JP2004069836A - Screen for front projection display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure the high quality of a display picture even under the environment of brightness exceeding the high-quality picture display limit of a conventional screen. <P>SOLUTION: The screen 20 for the front projection display is provided with a reflection layer 1 having a reflection surface 1A bent in a saw-toothed state; a transparent smoothing layer 2 brought into close contact with the saw-toothed reflection surface of the reflection layer; a light control layer 3 brought into close contact with the surface on the counter reflection layer side of the smoothing layer to transmit the light while scattering it or while making it advance straight depending on the incident direction of the light; or furthermore an antireflection layer 4 brought into close contact with the surface on the counter smoothing layer side of the light control layer and restraining the reflection from the surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a screen for a front projection display.
[0002]
[Prior art]
A front projection display projects an image from a projector onto a relatively large screen, and is a very useful display system that enables a large number of observers to see the same image at the same time. Has a drawback that the image quality on the screen deteriorates in a bright environment. In order to compensate for this drawback, the conventional screen has a surface shape in which minute transparent beads are dispersed on a flat surface, and the beads are formed such that incident light is scattered in a direction opposite to the incident direction. A material having a selected refractive index (a so-called bead screen) is used.
[0003]
[Problems to be solved by the invention]
However, in the conventional bead screen, external light is scattered similarly to the projector light. Therefore, when a practical viewing area is secured, the external light is always mixed with the projector light scattered from the screen toward the observer. Would. For this reason, there has been a problem that it is difficult to suppress a decrease in image quality under an environment having a brightness exceeding a certain limit.
[0004]
An object of the present invention is to provide a screen for a front projection display capable of securing a high display image quality even in an environment of brightness exceeding the high quality image display limit of the conventional screen in view of the problems of the conventional technology. And
[0005]
[Means for Solving the Problems]
The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that a reflecting plate whose reflecting surface is bent in a saw-tooth shape scatters and transmits only incident light in a specific angle range, and transmits straight incident light in other angle ranges. By composing a screen in combination with a polymer film having a light control function (Document # 1 = Okita et al .: Sumitomo Chemical 1991-I, pp. 37-48), only the projector light is scattered in the direction of the observer. The present invention has been made to realize a front projection display system that specularly reflects external light in a direction where no observer is present.
[0006]
The gist of the present invention is as follows.
(1) A reflection layer having a reflection surface bent in a sawtooth shape, a transparent smoothing layer in close contact with the sawtooth reflection surface of the reflection layer, and a light in close contact with the surface of the smoothing layer on the side of the anti-reflection layer. A light control layer for scattering transmission or straight transmission depending on the incident direction.
(2) The front projection display screen according to (1), further comprising an anti-reflection layer which is in close contact with the surface of the light control layer on the side opposite to the smoothing layer and suppresses reflection from the surface.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in FIG. 1, a screen 20 according to the present invention (hereinafter, also referred to as the present invention screen) has a reflection layer 1 having a reflection surface 1A bent in a saw-tooth shape, and is closely attached to the saw-tooth reflection surface of the reflection layer. It has a transparent smoothing layer 2 and a light control layer 3 which is in close contact with the surface of the smoothing layer on the side of the anti-reflection layer and scatters or transmits light depending on the incident direction thereof. As shown, it has a structure having an antireflection layer 4 which is in close contact with the surface of the light control layer 3 on the side opposite to the smoothing layer and suppresses reflection from the surface. In this screen 20, projector light is projected on the screen surface of the reflection layer 1 on the side of the sawtooth reflection surface 1A.
[0008]
The light control layer is made of, for example, a special polymer film as described in the above-mentioned document # 1 (in the document # 1, the trade name of a view control plate in which this polymer film and a transparent plastic material are combined is ""Lumisty"). The optical property that the light transmission state (scattering ⇔ straight transmission) changes drastically depending on the angle of the light incident on it due to the influence of the specific ordered structure inside. Have That is, as shown in FIG. 3, most of the light (for example, 80% or more of the entire light) incident from the region 5 corresponding to a specific angle range determined by the specific regular structure inside the light control layer 3 is used. The light is scattered to the area 6 and the rest is scattered to the area 5. On the other hand, light incident from the regions 7 and 9 outside the region 5 is transmitted to the regions 8 and 10, respectively. The thickness of the light control layer is suitably about 0.2 to 0.5 mm.
[0009]
The reflection layer has a reflection surface (mirror surface) bent in a sawtooth shape. The reflective layer may be made of any material as long as it can form such a saw-toothed mirror surface. The sawtooth pitch (the peak-to-peak or the valley-to-valley pitch of the saw-toothed mirror surface) is suitably about 200 to 300 μm.
One surface (back surface) of the smoothing layer is in close contact with the saw-toothed mirror surface. This smoothing layer is provided for bonding the light control layer and the reflection layer. The polymer film constituting the light control layer needs to have a flat surface in relation to its internal ordered structure in order to exhibit its optical characteristics, and the other surface of the smoothing layer (surface ) Is a plane. This plane is made as parallel as possible to the plane on which the peaks (or valleys) of the saw-toothed mirror surface ride to avoid variations in display quality depending on locations in the screen plane. As the material of the smoothing layer, a resin which is transparent and which is rich in at least one of thermosetting, thermoplastic and photocurable can be preferably used. Further, if total reflection occurs on the smoothing layer side of the interface between the light control layer and the smoothing layer, a part of the projector light may not return to the observer side and the display image on the screen may be darkened. In order to avoid total reflection, the material of the smoothing layer is preferably one whose refractive index is as close as possible to the refractive index (about 1.5 to 2.0) of the polymer film constituting the light control layer. . Further, the minimum thickness of the smoothing layer (corresponding to the distance between the surface of the smoothing layer and the peak of the saw-toothed mirror surface) is preferably as small as possible as long as the light control layer can be securely fixed.
[0010]
By making the reflecting surface into a sawtooth-bent mirror structure, for example, as shown in FIG. 4, the angle of the normal to the surface of the smoothing layer 2 is 0, the angle from the normal to the counterclockwise side is positive, and the clockwise. Within the angle range [−π / 2, π / 2] in which the angle to the side is negative, the larger one of the two different angles is represented by α, and the smaller one is represented by β (−π / 2 <β <α). <Π / 2), the light having entered the area 11 corresponding to the predetermined angle range [β, α] is reflected to the area 11, and the area 12 outside the area 11 Light incident from 13 can be designed to be reflected to region 12 or region 13. FIG. 5 shows the design procedure. In FIG. 5, Expressions (1) and (2) for light a and b are conditional expressions for the respective reflections to occur, and Expression (3) for light c is a conditional expression for this reflection not to occur. (This is because, when reflection such as light c occurs, the reflected light escapes to the end of the smoothing layer, which causes a loss of light, which is not preferable).
[0011]
If the combination of the reflection layer 1 and the smoothing layer 2 as shown in FIG. 4 is referred to as a reflection plate 30, the screen 20 of the first example of the present invention shown in FIG. It can be said that the light control layer 3 having the optical characteristics as shown in FIG. 3 is disposed on the surface (ie, the surface of the smoothing layer 2). The screen 20 includes a region 5 in FIG. 3 (that is, a region corresponding to an incident angle range in which most of the light incident on the light control layer 3 is scattered and transmitted) and a region 11 in FIG. It can be designed so that the incident angle range and the reflection angle range coincide with each other.
[0012]
In the screen designed in such a manner, as shown in FIG. 6, light incident on the screen 20 from the area 14 corresponding to the predetermined angle range [β, α] is scattered to the area 14, while the light outside the area 14 is Light incident from the regions 15 and 16 is reflected to the regions 15 and 16.
Therefore, in the front projection display system using the screen of the present invention, as shown in FIG. 7, the screen 20 is arranged such that the projector 21 and the observer 24 are located in the area 14 and the external light source 25 is located outside the area 14. By disposing the projector 21, only the scattered light of the projector light enters the eyes of the observer 24, and the reflected light of the external light does not enter the observer 24. Therefore, an environment having a brightness exceeding the high-definition image display limit of the conventional screen can be obtained. Even below, high display image quality can be ensured.
[0013]
Further, in the second example of the screen of the present invention shown in FIG. 2, the antireflection layer 4 is arranged on the surface of the light control layer 3 in the first example, so that reflection from the surface of the light control layer 3 is prevented. And higher image quality can be obtained. The antireflection layer 4 can be composed of a well-known “antireflection film” (for example, see “Iwanami Physical and Chemical Dictionary, 5th Edition”, p. 1075 (published by Iwanami Shoten, 1998)). Note that the thickness of the antireflection layer 4 is preferably about 0.1 to 100 μm.
[0014]
The screen of the present invention forms the light control layer by disposing the polymer film on the surface of the smoothing layer of the reflector, and preferably further forms an antireflection layer by disposing an antireflection film on the light control layer. Can be produced by
Further, the reflection plate is A: a method in which a groove having a saw-tooth cross section is provided on one surface of a metal plate of a reflection layer material, the groove surface is made a mirror surface, and this is filled with a transparent resin of a smoothing layer material to smooth the surface. Alternatively, B: a plate-like transparent resin for the smoothing layer material is used, a groove having a sawtooth cross section is provided on one surface thereof, and a metal of the reflective layer material is vapor-deposited on the groove to make the groove surface a mirror surface. Can. The metal to be deposited is preferably tin, aluminum, or the like.
[0015]
In the method A, as a means for providing a groove in the metal plate, a groove processing using a milling machine or the like can be given, but this is too expensive in processing. On the other hand, in the method B, as a means for providing a groove in the plate-shaped transparent resin, for example, a roll transfer method as shown in FIG. And then cured), which is advantageous over method A due to the lower processing costs.
[0016]
【Example】
A screen having a length of 50 mm, a width of 50 mm, and a thickness of 7 mm corresponding to the second example of the screen of the present invention shown in FIG. 2 was prototyped. The reflector was designed with α = 5 °, β = −40 °, and n = 1.4 in the design procedure of FIG. The reflection layer was manufactured by forming a groove on one side of an aluminum plate having a thickness of 5 mm. The sawtooth pitch was 2000 μm. The smoothing layer is formed by applying a two-component mixed-type curable transparent resin (material name: silicon rubber) having a refractive index equal to the design value to the saw-toothed reflective surface of the reflective layer so that the maximum thickness is 1000 μm. did. The light control layer controls about 80% of incident light from a region corresponding to an angle range of −40 ° to 5 ° (hereinafter abbreviated as “angle region”) in the polymer film manufactured by Sumitomo Chemical Co., Ltd. Light having a refractive index of 1.4 and having an optical property of transmitting light in a straight line with a refractive index of 1.4 and having a thickness of 1 mm was scattered and transmitted, and was adhered to the surface of the smoothing layer. An antireflection film having a thickness of 80 μm formed by vapor deposition was adhered to the surface of the light control layer.
[0017]
Projector light is incident on the prototype screen from an angle range of 0 ° to -20 °, while external light is incident on the screen from an angle range of 20 ° to 60 °, and the entire angle range (−90 ° to 90 °). Of the reflected (including scattered) light over the same angular range. In addition, an observer observes the screen from an angle range of −40 ° to 5 °.
FIG. 9 is a graph showing the relationship between the reflected light intensity (relative value) and the reflection angle measured for (a) projector light and (b) external light incident on the prototype screen. As shown in the figure, the projector light is substantially reflected into the observation area (an angle area of −40 ° to 5 °) (this reflection is mainly scattered because the reflected light intensity peak is broad). On the other hand, external light is reflected out of the observation region (this reflection is mainly regular reflection because the reflected light intensity peak is sharp). That is, it was confirmed that the projector light and the external light were separated by the screen of the present invention, and that the observer could observe a high-quality projected display image in which the external light was not mixed.
[0018]
【The invention's effect】
Thus, according to the present invention, there is an excellent effect that a high-quality projected display image can be observed even in an environment having a brightness exceeding the conventional high-quality image display limit.
[Brief description of the drawings]
FIG. 1 is a three-dimensional view (a) and a cross-sectional view (b) schematically showing a screen (first example) of the present invention.
FIG. 2 is a schematic view (a) and a sectional view (b) schematically showing a screen (second example) of the present invention.
FIG. 3 is a schematic explanatory diagram of optical characteristics of a light control layer.
FIG. 4 is a schematic explanatory diagram of reflection characteristics of a reflection surface.
FIG. 5 is a schematic explanatory view of a design procedure of a saw-toothed bent structure of a reflection surface.
FIG. 6 is a schematic explanatory view of the optical characteristics of the screen of the present invention.
FIG. 7 is a schematic explanatory diagram of a front projection display system using the screen of the present invention.
FIG. 8 is an explanatory diagram related to a preferred method of manufacturing a reflector.
FIG. 9 is a graph showing the relationship between the reflected light intensity (relative value) and the reflection angle measured for (a) projector light and (b) external light incident on the prototype screen.
[Explanation of symbols]
1 reflection layer 1A reflection surface (sawtooth reflection surface)
2 Smoothing layer 3 Light control layer 4 Antireflection layer 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 region (region corresponding to a certain angle range)
20 screen (screen of the present invention)
Reference Signs List 21 Projector 24 Observer 25 External light source 30 Reflector 40 Roll with sawtooth groove pattern 41 Plate-shaped transparent resin

Claims (2)

A reflection layer having a reflection surface bent in a saw-tooth shape; a transparent smoothing layer in close contact with the saw-tooth reflection surface of the reflection layer; And a light control layer that transmits light in a scattered or straight-forward manner. 2. The front projection display screen according to claim 1, further comprising an anti-reflection layer which is in close contact with the surface of the light control layer on the side opposite to the smoothing layer and suppresses reflection from the surface.

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