JP4575504B2 - Light guide plate - Google Patents

Description

  The present invention relates to a light guide plate that can be suitably used as a lighting material or a face material for a window portion or a fence portion.

  In order to brighten the room using daylight, the opening area of the window is increased. However, if the opening area is increased, the seismic strength of the building is reduced and the cost is increased. Therefore, the opening area cannot be increased in the dark clouds. In addition, if the opening area is increased, there is a risk that the temperature in the room in summer will increase and the heat insulation effect in winter will be reduced, and the possibility of peeping into the room from outside will increase.

Blinds and curtains are installed in the windows to suppress the rise in indoor temperature in summer and the decrease in the thermal insulation effect in winter, and to prevent situations where people can look into the room from outside. Therefore, there is a problem that incident light such as sunlight is blocked and the room becomes dark.
In addition, frosted glass is used for the window plate to make the surface a light diffusing surface, but in the case of frosted glass, light can only be diffused by the sun and light cannot be guided to the back of the room. .

  Therefore, for example, in Patent Document 1, by covering a window plate with a prism sheet subjected to minute prism processing, sunlight can be guided in a preferable direction, particularly in the interior of the room, and further, peep prevention is possible. Proposals have been made to add performance.

JP-A-11-280350

However, in the proposal of Patent Document 1, it is possible to prevent peeping from the horizontal front, but it is possible to peep inside the room only by changing the angle of view in the height direction, for example, 2 ° or more. Therefore, it is not suitable from the viewpoint of peep prevention.
On the other hand, if the angle intersecting the window plate is too small, incident light in the winter when the solar altitude is low will be blocked, resulting in conflicting problems.

  Therefore, the present invention is a new light guide that can guide incident light in the winter season into the room, and can prevent the person from looking into the room even if the line of sight is slightly changed from the horizontal front. It is intended to provide a light plate.

  In view of such a problem, the present invention is a light guide plate that is installed in the vicinity of an opening of a building so that the plate surface is vertical, and guides sunlight toward the interior side. Proposed is a light guide plate having a prism surface having a configuration in which unit prisms having a shape are continuously arranged in the width direction, and the apex angle of the unit prism constituting the prism surface is greater than 60 ° and less than 100 °. Is.

With a light guide plate having such a configuration, incident light from a low angle can be guided almost horizontally into the room. For example, if the light guide plate of the present invention is installed vertically along a window, particularly in wintertime. The incident angle into the room can be made closer to the horizontal and led to the interior of the room. Therefore, the illuminance of the entire room can be increased by taking in light. Moreover, when the room is viewed from the outside through the light guide plate, the room cannot be seen even if the angle of the line of sight is changed up and down. Moreover, by causing total reflection from the front, it is possible to reflect, for example, a nighttime headlight of a car incident on the window, and there is no unpleasant feeling.
As described above, the light guide plate of the present invention is particularly suitable as a lighting surface material installed almost vertically on a building, but it can also be used as a window material, a fence surface material, a balcony surface material, and other lighting materials. It can be suitably used.

It is the longitudinal cross-sectional view which showed an example of the light-guide plate of this invention. It is the expanded sectional view which showed an example of the unit prism in the light-guide plate of this invention. It is the fragmentary sectional perspective view which showed an example of the light-guide plate of this invention. It is sectional drawing for demonstrating the example of installation of the light-guide plate which concerns on an example of this invention, and the example of a function in that case. In an Example, it is explanatory drawing of the method which measured the transmission angle and the peep prevention angle using the automatic variable angle meter. When the sample sheet of Example 1 is installed, it is explanatory drawing which showed clearly the angle and light guide distance of the transmitted light when the sunlight (incident angle 78 degrees) of summertime injects. When the sample sheet of Example 2 is installed, it is explanatory drawing which showed clearly the angle and light guide distance of the transmitted light at the time of winter sunlight (incidence angle of 31 degrees) injecting.

  Next, this invention is demonstrated based on embodiment. However, the embodiment described below is an example of the embodiment of the present invention, and the scope of the present invention is not limited to the following embodiment.

<Configuration of the light guide plate>
As shown in FIGS. 1 to 4, the light guide plate 1 (referred to as “the present light guide plate”) 1 of the present embodiment includes a prism surface 3 on one side, for example, the indoor side, of the transparent resin plate 2. It is a plate or sheet provided with the light absorbing layer 4 on at least one side, for example, the outdoor side. However, the light absorption layer 4 is not necessarily provided.

(Transparent resin plate 2)
There are no particular restrictions on the material of the transparent resin plate 2. A transparent resin generally used as an exterior building material can be used. For example, transparent resin materials such as polycarbonate resin, polyester resin, methacrylic resin, styrene resin, polyvinyl chloride resin, polyolefin resin, and polyamide resin can be used. One or two or more of these may be mixed. Among these resins, polycarbonate resins are preferable in terms of transparency, heat resistance, impact resistance, and the like.

The polycarbonate-based resin is a linear polymer containing a carbonate ester bond in the main chain. For example, various dihydroxy diaryl compounds and phosgene are reacted by a phosgene method, or a dihydroxy diaryl compound and a carbonate ester such as diphenyl carbonate Is a polymer that can be obtained by reacting with a transesterification method. Specific examples include polycarbonate resins produced from 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), but are not limited thereto.
The molecular weight of the polycarbonate resin is not particularly limited. Those having a viscosity average molecular weight of about 15,000 to 30,000 that can be formed into a sheet by ordinary extrusion are preferred.

  Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyacrylate, polyether ether ketone, and the like.

  Examples of the methacrylic resin include polymers composed of various esters of methacrylic acid or copolymers with other monomers. For example, homopolymers of various methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, and copolymers of these methacrylates with various acrylic esters, acrylic acid, styrene, α-methylstyrene, etc. Etc.

  Examples of the styrene resin include a polymer made of a styrene monomer or a copolymer using a monomer copolymerizable with the styrene monomer. Examples of the styrenic monomer include styrene, α-methylstyrene, styrene derivatives in which a hydrogen atom of a benzene nucleus is substituted with a halogen atom or an alkyl group having 1 to 2 carbon atoms, specifically, styrene, o -Chlorstyrene, p-chlorostyrene, 2,4-dimethylstyrene, t-butylstyrene and the like. Examples of the copolymerizable monomer include acrylonitrile monomers such as (meth) acrylonitrile, α-chloroacrylonitrile, vinylidene cyanide, (meth) acrylic acid, methyl (meth) acrylate, (meth) (Meth) acrylic acid such as ethyl acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylic acid-2-ethylhexylbutyl, (meth) acrylic acid-β-hydroxyethyl, and these Various esters or vinyl acetate, vinyl chloride, vinylidene chloride, vinyl pyrrolidone, (meth) acrylamide, maleic anhydride, itaconic anhydride, maleimide and the like can be mentioned.

  Examples of the polyvinyl chloride resin include a vinyl chloride homopolymer, a vinyl chloride copolymer obtained by copolymerizing a small amount of a comonomer, a graft copolymer, and the like. Polymer blends of these with vinylidene chloride resin, ethylene / vinyl acetate copolymer, chlorinated polyethylene and the like may be used.

  Examples of the polyolefin resin include a homopolymer of α-olefin or a copolymer of α-olefin and another copolymerizable monomer. Examples include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer. It is done. Among these, low density polyethylene having a density of 0.910 to 0.935, ethylene-α-olefin copolymer, and ethylene-vinyl acetate copolymer having a vinyl acetate content of 30% by weight or less are excellent in transparency and weather resistance. ing. Among them, an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 wt% to 30 wt% is particularly excellent in transparency, flexibility and weather resistance.

  Examples of the polyamide-based resin include nylon-6, nylon-66, nylon-12, nylon-46, and the like.

The transparent resin plate 2 may contain a material that absorbs near infrared rays, for example, one or more of sulfur, sulfur compounds, copper compounds, and other near infrared absorbing materials. However, it does not need to be contained.
At this time, as the sulfur, a commercially available sulfur powder or the like can be used. For example, sulfur powder made by Tsurumi Chemical Co., Ltd. (JIS grade 2 equivalent) can be used.
Examples of sulfur compounds include lead sulfide and thiourea derivatives.
Examples of the copper compound include copper stearate, copper sulfide, and phthalocyanyl copper.
Examples of other near infrared ray absorbing substances include tungsten hexachloride, tin chloride, chromium, cobalt complex salts, anthraquinone derivatives, and the like.
The content of such a near-infrared absorbing material is not particularly limited, but it is preferable to contain 0.01 to 6 parts by weight in 100 parts by weight of the transparent resin. When the content is 0.01 to 6 parts by weight, preferably 0.01 to 2 parts by weight, particularly preferably 0.01 to 1 part by weight, the light absorption performance in the near infrared region is excellent, and the visible light transmittance is high. Is expensive.

  In addition, the transparent resin plate 2 has a heat stabilizer, an ultraviolet absorber, a colorant, a fluorescent brightener, a release agent, an antiblocking agent (silica, crosslinked polystyrene beads, etc.), as long as the effects of the present invention are not impaired. You may contain additives, such as a softening material and an antistatic agent.

(Prism surface 3)
As shown in FIGS. 1 to 4, the prism surface 3 is provided on one side of the transparent resin plate 2, for example, on the indoor side, that is, on the side opposite to the light incident side of the light guide plate 1, and has a triangular cross section and is long. A long triangular prism-shaped unit prism 3a is continuously arranged in the substantially vertical direction.

The unit prism 3a preferably has an isosceles triangle shape in a cross section perpendicular to the length direction, and it is important that the apex angle β of the unit prism 3a is greater than 60 ° and less than 100 °.
As shown in FIG. 4, the light guide plate 1 is arranged such that the prism surface 3 is positioned on the side opposite to the light incident side, and the length direction of the unit prism 3 a is substantially horizontal. If the apex angle β of the unit prism 3a is larger than 60 ° and smaller than 100 ° as described above, incident light from a low angle can be guided almost horizontally. it can. Therefore, in winter, when the sun angle becomes the lowest (winter solstice), the light can be guided almost horizontally into the room, and light can be taken into the room to increase the illuminance in the room. More specifically, light of 84 ° to 103 ° can be guided into the room with respect to the light guide resin plate at the winter solstice when the angle of the sun is the lowest.
In consideration of peep prevention, it is possible to prevent peep in the range of ± 1 ° to ± 34 ° from the front of the light guide resin plate.
From this viewpoint, the apex angle β of the unit prism 3a is more preferably 70 to less than 100 °, and particularly preferably 70 to 90 °.

  As shown in FIG. 3, the top of the unit prism 3a may be rounded. From the viewpoint of the light guide property that bends the angle of the light beam incident on the light guide plate 1, it is preferable that the radius of curvature of the top is as small as possible. From this point of view, the curvature radius R of the top is preferably larger than 0 mm and not larger than 0.5 mm, particularly preferably not larger than 0.3 mm, and particularly preferably not larger than 0.2 mm.

Moreover, it is preferable that the space | interval (prism pitch) L between the adjacent unit prisms 3a and 3a is 0.4 mm-15 mm. When the prism pitch is less than 0.4 mm, as the pitch of the mold for shaping the prism increases, it becomes difficult to perform the processing because fine processing is required for manufacturing the mold. In addition, when the top is rounded, the ratio of the curved portion (R portion) increases, so that the light guide performance may be reduced. On the other hand, if the prism pitch exceeds 14 mm, the groove between the unit prisms 3a and 3a becomes deep, which may reduce the strength of the light guide plate.
From this viewpoint, the prism pitch L is particularly preferably 1.0 mm to 10.0 mm, and particularly preferably 2.0 mm to 8.0 mm.

  The height H of the unit prism 3a is determined by the apex angle β of the unit prism 3a and the prism pitch L, but is preferably 0.3 mm to 10 mm, particularly 1.0 mm to 6.7 mm. Of these, it is particularly preferable that the thickness is 1.3 mm to 5.5 mm.

(Light Absorbing Layer 4)
The light absorption layer 4 can be formed as an ultraviolet absorption layer, a heat ray absorption layer, or a layer including both of them.

The ultraviolet absorbing layer can be formed by mixing an ultraviolet absorbing material with a transparent resin.
At this time, as the transparent resin, the transparent resin mentioned as the material of the transparent resin plate 2 can be used. Among these, it is preferable to use the same resin as the transparent resin plate 2 in consideration of adhesiveness, light scattering at the interface, and the like.
The ultraviolet absorbing material is not particularly limited as long as it has ultraviolet absorbing performance, and for example, benzotriazole, triazine and the like can be suitably used. However, it is not limited to these.

On the other hand, the heat ray absorbing layer can be formed by mixing a transparent resin with a heat ray absorbing material, that is, a near infrared ray absorbing material or an infrared ray absorbing material.
At this time, as the transparent resin, the transparent resin mentioned as the material of the transparent resin plate 2 can be used. Among these, it is preferable to use the same resin as the transparent resin plate 2 in consideration of adhesiveness, light scattering at the interface, and the like.
The heat ray absorbing material is not particularly limited as long as it has near infrared absorbing performance or infrared absorbing performance, and includes, for example, one or more of sulfur, sulfur compounds, copper compounds and other near infrared absorbing materials. You may do.

At this time, as the sulfur, a commercially available sulfur powder or the like can be used. For example, sulfur powder made by Tsurumi Chemical Co., Ltd. (JIS grade 2 equivalent) can be used.
Examples of sulfur compounds include lead sulfide and thiourea derivatives.
Examples of the copper compound include copper stearate, copper sulfide, and phthalocyanyl copper.
Examples of other near infrared ray absorbing substances include tungsten hexachloride, tin chloride, chromium, cobalt complex salts, anthraquinone derivatives, and the like.
The content of such a near-infrared absorbing material is not particularly limited, but it is preferable to contain 0.01 to 6 parts by weight in 100 parts by weight of the transparent resin. When the content is 0.01 to 6 parts by weight, preferably 0.01 to 2 parts by weight, particularly preferably 0.01 to 1 part by weight, the light absorption performance in the near infrared region is excellent, and the visible light transmittance is high. Is expensive.

(Layer structure)
The thickness of each layer of the transparent resin plate 2 and the light absorbing layer 4 is not limited as long as there is no problem in surface hardness and moldability, and the thickness ratio is also the same. In general, the transparent resin plate 2 has a thickness (h) of 1.8 mm to 10.0 mm, particularly 2.0 mm to 8.0 mm, and particularly preferably 2.4 mm to 7.0 mm. The thickness of 4 is 10 μm to 100 μm, particularly 20 μm to 70 μm, and particularly preferably 20 μm to 40 μm.

The light guide plate 1 may include other layers as long as the light guide plate 1 includes the transparent resin plate 2 and the light absorption layer 4 as described above.
Alternatively, a prism sheet provided with the prism surface 3 on one surface side of the sheet body may be formed separately from the transparent resin plate 2, and the prism sheet may be laminated on the transparent resin plate 2.

Furthermore, a diffusing material for diffusing light can be stacked. For example, by diffusing a diffusing material on at least one side of the prism surface 3, preferably on the indoor side, glare caused by light guided horizontally into the room by the prism surface 3 can be reduced.
In this case, the diffusing material is not particularly limited as long as it is a sheet body having a function of diffusing light. For example, a shoji, a nonwoven fabric or a frosted glass can be used.

<Manufacturing method>
As a method for laminating the transparent resin plate 2 and the light absorbing layer 4, a sheet provided with the light absorbing layer 4 may be laminated on the transparent resin plate 2 formed in advance with the prism surface 3, or After the resin constituting the transparent resin plate 2 (referred to as “transparent resin plate constituting resin”) and the resin constituting the light absorbing layer 4 (referred to as “ultraviolet absorbing layer constituting resin”) are coextruded and laminated, the prism surface 3 may be shaped.

When coextruding the transparent resin plate constituent resin and the ultraviolet absorbing layer constituent resin, for example, a main extruder for extruding the transparent resin plate constituent resin and a sub-extruder for extruding the ultraviolet absorbing layer constituent resin (usually the main extruder) Preferably smaller than the machine).
At this time, if a polycarbonate resin is used as the main component resin of the transparent resin plate constituting resin and the ultraviolet absorbing layer constituting resin, the temperature condition of the main extruder is usually 250 to 290 ° C., particularly 260 to 280 ° C. The temperature condition of the sub-extruder is usually 250 to 290 ° C, particularly preferably 260 to 280 ° C.
In order to remove foreign substances in the resin, it is preferable to install a polymer filter upstream of the T-die of the extruder.

In addition, as a method of laminating two types of molten resins by coextrusion, known methods such as a feed block method and a multi-manifold method can be used.
In the case of the feed block method, the molten resin laminated in the feed block is guided to a sheet forming die such as a T die, formed into a sheet shape, and then flowed into a forming roll (polishing roll) whose surface is mirror-finished. And a mirror finish and cooling while passing through the forming roll, thereby forming a laminate.
On the other hand, in the case of the multi-manifold system, the molten resin laminated in the multi-manifold die is formed into a sheet shape inside the die in the same manner as described above, followed by surface finishing and cooling with a forming roll to form a laminated body. can do.
The temperature of the die is usually 230 to 290 ° C., preferably 250 to 280 ° C., if the polycarbonate resin is used as the main component resin of the transparent resin plate constituting resin and the ultraviolet absorbing layer constituting resin, and the molding roll temperature As, it is 100-190 degreeC normally, Preferably it is 110-180 degreeC. As the roll, a vertical roll or a horizontal roll can be appropriately used.

  As a method for shaping the prism surface 3, for example, when the transparent resin plate 2 is extruded or when a laminated sheet of the transparent resin plate 2 and the light absorbing layer 4 is co-extruded, a predetermined prism surface is used. The prism surface 3 can be shaped by pressing and cooling the metal roll engraved so that 3 can be imprinted against the extruded transparent resin plate 2.

<Application>
The light guide plate 1 is installed in the vicinity of an opening of a building, for example, near a window so that the plate surface is vertical, and can guide sunlight toward the indoor side. In this case, the term “perpendicular” includes the case where the angle is 90 ° to about ± 10 °, preferably about ± 5 °. Moreover, the edge of a window includes the case where it laminates | stacks on the outer side or inner side of a window, or a window, for example.
Therefore, it can be used as a light guide plate (lighting material or face material) that is installed in a standing state, for example, along the opening of a building or substantially vertically on the outdoor side, and guides sunlight from the outdoor side to the indoor side. .
At this time, if the prism surface 3 is positioned on the side opposite to the light incident side, and the unit prism 3a is arranged so that the length direction thereof is substantially parallel to the horizontal direction, the light is taken into the room in the winter. The emission angle of sunlight transmitted through the light guide plate 1 can be controlled so that the illuminance can be increased. Especially in winter, when the angle of the sun is reduced (winter solstice), as shown in FIG. 4, the light can be guided almost horizontally to the room, so that light can be taken into the room and the illuminance in the room can be increased.
From the viewpoint of preventing peeping, it is possible to prevent peeping in the range of ± 1 ° to ± 34 ° from the front of the light guide resin plate.
Therefore, since the light guide plate 1 can change the angle of incident light as described above, for example, a lighting surface material installed almost vertically in a building, a surface material of a fence material installed outdoors, and a window material. It can also be suitably used as a screen material for a partition, a surface material for a balcony, a surface material attached to a window, and other daylighting materials.

<Explanation of terms>
In this specification, “X to Y” (X and Y are arbitrary numbers) means “X or more and Y or less” unless otherwise specified, and “preferably larger than X” or “preferably "Is smaller than Y".
In addition, when “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it is “preferably greater than X” or “preferably less than Y”. Includes intentions.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.

<Example 1>
An ultraviolet absorber-containing polycarbonate resin (“Panlite 5250ZS” manufactured by Teijin Chemicals Ltd.) as an ultraviolet absorbing layer constituting resin and a polycarbonate resin (“Novalex 7027U” produced by Mitsubishi Engineering Plastics) as a transparent resin plate constituting resin, Each was put into a separate hopper of an extruder, both were melted at a temperature of 280 ° C., and then co-extruded using a multi-manifold die. Then, the polycarbonate resin side of the ultraviolet absorbing layer 4 was set as the mirror metal roll side, and the opposite The surface is brought into contact with a metal roll engraved in a prism shape with an isosceles triangle and a height of 508 μm, and a prism surface 3 is provided on the opposite surface to cool and solidify to obtain a transparent sheet (sample) with a prism surface. It was.

The transparent sheet with a prism surface had a two-type two-layer configuration in which the total thickness was 2.5 mm and the thickness ratio of the UV absorbing layer / transparent resin layer was 40/2460.
In addition, the formed prism surface 3 includes triangular prism-shaped unit prisms 3a each having an isosceles triangle cross section arranged continuously in the width direction, and each unit prism 3a has a round top. The apex angle β was 80 °, the low angle α was γ: 50 °, the prism pitch L was 1 mm, and the height H of the unit prism 3a was 0.5 mm.

<Example 2>
A transparent sheet (sample) with a prism surface was obtained in the same manner as in Example 1 except that the prism shape engraved on the metal roll was changed.
In the formed prism surface 3, triangular prism unit prisms 3a each having an isosceles triangle cross section are continuously arranged in the width direction, and each unit prism 3a has a round top and a top angle. β: 90 °, low angle α, γ: 45 °, prism pitch L: 1 mm, unit prism 3a height H: 0.5 mm.

<Example 3>
A transparent sheet (sample) with a prism surface was obtained in the same manner as in Example 1 except that the prism shape engraved on the metal roll was changed.
In the formed prism surface 3, triangular prism unit prisms 3a each having an isosceles triangle cross section are continuously arranged in the width direction, and each unit prism 3a has a round top and a top angle. β: 70 °, low angle α, γ: 55 °, prism pitch L: 0.4 mm, and unit prism 3a height H: 0.5 mm.

<Comparative Example 1>
A transparent sheet (sample) with a prism surface was obtained in the same manner as in Example 1 except that the prism shape engraved on the metal roll was changed.
In the formed prism surface 3, triangular prism unit prisms 3a each having an isosceles triangle cross section are continuously arranged in the width direction, and each unit prism 3a has a round top and a top angle. β: 100 °, low angle α, γ: 40 °, prism pitch L: 0.6 mm, unit prism 3a height H: 0.5 mm.

<Comparative Example 2>
A transparent sheet (sample) with a prism surface was obtained in the same manner as in Example 1 except that the prism shape engraved on the metal roll was changed.
In the formed prism surface 3, triangular prism unit prisms 3a each having an isosceles triangle cross section are continuously arranged in the width direction, and each unit prism 3a has a round top and a top angle. β: 60 °, low angle α, γ: 60 °, prism pitch L: 0.3 mm, and unit prism 3a height H: 0.5 mm.

<Comparative Example 3>
In Example 1 above, a sheet (sample) that did not impart a prism shape was produced.
That is, an ultraviolet absorbent-containing polycarbonate resin (“Panlite 5250ZS” manufactured by Teijin Kasei Co., Ltd.) as an ultraviolet absorbing layer constituting resin and a polycarbonate resin (“Novalex 7027U” produced by Mitsubishi Engineering Plastics) as a transparent resin plate constituting resin Were respectively fed into hoppers of separate extruders, both melted at a temperature of 280 ° C., then coextruded using a multi-manifold die, and then cooled and solidified by passing between two mirror surface metal rolls. Got.

<Optical performance measurement test>
About the sheet | seat (sample) obtained by the said Example and comparative example, automatic variable angle meter CR-200 (Murakami Color Research Laboratory) was used, winter south-middle altitude (incidence angle 31 degrees), and summer south-middle. Assuming an altitude (incident angle 78 °), the transmission angle, the light guide distance, and the peep prevention angle at each incident angle were measured as follows.
As shown in FIG. 5, the automatic gonometer CR-200 has a light source fixed, and a sample sheet (prism plate) and a light receiver can be operated.

(1) Measurement of transmission angle and light guiding distance The transparent sheet with prism surface (sample, hereinafter referred to as “sample sheet”) obtained in the examples and comparative examples is arranged so that the prism side is the light receiver side, and the sample sheet The angle of incidence (angle X in FIG. 5) was set to 31 ° or 78 °.
Next, the angle at which the peak value appears (angle Z in FIG. 5) was measured by rotating the light receiver. The angle Z at which this peak value appears was taken as the transmission angle.
On the other hand, as for the light guide distance, the light guide distance was calculated based on the transmission angle measured as described above, assuming a fence height of 1 m (see FIGS. 6 and 7).

(2) Measurement of peeping prevention angle For the measurement of peeping prevention angle, the sample sheet was arranged vertically with respect to the light source, and rotated and fixed every 0 ° from 0 ° to 90 °. The light receiver was rotated up to 0 to 180 ° with respect to the sample sheet and measured. At that time, an angle at which a peak value of 50% or more of transmitted light did not appear with respect to incident light was defined as a peep prevention angle.
For example, when the peeping prevention angle is ± 17 °, it indicates that the peak value reaching 50% of the transmitted light was not measured while the sample sheet was rotated 0 to 17 °.

<Illuminance measurement test>
At a position 1 m away from the wall of the building on the outdoor side, the height of the lower surface of the window glass (horizontal 960 mm x vertical 1855 mm, sash: horizontal 1000 mm x 2010 mm, overall sliding sash width: 2055 mm) and sample sheet (horizontal 910 mm x The sample sheets obtained in Example 1 and Comparative Example 3 were placed so that the height of the lower surface of 1120 mm in length was the same, and the prism surface was directed to the indoor side. Then, at 12:00 on January 8, 2009 (measurement point south-central altitude 32.3 °), the illumination intensity on the incident side of the sample sheet, the illumination intensity on the transmission side of the sample sheet, and further, indoors, from the window The illuminance at heights of 0 m and 1 m from the floor surface at the depth of 0 m, 1 m, 2 m and 3 m was measured using an illuminometer (Minolta T-10). The results are shown in Table 2.

  From the results of Table 1, in Examples 2 and 3, light can be guided into the room at a transmission angle of 89 ° to 103 ° in winter, and the illuminance at the back of the room is increased as compared with Comparative Example 3. I can confirm that. The peeping prevention angle is ± 9 ° to ± 25, which is sufficient from the peeping prevention performance. However, in Comparative Example 1, the peeping prevention angle is ± 1 ° or less, and the peeping prevention performance is not sufficient. As for Comparative Example 2, the transmission angle was too large in winter and a sufficient amount of light could not be obtained.

  From the results of Table 2, in Comparative Example 3, it can be confirmed that the illuminance is high up to 1 m to 2 m of the room, but in Example 1, it can be confirmed that the illuminance is high up to 3 m of the room. As a result, it was confirmed that light was guided to the back of the room while ensuring peep prevention performance.

DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Transparent resin plate 3 Prism surface 3a Unit prism 4 Ultraviolet absorption layer

Claims (10)

Installed in the vicinity of the opening of the building so that the plate surface is vertical, the prism surface is located on the opposite side of the light incident side, and the length direction of the unit prism is in the horizontal direction. A light guide plate that leads to
Provided on one side of the transparent resin plate is a prism surface having a configuration in which unit prisms having an isosceles cross section are continuously arranged in the width direction, and the apex angle of the unit prism constituting the prism surface is 70 °. A light guide plate that is less than 100 °.   The light guide plate according to claim 1, wherein a top angle of the unit prism constituting the prism surface is 70 to 90 °.   3. The light guide plate according to claim 1, wherein a top portion of the unit prism constituting the prism surface is rounded, and a curvature radius of the top portion is greater than 0 mm and equal to or less than 0.5 mm.   The light guide plate according to claim 1, wherein a vertex interval between adjacent unit prisms is 0.4 mm to 15 mm.   The light guide plate according to claim 1, further comprising an ultraviolet absorbing layer on at least one side of the transparent resin plate.   The light guide plate according to claim 1, comprising a diffusing material.   The light guide plate according to claim 6, wherein the diffusing material is a shoji, a nonwoven fabric, or a frosted glass.   The light guide plate according to claim 1, wherein the light guide plate is used as a face material for a fence material installed outdoors.   The light guide plate according to claim 1, wherein the light guide plate is used as a face material to be attached to a window. The light guide plate according to any one of claims 1 to 7, wherein the light guide plate is used as a face material for a partition installed at a window.

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