JP2019029201A - Light guide plate and surface light source device - Google Patents

Abstract

[Problem] To provide a light guide plate for realizing a gradation surface light source suitable for spatial illumination in a simple manner. [Solution] A light guide plate having a light entrance surface into which light enters, and a light exit surface arranged in a direction intersecting the light entrance surface and emitting the light incident from the light entrance surface onto a surface, the light guide plate being characterized in that the luminance distribution of the light emitted from the light exit surface decreases from the light entrance surface side toward the opposite side, and the light exit surface is non-emitting at the end of the opposite side, the light guide plate having an absorbance per 1 mm ranging from 0.01 to 0.03, and an internal haze per 1 mm ranging from 0.59 to 0.64. [Selected Figure] Figure 1

Description

  Embodiments of the present disclosure relate to a light guide plate and a surface light source device.

  Surface light source devices are roughly classified into a direct type in which a light source is arranged directly under an optical member and an edge light type in which a light source is arranged on a side end surface of the optical member. The edge light type surface light source device is superior in that it can be made thinner than the direct type surface light source device.

  The edge-light type surface light source device disclosed in Patent Document 1 is disposed so as to face a light guide plate formed of highly translucent acrylic resin or the like and a side end surface (that is, a light incident surface) of the light guide plate. A light source, a diffusion plate disposed facing the surface of the light guide plate (that is, the light exit surface), and a scattering pattern disposed on the back surface of the light guide plate and including a light diffusive reflective material such as titanium oxide. ing. In this surface light source device, light incident from the light incident surface of the light guide plate enters the light while repeating total reflection at the interface between the light exit surface of the light guide plate and the air layer, or at the interface between the rear surface of the light guide plate and the air layer. From the surface side to the opposite side of the light incident surface. When the light enters the scattering pattern disposed on the back surface of the light guide plate, the light is diffused and reflected by the light diffusing and reflecting material contained in the scattering pattern to the light exit surface of the light guide plate, and is emitted from the light exit surface toward the diffuser plate. .

JP-A-9-178952

  Recently, so-called space effect lighting has been attracting attention, which creates an atmosphere of space to give the user a sense of calm and comfort. However, sufficient studies have not been made on the characteristics of the light guide plate for realizing a gradation surface light source suitable for space effect lighting by a simple method.

  An embodiment of the present disclosure has been made in view of the above points, and an object thereof is to provide a light guide plate for realizing a gradation surface light source suitable for space effect illumination by a simple method.

According to an aspect of the present invention, there is provided a light guide surface having a light incident surface on which light is incident and a light output surface that is disposed in a direction intersecting the light incident surface and emits light incident from the light incident surface on the surface. It is a light plate, and the luminance distribution of the light emitted from the light exit surface decreases from the light incident surface side to the opposite side, and does not emit light at the opposite end. There is provided a light guide plate having an absorbance per mm of 0.01 to 0.03 and an internal haze per mm of 0.59 to 0.64.
By setting the light guide plate to the above configuration, a gradation having a light guide distance of about 300 mm can be realized.
The material of the light guide plate is preferably polyvinyl chloride. Thereby, a flame retardance can be provided.

It is preferable that a hard coat layer is provided on at least one surface including the light incident surface. By providing the hard coat layer, scratches on the surface of the light guide plate can be prevented.
It is preferable that a light absorption layer or a light reflection layer is provided on at least one surface other than the light incident surface. Thereby, the leak light from surfaces other than a light emission surface can be prevented.
A non-reflective layer or a low reflective layer may be provided on at least one surface including the light incident surface. Thereby, the reflection loss at the light incident surface can be suppressed. In addition to the light incident surface, it is difficult to visually recognize the light guide plate when the light is turned off, and the design is not impaired. The light extraction efficiency from the light exit surface is improved.

Information may be printed on at least one surface of the light guide plate including the light incident surface. Thereby, it can be used as a signboard regardless of whether it is turned on or off.
Moreover, you may make it the design sheet which permeate | transmits light provided at least on the said light emission surface. This gives the same appearance as a normal wall when turned off.

The present invention is a surface light source device comprising: the light guide plate described above; and a light source that is provided at a position facing the light incident surface and that emits light to the light incident surface.
It is preferable that the said surface light source device is provided facing a wall surface, a ceiling surface, and a floor surface. Thereby, the design of the back side can be utilized at the time of light extinction.

It is preferable that at least one surface of the light guide plate is provided in contact with a wall surface, a ceiling surface, and a floor surface. Thereby, the design of the back side can be utilized at the time of light extinction.
A decorative sheet may be provided on the back side of the light guide plate. Thereby, the design of the back side at the time of light extinction can be produced with a decorative sheet.
The surface light source device may be embedded in a wall surface, a ceiling surface, a floor surface, or the ground. Thereby, the unevenness | corrugation which arises by installing a surface light source device can be eliminated.

  ADVANTAGE OF THE INVENTION According to this invention, the gradation surface light source suitable for space effect illumination can be provided by a simple method.

It is sectional drawing which shows the surface light source device of 1st Embodiment. It is a schematic diagram which shows the luminance distribution of a light-guide plate. It is a figure which shows the wavelength dependence of the light absorbency per mm of the light-guide plate shown in Table 1. It is a figure which shows the mode of surface light emission at the time of using the light guide plate of five types of different materials. It is sectional drawing which shows the structure which performed the hard coat to the light emission surface side of the light-guide plate by this embodiment. It is sectional drawing which shows the surface light source device of 2nd Embodiment. It is sectional drawing which shows the surface light source device of 3rd Embodiment. It is sectional drawing which shows the surface light source device of 4th Embodiment. It is sectional drawing which shows the surface light source device of 5th Embodiment.

  Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale and the vertical / horizontal ratio are appropriately changed and exaggerated.

  In addition, for example, terms such as “orthogonal” that specify the shape and geometric conditions and the degree thereof used in the present specification are not limited to strict meanings, and the same function can be expected. This should be interpreted including the range of.

  Further, in the present specification, the terms “plate” and “sheet”, “layer” and “sheet” are based only on the difference in names and are not distinguished from each other. For example, the “plate” is a concept including a member that can be called a sheet. Therefore, the “light guide plate” is not distinguished only by the difference in the name “light guide sheet”. Further, the “light scattering layer” is not distinguished only by the difference of the name “light scattering sheet”.

<First Embodiment>
FIG. 1 is a cross-sectional view showing the surface light source device of the first embodiment. The surface light source device 1 of the present embodiment is an edge light type surface light source device, but is different from that used as a normal lighting fixture, and is used for space effect lighting, producing a space atmosphere, It is a device that provides a user-friendly light space. The apparatus shown in FIG. 1 can provide a gradation surface light source having a light guide distance of, for example, about 100 mm to 500 mm, which is suitable for space effect illumination, by a simple method. The wavelength of the light source 2 may be in the visible light region, for example. The wavelength and intensity of the light source can be appropriately set in consideration of the color and intensity desired to be emitted and the absorption of the light guide plate.

  The surface light source device 1 is attached to a wall W of a room, for example, and is a long light source 2 and a light guide plate that is provided below the light source 2 and emits light from the light source 2 in a planar shape. 3 is provided. As the light source 2, a light emitting diode (including LED and OLED), a cold cathode tube, an incandescent lamp, a laser oscillation device, and the like can be used. LED is used. Therefore, the light source 2 of the present embodiment is composed of a long light source substrate and a plurality of point-like LEDs mounted on the light source substrate at regular intervals.

  As shown in FIG. 1, the light source 2 is held by an auxiliary building material 4. The auxiliary building material 4 is a member that covers the joint between the ceiling (not shown) and the wall W and improves the design. As the auxiliary building material 4, a member called “around edge” or “baseboard” can be used. The auxiliary building material 4 is fixed to the wall W by, for example, adhesion, screwing or the like.

  The light guide plate 3 is a rectangular thin plate, and has a pair of main surfaces facing each other and four side end surfaces defined between the pair of main surfaces. The light guide plate 3 is disposed below the light source 2 so that one of the four side end faces faces the light source 2. A side end surface facing the light source 2 is a light incident surface 31 on which light from the light source 2 is incident. The side end surface on the side opposite to the light incident surface 31 (that is, the side away from the light source 2) is a facing surface 32 that faces the light incident surface 31. The facing surface 32 corresponds to the “opposite end” of the light incident surface.

  On the other hand, of the pair of main surfaces, the main surface facing the interior of the room (in other words, the main surface away from the wall W) is the light exit surface 33, and the main surface opposite to the light exit surface 33 (that is, the main surface) The main surface adjacent to the wall W is a back surface 34. The light exit surface 33 intersects with the light entrance surface 31 (for example, orthogonal to 90 °), and emits light incident from the light entrance surface 31 toward the interior of the room. The light guide plate 3 is made of, for example, a resin material such as polyvinyl chloride resin, acrylic resin, methacrylic resin, PMMA, or polycarbonate having high translucency.

Although not shown, a light diffusion sheet facing the light exit surface 33 may be provided on the light exit surface 33 side of the light guide plate 3, and a light reflecting sheet facing the back surface 34 may be provided on the back surface 34 side. Various configurations capable of exhibiting a light diffusing function can be adopted for the light diffusing sheet. The diffusion characteristics of the light diffusing sheet may be isotropic or anisotropic.
When the light diffusion sheet is used, the glossiness of the surface can be eliminated and it can be melted into the surroundings without a sense of incongruity. Further, the light can be spread over a wider range, and if there is anisotropy, the light in any direction can be increased or decreased.
The light diffusion sheet preferably has a value of 1 to 30 as the haze value of the light diffusion sheet. If it is lower than this haze value range, the effect of the light diffusing sheet cannot be obtained, and if it is larger than this haze value range, it becomes cloudy and, on the contrary, cannot be dissolved in the surrounding appearance.

On the other hand, the light reflection sheet includes a white scattering reflection sheet, a sheet made of a material having a high reflectivity such as a metal, and a sheet containing a thin film (for example, a metal thin film) made of a material having a high reflectivity as a surface layer. Can be used. The reflection on the light reflecting sheet may be specular reflection (regular reflection) or diffuse reflection.
When the light reflection sheet is used, it is possible to increase the extraction of light to the light exit surface and increase the light use efficiency.
The light reflection sheet preferably has a reflectance in the range of 5% to 85%.
If the reflectivity is lower than this, the effect of the light reflecting sheet cannot be obtained, and if the reflectivity is higher than this, it becomes a perfect mirror surface, and the design behind the light cannot be seen through the light guide plate, so that it blends into the surrounding appearance. Absent.

  As shown in FIG. 1, a decorative sheet 5 is interposed between the light guide plate 3 and the wall W. The decorative sheet 5 is preferably attached to the entire surface of the wall W in order to obtain a sense of unity with the surroundings. As this decorative sheet 5, a paper-type decorative sheet, a resin-type decorative sheet (for example, a wood-like decorative sheet, a mirror-like decorative sheet), or the like can be used.

  In the edge light type surface light source device 1 configured as described above, the light emitted from the light source 2 enters the light guide plate 3 through the light incident surface 31. The light incident on the light guide plate 3 travels from the light incident surface 31 side to the opposite surface 32 side while repeating total reflection at the interface between the light exit surface 33 and the air layer or the interface between the back surface 34 and the air layer, and further exits the light. Light exits from the surface 33 toward the interior of the room.

  FIG. 2 is a schematic diagram showing the luminance distribution of the light guide plate 3. In the present embodiment, the light guide plate 3 gradually decreases as the luminance distribution of the light emitted from the light exit surface 33 goes from the light incident surface 31 side to the facing surface 32 side (from top to bottom in FIG. 1), and The opposing surface 32 is formed so as not to emit light. In other words, one target is a gradation surface light source having a light guide distance of about 300 mm. Specifically, as shown in the luminance distribution graph on the right side of FIG. 2, the luminance at the light incident surface 31 is the highest, and the luminance is drawn so as to draw a convex curve downward from the light incident surface 31 toward the opposite surface 32. It gradually decreases and does not emit light on the facing surface 32. Here, “non-light emission” means that the luminance is completely zero, but includes that within a range where the luminance peak value is reduced to, for example, about 20%. .

  Here, as the luminance distribution graph, the luminance gradually decreases so as to draw a downward convex curve from the light incident surface 31 to the opposing surface 32, and the luminance on the opposing surface 32 becomes almost zero. Alternatively, the luminance may gradually decrease linearly downward from the light incident surface 31 toward the opposing surface 32, and the luminance at the opposing surface 32 may be substantially zero.

  According to the surface light source device 1 configured as described above, the light guide plate 3 is configured such that the luminance distribution of light emitted from the light exit surface 33 gradually decreases from the light incident surface 31 side to the facing surface 32 side, and the facing surface. 32 so that the luminance is almost zero. For this reason, the light emitted from the light exit surface 33 is bright on the light incident surface 31 side, gradually becomes darker as it goes from the light incident surface 31 side to the opposing surface 32 side, and the decorative sheet on the opposing surface 32 side. 5 can be melted. By adding bright and dark gradations in this way, the presence as a light source of the surface light source device 1 can be diminished, and the atmosphere of the space can be produced.

  In addition, since the luminance distribution gradually decreases from the light incident surface 31 side toward the opposing surface 32 side, the surface reflection on the light exit surface 33 can be suppressed without causing a luminance step on the light exit surface 33. In addition, since the brightness at the facing surface 32 is almost zero, the occurrence of leakage light from the facing surface 32 can be prevented. As a result, the presence of the surface light source device 1 as a light source can be further diminished, and the surface light source device 1 can be melted into the surroundings without a sense of incongruity. It becomes possible, and the atmosphere of the space can be effectively produced. Further, when the surface light source device 1 is not lit, the design of the wall surface of the wall W can be observed through the light guide plate 3, so that the presence of the surface light source device 1 is not conscious.

Below, the characteristic of the light-guide plate 3 of this embodiment is demonstrated in detail.
Table 1 is a table | surface which shows the material and characteristic of the light-guide plate 3 of this embodiment. In addition, the light guide plate 3 used as a comparative example is also shown. FIG. 3 is a diagram showing the wavelength dependence of the absorbance per mm of the light guide plate 3 shown in Table 1. FIG. 4 is a diagram showing a state of surface light emission when a light guide plate made of five different materials is used.

As shown in Table 1, in this embodiment, two types of light guide plates 3 of the light guide plate 1) and the light guide plate 2) were used.
The light guide plates 1) and 2) have a total light transmittance Tt of 75.2 and 82.4, respectively. Further, the diffuse transmittance Td is 4.2 and 5.7, respectively. Thus, the internal haze is 3.2, 3.0.
The internal haze per unit thickness when the haze is assumed to be proportional to the thickness is 0.64 and 0.59, respectively.

  The light guide distances (mm) obtained from FIG. 4 are 120 mm and 240 mm, respectively, when colored and guided, and 60 mm and 120 mm, respectively, in the case of white light.

On the other hand, the light guide plates used as comparative examples are from the light guide plate 3) to the light guide plate 5). Table 1 also shows Tt, Td, internal haze, and internal haze per unit thickness.
The haze value was measured in accordance with JIS K 7136 using a haze meter (manufactured by Murakami Color Research Laboratory (HM-150)).
The light guide distances (mm) obtained from FIG. 4 are 30 mm, 0 mm, and 300 mm or more, respectively, when colored and guided, and in the case of white light guide, they are 30 mm, 0 mm, and 300 mm or more, respectively. is there.

Further, as shown in FIG. 3, the absorbance in the wavelength band from 400 nm to 800 nm corresponding to the visible light wavelength band was measured on the light guide plate of each material shown in Table 1.
Absorbance was measured as follows.
Using a spectrophotometer (Y670, manufactured by JASCO), the measurement was performed under the following conditions.
Measurement mode: Abs
Wavelength: 400 nm to 800 nm
Step: 1nm

As shown in FIG. 3, the absorbance in the wavelength band from 400 nm to 800 nm corresponding to the visible light wavelength band is between 0.01 and 0.03 in the light guide plates 1) and 2). On the other hand, in the light guide plate 3), the absorbance is 0.09 or more, and in the light guide plate 4) and the light guide plate 5), the absorbance is 0.01 or less.
From the above results, it is desirable that the material of the light guide plate suitable for the gradation surface light source having a light guide distance of about 300 mm satisfies the following conditions.
1) Absorbance per mm of 0.01 to 0.03
Incidentally, if the absorbance is higher than this, it will be attenuated immediately and the light will not spread. If the absorbance is lower than this, it becomes nearly uniform and does not produce gradation. That is, it does not disappear at a desired distance of about 300 mm.
2) The internal haze per mm is 0.59 to 0.64.
Here, it was assumed that haze was proportional to thickness. If the internal haze per mm is higher than this, the light diffuses immediately and the light does not spread to the light guide plate. On the other hand, when the internal haze per 1 mm is lower than this, light does not come out from the light emitting surface side.

As described above, according to the present embodiment, the light incident surface on which light is incident and the light exit surface that is arranged in a direction intersecting the light incident surface and emits the light incident from the light incident surface onto the surface. In the light guide plate having the following conditions, the luminance distribution of the light emitted from the light exit surface decreases as it goes from the light incident surface side to the opposite side, and the luminance becomes substantially zero at the opposite end. A light plate can be provided.
1) Absorbance per mm is in the range of 0.01 to 0.03.
2) The internal haze per mm is in the range of 0.59 to 0.64.
For example, it can be set as said range by using for the light-guide plate made from polyvinyl chloride. Furthermore, flame retardancy can be imparted.

  Although not shown, in the present embodiment, a design sheet that transmits light may be provided on the light exit surface 33 of the light guide plate 3. The design sheet is preferably the same as the decorative sheet 5 described above. The design sheet may include any of paper, resin, cloth and the like. An air layer, an adhesive layer, or an adhesive layer may be interposed between the design sheet and the light exit surface 33.

If it does in this way, it will become the same appearance as a normal wall at the time of light extinction. The transmittance of the design sheet is preferably 5% to 50%. Above this value, the panel will show through. On the other hand, if the value is less than this value, the light extraction efficiency becomes low and the light source does not function.
The in-plane distribution of the internal haze may be changed within the above range. Thereby, the light guide distance and the light emission intensity can be changed, and the design can be widened.
Further, if the surface light source device is embedded in a wall surface, a ceiling surface, a floor surface, or the ground, unevenness generated by installing the surface light source device can be eliminated.

<Hard coat layer 36>
FIG. 5 is a cross-sectional view illustrating a structure in which a hard coat layer 36 is provided on the light exit surface 33 side of the light guide plate 3 according to the present embodiment.
As the hard coat layer 36, a hard film formed on the surface in order to increase the hardness can be used. Alternatively, a film coated with the hard coat layer 36 may be attached.
The hard coat layer 36 is known to form the hard coat layer 36 on the substrate surface in order to improve the scratch resistance of the substrate surface such as glass, plastic sheet, plastic lens, resin film, display device front plate and the like. As such a hard coat layer 36, an organic resin film or an inorganic film is formed on the surface of glass, plastic or the like. Furthermore, it is practiced to further improve the scratch resistance by blending resin particles or inorganic particles such as silica in an organic resin film or an inorganic film.
Thus, by providing the hard coat layer 36 on at least one surface including the light incident surface, it is possible to prevent the surface of the light guide plate 3A from being damaged.

  In addition, the surface light source device of this embodiment may be provided facing a wall surface, a ceiling surface, and a floor surface. Or At least one surface of the light guide plate 3A may be provided in contact with the wall surface, ceiling surface, and floor surface. By arranging in this way, the design on the back side can be utilized when the light is turned off.

Second Embodiment
FIG. 6 is a cross-sectional view showing the surface light source device of the second embodiment. The surface light source device 1 </ b> A of the present embodiment is different from the first embodiment in that a light absorption layer 41 is further provided on the facing surface 32 of the light guide plate 3. Since other configurations are the same as those of the first embodiment, a duplicate description is omitted.

  The light absorption layer 41 may be formed, for example, by applying a resin in which a pigment that absorbs light, carbon-based garbon black, a colored pigment, a dye, or the like is dispersed, or a film including these materials is attached. It may be formed.

  According to the surface light source device 1A of the present embodiment, the same effects as those of the first embodiment described above can be obtained, and the light absorbing layer 41 is provided on the facing surface 32 of the light guide plate 3, so that the facing Even if leakage light from the surface 32 occurs, the leakage light is absorbed by the light absorption layer 41, so that emission to the outside can be prevented. For this reason, generation | occurrence | production of the leak light from the opposing surface 32 can be prevented more reliably. In addition, it is possible to prevent an increase in luminance near the light-receiving surface due to the reflected light from the facing surface 32.

<Third Embodiment>
FIG. 7 is a cross-sectional view showing the surface light source device of the third embodiment. The surface light source device 1 </ b> B of this embodiment is different from the first embodiment in that a light reflection layer 42 is further provided on the facing surface 32 of the light guide plate 3. Since other configurations are the same as those of the first embodiment, a duplicate description is omitted.

  The light reflecting layer 42 may be the same as the above light reflecting sheet, or may be formed by forming a metal such as aluminum or silver, a dielectric multilayer film, or metal particles or white pigment. It may be formed by applying a resin in which is dispersed, or may be formed by attaching a film containing these materials.

According to the surface light source device 1B of the present embodiment, the same operational effects as those of the first embodiment described above can be obtained, and the light reflecting layer 42 is provided on the facing surface 32 of the light guide plate 3, so Even if leakage light from the surface 32 occurs, the leakage light is folded back to the inside of the light guide plate 3 by the light reflection layer 42, so that emission to the outside can be prevented. For this reason, generation | occurrence | production of the leak light from the opposing surface 32 can be prevented more reliably. Further, as an effect of the light reflecting layer 42, the design of the decorative sheet 5 appears to be reflected when viewed from the outside, so that the boundary is not conspicuous. By providing the decorative sheet 5 on the back surface 34 side of the light guide plate 3, the design on the back side when the light is turned off can be produced with the decorative sheet 5.
Information may be printed on at least one surface including the light incident surface. Information includes, for example, public notices. Thereby, it can be used as a signboard regardless of whether it is turned on or off.

<Fourth embodiment>
FIG. 8 is a cross-sectional view showing the surface light source device of the fourth embodiment. The surface light source device 1 </ b> C of the present embodiment is different from the first embodiment in that a light reflection layer 42 and a wall member 43 are further provided on the facing surface 32 of the light guide plate 3. Since other configurations are the same as those of the first embodiment, a duplicate description is omitted.

  Specifically, the light reflecting layer 42 and the wall material portion 43 are formed in order on the facing surface 32 from the inside toward the outside. The wall member 43 is formed in a sheet shape from the same material as the wall W, for example, and is attached to the light reflecting layer 42 by adhesion or the like so as to cover the light reflecting layer 42.

  According to the surface light source device 1 </ b> C of the present embodiment, the same effects as those of the first embodiment described above can be obtained, and the light reflection layer 42 is provided on the facing surface 32 of the light guide plate 3. Even if light leaking from the surface 32 occurs, the light leakage is folded back into the light guide plate 3 by the light reflecting layer 42, so that the generation of light leaking from the facing surface 32 can be more reliably prevented. Furthermore, since the wall material part 43 which covers the light reflection layer 42 is provided, there exists an effect which reduces the protrusion feeling of the lower part of the light-guide plate 3 containing the opposing surface 32. FIG. As a result, the lower part of the light guide plate 3 becomes inconspicuous and can be melted with the surroundings.

<Fifth Embodiment>
FIG. 9 is a cross-sectional view showing a surface light source device of a fifth embodiment. The surface light source device 1D of the present embodiment is different from the first embodiment in that the opposing surface 32 of the light guide plate 3 is formed in a tapered shape and the non-reflective layer 44 is provided on the light exit surface 33 and the opposing surface 32. Yes. Since other configurations are the same as those of the first embodiment, a duplicate description is omitted.
Or you may comprise so that the thickness of the light-guide plate 3 may become thin as it leaves | separates from a light-incidence surface (the light-emitting surface is formed in the taper shape).

  As shown in FIG. 9, the facing surface 32 opposite to the light incident surface 31 is formed in a tapered shape so as to be inclined toward the wall W side. A non-reflective layer 44 is applied to the light exit surface 33 and the facing surface 32. For the non-reflective layer 44, a known technique can be used. Here, a non-reflective layer 44 may be further provided on the back surface 34. Further, a low reflection layer may be used in place of the non-reflection layer 44.

  According to the surface light source device 1D of the present embodiment, the same operational effects as those of the first embodiment described above can be obtained, and the facing surface 32 is tapered so as to be inclined toward the wall W side. There is an effect of reducing the protruding feeling of the lower portion of the light guide plate 3 including the facing surface 32. As a result, the lower part of the light guide plate 3 becomes inconspicuous and can be melted with the surroundings. Furthermore, since the non-reflective layer 44 is provided on the light exit surface 33 and the facing surface 32, the occurrence of surface reflection on these surfaces can be further suppressed.

<Example 1>
Hereinafter, the light guide plate 1) to the light guide plate 5) used in the above embodiment will be described in detail.
As materials such as the light guide plate 1) and the light guide plate 2) having an absorbance per mm of 0.01 to 0.03 and an internal haze per mm in the range of 0.59 to 0.64. Although not limited, for example, polyvinyl chloride (vinyl chloride) such as ESS8800 and RTS110PE manufactured by Takiron Sea Eye Co., Ltd. can be used.
Further, the light guide plate 3), the light guide plate 4), the light guide plate having an absorbance per mm outside the range of 0.01 to 0.03 or an internal haze per mm outside the range of 0.59 to 0.64. The light plates 5) are Delagras AL 997 from Asahi Kasei Technoplus Co., Ltd., Acrylite L001 from Mitsubishi Chemical Corporation, and Acrylite L435 from Mitsubishi Chemical Corporation, respectively.
Note that the materials described as examples in the first embodiment are merely examples and are not limited to these materials. As described above, the materials per 1 mm or the processed materials may be used. Any light guide plate having an absorbance in the range of 0.01 to 0.03 and an internal haze per mm in the range of 0.59 to 0.64 falls within the scope of the present invention.

In the above-described embodiment, the configuration and the like illustrated in the accompanying drawings are not limited to these, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.
Each component of the present invention can be arbitrarily selected, and an invention having a selected configuration is also included in the present invention.

1, 1A, 1B, 1C, 1D Surface light source device 2 Light source 3, 3A Light guide plate 4 Auxiliary building material 5 Decorative sheet 31 Light incident surface 32 Opposing surface 33 Light exit surface 34 Back surface 36 Hard coat layer 41 Light absorption layer 42 Light reflection layer 44 Non-reflective layer W Wall

Claims (12)

A light guide plate having a light incident surface on which light is incident and a light exit surface that is arranged in a direction intersecting the light incident surface and emits light incident from the light incident surface on the surface;
The luminance distribution of the light emitted from the light exit surface decreases from the light entrance surface side to the opposite side, and does not emit light at the opposite end, and the absorbance per mm. Is 0.01 to 0.03, and the internal haze per mm is in the range of 0.59 to 0.64. The light guide plate according to claim 1, wherein a material of the light guide plate is polyvinyl chloride. The light guide plate according to claim 1, wherein a hard coat layer is provided on at least one surface including the light incident surface. The light guide plate according to any one of claims 1 to 3, wherein a light absorption layer or a light reflection layer is provided on at least one surface other than the light incident surface. The light guide plate according to any one of claims 1 to 4, wherein a non-reflective layer or a low-reflective layer is provided on at least one surface including the light incident surface. The light guide plate according to claim 1, wherein information is printed on at least one surface of the light guide plate including a light incident surface. The light guide plate according to any one of claims 1 to 6, wherein a design sheet that transmits light is provided at least on the light exit surface. The light guide plate according to any one of claims 1 to 7,
A surface light source device comprising: a light source that is provided at a position facing the light incident surface and that irradiates light to the light incident surface. The surface light source device according to claim 8, wherein the surface light source device is provided to face a wall surface, a ceiling surface, and a floor surface. The surface light source device according to claim 8, wherein at least one surface of the light guide plate is provided in contact with a wall surface, a ceiling surface, and a floor surface. The surface light source device according to any one of claims 8 to 10, wherein a decorative sheet is provided on a back surface side of the light guide plate. The surface light source device according to any one of claims 8 to 11, which is embedded in a wall surface, a ceiling surface, a floor surface, or the ground.

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