JP2002091331A - Light reflection sheet and screen for projecting display image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light reflection sheet which is a new optical control material suitable for a large-sized display device or the like, and to provide a screen for projecting a display image using the same and a surface light source device. SOLUTION: A large number of basic units 12 consisting of concave reflection planes 13 are arranged on the surface of a substrate 11 at a pitch of 5000 μm or less. The main reflective direction of the concave reflection planes 13 of the basic units 12 is almost identical. The reflectance of the concave reflection plane 13 is 70% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light reflecting sheet and a screen for projecting a display image, and more particularly to a novel light controlling member, for example, a light reflecting sheet suitably used as a backlight of a transmission type liquid crystal display device. And an image projection screen such as a projector device formed with the light reflection sheet.

[0002]

2. Description of the Related Art Recently, new display devices such as liquid crystal display devices and projector devices have been developed and put to practical use, and it has been already well known that the area of these display devices has been increasing. Are known.

[0003]

However, these conventional large-area display devices have a problem that the structure is still complicated. The reason is that there is no appropriate light control member applicable especially to a large-area display device or the like, so that the structure has to be complicated, and as a result, the cost becomes high and the spread of this type of display device is hindered. It has become.

As an example, a description will be given of a projection type projector device using a liquid crystal display device or the like as an optical engine. This type of projector device does not have an appropriate image projection screen, and therefore has very poor visibility in a bright room environment. And the contrast is lowered.

As another example, a surface light source device (backlight)
In a transmissive liquid crystal display device that uses a liquid crystal display, the illumination optical system of the backlight is complicated, and optical sheets such as a prism sheet must be used extensively. Therefore, the assemblability is poor and the yield is low. I was invited.

An object of the present invention is to solve such a conventional problem, and is a novel light control member suitably used for a large-area display device and the like, and is particularly suitable for a surface light source device and the like. An object of the present invention is to provide a light reflection sheet that can be used and a display image projection screen formed by the light reflection sheet.

[0007]

SUMMARY OF THE INVENTION The present invention is a light reflecting sheet, and is constituted as follows in order to solve the above-mentioned technical problem. That is, in the light reflecting sheet of the present invention, a large number of basic units each having a concave reflecting surface have a pitch of 5
000 μm or less and arranged on the surface, and the main reflection direction of the concave reflection surfaces of many basic units is set to be substantially constant, and the reflectance of the concave reflection surfaces is set to 70% or more. Features.

<Specific Configuration in the Present Invention> The light reflecting sheet of the present invention is composed of the above-mentioned essential components, but is established even when the components are specifically as follows. The specific constituent elements are characterized in that the basic units have a sawtooth cross section, and the ridge lines of the concave reflecting surfaces in a number of basic units arranged on the surface are arranged in parallel.

Further, in the light reflecting sheet of the present invention, a concave mirror having a maximum diameter of 5000.0 μm or less is used as a concave reflecting surface constituting the basic unit, and a large number of concave mirrors can be arranged. Further, it is preferable that the concave reflecting surface has a polygonal cross section. Further, the main reflection direction of the concave reflecting surface constituting the basic unit and the normal direction of the light reflecting sheet are one.
Preferably, the angle is 5 degrees or more.

In the light reflecting sheet of the present invention, the concave reflecting surface can be formed by a silver or aluminum coating layer. It is also preferable that the concave reflecting surface is formed of a diffusely reflective white material. Further, it is preferable to provide a coat layer made of a transparent material on the concave reflecting surface. At this time, the coat layer made of a transparent material can be an optical thin film.

Further, in the light reflecting sheet of the present invention, the concave reflecting surface can be subjected to a matting treatment, and a coating layer made of a transparent bead coating layer is provided as a treatment for obtaining an effect substantially equivalent to the matting treatment. Can also. The present invention is a screen for projecting a display image that solves the conventional technical problem by being formed of a light reflecting sheet having the above-described features.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a light reflection sheet and a display image projection screen according to the present invention. FIG. 1 shows a main part of a light reflection sheet 10 according to one embodiment of the present invention, and FIG. 2 shows a main part of a light reflection sheet 20 according to another embodiment of the present invention as a representative example of the present invention. ing.

The light reflecting sheets 10 and 20 according to the two embodiments of the present invention shown in FIGS. 1 and 2 are constituted by arranging (forming) a large number of basic units 12 on the surface of a base material 11. The many basic units 12 include those having substantially the same shape and / or substantially similar shapes, and have a function as a so-called concave mirror, that is, a function of condensing light.

When the light reflecting sheets 10 and 20 are used for a display device or the like, the basic unit 12 itself has a pitch P of at least 5000 μm, preferably at most 1000 μm, in order to make the basic unit 12 itself difficult to visually recognize. Preferably, it is formed with a thickness of 500 μm or less.

Here, the basic unit 12 is shown in FIGS.
As shown in the above, the basic shape unit of the light reflecting sheet obtained as an aggregate of the concave reflecting surfaces 13 having substantially the same shape and / or substantially similar shape. In other words, it is the smallest shape unit, that is, the so-called unit cell, in which the identity or similarity is lost when divided further. The pitch P is
As shown in FIG. 3 to FIG.
Is defined as the minimum length of the basic period created by the array of.

In the light reflecting sheets 10 and 20 in the two embodiments described as representative examples, the basic unit 1
2 main reflection direction (basic unit 1)
The basic units 12 are arranged such that the direction in which the light beam perpendicularly incident on 2 is mainly reflected) is directed in a substantially constant direction, so that the incident light is given a strong light intensity in a specific direction. It is possible to collect light. Even if the concave reflecting surface 13 of the basic unit 12 has substantially the same shape and / or substantially similar shape, it is not an object of the present invention if the main reflection direction is randomly oriented.

The light reflecting sheets 10, 2 of the above-described embodiment
0 is a so-called “sheet” having a thickness of 10 having flexibility.
It is preferable that the substrate 11 be made of about 00 μm or less. However, the thickness of the substrate 11 is appropriately selected depending on the application object, and is not necessarily limited to this.

For example, when there is no need to bend and store such as a projection screen in a movie theater or an aircraft,
The substrate 11 may be a thicker plate. In short, it is important that the basic unit 12 composed of the minute concave reflecting surface 13 and having substantially the same shape and / or similar shape is formed on the surface, and the concave reflecting surface has a high reflectance. It is important that the surface has

Here, in the present invention, the reflectance of 70% or more means that the reflectance is achieved in the visible light spectrum region since it is used for display purposes for human visual observation. . That is, J
As defined in IS-Z8120, the ratio of the reflected luminous flux energy to the incident luminous flux energy in the visible light spectrum region has the above value, and is preferably 7
It is 5% or more, more preferably 85% or more, particularly preferably 88% or more, and very preferably 91% or more.

In the present invention, a change in color tone in the light reflection sheet portion should be avoided, and it is preferable that the light reflection sheet portion has a reflection characteristic as flat as possible in the visible light spectrum range. Therefore, the value of the spectral reflectance at 550 nm, which is located substantially at the center of the visible spectrum, is used as the reflectance, and a preferable value range can be defined.

In addition, the above-mentioned reflectance means the reflectance of the material located on the surface of the inclined surface that substantially causes reflection, and specifically, the surface of the inclined surface is typified by silver or aluminum. As described above, it is preferable to provide a material having a high reflectance and a small change in color tone. In some cases, the protective layer 16 or the like is provided on the reflective surface. The reflectance referred to here is the reflectivity of the surface of the material itself, which does not have the protective layer 16 and the like and substantially contributes to reflection such as a metal material. It means.

Regarding the directivity of the reflection, the specular reflection and the diffuse reflection depend on the optical characteristics of the required illumination light.
It is appropriately selected, but in general, a mirror reflection layer made of silver, aluminum, or the like is preferably used for obtaining high directivity, and a white pigment is used for obtaining a wide emission angle distribution. A diffuse reflection layer made of a kneaded resin or a foamable resin is preferably used.

A light reflecting sheet suitable as an embodiment of the present invention has a structure in which the basic unit 12 has a sawtooth cross section and the basic unit 12 has periodicity only in one axial direction. That is, as shown in FIGS. 1, 3 (a) and 3 (b) and FIGS. 6 (a) and 6 (b), the ridge lines 14 of the multiple basic units 12 are formed so as to be arranged in parallel. In particular, it is most preferable that the ridge line 14 is a straight line as shown in FIG.

The reason for this is that in a mode in which the straight ridge lines 14 are arranged in parallel, it is easy to apply a cutting process using a diamond bite or an end mill, so that it is very easy to manufacture a mold for shaping. This is because miniaturization is easy and mass productivity is high.

The arrangement of the ridge lines 14 of the many basic units 12 in a parallel state does not mean that the ridge lines 14 of the many basic units 12 are maintained in a completely parallel state, but is substantially parallel. It means that they are arranged. That is, as shown in FIG. 17, it is possible to implement a mode in which adjacent ridge lines are arranged while slightly rattling, and in such a mode, optical interference with the gate array of the liquid crystal panel is prevented. Thus, it is possible to obtain favorable illumination light characteristics as a backlight device.

A light reflecting sheet suitable as another embodiment of the present invention is shown in FIGS. 2, 4 (a), (b), and FIG.
As shown in (a) and (b), this is a case where a concave mirror is used as the concave reflecting surface 13 and a structure in which many concave mirrors are arranged is used. In the mode in which a large number of concave mirrors are arranged, each concave mirror is miniaturized to the extent that it is difficult to view,
The maximum diameter is 5000 μm or less, preferably 1000 μm or less, more preferably 500 μm or less. In such an embodiment, light can be converged not only in one direction but also in two orthogonal directions, so that light controllability can be further improved.

More preferably, the concave reflecting surface 13 has a polygonal cross section. This is because when a mold for transferring the shape of the concave reflecting surface 13 is manufactured, cutting using a diamond tool or the like is generally used. This is because of the shape.

For this reason, the concave reflecting surface 13 which is easiest to manufacture a mold has a polygonal cross section shown in FIG.
The reason for this is that, in the concave reflecting surface 13 having a polygonal cross section shown in FIG. 7, the cross-sectional contour line forming the concave reflecting surface is not a curved line, but two flat inclined surfaces 13a divided by straight lines. This is because a concave reflecting surface is formed by making 13b continuous.

The light reflecting sheet of the present invention preferably has a function of changing the direction of a light beam incident on the reflecting sheet. In other words, the light rays that are vertically incident on the light reflecting sheets 10 and 20 are not reflected vertically but are converted and reflected in a direction in which the main reflection direction with respect to the normal direction of the light reflecting sheets is 15 degrees or more.

By having such a function, for example, when used as a screen of a projection type projector device, a projection image from a projector device 31 installed on a ceiling 30 as shown in FIG. Since the light is reflected in the direction of the observer, a reflected image with little reflection of external light and a high contrast display image can be obtained. In FIG. 8, a reflection direction line 32 indicated by a dotted line indicates a main direction of light reflected by an ordinary screen.

The light reflecting sheet of the present invention can be used, for example, as a backlight (surface light source device) of a transmission type liquid crystal display device. An example of this surface light source device is indicated by reference numeral 33 in FIG. This surface light source device 3
The light guide 3 has a light guide 34 having one surface as a light exit surface 34a, and a light source 35 is disposed on at least one side end 34b of the light guide 34. The light source 35 is
5 is covered with the reflector 36 so that the light beam emitted from the light source 5 enters the light guide 34 from one end 34b.

The light reflecting sheet of the present invention is disposed near a surface 34c of the light guide 34 opposite to the light exit surface 34a. The light guide 34 in the surface light source device 33 extracts light in which at least 65% or more of all outgoing rays emitted from the light guide 34 exit to the light reflection sheet side (the outgoing rays are indicated by reference numeral 37). A mechanism is provided. This light extraction mechanism will be described later.

As described above, by adopting a structure in which most of all the outgoing light rays emitted from the light guide 34 are emitted to the light reflecting sheet side, the light reflecting sheet of the present invention can simultaneously achieve the light collection and the direction change. Accordingly, the same performance can be obtained without using a member such as a prism sheet used in a conventional surface light source device.

The reflecting material of the concave reflecting surface 13 in the light reflecting sheet of the present invention is not particularly limited, but as shown clearly in FIGS. 1 and 2, the surface is coated with silver or aluminum to reflect the light. It is most preferable to form the surface, that is, the reflective layer 15 from the viewpoint of ease of production.
In particular, a method of forming a thin silver reflective layer by using a dry process such as vacuum deposition, sputtering, or ion plating and coating the surface of the substrate 11 is most preferable.

Further, the matte treatment may be performed by, for example, sandblasting the surface of the sheet as the base material 11 on which the concave reflecting surface array is formed before performing the vacuum deposition with silver. By applying such a matting process, the regular reflection surface can be given an appropriate light diffusing property, and when used as an image projection screen, the glare of the projected image can be suppressed. And when used as a light-reflecting sheet for the backlight of a transmissive liquid crystal display device, it is possible to prevent the occurrence of moiré patterns due to interference between the concave reflecting surface array and the gate array of the liquid crystal cell. It becomes.

Also, since the glossy metal surface such as the silver reflection layer is very easily damaged and easily oxidized and deteriorated, an ultraviolet curable acrylic resin paint is applied as a protective layer 16 on the surface. It is preferable to prevent the deterioration of the optical characteristics due to scratches or the like. Further, by providing a coating layer of light-transmitting beads typified by acrylic beads or the like as the protective layer 16, the same effect as that obtained by matting the concave reflection surface array portion described above can be obtained. Become.

In addition, the transparent coat layer, ie, the protective layer 16
Can be provided with a function as an optical thin film, and the controllability of incident light can be further enhanced. For example, an anti-reflection film,
The reflection increasing film and the like can be realized by a combination of conventionally known simple optical thin films, and further, by stacking thin film layers, a function of controlling a polarization state of an incident light beam such as a beam splitter function and a polarization conversion function. The obtained light reflecting sheet can also be obtained.

The reflection layer 15 is not limited to a reflection layer made of a metal material having regular reflection properties. For example, a reflection layer made of a polyester resin kneaded with a white pigment such as titania is used. You can also. In this case, the incident light is scattered in various directions by the diffuse reflection surface, so that the directivity of the reflected light can be expanded. For example, when the light is used for a screen, glare occurs in a wider angle range. It is possible to provide a screen that allows the user to visually recognize an image.

Further, when the light-reflecting sheet is used for a backlight of a transmissive liquid crystal display device, the viewing angle characteristics of the illuminating light can be expanded more than when a regular reflection layer is used. As a method for forming the diffuse reflection layer, in addition to the above, a mode in which a diffuse reflection layer is obtained from an expandable polyester resin, an expandable polyolefin resin, an expandable ABS resin, or the like; Examples include a mode of coating a paint made of a white pigment.

By using the light reflecting sheet of the present invention for an image projection screen such as the projector device 31 as shown in FIG. 8, only the light components contributing to the display from the projector device are projected toward the observer, and Since external light from the screen is not reflected on the screen, it is possible to obtain an image with extremely high contrast without having to darken the room and project an image as in the conventional case, and obtain a screen with more practicality. Will be able to do it.

In particular, it is extremely suitable for use in exhibitions in showrooms, projection in aircraft, and the like, and can provide clear display images even in an environment with bright surroundings. In addition, by using the light reflecting sheet of the present invention in the illumination optical system of the transmission type liquid crystal display device, it is possible to obtain a surface light source of superior quality with a simpler configuration.

Further, by using the light reflecting sheet of the present invention, for example, as shown in FIG. 9, the light from the light source 35 disposed at least at one end 34b of the light guide 34 is transmitted to the light guide. 34, and a surface light source can be obtained on the light guide 34. In this case, at least 65% or more, preferably 70% or more of the total emitted light emitted from the light guide 34.
% Or more, more preferably 75% or more, by providing a light extraction mechanism that emits light to the side of the light reflection sheet, so that the light reflection sheet of the present invention collects outgoing light rays and at the same time, the normal line 38 of the light guide. Since the angle is changed in the direction, the surface light source can be obtained very easily.

In this case, the pitch of the basic unit 12 composed of the concave reflecting surface 13 is set to 1000.0 μm or less in order to prevent the pattern from being seen on the display image surface, and as shown in FIG. The concave reflecting surface 13 is formed so that the light ray 37a perpendicularly incident on the light reflecting sheet 10 is changed in angle of at least 5 degrees to become a reflected light ray 37b, preferably 10 degrees or more, and more preferably 15 degrees or more.
It is preferable to determine the shape of the basic unit 12 composed of:

Here, various modes are conceivable as a light extraction mechanism provided in the light guide 34 so as to emit at least 65% or more of all outgoing light rays emitted from the light guide 34 to the light reflecting sheet side. There is no particular limitation. However, the most preferable mode for this light extraction mechanism is shown in FIG.
1 (a), the light exit surface 34a of the light guide 34
The projection 39 is formed on the surface 34c on the opposite side (the surface on the light reflection sheet side).

At this time, as shown in FIG. 11B, the height is defined by the height of the protrusion 39, in other words, the depth h of the protrusion 39 and the minimum opening width w when viewed from inside the light guide 34. Value h
/ W is 0.5 or more, preferably 0.6 or more, and more preferably 0.7 or more. By doing so, FIG.
As shown in FIG. 1 (b), the light ray 40 incident on the projection 39
Is mostly directed toward the light reflecting sheet. Here, the minimum opening width w of the projection 39 means the minimum width of the opening shape when the projection 39 is viewed from above as shown in FIG.

In addition to the above, as shown in cross sections in FIGS.
This makes it possible to design the light extraction mechanism so that most outgoing light rays emitted from the light guide 34 are directed toward the light reflecting sheet. That is, in the mode shown in FIG. 13A, the projection 4 having a triangular cross section is formed on the surface of the light guide 34 opposite to the light exit surface 34a, that is, the surface 34c on the light reflecting sheet side.
1 to form a light extraction mechanism.

The mode shown in FIG.
No. 4, a concave surface is formed on the surface opposite to the light emitting surface 34a, that is, the surface 34c on the light reflecting sheet side, thereby forming a light extraction mechanism. In the mode shown in FIG. 13C, a concave portion 42 having a triangular cross section is formed on the light emitting surface 34a of the light guide 34, thereby forming a light extraction mechanism.

Further, in the mode shown in FIG. 13D, a concave portion 43 having a triangular cross section is formed on the surface of the light guide 34 opposite to the light exit surface 34a, that is, the surface 34c on the light reflecting sheet side. A relatively protruding portion is formed, thereby forming a light extraction mechanism. Further, in the mode shown in FIG. 13E, a light extraction mechanism is formed by forming a projection 44 having a mountain-shaped cross section on the light emitting surface 34a of the light guide 34.

Here, in the light guide used in the present invention, the ratio of the light flux emitted to the light reflecting sheet side to the total light flux emitted from the light guide is 65% or more, according to the optical design according to the present invention. As described above, it is necessary to make the above-mentioned effect work effectively. The measuring means for measuring the selectivity in the direction in which the light beam is emitted is as follows.

That is, first, the black sheet 61 that absorbs light almost completely is provided at the position where the normal light reflection sheet is provided.
(Flocked paper or the like) is disposed, and as shown in FIG. 18, the light guide 34 is set in a normal direction and turned on in the integrating sphere 62, and the light exit surface of the light guide 34 obtained at this time is provided. The total luminous flux emitted from the side is defined as Σa.

Next, the direction of the light guide 34 is set upside down as usual (originally, the surface facing the light reflecting sheet is set to the light emitting surface side), and the integrating sphere 62 is similarly set. And the total amount of luminous flux emitted from the surface opposite to the light exit surface of the light guide 34 obtained at this time is represented by Δb. At this time, the obtained numerical value, Σb / (Σa + Σb) × 100, is the ratio (%) of the luminous flux selectively emitted to the light reflecting sheet side.
This value is 65% or more, preferably 70%.
%, More preferably 75% or more.

Further, as shown in FIGS. 14 and 15, on the surface of the light guide on the side where the light extraction mechanism for emitting most of all the outgoing light rays to the light reflection sheet side is not provided, Pitch 200 μm or less, preferably 150 μm
Hereinafter, more preferably, a mountain-shaped or corrugated uneven portion 45 of 100 μm or less is provided with
By providing the ridge line so as to be substantially perpendicular to 4b, the light condensing property of the surface light source device can be further enhanced.

When the light reflecting sheet of the present invention is used for a backlight of a transmission type liquid crystal display device, the present invention is not limited to a backlight using a light guide, but is shown in FIG. Thus, it can be used for a so-called hollow surface light source device 50 that does not use a light guide. In the hollow surface light source device 50 shown in FIG. 16, reference numeral 51 denotes a light reflecting surface, and reference numeral 52 denotes an opening.

In a preferred embodiment of the present invention, the light reflecting sheet is formed of a resin material. Especially polyester resin, acrylic resin, polycarbonate resin,
Alternatively, a cyclic polyolefin-based resin is suitably used, and shaping by hot press molding or shaping with a photocurable resin is suitably used for forming a large number of basic units each having a concave reflecting surface.

[0055]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. Example 1 A display image projection screen having the structure shown in FIG. 1 was manufactured. The pitch was 3000.0 μm, and a screen having a concave reflecting surface array as shown in FIG. 1 was prepared. A 1.5 mm-thick polycarbonate resin plate was used as a substrate, a concave reflection surface array was formed by hot press molding, and aluminum was vapor-deposited on the surface to form a reflection surface.

Light rays 37 perpendicularly incident on the concave reflecting surface array
a, the surface shape is designed so as to be deflected by about 15 degrees as shown in FIG. 10, and the ceiling 30 as shown in FIG.
The projection light from the projector device 31 disposed at the position is selectively directed to the observer side. Since only the projection light from the projector device is directed toward the observer, the displayed image can be clearly recognized without darkening the room with a dark curtain or the like, and an extremely high contrast is obtained.

Example 2 A display image projection screen having the structure shown in FIG. 2 was manufactured. The concave mirror array having a diameter of 2000.0 μm is arranged.
Using a 5 mm polycarbonate resin plate, a concave reflecting surface array was formed by hot press molding, and aluminum was vapor-deposited on the surface to form a reflecting surface. The reflective surface is coated with an acrylic resin to prevent damage and oxidative deterioration of the reflective layer.

Light ray 37 perpendicularly incident on the concave reflecting surface array
a is designed such that the surface shape is changed by about 20 degrees as shown in FIG. 10, and the ceiling 30 is formed as shown in FIG.
The projection light from the projector device 31 disposed at the position is selectively directed to the observer side. Projector device 31
Since only the projection light from the camera heads toward the observer, the displayed image can be recognized very clearly without darkening the room with a dark curtain or the like, and an extremely high contrast is obtained.

(Embodiment 3) 350.0 as the light guide 34
When a linear light source 35 composed of a cold cathode tube is disposed on two long sides using acrylic resin having a size of 285.0 mm and a thickness of 5 mm, the linear light source 35 is separated from the linear light source 35 as shown in FIG. The convex projections 39 serving as a light extraction mechanism were formed on the light guide by patterning so that the arrangement density became denser in accordance with (1). As shown in an enlarged scale in FIG. 12, the projection amount h is 30.0 μm, and the minimum opening width w of the projection 39 is 25.0 μm.

The projections 39 are provided on the surface 34c on the side where the light reflecting sheet is disposed, and 87% of the light emitted from the light guide is 87% of the light emitted from the light guide due to the effect of using these projections 39 as a light extraction mechanism. Out. As the light reflecting sheet, a light reflecting sheet 10 having a sectional shape shown in FIG.
Was used. The pitch is 120 μm, and the reflection layer 15
Uses a silver vapor deposition layer, and the surface of the silver vapor deposition layer is coated with an acrylic resin.

Due to the effect of the concave reflecting surface array according to the present invention, most of the light emitted from the light guide is deflected in the direction of the observer and condensed at the same time. A surface light source device suitable for use as a backlight of a transmissive liquid crystal display device having high luminance can be obtained.

(Example 4) In the surface light source device described in Example 3, as the light reflecting sheet, a light reflecting sheet having a silver vapor deposition layer in which minute concave mirrors as shown in FIG. A surface light source device was prepared in the same manner as in Example 3 except that the above was used. Since the light was condensed in two directions by the effect of the concave mirror array, the front luminance was increased by 17% as compared with the third embodiment.

(Embodiment 5) In the surface light source device described in Embodiment 3, a triangular prism array having a top angle of 90 ° and a pitch of 50 μm is provided on the light emitting surface 34a side of the light guide as shown in FIG. A surface light source device was prepared in the same manner as in Example 3 except that the surface light source device was provided. A high light-collecting effect was obtained by the effect of the triangular prism array on the light guide, and the front luminance was increased by 24% as compared with Example 3.

[0064]

As described above, according to the light reflecting sheet of the present invention, a large number of basic units each having a concave reflecting surface are arranged at a minute pitch on the surface of the substrate, and the concave reflecting surface of each basic unit is arranged. By making the main reflection direction of the light to be almost constant and making the reflectance highly efficient, the incident light can be deflected to a specific direction and focused so as to give a strong light intensity at the same time It is possible to provide an inexpensive light control member having a simple structure and a simple structure.

Further, according to the display image projection screen of the present invention using the above-described light reflection sheet, for example, only the light component contributing to the display from the projector device is projected in the direction of the observer, and for example, the light component outside the window is projected. Since light or the like is not reflected, it is possible to obtain an image with extremely high contrast without having to darken the room and project an image as in the related art.

Further, according to the surface light source device of the present invention using the above-described light reflecting sheet, by using this surface light source device as, for example, an illumination optical system of a transmission type liquid crystal display device, the quality can be improved with a simpler configuration. An excellent surface light source can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial perspective view showing a main part of a light reflection sheet according to an embodiment of the present invention.

FIG. 2 is a partial perspective view showing a main part of a light reflection sheet according to another embodiment of the present invention.

FIG. 3 is a partial plan view and a sectional view showing another shape of the basic unit constituting the light reflecting sheet of the present invention.

FIG. 4 is a partial plan view and a sectional view showing still another shape of the basic unit constituting the light reflecting sheet of the present invention.

FIG. 5 is a partial plan view and a sectional view showing another shape of the basic unit constituting the light reflecting sheet of the present invention.

FIG. 6 is a partial plan view and a sectional view showing still another shape of the basic unit constituting the light reflecting sheet of the present invention.

FIG. 7 is a partial cross-sectional view showing a shape easily manufactured in a basic unit constituting the light reflection sheet of the present invention.

FIG. 8 is a configuration explanatory view schematically showing an example in which the light reflection sheet of the present invention is used as a display image projection screen for a projection type projector device.

FIG. 9 is a configuration explanatory view schematically showing an example in which the light reflecting sheet of the present invention is used for a surface light source device of a transmission type liquid crystal display device.

FIG. 10 is a structural explanatory view schematically showing a state in which a light beam perpendicularly incident on the light reflecting sheet of the present invention is changed in direction and reflected by its effect.

11 is a side view schematically showing an example of a light extraction mechanism formed on a light guide in the surface light source device shown in FIG. 9, and a cross-sectional view showing a part of the mechanism in an enlarged manner.

FIG. 12 is a partial perspective view illustrating definitions of a minimum opening width and a depth of a projection which is the light extraction mechanism shown in FIG.

13 is a partial cross-sectional view schematically showing various aspects of a light extraction mechanism that causes most of all outgoing light rays emitted from the light guide to go to the light reflecting sheet side in the surface light source device shown in FIG. FIG.

FIG. 14 is a perspective view schematically showing a main part of a surface light source device in which an uneven portion is formed on a surface of the light guide where no light extraction mechanism is provided.

FIG. 15 is a perspective view schematically showing a main part of a surface light source device in which an uneven portion is formed on a surface of the light guide where no light extraction mechanism is provided.

FIG. 16 is a structural explanatory view schematically showing a hollow surface light source device using the light reflecting sheet of the present invention.

FIG. 17 is a partial perspective view of another example of the reflection sheet of the present invention.

FIG. 18 is an explanatory view showing a method for measuring the direction selectivity of a light beam of the light guide according to the present invention.

[Explanation of symbols]

Reference Signs List 10 light reflection sheet of one embodiment 11 base material 12 basic unit 13 concave reflection surface 13a inclined surface 13b inclined surface 14 ridgeline 15 reflection layer 16 protective layer 20 light reflection sheet of another embodiment 30 ceiling 31 projector device 32 ordinary Main direction of light reflected by the screen 33 Surface light source device 34 Light guide 34a One surface (light emission surface) 34b Side end 34c Surface opposite to light emission surface (surface on light reflection sheet side) 35 Light source 36 Reflector 37 Light rays emitted from the surface opposite to the light emission surface 37a Light rays perpendicularly incident on the light reflection sheet 37b Light rays deflected by the light reflection sheet and reflected 38 Normal line of the light guide 39 Convex as light extraction mechanism Projection 40 Light beam incident on projection 41 Convex projection of another shape as light extraction mechanism 42 Light extraction mechanism on light emission surface Triangular cross-section recess formed as a result 43 Triangular cross-section recess formed as a light extraction mechanism on the side of the light reflecting sheet 44 Projection with a cross-section formed as a light extraction mechanism on the light emitting surface 45 Mountain-shaped or corrugated Concavo-convex portion 50 Hollow surface light source device 51 Light reflecting surface 52 Opening

Continued on front page F-term (reference) 2H042 DA02 DA04 DA11 DA17 DD08 DE04 2H091 FA14Z FA16X FA41Z FB08 FD04 FD07 FD13 FD23 LA03 LA11 LA18 5G435 AA00 AA02 FF03 GG46 LL15

Claims (12)

[Claims] 1. A large number of basic units each having a concave reflection surface are arranged on a surface at a pitch of 5000 μm or less, and the main reflection direction of the large number of basic units by the concave reflection surface is substantially constant. And a reflectance of the concave reflecting surface is 70% or more. 2. The basic unit has a saw-tooth cross section,
2. The light reflection sheet according to claim 1, wherein ridge lines of the concave reflection surfaces in the plurality of basic units arranged on the surface are arranged in parallel. 3. 3. The basic unit has a maximum diameter of 5000.0.
The light reflecting sheet according to claim 1, wherein the light reflecting sheet is formed by a concave mirror of μm or less, and is formed by arranging a large number of the concave mirrors. 4. The light reflecting sheet according to claim 1, wherein the concave reflecting surface has a polygonal cross section. 5. The method according to claim 1, wherein the main reflection direction of the concave reflection surface constituting the basic unit and the normal direction of the light reflection sheet form an angle of 15 degrees or more. The light reflecting sheet according to any one of the above. 6. The method according to claim 1, wherein the concave reflecting surface is made of a silver or aluminum coating layer.
The light reflecting sheet according to any one of the above. 7. The light reflection sheet according to claim 1, wherein the concave reflection surface is made of a diffusely reflective white material. 8. A coating layer made of a transparent material is provided on the concave reflecting surface.
The light reflecting sheet according to any one of the above. 9. The light reflecting sheet according to claim 8, wherein the coating layer made of the transparent material is an optical thin film. 10. The light reflecting sheet according to claim 6, wherein a matting process is performed on the concave reflecting surface. 11. The concave reflection surface is provided with a transparent bead coating layer.
10. The light reflecting sheet according to any one of 9 above. 12. A display image projecting screen comprising the light reflecting sheet according to any one of claims 1 to 11.