JP3877293B2 - Light guide sheet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light guide sheet, and particularly to a light guide sheet with a large amount of light to be guided.
[0002]
[Prior art]
Conventionally, as a system for taking sunlight into a room,
A. A light reflector is installed in a street like a catwalk, and sunlight is reflected by the light reflector and taken in (for example, JP-A-10-269811, JP-A-5-60964, JP-A-11-25726) ),
B. Taking sunlight directly from the skylight (for example, JP-A-11-218720),
C. Those using optical fibers (for example, JP-A-7-57525, JP-A-7-33004), etc.
Has been proposed.
[0003]
[Problems to be solved by the invention]
However, in the above A and B, it is difficult to guide sunlight to an arbitrary place and use it for illumination. In C, a large number of optical fibers are required, and it is difficult to install easily and inexpensively.
[0004]
Then, it is possible to guide sunlight to a predetermined position using a sheet-like plastic film as a light guide.
[0005]
However, as a plastic film, there is no practically high refractive index having a refractive index exceeding 1.6. Therefore, it is difficult to increase the amount of guided light. The amount of light guided depends on the NA of the light guide, and the NA of the light guide increases as the refractive index of the light guide increases.
[0006]
This invention is made | formed in view of such a problem of a prior art, The objective is to provide the light guide sheet which can take in much sunlight etc. and can guide | emit to arbitrary places.
[0007]
[Means for Solving the Problems]
The light guide sheet of the present invention that achieves the above object is a coating layer in which high refractive index fine particles are mixed in an organic resin on both sides of a transparent film to increase the refractive index, and has a higher refractive index than the transparent film. The light is guided without emitting light guided outside the light guide sheet.
[0008]
In the present invention, a coating layer in which high refractive index fine particles are mixed in an organic resin to increase the refractive index is formed on both surfaces of the transparent film, and a layer having a higher refractive index than the transparent film is formed. Since the total reflection of light is performed at the interface between the high refractive index coating layer and the air, light with a large numerical aperture is also totally reflected, so that a larger amount of light is guided than with a transparent film alone. Thus, the amount of light guided by sunlight or the like can be increased. Further, such a light guide sheet of the present invention has a great merit that it can be produced by a simple method in which fine particles are mixed in an organic resin and applied to the surface of a transparent film.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The basis of the present invention is that, as a light guide sheet, on both sides of a transparent film having an arbitrary refractive index, a high refractive index fine particle is mixed in an organic resin to provide a coating layer with an increased refractive index. The amount of light that can be guided by the light guide sheet is increased. Here, as the high refractive index fine particles mixed in the organic resin, ZnO (refractive index 1.90), TiO ₂ (refractive index 2.3 to 2.7), CeO ₂ (refractive index higher than that of plastics) are used. Refractive index 1.95), Sb ₂ O ₅ (refractive index 1.71), SnO ₂ , ITO (refractive index 1.95), Y ₂ O ₃ (refractive index 1.87), La ₂ O ₃ (refractive index) 1.95), ZrO ₂ (refractive index 2.05), Al ₂ O ₃ (refractive index 1.63) and other metal oxides, metal nitrides, metal carbides, etc. In order to avoid light scattering, a light having a wavelength equal to or smaller than the wavelength of the guided light is used.
[0010]
In FIG. 1, the top view (a) and sectional drawing (b) of the light guide sheet 1 of one Example of this invention are shown. This light guide sheet 1 is made of a transparent organic resin and is applied to a relatively low refractive index central sheet 10 and both sides thereof, and a high refractive index fine particle 12 is mixed in the transparent organic resin to increase the refractive index. The surface layer 11 having a high refractive index, and light such as sunlight incident on one end of the surface layer 11 is reflected in the light guide sheet 1 while being totally reflected at the interface between the high refractive index surface layer 11 and the air. The light is guided to the other end with multiple reflections. At this time, since the total reflection is performed at the interface between the surface layer 11 having a high refractive index and the air, light having a large numerical aperture is also totally reflected. The light is guided through the sheet 1.
[0011]
As a specific example, for example, a PET (polyethylene terephthalate) film having a refractive index n of n≈1.5 and a thickness of 200 μm is used for the center sheet 10, and TiO ₂ having a particle diameter of 0.1 μm is used as the surface layer 11 at 20 w%. In the PVA (polyvinyl alcohol), a light guide sheet 1 can be used which is formed by coating and curing to a thickness of 50 μm and comprising a layer having a refractive index n of n≈1.65.
[0012]
If no reflecting member is provided on both side surfaces of the light guide portion of the light guide sheet 1, there is a possibility that part of the guided light leaks from both side surfaces and escapes. It is desirable to form a layer, a low refractive index paint layer, or a metal reflective layer 14 by coating or the like.
[0013]
Here, the thickness of the center sheet 10 is preferably selected in the range of 10 to 20000 μm. If the thickness is less than this range, the strength is too low, and the light guiding efficiency is reduced. If it is too thick, it will be difficult to bend it flexibly during installation. In addition, the material cost is expensive. The thickness range is more preferably in the range of 100 to 10,000 μm, and most preferably in the range of 150 to 2000 μm.
[0014]
The thickness of the surface layer 11 is preferably in the range of 1 to 200 μm. If the thickness is less than this range, it is difficult to form the surface layer 11 mixed with the fine particles 12 by coating. If it is too thick, not only is it difficult to form a layer, but a problem of destruction such as cracking of the surface layer 11 when the light guide sheet 1 is bent tends to occur. The thickness range is more preferably in the range of 5 to 100 μm.
[0015]
Further, the particle diameter of the high refractive index fine particles 12 to be mixed in the surface layer 11 depends on the wavelength of the light to be guided, but is preferably selected in the range of 1 to 1000 nm, and more preferably in the range of 5 to 500 nm. Preferably, the range of 10 to 300 nm is most preferable.
[0016]
In the form of FIG. 1, total reflection occurs at the interface with air on the surface side of the high refractive index surface layer 11 of the light guide sheet 1, and guided light is guided through the surface layer 11. If a foreign substance adheres to or contacts the interface, the total reflection condition may be lost and light may leak to the outside. Therefore, as shown in the cross-sectional view of FIG. Alternatively, the low refractive index transparent layer 13 may be provided.
[0017]
FIG. 3 is a side view showing an example of the configuration when sunlight is used for indoor lighting using the light guide sheet 1 as described above. The light guide sheet 1 is configured to be long, and The same side surface of the predetermined length portions of both end portions 2 and 3 in the longitudinal direction is processed into a sandblasted surface (uneven surface, rough surface) 5 having a surface average roughness Ra, and the other surface is a smooth surface. Yes. Further, a portion 4 between both end portions 2 and 3 is a smooth surface on both sides. Here, the sandblasted surface (uneven surface, rough surface) 5 of both end portions 2 and 3 may be provided only on the surface layer 11, but the surface of the central sheet 10 is also uneven surface along the uneven surface of the surface layer 11. The surface layer 11 may be formed on the uneven surface of the center sheet 10. The uneven surface of the surface layer 11 or the center sheet 10 is created by bringing a mold into contact with a thermoplastic resin in thermal transfer or molding (injection molding, extrusion molding, etc.), or is applied to the surface by adding fine beads to a binder. It can be created by adopting various methods such as forming with a resist.
[0018]
In FIG. 3, the light guide sheet 1 has such a configuration, the one end portion 2 functions as a light introducing portion, the intermediate portion 4 functions as a light guiding portion, and the other end portion 3 functions as a light emitting portion. The light incident on the concave / convex surface 5 on one side is then scattered in the light guide sheet 1, and most of the scattered light is determined by the difference between the refractive index of air and the refractive index of the surface layer 11 on both sides of the light guide sheet 1. The light is incident at an angle equal to or greater than the angle, is totally reflected, is converted into light that is multiple-reflected in the light guide sheet 1 and is guided, and the light guide light passes through the light guide portion 4 to the light emitting portion 3 at the other end. The light incident on the concave / convex surface 5 on one side is mostly scattered outside the light guide sheet 1 and emitted, and can be used as illumination light or the like.
[0019]
In addition, the light incident on the end face of the light introducing part 2 and the end face of the light emitting part 3 goes out and is not used effectively. Therefore, at least these end faces are provided with a light reflecting layer 6 such as a light reflecting metal such as Ag, Al, Au, Pt, or Cu, white paint, etc., and the guided light incident on these end faces is reflected to the opposite side. It is desirable to be able to use it effectively.
[0020]
Here, as the surface average roughness Ra of the concavo-convex surface 2 formed on one surface of the light introducing portion 2 and the light emitting portion 3, it is selected to be in the range of 0.1 to 1000 μm for efficiently introducing light. More preferably, it is more preferably selected in the range of 1 to 100 μm, and most preferably in the range of 2 to 50 μm.
[0021]
As schematically shown in FIG. 4, such a light guide sheet 1 of the present invention is installed on the roof of the house H so that the uneven surface 5 of the light introduction portion 2 faces the sky, and the light introduction portion. Light from the sun S is introduced by installing the light emitting part 3 in the house H so that the uneven surface 5 of the light emitting part 3 faces downwards. The light is introduced into the light guide sheet 1 by the uneven surface 5 of the portion 2, the sunlight is guided to the light emitting portion 3 through the light guide portion 4, and is emitted from the uneven surface 5 of the light emitting portion 3 to the outside of the light guide sheet 1. It can be used for indoor lighting.
[0022]
As mentioned above, although the light guide sheet of this invention was demonstrated based on the Example, this invention is not limited to these Examples, A various deformation | transformation is possible. Also, the light guide sheet can be used not only for indoor introduction of sunlight but also for other purposes. For example, in the liquid crystal display device, the light guide sheet of the present invention can be used to guide external light as illumination light for the liquid crystal display device as an auxiliary to the backlight.
[0023]
The above light guide sheet of the present invention can be configured as follows, for example.
[0024]
[1] A coating layer in which high refractive index fine particles are mixed in an organic resin to increase the refractive index on both surfaces of the transparent film, and a layer having a higher refractive index than the transparent film is formed. Light guide sheet.
[0025]
[2] The light guide sheet according to claim 1, wherein the high refractive index fine particles have a particle size of 1000 nm or less, 1 nm or more, and a refractive index of 1.6 or more.
[0026]
[3] The light guide sheet according to claim 1 or 2, wherein a clad layer having a refractive index lower than that of the coating layer is formed on the surface of the coating layer.
[0027]
[4] The light guide sheet is provided with light introducing means and light emitting means, and light introduced from the light introducing means to the light guiding sheet is guided to the light emitting means, and light is emitted from the light emitting means. The light guide sheet according to any one of claims 1 to 3, wherein the light guide sheet is emitted.
[0028]
[5] The light guide sheet according to any one of claims 1 to 4, which is used for light guide of sunlight.
[0029]
【The invention's effect】
As is clear from the above description, in the light guide sheet of the present invention, on both sides of the transparent film, high refractive index fine particles are mixed in an organic resin to increase the refractive index. A layer with a high refractive index is formed, and total reflection of guided light is performed at the interface between the high refractive index coating layer and air, so light with a large numerical aperture is also totally reflected. A larger amount of light is guided, and the amount of guided light such as sunlight can be increased. Further, such a light guide sheet of the present invention has a great merit that it can be produced by a simple method in which fine particles are mixed in an organic resin and applied to the surface of a transparent film.
[Brief description of the drawings]
FIG. 1 is a plan view and a cross-sectional view of a light guide sheet according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a modification of the light guide sheet of the present invention.
FIG. 3 is a side view showing an example of the configuration when sunlight is used for indoor illumination using the light guide sheet of the present invention.
FIG. 4 is a diagram schematically showing an example in which sunlight is guided indoors using the light guide sheet of the present invention and used for illumination.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light guide sheet 2 ... Light introducing | transducing part 3 ... Light-emitting part 4 ... Light guide part 5 ... Sandblasting surface (uneven surface, rough surface)
6 ... light reflection layer 10 ... center sheet 11 ... surface layer 12 ... high refractive index fine particles 13 ... low refractive index transparent layer 14 ... reflection layer H ... house S ... sun

Claims (1)

Both surfaces of the transparent film, it is a layer having a higher refractive index than the transparent film a coating layer which increases the refractive index is mixed a high refractive index fine particles in an organic resin is formed and the light guide sheet outside guide A light guide sheet that guides light without emitting light.

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