JP5792031B2 - Light guide plate, surface light source device, and transmissive image display device - Google Patents

Description

  The present invention relates to a light guide plate, a surface light source device, and a transmissive image display device.

  A transmissive image display device such as a liquid crystal display device generally has a surface light source device as a backlight. The edge light type surface light source device includes a light guide plate (translucent resin sheet) and a light source that supplies light to an end surface of the light guide plate.

  2. Description of the Related Art As a light guide plate of an edge light type surface light source device, one having an uneven shape on an end surface which is a light incident surface is known (see Patent Document 1). Thus, it is expected that the light from the point light source (LED light source) is dispersed in the thickness direction of the light guide plate by providing the uneven shape on the end face.

JP 2008-10291 A

  However, in the light guide plate applied to the conventional surface light source device, the light incident from the end face cannot be made sufficiently uniform, and the brightness between adjacent light sources is insufficient near the end of the light guide plate. There is a problem that an area to be generated occurs. For this reason, it has been difficult to reduce the number of installed light sources.

  In addition, when there is a region where the brightness is insufficient at the peripheral portion of the light guide plate, the region where the brightness is insufficient is hidden by a frame of the transmissive image display device so as not to be seen from the front side. There is a need. When the frame becomes large, there is a problem that the image display device looks bad.

  Therefore, an object of the present invention is to provide a light guide plate, a surface light source device, and a transmissive image display device that can sufficiently disperse light incident from an end face and reduce a region where brightness is insufficient. .

The present invention provides a light guide having an end surface that is an incident surface on which light is incident, a light exit surface that is formed in a direction intersecting with the end surface and that emits light incident from the end surface, and a back surface that faces the light exit surface. In the optical plate, the thickness direction is the first direction, the longitudinal direction of the end face is the second direction, the direction orthogonal to the first direction and the second direction is the third direction, and the end face has the first direction A plurality of convex portions are formed extending in the direction and arranged side by side in the second direction, and the outer tip in the third direction of the convex portions intersects the inclined surfaces of the convex portions. The groove formed by the inclined surfaces of the adjacent convex portions is arranged at a position corresponding to the point light source that emits light, and the third of the adjacent convex portions is formed. The interval in the second direction between the outer bending points B in the direction is P, and the third direction of the adjacent convex portions When the distance in the second direction of the bending point C between the definitive inside is T, the angle θ which the pair of inclined surfaces of the convex portions adjacent intersect provides a light guide plate satisfies the following formula (1) .

However, in the formula (1),

In the light guide plate according to the present invention, a plurality of convex portions are provided on the end surface, and the plurality of convex portions have a pair of inclined surfaces that intersect at an angle θ that satisfies the above-described formula (1). As a result, the light incident from the end face is sufficiently dispersed in the second direction, which is the longitudinal direction of the end face, so that the positions where the light emitted from the light sources adjacent in the second direction intersect each other are Can be approached. As a result, it is possible to reduce the area where the brightness is insufficient at the end of the light exit surface, and to reduce the number of light sources installed. Moreover, the frame part for concealing the area | region where brightness is insufficient can be narrowed.

Moreover, satisfying the following formula (3) is mentioned as a preferable range of the angle θ.

However, in the formula (3),

Moreover, as a more preferable range of the angle θ, the following formula (5) is satisfied.

However, in the formula (5),

  Moreover, this invention provides a surface light source device provided with said light guide plate and the light source which supplies light to the end surface of the said light guide plate. Since this surface light source device includes the light guide plate according to the present invention, the position where the light emitted from the light sources adjacent to each other in the second direction crosses each other can be brought close to the end surface. As a result, it is possible to reduce the area where the brightness is insufficient at the end of the light exit surface, and to reduce the number of light sources installed. Moreover, the frame part for concealing the area | region where brightness is insufficient can be narrowed.

  In addition, the present invention includes a light transmission plate that includes the light guide plate described above, a light source that supplies light to an end surface of the light guide plate, and a transmissive image display unit that is illuminated by light emitted from the light emission surface of the light guide plate. A type image display apparatus is provided. Since the transmissive image display device includes the light guide plate according to the present invention, the position where the light emitted from the light sources adjacent in the second direction intersects each other can be brought close to the end surface. As a result, the area where the brightness is insufficient at the end of the light exit surface can be reduced, and the number of installed light sources can be reduced. Moreover, the frame part for concealing the area | region where brightness is insufficient can be narrowed.

  According to the present invention, a light guide plate capable of sufficiently dispersing light incident from an end face and reducing a region where brightness is insufficient, a surface light source device including the light guide plate, and a transmissive image display device are provided. can do. According to the present invention, since the light incident from the end face can be dispersed in the longitudinal direction of the end face, the frame portion for concealing the region where the brightness of the peripheral portion of the light exit surface is insufficient can be narrowed.

It is sectional drawing which shows one Embodiment of a transmissive image display apparatus provided with a surface light source device. It is a top view of the side in which the reflective dot of the light-guide plate is formed. It is a front view which expands and shows the positional relationship of the LED light source arrange | positioned facing the edge part and this edge part of a light-guide plate. It is a graph which shows an example of the light emission distribution of a LED light source. It is a front view which shows one Embodiment of a transmissive image display apparatus provided with a light-guide plate. It is a front view which expands and shows the convex-shaped part provided in the edge part of a light-guide plate. FIG. 7 is a chart showing the difference in uniformity according to the angle θ at which the inclined surfaces intersect and the length ratio {T / (PT)} in the second direction of the flat portion formed between the convex portions. is there. It is a graph which shows the area | region where the calculation result of the uniformity was favorable. It is a figure showing the light ray image after incidence of the light which entered from the edge part about the light guide plate concerning a comparative example. It is a figure showing the light ray image after incidence of the light which entered from the edge part about the light guide plate concerning an example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent element, and the overlapping description is abbreviate | omitted. The dimensional ratios in the drawings do not necessarily match those described.

  FIG. 1 is a cross-sectional view showing a transmissive image display device including an embodiment of a light guide plate according to the present invention. The transmissive image display device 100 shown in FIG. 1 is mainly composed of a surface light source device 20 and a transmissive image display unit 30. The surface light source device 20 is an edge light type surface light source device that includes a light guide plate 1 and a light source 3 that is provided on a side of the light guide plate 1 and supplies light to the light guide plate 1.

  As shown in FIG. 1, the transmissive image display unit 30 is disposed to face the light guide plate 1 on the light exit surface S1 side of the light guide plate 1. The transmissive image display unit 30 is, for example, a liquid crystal display unit having a liquid crystal cell.

  Further, the transmissive image display device 100 may have a configuration in which various films 51 are disposed between the transmissive image display unit 30 and the light guide plate 1. Examples of the various films 51 include a diffusion film, a prism film, and a brightness enhancement film.

The light guide plate 1 has a substantially rectangular parallelepiped shape, and an exit surface S1, the opposite side of the back S2 of the exit surface S1, and four end surfaces (side _surfaces) S3 1 to S3 ₄ intersecting the emitting surface S1 and the back surface S2 Have. In the present embodiment, the four end surfaces S3 _{1 to} S3 ₄ are substantially orthogonal to the emission surface S1 and the back surface S2.

  The light guide plate 1 is made of a translucent resin. The translucent resin is a resin that transmits light. The refractive index of the translucent resin is usually 1.49 to 1.59. As the translucent resin used for the light guide plate 1, methacrylic resin is mainly used. As the translucent resin used for the light guide plate 1, other resins may be used, or styrene resins may be used. As the translucent resin, acrylic resin, styrene resin, carbonate resin, cyclic olefin resin, MS resin (acrylic and styrene copolymer), and the like can be used. When the light guide plate 1 is applied to a liquid crystal display device (transmission type image display device 1), a light diffusing agent, an ultraviolet absorber, a heat stabilizer, a photopolymerization stabilizer, or the like may be added to the light guide plate.

  The light guide plate 1 is preferably a poly (meth) acrylic acid alkyl resin sheet, a polystyrene sheet, or a polycarbonate resin sheet, and among these, a polymethyl methacrylate resin sheet (PMMA resin sheet) is preferable. The translucent resin sheet may contain diffusing particles. The surface (exit surface S1) opposite to the surface (back surface S2) on which the reflective dots 12 of the translucent resin sheet are formed may be a flat surface as in the present embodiment, but has an uneven shape. You may do it. In addition, it is preferable that the thickness of a translucent resin sheet is 1.0 mm or more and 4.5 mm or less.

  The back surface S2 of the light guide plate 1 is subjected to reflection processing (for example, silk printing) for irregularly reflecting light. As a printing method performed as reflection processing, ink jet printing may be performed in addition to silk printing. Alternatively, as a method of reflection processing, dot-shaped irregularities may be imparted by laser irradiation instead of printing, or dot-shaped irregularities are imparted by injection molding using a shape-shaped mold to which the shape is imparted. Or you may give a dot-shaped unevenness | corrugation by extrusion molding using the shape roll by which the shape was engraved. In printing dot patterns, ink having diffusing particles that diffuse light is used. Further, the gradation change is given so that the diameter of each dot (printing dot) constituting the dot pattern increases as the distance from the light source side increases. The maximum thickness of each reflective dot 12 is preferably 20 μm or less, more preferably 15 μm or less.

  As shown in FIG. 2, the plurality of reflective dots 12 are arranged on the back surface S2 so as to be separated from each other. FIG. 2 is a plan view when the light guide plate is viewed from the back side. In FIG. 2, the light source 3 is also shown for convenience of explanation. In FIG. 2, the reflective dots 12 are spaced apart from each other. The number and arrangement pattern of the reflective dots 12 are adjusted so that uniform planar light is efficiently emitted from the emission surface S1.

As shown in FIGS. 1 and 2, the light source 3 is disposed on the side of a pair of end faces S3 ₁ and S3 ₂ facing each other. The light source 3 is a point light source such as an LED. As shown in FIG. 2, a plurality of point light sources are arranged along two sides of the light guide plate 1 that are opposed to each other among four sides that form, for example, a rectangle.

In the following description, the thickness direction of the light guide plate 1 is referred to as the Z direction (first direction), and the longitudinal direction of the end faces S3 ₁ and S3 _{2 on} which the light from the light source 3 is incident is referred to as the X direction (second direction). The direction orthogonal to the Z direction and the X direction is referred to as the Y direction (third direction).

The plurality of light sources 3 are discretely arranged along the longitudinal direction (second direction) X of the end surfaces S3 ₁ and S3 ₂ that are incident surfaces. FIG. 3 is an enlarged front view showing the positional relationship between the end portion of the light guide plate and the LED light source disposed facing the end portion. As shown in FIG. 3, the arrangement | positioning space | interval L of the light source 3 is about 5 mm-150 mm, and the space | interval L is about 8 mm in this embodiment. The distance D between the light source 3 and the end faces S3 ₁ and S3 ₂ is about 0.5 mm to 5 mm.

Further, the distance y shown in FIG. 3 is the Y direction (third direction) of the point Pc where the emission light distributions of the adjacent light sources 3 overlap in calculation when the end faces S3 ₁ and S3 ₂ are not shaped. Indicates distance. A distance half of the distance y is expressed as y / 2.

  The light source 3 may be a white LED, and a plurality of LEDs may be arranged in one place to constitute one light source unit. For example, as one light source unit, LEDs of three colors different in red, green, and blue may be arranged close to each other. And the light source unit which has several LED is discretely arrange | positioned according to the arrangement | positioning direction mentioned above. In such a case, it is preferable that different LEDs are arranged as close as possible.

  As the LED light source, those having various light output distributions can be used. Specific examples of the LED light source type include a Lambertian type, a shell type, and a side emission type.

  FIG. 4 is a graph showing an example of the light output distribution of the LED light source. The relationship between the emission angle φ and the emission light intensity is shown with the emission light intensity in the normal direction of the LED light source 3 (emission angle φ = 0 °) being 1.0 (reference). In the LED light source 3 having the light emission distribution shown in FIG. 4, the full width at half maximum is about 60 °. In addition, you may use the LED light source which has another light emission distribution.

  As the light source 3 of the present embodiment, for example, a Lambertian LED light source with a 120-degree light distribution having a width W (length in the X direction) of 3.5 mm is applicable.

FIG. 5 is a front view showing the image display apparatus according to the embodiment of the present invention. In the transmissive image display device 100, a frame 101 that covers the peripheral edge of the transmissive image display unit 30 is formed. Accordingly, the peripheral edge (end face) of the light guide plate 1 indicated by a broken line in FIG. 5 is not visible from the front side. In addition, the size of the frame is set in the vicinity of the end faces S3 ₁ and S3 ₂ where the light source 3 of the light guide plate 1 is disposed so that a region with insufficient brightness cannot be visually recognized from the front side.

  As shown in FIG. 5, the light guide plate 1 has a rectangular shape. The size of the light guide plate 1 in a plan view is selected so as to match the target screen size of the transmissive image display device 100, but is usually 250 mm × 440 mm or more, preferably 1020 mm × 1800 mm or less. The planar view shape of the light guide plate 30 is not limited to a rectangle but may be a square, but in the following, it will be described as a rectangle unless otherwise specified.

  In addition, the rectangle of 250 mm × 440 mm or more means a rectangle having one side of 250 mm or more and the other side of 440 mm or more. Further, the rectangle of 1020 mm × 1800 mm or less means a rectangle having one side of 1020 mm or less and the other side of 1800 mm or less.

Here, as shown in FIG. 6, a plurality of convex portions 41 projecting outward in the Y direction are formed on the end faces S3 ₁ and S3 ₂ . The convex portion 41 extends in the thickness direction (Z direction) of the light guide plate 1, and the plurality of convex portions 41 are arranged side by side in the longitudinal direction (X direction) of the end faces S3 ₁ and S3 ₂ . The plurality of convex portions 41 are arranged in parallel.

  A pair of inclined surfaces 43 and 43 of the convex portions 41 and 41 adjacent in the Y direction form a groove 44 (concave portion). The bottom of the groove 44 (between the ends C inside the Y direction of the pair of inclined surfaces 43) forms a surface parallel to the X direction and the Z direction (hereinafter referred to as a flat surface 45). Moreover, the front-end | tip (outer edge part in a Y direction) of the convex-shaped part 41 cross | intersects the inclined surfaces 43 and 43, and forms the vertex B (outer bending point B in a 3rd direction).

The angle θ at which the inclined surfaces 43 intersect at the bottom of the groove 44 satisfies the following formula (1). Note that the interval in the X direction between the outer bending points B (vertices) in the Y direction of adjacent convex portions 41 is P. The distance in the X direction between the inner bending points C in the Y direction of adjacent convex portions 41 is defined as T. The bending point C is an intersection of the bottom surface 44 of the groove 44 and the inclined surface 43. The distance T is the length between the end portions (C) in the X direction of the bottom surface 44 of the groove 44.

However, in Formula (1),

A preferable range of the angle θ at which the pair of inclined surfaces 43 and 43 intersect each other is to satisfy the following formula (3).

However, in the formula (3),

A more preferable range of the angle θ at which the pair of inclined surfaces 43 and 43 intersect each other is to satisfy the following formula (5).

However, in the formula (5),

  Next, a method for forming the light guide plate 1 will be described. The light guide plate 1 can be formed by methods such as extrusion molding, cast molding, and injection molding. The thickness t of the light guide plate 1 is not particularly limited, but is preferably, for example, 1.0 mm to 10.0 mm, more preferably 1.5 mm to 8.0 mm, and 2.0 mm to 4.0 mm is particularly preferable.

The uneven shapes (convex portions 41) of the end faces S3 ₁ and S3 ₂ of the light guide plate 1 can be formed by cutting, laser processing, injection molding, or the like. In the cutting process, the light guide plate 1 is cut using a cutting tool to form grooves 44 in the end faces S3 ₁ and S3 ₂ of the light guide plate 1 to form the convex portions 41. In the laser processing, convex portions 41 are formed on the end surfaces S3 ₁ and S3 ₂ of the light guide plate 1 using laser light. In the case of the injection molding method, it is preferable that an opposite mold having a shape corresponding to the convex portion 41 is provided on the inner wall of the injection mold.

  If the interval (pitch) in the X direction of the plurality of convex portions 41 is too small, there is a concern about a decrease in processing accuracy, and if it is too large, the region where the brightness is insufficient in the peripheral portion of the light guide plate 1 with the uneven shape. Therefore, when the light guide plate 1 is incorporated in the liquid crystal display device 100, a frame portion for concealing the peripheral portion of the light guide plate 1 so as not to be seen from the liquid crystal display screen becomes large. The pitch of the plurality of convex portions 41 is preferably 0.03 mm to 10 mm.

According to such a light guide plate 1 according to the present embodiment, light from a plurality of light sources 3 that are arranged to face the side surfaces S3 ₁ and S3 ₂ of the light guide plate 1 are incident from the side surfaces S3 ₁ and S3 _2. Planar light can be emitted from the emission surface S1 orthogonal to (intersect) the side surfaces S3 ₁ and S3 ₂ . The light incident from the side surfaces S3 ₁ and S3 _{2 of the} light guide plate 1 is refracted by the inclined surface 43 of the convex portion 41 and spread in the X direction. Thus the brightness at the edge of the light guide plate 1 (side S3 _1, S3 ₂ vicinity) can reduce the area to be insufficient. According to the light guide plate 1, it is possible to reduce a region where the brightness is insufficient between adjacent light sources, and thus it is possible to reduce the number of installed light sources 3.

Further, according to the transmission type image display part 30 and the transmission type image display apparatus 100 including the same according to the present embodiment, faces the side surface S3 _1, S3 ₂ as the incident surface of the light guide plate 1, the side surface S3 _1, comprising a plurality of light sources 3 which are discretely arranged in S3 ₂ in the longitudinal direction (X direction), the light from these light sources 3 is incident from the side _S3 1, S3 _2, perpendicular to the side surface _S3 1, S3 ₂ The planar light can be emitted from the outgoing surface S1. The light incident from the side surfaces S3 ₁ and S3 _{2 of the} light guide plate 1 is refracted by the inclined surface 43 of the convex portion 41 and spread in the X direction. Thereby, the area | region where brightness is insufficient in the edge part (incident surface vicinity) of the light-guide plate 1 can be reduced. Therefore, the frame part for concealing the region where the brightness is insufficient at the end of the light guide plate 1 so as not to be seen from the display screen can be reduced. The degree of freedom in designing the frame portion that is the peripheral portion of the display screen of the transmissive image display device 1 can be increased.

(Example)
Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.

First, a light guide plate having no convex portion formed on the end face was prepared, and the point light source 3 was disposed so as to face the end face. As shown in FIG. 3, as the point light sources 3, Lambertian LEDs with a width of 3.5 mm and 120-degree light distribution are arranged at intervals of 8 mm. And the position y where the light which injected into the light-guide plate cross | intersect was calculated from adjacent LED3,3. The specification and measurement conditions of the light guide plate according to the comparative example are shown below.
Light guide plate: Resin material PMMA (manufactured by Sumitomo Chemical Co., Ltd.)
Refractive index of air n ₁ 1.00
Refractive index n _{2 of} light guide plate 1.49
Light source width W 3.5mm
Distance L between light sources 8.0 mm
Length of light source in Y axis direction 2.0mm
Incident angle α ₁ 60.0 [deg]
Incident angle α ₂ 35.5 [deg]
Distance between light source and end face D 2 μm
Distance X direction of the light source and to the entrance point _{P i x 1} ≒ 0mm
Distance in the X direction from the incident point P _i to the intersection point P _{c of} light x ₂ = 2.25 mm
The distance y in the Y direction from the incident point P _i to the light intersection P _c = 3.15 mm
Point distance in the Y direction is half of the position of an intersection _{P c P C / 2} distance to y / 2 = 1.58 mm

Next, light receivers are set at the intersections P _C {y} and P _{c / 2} {y / 2} of the light calculated in the comparative example, and the illuminance distribution in these light receivers is calculated by the ray tracing software. did. For convenience of calculation, the calculation is performed for the case where only one LED light source 3 is present, and the illuminance distribution is assumed on the assumption that there are a plurality of LED light sources by superimposing the illuminance distribution according to the arrangement interval of the LED light sources 3 later. It was created. And the uniformity was calculated about the obtained illumination distribution.

As shown in FIG. 6, the ratio {T / () of the angle θ (vertical angle θ of the concave prism) between the inclined surfaces 43 of the convex portion 41 and the flat portion (the length of the bottom portion of the groove 44 in the X direction). P−T)} was calculated for a plurality of patterns. At this time, the interval P (prism width P) between the apexes B of the convex portion 41 was fixed to 400 μm. Specifically, angle θ [deg] (θ = 50, 60, 70, 80, 90, 100, 110 , 120, 130), flat portion ratio {T / (P−T)} × 100 [%] ( = 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100) The calculation was performed for 99 combinations of patterns. The flat portion ratio {T / (P−T)} is a ratio of the width between the flat portion 45 and the convex portion 41. T is the width (length in the X direction) of the flat portion 45 for one cycle. (PT) is the width (length in the X direction) of the convex portion 41 for one period.

(Search results)
FIG. 7 is a chart showing the difference in uniformity according to the angle θ at which the inclined surfaces intersect and the length ratio {T / (P−T)} of the flat surface 45 formed between the convex portions 41. It is. FIG. 7 illustrates a case where a light receiver is set at the point P _{c / 2} {y / 2}.

FIG. 8 is a chart showing a region where the calculation result of the uniformity of the illuminance distribution is good. Based on FIG. 7, a region where the calculation result of the uniformity was good was searched, and the range of FIG. 8 was selected. Specifically, a range in which the uniformity of illuminance is approximately 15.0 [%] or more was set as a range where the result was good. The ranges shown in FIG. 8 are as follows. In FIG. 8, the range indicated by the solid line L1 corresponds to the range indicated by the following formulas (1) and (2).

However, in the formula (1),

In FIG. 8, the range indicated by the alternate long and short dash line L2 corresponds to the range indicated by the following formulas (3) and (4).

However, in the formula (3),

In FIG. 8, the range indicated by the broken line L3 corresponds to the range indicated by the following equations (5) and (6).

However, in the formula (5),

(Ray image after incident)
FIG. 9A shows a light guide plate according to a comparative example, in which light receivers are set at the intersections PC {y} and Pc / 2 {y / 2}, and the illuminance distribution in these light receivers is determined by the ray tracing software. The calculated result is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm 2]. FIG. 9B represents the illuminance distribution. FIG. 9 illustrates the case of the convex portion 41 in which θ = 50 deg, {T / (P−T)} × 100 = 20%.

FIG. 10A shows a light guide plate according to the embodiment, in which light receivers are set at the intersections PC {y} and Pc / 2 {y / 2}, and the illuminance distribution in these light receivers is determined by the ray tracing software. The calculated result is represented, the horizontal axis represents the position in the X direction, and the vertical axis represents the illuminance [W / mm 2]. FIG. 10B represents the illuminance distribution. In FIG. 10, the convex portion 41 (θ = 100 deg, {T / (P−T)} × 100 = the uniformity at the point Pc / 2 {y / 2} is the highest (excellent in uniformity ). 10%) is illustrated. Referring to FIGS. 9A and 10A, the embodiment shown in FIG. 10A is superior in uniformity at the intersections Pc {y} and PC / 2 {y}. I understand.

  As mentioned above, although this invention was concretely demonstrated based on the embodiment, this invention is not limited to the said embodiment. For example, the point light sources may be arranged along one side surface extending in the long side direction of the optical sheet, or may be arranged along one side surface extending in the short side direction. Good. Moreover, the structure by which a point light source is arranged in two side surfaces extended in a long side direction may be sufficient, and the structure arranged in one side surface extended in a short side direction may be sufficient. In addition, it is preferable that the point light source is arrange | positioned in the position corresponding to the groove | channel 44 formed of the inclined surface 43 of the adjacent convex-shaped part 41. FIG.

The longitudinal direction of the side surface serving as the incident surface is the Y direction in the side surfaces S3 ₁ and S3 ₂ facing the X direction, and the X direction in the side surfaces S3 ₃ and S3 ₄ facing the Y direction (FIG. 2).

DESCRIPTION OF SYMBOLS 1 ... Light guide plate, 3 ... Light source, 12 ... Reflection dot, 20 ... Surface light source device, 30 ... Transmission-type image display part, 41 ... Convex part, 43 ... Inclined surface, 44 ... Groove (concave part, prism shape), 44 ... Flat surface (bottom part of groove), 51 ... Film, 100 ... Transmission type image display device (liquid crystal display device), 101 ... Frame, B ... Vertex (bending point on the outside in the third direction), C ... Bending point ( Bending point on the inner side in the third direction), S1... Exit surface, S2... Back surface, S3 _{1 to} S3 ₄ .

Claims (5)

In a light guide plate having an end surface that is an incident surface on which light is incident, a light exit surface that is formed in a direction intersecting with the end surface, and that emits light incident from the end surface, and a back surface that faces the light exit surface.
The thickness direction is the first direction, the longitudinal direction of the end face is the second direction, the first direction and the direction orthogonal to the second direction are the third direction,
The end surface is formed with a plurality of convex portions extending in the first direction and arranged in the second direction,
The outer front end portion in the third direction of the convex portion is an apex formed by intersecting inclined surfaces of the convex portion.
The groove formed by the inclined surfaces of the adjacent convex portions is disposed at a position corresponding to a light source that supplies light to the end surface,
The interval in the second direction between the bending points B that are the vertices on the outside in the third direction of the adjacent convex portions is P,
When the interval in the second direction between the inner bending points C in the third direction of the adjacent convex portions is T,
The angle θ at which the pair of inclined surfaces of the adjacent convex portions intersect each other satisfies the following formula (1).
Light guide plate.

However, in the formula (1),
The light guide plate according to claim 1, wherein the angle θ satisfies the following formula (3).

However, in the formula (3),
The light guide plate according to claim 1, wherein the angle θ satisfies the following formula (5).

However, in the formula (5),
The light guide plate according to any one of claims 1 to 3,
A light source for supplying light to the end face of the light guide plate,
A surface light source device. The light guide plate according to any one of claims 1 to 3,
A light source for supplying light to the end face of the light guide plate,
A transmissive image display unit illuminated by light emitted from the light exit surface of the light guide plate;
A transmissive image display device.