not visible to the observer 3 in front.

According to this embodiment, the following effects are achieved.
In this embodiment, the reflective screen 2 has a polarizing material layer 10, which converts the projected light from linearly polarized light to circularly polarized light. Therefore, even when a resin sheet such as PET is used as the base layer 8, the occurrence of color unevenness can be suppressed.

In addition, in this embodiment, since the base layer 8 is made of PET, there is no need to reinforce it with other materials, and the base layer 8 can be provided at a desired thickness using PET alone at low cost.

In addition, in this embodiment, the polarizing material layer 10 is formed from a 1/4 λ sheet. The 1/4 λ sheet has the function of converting linearly polarized light into circularly polarized light. Therefore, according to this embodiment, even if the substrate layer 8 uses a resin sheet such as PET, the occurrence of color unevenness can be suppressed.

In addition, in this embodiment, the diffuse reflection layer (projection layer) 12 has a reflective surface 14 made of a vacuum-deposited metal film 20. This makes it possible to easily form the reflective surface 14 on top of the minute irregularities for diffusing the projection light, without significantly increasing the thickness of the screen 2.

In addition, in this embodiment, the cross section of the reflective surface 14 of the diffuse reflection layer 12 is sawtooth-shaped, so the projection light can be reliably reflected even if the projection device 4 is placed below the screen 2.

In this embodiment, the reflective surface 14 has a sawtooth cross section, but the cross-sectional shape of the reflective surface 14 is not limited to this. For example, in this embodiment, the cross sections of the horizontal surface 15 and the inclined surface 16 are linear, but they may be arcs, ellipses, or other free curves.

In addition, in this embodiment, the reflective surface 14 having a sawtooth surface is formed on the surface of the transmissive layer 12B made of UV-curable resin. In this way, by molding the transmissive layer 12B of the diffuse reflective layer 12 from UV-curable resin, minute irregularities can be easily formed on the reflective surface 14.

In addition, in this embodiment, the transmittance of the screen 2 is 30% or more, and the haze value is 20 or less. This allows the background behind the screen 2 to be fully transmitted, allowing it to function as a so-called transparent screen.

In addition, since conventional reflective surfaces are arranged parallel to the horizontal plane 15, the diffusion direction of the projected light is vertical. In contrast, according to the embodiment of the above configuration in which the cross section of the reflective surface 14 of the diffuse reflective layer 12 is sawtooth-shaped, the projected light projected from below, for example, can be reliably reflected in a direction approximately parallel to the horizontal plane 15. Even if the distance between the reflective screen 2 and the projection device 4 is short, the projected light can be projected from the side, such as below or above.

The screen 2 is composed of a base layer 8, a polarizing material layer 10, and a diffuse reflection layer 12, but they may not be in direct contact with each other, and a light absorbing layer or a transparent plate layer may be present between or on the outside. Furthermore, the layers may not be bonded together, but rather the ends may simply be fixed in place.

Second Embodiment
In the first embodiment, the case of a reflective screen in which the observer 3 visually recognizes the reflected projection light has been described, but the present invention is not limited to this, and can also be applied to the case of a transmissive screen in which the observer 3 visually recognizes the image projected onto the screen 2 from the opposite direction to the projection device 4. A second embodiment of the present invention applied to such a transmissive screen will be described below with reference to Figures 3 and 4. In the following description, the same reference numerals are used for configurations similar to or corresponding to those in the first embodiment, and detailed description will be omitted. The directions will also be expressed in the same way as in the first embodiment.

Fig. 3 is a schematic perspective view of a projection system 101 according to a second embodiment of the present invention in the case where an observer 3 is behind the screen. As shown in Fig. 3, the projection system 101 includes a transmissive screen 32 and a projection device (projector) 4. The transmissive screen 32 is a so-called transparent screen that can diffuse the projection light emitted from the projection device 4 to project an image on a projection surface, and can transmit horizontal light from the front and rear to the opposite side. As in the first embodiment, the projection device 4 is disposed in front of the screen 32 and projects projection light obliquely upward toward the screen 32.
3, the path of the projection light emitted from the light source 6 in the projection device 4 until it reaches the observer's eye is indicated by arrows. The observer 3 behind the screen can observe the projection light that passes through the translucent screen 32 and is diffused.

Next, the configuration of the rear projection screen 32 will be described in detail with reference to Fig. 4. Fig. 4 is a side cross-sectional view of the rear projection screen 32 in the projection system 101 shown in Fig. 3. The rear projection screen 32 includes a base layer 8, a polarizing material layer 10 provided in front of the base layer 8, and a diffusion layer (projection layer) 42 provided behind the base layer 8.
In addition, in this embodiment, the base layer 8, the polarizing material layer 10, and the diffusion layer 42 are all the same rectangular shape, but it is sufficient that the polarizing material layer 10 and the diffusion layer 42 are provided at any location where an image is desired to be projected.

The diffusion layer 42 has an incident layer 42A and a transmission layer 42B. The front surface of the diffusion layer 42 contacts the base layer 8, and the rear surface has an outer surface 22 that does not contact any surface. In the middle of the layer thickness direction in the diffusion layer 42, the front surface of the transmission layer 42B is formed as a sawtooth surface 44. In this embodiment, the sawtooth surface 44 is composed of horizontal surfaces 45 and inclined surfaces 46 arranged alternately in the height direction. The horizontal surfaces 45 extend horizontally, and the inclined surfaces 46 are inclined so as to advance upward and forward. The angle formed by the inclined surfaces 46 is an angle that does not cause light from behind the observer 3 to be regularly reflected to the observer 3, and it is desirable that the angle be aligned in a direction along the outer surface 22 between about 5 and 20 degrees. The surface of the incident layer 42A has minute irregularities. In this embodiment, the incident layer 42A and the transmission layer 42B are molded from the same UV-curable resin.

Next, the path of the projection light until it reaches the observer's eye will be described with reference to FIG. 4. The projection light emitted from the light source 6 provided in the projection device 4 enters the polarizing material layer 10 of the transmissive screen 32, where the projection light is converted into circularly polarized light, passes through the base material layer 8, and reaches the sawtooth surface 44 of the diffusion layer 42. The sawtooth surface 44 has minute irregularities. The projection light that reaches the wedge-shaped surface 44 is partially transmitted. The projection light that passes through the sawtooth surface 44 (hereinafter referred to as transmitted light) is diffused by the minute irregularities and reaches the observer 3. A portion of the light from behind the observer 3 is reflected, but since it is reflected downward by the sawtooth surface 44, the reflected light is not visible to the observer 3.

According to this embodiment, the following effects are achieved.
In the present embodiment, the transmissive screen 32 has the polarizing material layer 10, so that the projection light is converted from linearly polarized light to circularly polarized light. Therefore, when a resin sheet such as PET is used as the base layer 8, the occurrence of color unevenness can be suppressed.

In this embodiment, since the diffusion layer 42 has a sawtooth surface 44, the projection light can be efficiently transmitted even if the projection device 4 is disposed to the side, such as above or below the front, of the transmissive screen 32. Furthermore, even for light coming from behind the observer 3, the sawtooth surface 44 reflects the light downward, preventing the reflected light from impeding the observer 3's visibility.

In this embodiment, the diffusion layer 42 has a sawtooth surface 44 with a horizontal surface 45 and an inclined surface 46 that are linear, but the shape of the diffusion layer 42 is not limited to a sawtooth surface. For example, in this embodiment, the cross sections of the horizontal surface 45 and the inclined surface 46 of the sawtooth surface 44 are linear, but this is not limited thereto, and they may be arcs, ellipses, or other free curves.

In this embodiment, a sawtooth surface 44 is formed on the surface of the transparent layer 42B of the diffusion layer 42. By molding the transparent layer 42B of the diffusion layer 42 from a UV-curable resin, minute irregularities can be easily formed on the surface of the sawtooth surface 44.

In the above embodiments, a polarizing plate that converts linearly polarized light into circularly polarized light is used as the polarizing material layer 10, but the present invention is not limited to this, and a polarizing plate that converts linearly polarized light into elliptically polarized light may also be used. Even in such a case, the same effect is achieved.

An embodiment of the screen of the present invention will now be described.
As an example, the reflective screen 2 described with reference to Fig. 2 was formed. PET was used for the base layer 16, and a 1/4λ sheet of polarizing film was used for the polarizing material layer 10.
As a comparative example, a screen was formed in which the polarizing layer 10 was omitted from the reflective screen 2 described with reference to FIG.
For these examples and comparative examples, chromaticity was measured using a color luminance meter in accordance with JIS Z 8722. Note that as the color luminance meter, a color luminance meter BM-5AC manufactured by Topcon Technohouse Corporation was used.
The chromaticity coordinates of the reflected light from the screen of the example were x 0.35 and y 0.36, whereas the chromaticity coordinates of the reflected light from the comparative example were x 0.39 and y 0.40.

In this way, the present invention can prevent uneven coloring.

1: Projection system 2: Reflection screen 3: Observer 4: Projection device 6: Light source 8: Substrate layer 10: Polarizer layer 12: Diffuse reflection layer 12A: Incident layer 12B: Transmitting layer 14: Reflecting surface 15: Horizontal surface 16: Inclined surface 20: Metal film 22: Outer surface 32: Transmissive screen 42: Diffusion layer 42A: Incident layer 42B: Transmitting layer 44: Sawtooth surface 45: Horizontal surface 46: Inclined surface 101: Projection system

Claims (8)

A transparent screen having a base layer made of PET and a projection layer made of a diffuse reflection layer or a diffusion layer, in which projection light emitted from a projection device passes through the base layer and is projected onto the projection layer,
A polarizing layer that converts the projected light from linearly polarized light to circularly polarized light or elliptically polarized light ,
the polarizing layer is disposed closer to the projection device than the base layer, and the projection layer is disposed only on the opposite side of the base layer to the polarizing layer;
A screen characterized by: The polarizing layer includes a 1/4 λ sheet, a laminated sheet of a 1/2 λ sheet and a 1/4 λ sheet, or a reverse dispersion sheet.
2. The screen of claim 1 . The polarizing layer is bonded to one surface of the base layer with an adhesive.
3. A screen according to claim 1 or 2 . the projection layer is a diffuse reflective layer, the diffuse reflective layer comprising a vacuum-deposited metal film;
A screen according to any one of claims 1 to 3 . The projection layer is a diffuse reflection layer, and the cross section of the reflection surface of the diffuse reflection layer is sawtooth-shaped.
A screen according to any one of claims 1 to 4 . The sawtooth reflective surface of the diffuse reflective layer is formed on the surface of a UV-curable resin.
6. The screen of claim 5 . The screen has a transmittance of 30% or more and a haze value of 20 or less.
A screen according to any one of claims 1 to 6 . A screen according to any one of claims 1 to 7 ;
a projection device that emits projection light onto the screen.

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