JP6453271B2 - Surface lighting device - Google Patents

Description

  The present invention relates to a planar lighting device.

  Conventionally, some planar illumination devices used as illumination means such as a liquid crystal display panel have an optical sheet such as a diffusion sheet disposed on the surface of a light guide plate. In such a planar lighting device, for example, the optical sheet is fixed to the edge of the light guide plate using a double-sided tape. Here, as the double-sided tape for fixing the optical sheet, a tape using a transparent adhesive is often used.

JP 9-203811 A

  However, when a double-sided tape using a transparent adhesive is used to fix the optical sheet, light is lost at the edge of the light guide plate by transmitting light to the adhesive of the double-sided tape, As a result, the uniformity of luminance in the planar illumination device may be reduced.

  This invention is made | formed in view of the above, Comprising: It aims at providing the planar illuminating device excellent in the uniformity of a brightness | luminance.

In order to solve the above-described problems and achieve the object, a planar illumination device according to one embodiment of the present invention includes a light guide plate, a light source, and a plurality of optical sheets. The light guide plate has a main surface including a light emission region and a plurality of end surfaces. A light source is arrange | positioned at the 1st end surface side of the said light-guide plate, and enters light from the said 1st end surface. A plurality of optical sheets, the arranged is laminated on said main surface of the light guide plate, double-sided tape to the fixed area provided in the edges of the different that the end surface side to the first end surface on the main surface It is fixed using. And the said double-sided tape has a strip | belt-shaped base material and the adhesion layer formed in both surfaces of the said base material, and the said adhesion layer of the said base material and the said light-guide plate side reflects the said light. It is formed to be a color. Moreover, the said light guide plate is formed in the step shape in which the said edge part in which the said fixed area | region on the said main surface was provided has a level | step difference in the thickness direction of the said light guide plate. In the plurality of optical sheets, a part of each optical sheet is individually fixed to each step of the edge portion formed in a step shape of the light guide plate using the double-sided tape.
The planar illumination device according to one aspect of the present invention is disposed on a light guide plate having a main surface including a light emission region and a plurality of end surfaces, on a first end surface side of the light guide plate, A light source that receives light from one end surface, and is stacked on the main surface of the light guide plate, and is provided on an edge portion on one end surface side that is different from the first end surface on the main surface. A plurality of optical sheets fixed using double-sided tape only in the fixed region, and the light guide plate has the edge provided with the fixed region on the main surface in the thickness direction of the light guide plate. In the plurality of optical sheets, a part of each optical sheet is individually attached to each step of the edge portion formed in a step shape of the light guide plate. Fixed using.

  According to one embodiment of the present invention, a planar lighting device having excellent luminance uniformity can be provided.

FIG. 1 is a plan view of the planar illumination device according to the first embodiment. 2 is a cross-sectional view taken along line AA shown in FIG. FIG. 3 is a cross-sectional view taken along the line BB shown in FIG. FIG. 4 is a cross-sectional view of the double-sided tape according to the first embodiment. FIG. 5 is a plan view of the planar illumination device according to the second embodiment. FIG. 6 is a cross-sectional view taken along line CC shown in FIG. 7 is a cross-sectional view taken along the line DD shown in FIG. FIG. 8 is a perspective view showing a fixing portion of the light guide plate, the first optical sheet, the second optical sheet, and the third optical sheet according to the second embodiment. FIG. 9 is a diagram showing the effects of the first and second embodiments.

  Hereinafter, an embodiment of a planar illumination device according to the present application will be described with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the component which plays the same role.

(First embodiment)
FIG. 1 is a plan view of the planar illumination device according to the first embodiment. 2 is a cross-sectional view taken along the line AA shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line BB shown in FIG.

  For example, as illustrated in FIGS. 1 to 3, the planar illumination device 10 according to the first embodiment includes a light guide plate 11, a light source 12, an optical sheet 13, a reflective sheet 14, and a frame 15.

  The light guide plate 11 has a main surface including a light emission region and a plurality of end surfaces. For example, the light guide plate 11 is a plate-like member formed in a substantially rectangular shape in plan view, and includes a first main surface 11b including a light emission region 11a and a second main surface 11b facing the first main surface 11b. Main surface 11c. In addition, the light guide plate 11 is substantially orthogonal to the first end surface 11d where light is incident, the second end surface 11e facing the first end surface 11d, and the first end surface 11d, and facing each other. It has the 3rd end surface 11f and the 4th end surface 11g. The light guide plate 11 is made of a material that transmits light emitted from the light source 12, and the light incident from the first end surface 11d is emitted from the first main surface 11b. It is comprised so that it may radiate | emit from.

  The light source 12 is disposed on the first end face 11d side of the light guide plate 11, and receives light from the first end face 11d. For example, the light source 12 includes a plurality of LEDs (light emitting diodes) 12 a, and the LEDs 12 a are arranged along the first end surface 11 d of the light guide plate 11. More specifically, for example, the LED 12a is a white LED that emits white light.

  The optical sheet 13 is disposed on the first main surface 11 b including the emission region 11 a of the light guide plate 11. For example, the optical sheet 13 is a thin plate-like member formed of resin or the like, and is disposed on the first main surface 11 b so as to cover the emission region 11 a of the light guide plate 11. Here, for example, the optical sheet 13 is a diffusion sheet that transmits light emitted from the emission region 11 a of the light guide plate 11 while diffusing.

  The reflection sheet 14 is disposed on the second main surface 11 c of the light guide plate 11, and reflects the light incident on the light guide plate 11 by the light source 12 into the light guide plate 11.

  The frame 15 is a frame-shaped member formed in a substantially rectangular shape, and accommodates and supports the light guide plate 11, the light source 12, and the optical sheet 13 inside. In addition, the reflection sheet 14 is attached to the frame 15 on the side where the second main surface 11 c of the light guide plate 11 is disposed. The frame 15 may be a bottomed frame-like member, for example.

  Under such a configuration, in the present embodiment, the optical sheet 13 is fixed to the fixing region 11 h provided at the edge on the first main surface 11 b of the light guide plate 11 using the double-sided tape 16. . Here, the fixing region 11h to which the optical sheet 13 is fixed is provided at the edge on the end surface side different from the first end surface 11d into which the light on the first main surface 11b is incident.

  For example, as shown in FIGS. 1 to 3, the optical sheet 13 uses a double-sided tape 16 in a fixing region 11 h provided at an edge portion on the fourth end surface 11 g side which is an end surface substantially orthogonal to the first end surface 11 d. Is fixed. The optical sheet 13 is fixed only to the fixing region 11h provided on the fourth end surface 11g side which is one end surface of the plurality of end surfaces of the light guide plate 11. In the present embodiment, the length of the fourth end surface 11g where the fixed region 11h is formed is shorter than the length of the first end surface 11d.

  And in this embodiment, the double-sided tape 16 has a strip-like base material and an adhesive layer formed on both surfaces of the base material, and at least the base material and the adhesive layer on the light guide plate side emit light. It is formed to have a reflective color. For example, the color of the adhesive layer on the substrate and the light guide plate side is formed to be white.

  FIG. 4 is a cross-sectional view of the double-sided tape 16 according to the first embodiment. FIG. 4 shows a cross section of the double-sided tape 16 along the width direction. For example, as shown in FIG. 4, the double-sided tape 16 has a base material 16a, an adhesive layer 16b disposed on the light guide plate 11 side, and an adhesive layer 16c disposed on the optical sheet 13 side. And in this embodiment, the base material 16a and the two adhesion layers 16b and 16c are each formed so that it may become white. For example, the base material 16a is formed by mixing a white paint into a PET (polyethylene terephthalate) resin. The two adhesive layers 16b and 16c are formed by mixing a white paint into a transparent adhesive.

  Here, if a double-sided tape using a transparent adhesive is used as the double-sided tape 16 described above, light is transmitted to the adhesive of the double-sided tape, and light is lost at the edge of the light guide plate. As a result, luminance uniformity in the planar lighting device may be reduced. Specifically, in the light guide plate 11, the loss of light from the fixed region 11h to which the double-sided tape 16 is attached increases, and as a result, the luminance uniformity (luminance symmetry) in the emission region 11a decreases. possible.

  In contrast, in this embodiment, at least the base material 16a of the double-sided tape 16 and the color of the adhesive layer 16b on the light guide plate 11 side are formed so as to reflect light. Therefore, the light that has entered the light guide plate 11 by the light source 12 and reached the double-sided tape 16 can be reflected into the light guide plate 11. Thereby, it becomes possible to suppress the loss of light from the fixed region 11h to which the double-sided tape 16 is attached, and the luminance uniformity in the emission region 11a can be improved.

  Therefore, according to the present embodiment, it is possible to provide the planar lighting device 10 having excellent luminance uniformity.

  In addition, for example, when the optical sheet 13 is fixed to both sides of the light guide plate 11, the positions of both ends of the optical sheet 13 are fixed, so when the optical sheet 13 expands due to environmental changes such as temperature, The optical sheet 13 may be wrinkled.

  On the other hand, in this embodiment, the optical sheet 13 is fixed only to the fixed region 11h provided on the fourth end surface 11g side among the plurality of end surfaces. Therefore, only one side of the optical sheet 13 is fixed, and even when the optical sheet 13 expands due to an environmental change such as temperature, the occurrence of wrinkles in the optical sheet 13 can be suppressed. Thereby, the reliability of the planar illumination device 10 can be improved. That is, the reliability can be enhanced without reducing the uniformity of luminance (luminance symmetry) of the planar illumination device 10.

  In addition, in this embodiment, about the example in case the base material 16a, the adhesion layer 16b arrange | positioned at the light-guide plate 11 side, and the adhesion layer 16c arrange | positioned at the optical sheet 13 side are each formed so that it may become white. Although described, the embodiment is not limited to this. For example, as long as the base material 16a and each adhesion layer are the colors which reflect light, colors other than white may be sufficient. For example, the color of the base material 16a and each adhesive layer may be black, gray, amber, or the like.

  For example, the base material 16a and each adhesion layer may be formed so that it may become the same color as the color of the light which the light source 12 emits. For example, when the light source 12 emits white light as in this embodiment, the base material 16a and each adhesive layer are formed to be white. For example, when the light source 12 emits red light, the base material 16a and each adhesive layer are formed to be red.

  Moreover, although this embodiment demonstrated the example in case both the adhesion layer 16b arrange | positioned at the light-guide plate 11 side and the adhesion layer 16c arrange | positioned at the optical sheet 13 side were demonstrated, it arrange | positions at the optical sheet 13 side. The applied adhesive layer 16c may be a color other than white. For example, the adhesive layer 16c disposed on the optical sheet 13 side may be transparent, black, gray, amber, or the like.

(Second Embodiment)
In the first embodiment described above, an example in which the planar illumination device 10 includes one optical sheet 13 has been described, but the embodiment is not limited thereto. For example, the planar illumination device may include a plurality of optical sheets. Below, the example in case a planar illuminating device is provided with a some optical sheet is demonstrated as 2nd Embodiment.

  In addition, the planar illuminating device which concerns on 2nd Embodiment is equipped with the structure similar to the planar illuminating device 10 shown in FIGS. 1-3 except a light-guide plate, an optical sheet, and a double-sided tape. Therefore, in the following, the planar illumination device according to the second embodiment will be described with a focus on the configuration of the light guide plate, the optical sheet, and the double-sided tape, and the configuration common to the planar illumination device 10 shown in FIGS. Detailed description of elements is omitted.

  FIG. 5 is a plan view of the planar illumination device according to the second embodiment. 6 is a cross-sectional view taken along the line CC shown in FIG. 5, and FIG. 7 is a cross-sectional view taken along the line DD shown in FIG.

  For example, as illustrated in FIGS. 5 to 6, the planar illumination device according to the second embodiment includes a light guide plate 21 and a plurality of optical sheets. Specifically, the planar illumination device according to the present embodiment includes a first optical sheet 23a, a second optical sheet 23b, and a third optical sheet 23c. Although not shown in FIGS. 5 to 6, the planar illumination device according to the present embodiment also includes the light source 12, the reflection sheet 14, and the frame 15 illustrated in FIG. 1.

  The light guide plate 21 has a main surface including a light emission region and a plurality of end surfaces. For example, the light guide plate 21 is a plate-like member formed in a substantially rectangular shape in plan view, and includes a first main surface 21b including a light emission region 21a and a second main surface 21b facing the first main surface 21b. Main surface 21c. In addition, the light guide plate 21 is substantially orthogonal to the first end surface 21d into which light is incident, the second end surface 21e facing the first end surface 21d, and the first end surface 21d, and is opposed to each other. A third end face 21f and a fourth end face 21g are provided. The light guide plate 21 is formed of a material that is transparent to light generated from the light source 12, and light incident from the first end surface 21d is emitted from the first main surface 21b. It is comprised so that it may radiate | emit from.

  The first optical sheet 23 a, the second optical sheet 23 b, and the third optical sheet 23 c are stacked on the first main surface 21 b of the light guide plate 21. Each optical sheet is a thin plate-like member formed of a resin or the like, and is stacked on the first main surface 21 b so as to cover the emission region 21 a of the light guide plate 21.

  Specifically, the first optical sheet 23a is disposed on the first main surface 21b of the light guide plate 21, the second optical sheet 23b is disposed on the first optical sheet 23a, and the third The optical sheet 23c is disposed on the second optical sheet 23b. Here, for example, the first optical sheet 23 a is a diffusion sheet that transmits light emitted from the emission region 21 a of the light guide plate 21 while diffusing. For example, the second optical sheet 23b and the third optical sheet 23c are prism sheets in which a plurality of linearly formed prisms are arranged in parallel.

  Under such a configuration, in the present embodiment, the first optical sheet 23a, the second optical sheet 23b, and the third optical sheet 23c are arranged on the edge portion on the first main surface 21b of the light guide plate 21. The double-sided tape 26 is used to fix the fixing area 21h. Here, the fixing region 21h to which each optical sheet is fixed is provided at the edge on the end surface side different from the first end surface 21d into which the light on the first main surface 21b is incident.

  For example, as illustrated in FIGS. 5 to 6, the first optical sheet 23 a, the second optical sheet 23 b, and the third optical sheet 23 c are fourth end surfaces 21 g that are end surfaces substantially orthogonal to the first end surface 21 d. A double-sided tape 26 is used for fixing to a fixing region 21 h provided at the side edge. Each optical sheet is fixed only to a fixing region 21h provided on the fourth end surface 21g side which is one end surface of the plurality of end surfaces of the light guide plate 21.

  Here, in the present embodiment, the light guide plate 21 is formed in a stepped shape in which the edge portion provided with the fixed region 21 h on the first main surface 21 b has a step in the thickness direction of the light guide plate 21. Yes. The first optical sheet 23a, the second optical sheet 23b, and the third optical sheet 23c are individually provided on each step of the edge portion of the light guide plate 21 in which a part of each optical sheet is formed. It is fixed using a double-sided tape 26. Note that the stepped edge provided in the light guide plate 21 is formed to have the same number of steps as the number of optical sheets.

  FIG. 8 is a perspective view showing fixed portions of the light guide plate 21, the first optical sheet 23a, the second optical sheet 23b, and the third optical sheet 23c according to the second embodiment. For example, as shown in FIG. 8, in the present embodiment, in the light guide plate 21, the edge on the fourth end surface 21 g side where the fixed region 21 h on the first main surface 21 b is provided is the thickness of the light guide plate 21. The first step surface 21i, the second step surface 21j, and the third step surface 21k are stepped and have a step in the vertical direction.

  Here, the first step surface 21i is provided on a side near the first end surface 21d at the edge of the light guide plate 21 and at a position lower than the second step surface 21j by the step d1. The third step surface 21k is provided on the side near the second end surface 21e at the edge of the light guide plate 21 and at a position higher than the second step surface 21j by the step d2. The second step surface 21j is located between the first step surface 21i and the third step surface 21k at the edge of the light guide plate 21, and the first step surface 21b of the light guide plate 21 They are provided on the same plane.

  On the other hand, at the end of the first optical sheet 23a, a portion of the light guide plate 21 that faces the first step surface 21i protrudes, and a portion that faces the second step surface 21j and the third step surface 21k is cut away. It is formed so as to have a shape. The end of the second optical sheet 23b protrudes from the portion of the light guide plate 21 facing the first step surface 21i and the second step surface 21j, and the portion facing the third step surface 21k is cut away. It is formed so as to have a shape.

  The protruding portion of the end portion of the first optical sheet 23 a is fixed to the first step surface 21 i of the light guide plate 21 using a double-sided tape 26. Further, the protruding portion of the end portion of the second optical sheet 23b is attached to the second step surface 21j of the light guide plate 21 through the notched portion of the end portion of the first optical sheet 23a. It is fixed using. In addition, the end portion of the third optical sheet 23c is connected to the third end portion of the light guide plate 21 through the notched portions of the end portion of the first optical sheet 23a and the end portion of the second optical sheet 23b. The double-sided tape 26 is fixed to the step surface 21k.

  Here, the double-sided tape 26 is attached to the light guide plate 21 while being bent in accordance with the shape of the edge portion formed in a stepped shape of the light guide plate 21. The level difference d1 between the first step surface 21i and the second step surface 21j is set to a height lower than the thickness of the double-sided tape 26 in consideration of the elasticity of the adhesive layer in the double-sided tape 26. The step d2 between the second step surface 21j and the third step surface 21k is the same height as the thickness of the second optical sheet 23b.

  And in this embodiment, the double-sided tape 26 has the strip | belt-shaped base material and the adhesion layer formed on both surfaces of the said base material similarly to the double-sided tape 16 shown in FIG. The adhesive layer on the side of the material and the light guide plate is formed to have a color that reflects light. For example, the base material and the pressure-sensitive adhesive layer on the light guide plate side are formed to have the same color as the color emitted by the light source 12. More specifically, for example, the color of the adhesive layer on the substrate and the light guide plate side is formed to be white.

  Therefore, similarly to the first embodiment, the light that has entered the light guide plate 21 by the light source 12 and reached the double-sided tape 26 can be reflected into the light guide plate 21. Thereby, it becomes possible to suppress the loss of light from the fixed region 21h to which the double-sided tape 26 is attached, and the luminance uniformity in the emission region 21a can be improved.

  Therefore, according to the present embodiment, it is possible to provide a planar lighting device that is excellent in luminance uniformity, as in the first embodiment.

  In the present embodiment, the first optical sheet 23a, the second optical sheet 23b, and the third optical sheet 23c are provided only in the fixed region 21h provided on the fourth end surface 21g side of the plurality of end surfaces. Fixed. Therefore, according to the present embodiment, as in the first embodiment, only one side of each optical sheet is fixed, and even when each optical sheet expands due to environmental changes such as temperature, Generation of wrinkles in the optical sheet can be suppressed. Thereby, the reliability of a planar illuminating device can be improved. That is, the reliability can be improved without reducing the uniformity of luminance (luminance symmetry) of the planar illumination device.

  In addition, although this embodiment demonstrated the example in the case of fixing a some optical sheet using the single double-sided tape 26, embodiment is not restricted to this. For example, each optical sheet may be fixed using a separate double-sided tape.

  Moreover, although this embodiment demonstrated the example in case the planar illuminating device is provided with three optical sheets, embodiment is not restricted to this. For example, two or four or more optical sheets may be provided in the planar illumination device. In any case, when a plurality of optical sheets are used, the stepped edges provided on the light guide plate 21 are formed so as to have the same number of steps as the number of optical sheets, as in the example described above. Is done. At this time, the step surface to which the optical sheet disposed at the position closest to the light guide plate 21 is fixed is provided at a position lower than the first main surface 21b of the light guide plate 21, and the other optical sheets are fixed. The stepped surface is provided so as to increase stepwise from the height of the first main surface 21 b of the light guide plate 21.

  The planar illumination device according to the first and second embodiments has been described above. Here, the effect obtained by the above-described embodiment will be described more specifically based on the measurement result of the luminance of the light guide plate.

  FIG. 9 is a diagram showing the effects of the first and second embodiments. In addition, FIG. 9 shows the measurement results of the respective luminance values when the optical sheet is fixed with a double-sided tape using a transparent adhesive and when the optical sheet is fixed with a double-sided tape using a white adhesive. An example in which three optical sheets are used as in the second embodiment is shown as an example. Note that a white member is used as the base material.

  Specifically, (a) of FIG. 9 shows a state of the emission region of the light guide plate when the optical sheet is fixed with a double-sided tape using a transparent adhesive, and (b) of FIG. The mode of the emission area | region of the light-guide plate at the time of fixing an optical sheet with the double-sided tape using a white adhesive is shown. Here, nine white circles shown in (a) and (b) of FIG. 9 indicate luminance measurement points, respectively. The right side of each light guide plate is the side on which the double-sided tape is disposed.

Moreover, (c) of FIG. 9 has shown the measurement result of the brightness | luminance (cd / mm < ² >) in each measurement point of the light-guide plate shown to (a) of FIG. 9, (d) of FIG. The measurement result of the brightness | luminance (cd / mm < ² >) in each measurement point of the light-guide plate shown to (b) of (b) is shown. Moreover, (e) of FIG. 9 shows the result of comparing the measurement results at the three measurement points on the side close to the double-sided tape among the measurement results shown in (c) and (d) of FIG. 9 for each measurement point. ing. Note that “Cnt” shown in (c) and (d) of FIG. 9 indicates the luminance at the measurement point located at the center of the emission region of the light guide plate. “Avg” represents an average value of luminance at nine measurement points. “Unif” indicates a value obtained by dividing the minimum value of the luminance at the nine measurement points by the maximum value as a value indicating the uniformity of the luminance.

  Here, as described in the above-described embodiment, when the optical sheet is fixed with a double-sided tape using a white adhesive, compared to the case where the optical sheet is fixed with a double-sided tape using a transparent adhesive. Thus, the loss of light from the fixed area to which the double-sided tape is attached is suppressed.

  As a result, for example, as shown in FIGS. 9A and 9B, when the optical sheet is fixed with a double-sided tape using a white pressure-sensitive adhesive, the double-sided tape using a transparent pressure-sensitive adhesive is optical. Compared with the case where the sheet is fixed, in the emission region of the light guide plate, the darkened portion on the side where the double-sided tape is disposed can be reduced. That is, it is possible to improve the left / right symmetry of the luminance in the exit region of the light guide plate.

  For example, as shown in “Avg” in FIGS. 9C and 9D, when the optical sheet is fixed with a double-sided tape using a white adhesive, both sides using a transparent adhesive are used. Compared with the case where the optical sheet is fixed with the tape, the average value of the luminance at the nine measurement points is increased. That is, according to the above-described embodiment, the luminance of the entire light exit surface of the light guide plate can be increased.

  For example, as shown in “Unf” of FIGS. 9C and 9D, when the optical sheet is fixed with a double-sided tape using a white adhesive, both sides using a transparent adhesive are used. Compared with the case where the optical sheet is fixed with a tape, the uniformity of luminance is increased. That is, according to the above-described embodiment, it is possible to improve the uniformity of luminance on the exit surface of the light guide plate.

  Therefore, according to the above-described embodiment, it is possible to provide a planar illumination device having excellent optical characteristics by fixing an optical sheet to a light guide plate using a double-sided tape that reflects light. it can.

  In the above-described embodiment, an example has been described in which the optical sheet is fixed to the edge portion on the fourth end surface side which is an end surface substantially orthogonal to the first end surface where light is incident. The embodiment is not limited to this. For example, the optical sheet may be fixed to an edge portion on the third end surface side that is a surface substantially orthogonal to the first end surface in the same manner as the fourth end surface, or the second facing the first end surface. It may be fixed to the edge on the end face side.

  Moreover, although embodiment mentioned above demonstrated the example in case an optical sheet was fixed only to the fixed area | region provided in one end surface side of the some end surface which a light-guide plate has, embodiment is to this Not limited. For example, if the change in the size of the optical sheet is small, such as when the planar lighting device is used in a place where there is little environmental change such as temperature, double-sided tape is attached to both ends of the light guide plate. It may be fixed using.

  As mentioned above, although embodiment of the planar illuminating device which concerns on this application was described, this invention is not limited by the said embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

DESCRIPTION OF SYMBOLS 10 Planar illuminating device 11 Light guide plate 12 Light source 13 Optical sheet 16 Double-sided tape

Claims (7)

A light guide plate having a main surface including a light emission region, and a plurality of end surfaces;
A light source disposed on the first end face side of the light guide plate and receiving light from the first end face;
Are arranged stacked on the principal surface of the light guide plate, which is fixed using a double-sided tape to a fixed area provided in the edges of the different that the end surface side to the first end surface on the main surface A plurality of optical sheets, and
The double-sided tape has a belt-like base material and an adhesive layer formed on both surfaces of the base material, and at least the base material and the light guide plate-side adhesive layer reflect the light; so as to be formed,
The light guide plate is formed in a stepped shape having a step in the thickness direction of the light guide plate, the edge portion where the fixed region on the main surface is provided,
In the plurality of optical sheets, a part of each optical sheet is individually fixed to each step of the edge portion formed in a step shape of the light guide plate using the double-sided tape.
Planar lighting device. The optical sheet is fixed only to a fixing region provided on one end face side of the plurality of end faces.
The planar illumination device according to claim 1. The end surface different from the first end surface is an end surface substantially orthogonal to the first end surface.
The planar illumination device according to claim 1 or 2. The base material and the pressure-sensitive adhesive layer on the light guide plate side are formed to be white,
The planar illumination device according to any one of claims 1 to 3 . The base material and the pressure-sensitive adhesive layer on the light guide plate side are formed to have the same color as the color of light emitted from the light source,
The planar illuminating device as described in any one of Claims 1-4 . A light guide plate having a main surface including a light emission region, and a plurality of end surfaces;
A light source disposed on the first end face side of the light guide plate and receiving light from the first end face;
Arranged on the main surface of the light guide plate in a stacked manner, and fixed using a double-sided tape only to a fixed region provided on an edge of one end surface different from the first end surface on the main surface. With multiple optical sheets
With
The light guide plate is formed in a stepped shape having a step in the thickness direction of the light guide plate, the edge portion where the fixed region on the main surface is provided,
In the plurality of optical sheets, a part of each optical sheet is individually fixed to each step of the edge portion formed in a step shape of the light guide plate using the double-sided tape.
Planar lighting device. The belt-like base material of the double-sided tape is formed to be white,
The planar illumination device according to claim 6.