WO2012099123A1

WO2012099123A1 - Light guide plate, surface light source device, and transmissive image display device

Info

Publication number: WO2012099123A1
Application number: PCT/JP2012/050859
Authority: WO
Inventors: 寛史太田; 健太郎百田; 関口　泰広
Original assignee: 住友化学株式会社
Priority date: 2011-01-21
Filing date: 2012-01-17
Publication date: 2012-07-26
Also published as: TW201235718A; JP5930729B2; JP2013065539A

Abstract

Provided are a light guide plate capable of improving the brightness in the front direction, a surface light source device containing said light guide plate, and a transmissive image display device. A light guide plate (50) disposed on the rear side of a prism plate (40) of which one surface is arranged, in parallel, with a plurality of prism units (41) extending in one direction, the light guide plate being provided with: a main body (51) having a first and second surface (51a, 51b) facing one another and an incidence surface intersecting with the first and second surface; and a plurality of lens units (52) formed on the second surface. Each lens unit has an outer shape such that the ratio of the amount of light entering a predetermined region from a given point on the first surface relative to the entire amount of light emitted from the aforementioned given point is greater than 0.252%. The predetermined region has an angular range between 25° and 35° in relation to the normal line of the first surface and has an angular width of 10° around the normal line.

Description

Light guide plate, surface light source device, and transmissive image display device

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 is generally disposed on the back side of a transmissive image display unit such as a liquid crystal display panel. The transmissive image display device includes a surface light source device that supplies a backlight to the transmissive image display unit. As such a surface light source device, an edge light type surface light source device is known (see, for example, Patent Document 1).

The edge-light type surface light source device includes a light-transmitting light guide plate and a light source that is disposed on the side of the light guide plate and supplies light to the side surface of the light guide plate. White dots for reflecting light are provided on the back side of the light guide plate. In this configuration, the light output from the light source enters the light guide plate from the side surface of the light guide plate facing the light source. The light incident on the light guide plate propagates while totally reflecting inside the light guide plate. Since a plurality of white dots are formed on the back side of the light guide plate (see, for example, Patent Document 1), the light reflected by the white dots is emitted from the exit surface on the transmissive image display unit side of the light guide plate.

2. Description of the Related Art Conventionally, in a transmissive image display device, a light guide plate, a transmissive image display unit, A prism plate is arranged between the two. As such a prism plate, there is one in which a plurality of prism portions are arranged in parallel on the surface on the transmissive image display portion side.

JP 2005-38768 A

However, when the prism plate having the prism portion formed on the surface opposite to the light guide plate as described above is arranged with respect to the light guide plate having white dots, the luminance in the front direction cannot be sufficiently improved. There was a thing.

Therefore, an object of the present invention is to provide a light guide plate capable of improving luminance in the front direction, a surface light source device including the light guide plate, and a transmissive image display device.

The light guide plate according to the present invention is a prism plate having a plurality of prism portions formed on one side, each of the plurality of prism portions extending in one direction, and the plurality of prism portions extending from the prism portion. The light guide plate is provided on the back side opposite to the one side with respect to the prism plates arranged in parallel in a direction substantially orthogonal to the direction. The light guide plate intersects the first surface located on the prism portion side, the second surface located on the opposite side of the first surface, and the first and second surfaces, and light is incident thereon. An incident surface and a plurality of lens portions formed on the second surface and convex on the opposite side of the first surface. Each of the plurality of lens portions has an outer shape such that the ratio of the second light amount to the first light amount of the emitted light that is incident from the incident surface and emitted from the first surface is greater than 0.252%. The first light quantity is an amount per unit time of all emitted light emitted from one point of the first surface, and the second light quantity is emitted light emitted from the one point to a predetermined region. The predetermined area has an angle range with respect to the normal line of the first surface of 25 ° or more and 35 ° or less and ± 5 with respect to a direction substantially orthogonal to the extending direction of the prism portion. It has an angular width around the normal of °.

The surface light source device according to the present invention is a prism plate having a plurality of prism portions formed on one side, each of the plurality of prism portions extending in one direction, and the plurality of prism portions being prism portions. This is a surface light source device that supplies light to a surface opposite to one surface of a prism plate arranged in parallel in a direction substantially orthogonal to the extending direction. The surface light source device (1) (1a) intersects the first surface located on the prism portion side, the second surface located opposite to the first surface, and the first and second surfaces. A plate-like main body having an incident surface on which the incident light is incident; and (1b) a guide having a plurality of lens portions formed on the second surface and convex on the opposite side of the first surface. A light plate; and (2) a light source unit that is disposed on the side of the incident surface of the light guide plate and supplies light to the incident surface. Each of the plurality of lens portions has an outer shape such that the ratio of the second light amount to the first light amount of the emitted light that is incident from the incident surface and emitted from the first surface is greater than 0.252%. The first light quantity is an amount per unit time of all emitted light emitted from one point of the first surface, and the second light quantity is emitted light emitted from the one point to a predetermined region. The predetermined area has an angle range with respect to the normal line of the first surface of 25 ° or more and 35 ° or less and ± 5 with respect to a direction substantially orthogonal to the extending direction of the prism portion. It has an angular width around the normal of °.

Further, the transmissive image display device according to the present invention is (A) a prism plate having a plurality of prism portions formed on one side, and each of the plurality of prism portions extends in one direction, A prism plate in which a plurality of prism portions are arranged in parallel in a direction substantially orthogonal to the extending direction of the prism portion, and (B) a light guide plate provided on the back side opposite to one side with respect to the prism plate, (B1) A first surface located on the prism portion side, a second surface located on the opposite side of the first surface, and an incident surface that intersects the first and second surfaces and receives light. And (B2) a light guide plate having a plurality of lens portions formed on the second surface and convex on the opposite side of the first surface, and (C) a light guide plate A light source unit that supplies light to the incident surface, and (D) on one side of the prism plate. Vignetting and includes a transmission type image display unit that displays an image is illuminated by light emitted from the prism sheet, a. Each of the plurality of lens portions has an outer shape such that the ratio of the second light amount to the first light amount of the emitted light that is incident from the incident surface and emitted from the first surface is greater than 0.252%. The first light quantity is an amount per unit time of all emitted light emitted from one point of the first surface, and the second light quantity is emitted light emitted from the one point to a predetermined region. The predetermined area has an angle range with respect to the normal line of the first surface of 25 ° or more and 35 ° or less and ± 5 with respect to a direction substantially orthogonal to the extending direction of the prism portion. It has an angular width around the normal of °.

Hereinafter, the surface of the prism plate that faces the light guide plate (the surface opposite to the one surface) is referred to as the back surface.

In the light guide plate, the surface light source device, and the transmissive image display device configured as described above, the light incident from the incident surface of the light guide plate propagates while being totally reflected in the light guide plate. When the light propagating in the light guide plate enters the lens unit provided on the second surface, the light propagating in the light guide plate is reflected by the lens unit under a condition different from the total reflection condition. Therefore, the light reflected by the lens unit is emitted from the first surface of the main body unit. In this way, the light emitted from the first surface is formed in a shape satisfying the above-described conditions, so that each of the plurality of lens portions formed on the second surface is 25 ° to 35 °. It is easy to be emitted with an emission angle in the range. Since the light guide plate is provided on the back surface side of the prism plate, the light emitted from the light guide plate enters the prism plate from the back surface of the prism plate. The incident angle of the light to the prism plate is substantially equal to the outgoing angle of the light from the light guide plate. Therefore, the incident angle of the emitted light from the first surface to the prism plate tends to be in the range of 25 ° to 35 °. When the light incident at such an incident angle is emitted from the prism portion, more light is emitted in the front direction. As a result, the luminance in the front direction is improved. In the transmissive image display device according to the present invention, since the transmissive image display unit is provided on the prism plate, the transmissive image display unit is illuminated with light having higher luminance in the front direction. As a result, it is possible to improve the luminance of the image displayed on the transmissive image display unit.

According to the present invention, a light guide plate capable of improving luminance in the front direction, a surface light source device including the light guide plate, and a transmissive image display device can be provided.

FIG. 1 is a schematic diagram showing a schematic configuration of a transmissive image display device to which an embodiment of a light guide plate according to the present invention is applied. FIG. 2 is a plan view when the light guide plate shown in FIG. 1 is viewed from the back side. FIG. 3 is a diagram for explaining the shape of the lens unit, FIG. 3A is a diagram showing a setting state of a local coordinate system on the exit surface, and FIG. FIG. 3 is a drawing for explaining a method for defining an angle from the z-axis and the x-axis in the coordinate system shown in FIG. 3A, and FIG. 3C is a drawing for explaining a predetermined region. FIG. 4 is a diagram for explaining an example of the outer shape of the lens unit. FIG. 5 is a chart showing conditions for defining the outer shape of the lens portion. 6 is a partially enlarged view of the transmissive image display device shown in FIG. FIG. 7 is a schematic diagram illustrating an example of the configuration of a light guide plate in which a plurality of white dots are formed on the back surface. Figure 8 is a graph showing the results of measuring the intensity distribution of the emitted light with respect to emission angle theta _o. FIG. 9 is a schematic diagram showing a simulation model. FIG. 10 is a drawing showing the outer shape of the lens unit used in the simulation. FIG. 11 is a chart showing the relationship between the lens shape used in the simulation and the light quantity ratio. FIG. 12 is a chart showing the relationship between the lens shape used in the simulation and the light quantity ratio. Figure 12 is a table showing the k _a and aspect ratio [h _{a /} w _{_a]} and de determined lens radius of curvature r of the tip to the width w _a of the shape shown in FIG. 11. Figure 14 is a table showing the k _a and aspect ratio [h _{a /} w _{_a]} and de determined lens radius of curvature r of the tip to the width w _a of the shape shown in FIG. 12. Figure 15 is a table showing the bottom angle of the lens shape determined out with k _a and an aspect ratio shown in FIG. _{_{11 [h a / w a]}} . Figure 16 is a table showing the bottom angle of the lens shape determined out with k _a and aspect ratio [h _{a /} w _{_a]} shown in FIG. 12.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same reference numerals are given to the same elements, and duplicate descriptions are omitted. The dimensional ratios in the drawings do not necessarily match those described.

FIG. 1 is a schematic diagram showing a schematic configuration of a transmissive image display device to which an embodiment of a light guide plate according to the present invention is applied. In FIG. 1, the cross-sectional configuration of the transmissive image display device 10 is shown in an exploded manner. In FIG. 1, light is schematically shown as light rays. The transmissive image display device 10 can be suitably used as a display device for a mobile phone or various electronic devices, or a television device.

The transmissive image display device 10 includes a transmissive image display unit 20, a surface light source device 30 that outputs planar light to be supplied to the transmissive image display unit 20, a transmissive image display unit 20, and a surface light source device. 30 and a prism plate 40 disposed between them. Hereinafter, for convenience of explanation, as shown in FIG. 1, the direction in which the prism plate 40 and the transmissive image display unit 20 are arranged with respect to the surface light source device 30 is referred to as a Z direction or a front direction. Two directions orthogonal to the Z direction are referred to as an X direction and a Y direction. The X direction and the Y direction are orthogonal.

The transmissive image display unit 20 displays an image by being illuminated with planar light emitted from the light guide plate 50. An example of the transmissive image display unit 20 is a liquid crystal display panel as a polarizing plate bonding body in which linear

polarizing plates

22 and 23 are arranged on both surfaces of a liquid crystal cell 21. In this case, the transmissive image display device 10 is a liquid crystal display device (or a liquid crystal television). As the liquid crystal cell 21 and the

polarizing plates

22 and 23, those used in a transmissive image display device such as a conventional liquid crystal display device can be used. Examples of the liquid crystal cell 21 are a TFT type liquid crystal cell and an STN type liquid crystal cell.

The prism plate 40 is used to collect light emitted from the light guide plate 50 in the front direction. The prism plate 40 is an optical sheet in which a plurality of prism portions 41 are formed on a surface 40a that is one surface on the transmission image display unit 20 side. The plan view shape of the prism plate 40 is substantially rectangular.

The prism portion 41 extends in one direction (Y direction in FIG. 1). The plurality of prism portions 41 are arranged in parallel in the extending direction of the prism portion 41. The prism portion 41 has a triangular prism shape, and the cross-sectional shape orthogonal to the extending direction of the prism portion 41 is a right triangle whose apex angle α is substantially a right angle. The apex angle α may be an angle within the range of 80 ° to 100 °. The apex angle α is more preferably 80 ° or greater and 90 ° or less, and even more preferably 90 °. The cross-sectional shape of the prism portion 41 is preferably a right isosceles triangle. The shape of the top portion 41a of the prism portion 41 may be a curved shape that is caused by a manufacturing error or the like.

The prism plate 40 is made of a translucent material (or a transparent material). Examples of the refractive index of the translucent material are 1.46 to 1.62. Examples of the translucent material are a translucent resin material and a translucent glass material. Examples of the translucent resin material include polycarbonate resin (refractive index: 1.59), MS resin (methyl methacrylate-styrene copolymer resin) (refractive index: 1.56 to 1.59), polystyrene resin (refractive index). Rate: 1.59), AS resin (acrylonitrile-styrene copolymer resin) (refractive index: 1.56 to 1.59), acrylic ultraviolet curable resin (refractive index: 1.46 to 1.58), poly And methyl methacrylate (PMMA) (refractive index: 1.49). A diffusion agent or the like may be added to the prism plate 40 as long as the light collecting function of the prism plate 40 is not impaired. The back surface 40b of the prism plate 40 is usually a smooth surface. However, the back surface 40b may be a rough surface having a roughness that does not significantly impair the light collecting function of the prism plate 40. When the back surface 40b is the rough surface described above, for example, when another optical member is disposed between the prism plate 40 and the light guide plate 50, the optical member and the prism plate 40 can be prevented from sticking to each other. .

The thickness of the prism plate 40 may be the distance between the top 41a of the prism portion 41 and the substantially flat back surface 40b (surface opposite to the front surface 40a) of the prism plate 40. An example of the thickness of the prism plate 40 is 0.1 mm or more and 5 mm or less.

The surface light source device 30 is an edge light type backlight unit that supplies a backlight to the transmissive image display unit 20. The surface light source device 30 includes a light guide plate 50 and

light source units

60 and 60 disposed on the side surfaces 50a and 50b of the light guide plate 50 facing each other.

The

light source units

60 and 60 have a plurality of point light sources 61 arranged in a line (in FIG. 1, arranged in the Y direction). An example of the point light source 61 is a light emitting diode. The light source unit 60 may include a reflector as a reflection unit that reflects light on the side opposite to the light guide plate 50 in order to efficiently make light incident on the light guide plate 50. Here, the light source unit 60 including the plurality of point light sources 61 is illustrated, but the light source unit 60 may be a linear light source such as a fluorescent lamp.

The surface light source device 30 may include a reflecting unit 70 located on the opposite side of the transmissive image display unit 20 with respect to the light guide plate 50. The reflection unit 70 is for causing the light emitted from the light guide plate 50 to the reflection unit 70 side to enter the light guide plate 50 again. The reflection part 70 may be a sheet-like thing as FIG. 1 shows. The reflection unit 70 may be a bottom surface of the housing of the surface light source device 30 that accommodates the light guide plate 50 and that is mirror-finished.

The light guide plate 50 will be described with reference to FIGS. 1 and 2. FIG. 2 is a plan view when the light guide plate 50 shown in FIG. 1 is viewed from the back side. The light guide plate 50 may have a substantially rectangular shape in plan view.

The light guide plate 50 includes a plate-shaped main body 51 and a plurality of lens portions 52 formed on the main body 51. The main body 51 is made of a translucent material (or a transparent material). Examples of the refractive index of the translucent material are 1.46 to 1.62. Examples of the translucent material are a translucent resin material and a translucent glass material. Examples of the translucent resin material include polycarbonate resin (refractive index: 1.59), MS resin (methyl methacrylate-styrene copolymer resin) (refractive index: 1.56 to 1.59), polystyrene resin (refractive index). Rate: 1.59), AS resin (acrylonitrile-styrene copolymer resin) (refractive index: 1.56 to 1.59), acrylic ultraviolet curable resin (refractive index: 1.46 to 1.58), poly And methyl methacrylate (PMMA) (refractive index: 1.49). As the translucent resin material, PMMA is more preferable from the viewpoint of transparency.

As shown in FIG. 1, the main body 51 has an emission surface (first surface) 51a and a back surface (second surface) 51b that face each other in the thickness direction. The emission surface 51a and the back surface 51b are substantially flat. The main body 51 has four

side surfaces

51c, 51d, 51e, and 51f that intersect the emission surface 51a and the back surface 51b. In FIG. 1, two

side surfaces

51c and 51d that face each other in the X direction are shown. The side surface 51 c and the side surface 51 d are also the side surface 50 a and the side surface 50 b facing the light source unit 60. Of the four

side surfaces

51c, 51d, 51e, 51f of the main body 51, the remaining two

side surfaces

51e, 51f (see FIG. 3) face each other in the Y direction. FIG. 1 shows a state in which the side surface 51c and the side surface 51d are substantially orthogonal to the output surface 51a and the back surface 51b as an example of the arrangement relationship between the side surface 51c and the side surface 51d and the output surface 51a and the back surface 51b. In the present embodiment, a mode in which the

other side surfaces

51e and 51f of the main body 51 are also orthogonal to the emission surface 51a and the back surface 51b will be described.

1 and 2, the plurality of lens portions 52 are formed on the back surface 51b. The lens part 52 is transparent and is for emitting light propagating through the light guide plate 50 from the emission surface 51a side. The outer shape of each lens portion 52 is a dome shape.

The shape of each lens part 52 will be described. For simplification of description, a mode in which the sizes of the plurality of lens units 52 are the same will be described.

When light is emitted from an arbitrary point (one point) p on the emission surface 51a, the lens unit 52 has a ratio (ratio) of the second light quantity to the first light quantity emitted from the point p that is the emission position. The outer shape is larger than 0.252%. The first light amount is an amount per unit time of all emitted light emitted from the point p. The second light amount is an amount per unit time of the emitted light emitted from the point p to the predetermined area. The predetermined region is a region where the angle range with respect to the normal line of the emission surface 51a at the point p is 25 ° or more and 35 ° or less, and the angular width around the normal line is ± 5 ° with respect to the X direction. The shape of the lens unit 52 will be described more specifically with reference to FIG.

FIG. 3 is a drawing for explaining the shape of the lens portion 52. FIG. 3A is a diagram showing a local coordinate system setting state on the emission surface 51a. FIG. 3B is a diagram for explaining a method for defining angles from the z-axis and the x-axis in the coordinate system shown in FIG. FIG. 3C is a diagram for explaining the predetermined area.

As shown in FIG. 3A, a local xyz coordinate system with an arbitrary point p on the emission surface 51a as the origin is set, and a unit sphere with the origin as the center is assumed. In the xyz coordinate system, the z axis is orthogonal to the exit surface 51a. That is, the z-axis axis corresponds to the normal line of the exit surface 51a. The x axis is substantially parallel to the X direction. That is, the x-axis is a direction substantially orthogonal to the side surfaces 51c and 51d that are incident surfaces. In this case, the y axis substantially coincides with the Y direction. The x-axis, y-axis, and z-axis correspond to the X direction, the Y direction, and the Z direction as well in FIGS. 3B and 3C. *

As shown in FIG. 3B, the angle (deflection angle) formed between the direction of the emitted light emitted from the point p and the z axis is θ, and the angle formed between the direction of the emitted light and the x axis ( The declination is φ. In this setting, the range of the angle with respect to the normal line of the exit surface 51a at the point p corresponds to the angle range of θ that is a declination from the z-axis, and the angle width around the normal line is an angle range that φ satisfies Corresponds to the width. Further, the first light amount that is the amount per unit time of all the light emitted in the range of 0 ° ≦ θ ≦ 90 ° and 0 ° ≦ φ ≦ 360 ° (the upper hemisphere of the sphere shown in FIG. 3) is obtained. Q ₁ and, as shown in FIG. 3C, a predetermined region as a range of 25 ° ≦ θ ≦ 35 ° and −5 ° ≦ φ ≦ 5 ° (hatching region on the surface of the sphere shown in FIG. 3) Let Q ₂ be the _second light amount that is the amount of light emitted per unit time per unit time. Further, a light amount ratio that is a ratio of the light amount Q ₂ to the light amount Q ₁ is defined as Q (= Q ₂ / Q ₁ × 100) (%).

At this time, the outer shape of the lens unit 52 is:
0.252 (%) <Q
It is a shape satisfying.

FIG. 4 is a diagram for explaining an example of the outer shape of the lens unit 52. FIG. 4 is a schematic diagram of a cross-sectional configuration of the light guide plate 50 including the central axis C of the lens unit 52.

In the lens unit 52, the top of the lens unit 52 located on the opposite side of the back surface 51b is referred to as the tip 52a of the lens unit 52, and the back surface 51b side of the lens unit 52 is referred to as the bottom 52b of the lens unit 52. In the present embodiment, it is assumed that the shape of the lens portion 52 is a shape in which the cross-sectional shape shown in FIG. 4 is rotated about the central axis C as the rotation axis. Therefore, the shape of the lens portion 52 is bilaterally symmetric in an arbitrary cross section including the central axis C. The lens portion 52 has an outer shape such that the angle formed between the tangential plane in contact with the lens portion 52 and the back surface 51b monotonously decreases from the bottom 52b side to the tip end portion 52a side of the lens portion 52.

With reference to FIG. 4, various examples of the outer shape of the lens unit 52 will be described. In FIG. 4, the width (diameter) of the lens portion 52 is w _a (μm), and the maximum height of the lens portion 52 is h _a (μm).

The outer shape of the lens unit 52 to light quantity ratio Q (%) satisfies the above range is the aspect ratio and h _{a /} w _a is the ratio of the maximum height h _a for (I) the width w _a, (II) Lens If the radius of curvature of the tip portion 52a of the part 52 is the r ([mu] m), a width _{w a} ratio of radius of curvature r is the r / _{w a} relative, and, (III) back 51b of the bottom portion 52b of the lens unit 52 Where h _a / w _a , r / w _a and γ are defined by any of the combinations in the chart shown in FIG. 5 when the angle with respect to (hereinafter referred to as the bottom angle) is γ (°). The shape can be made.

Hereinafter, the condition of the shape that the lens unit 52 satisfies according to the case classification based on the aspect ratio [h _a / w _a ] shown in the chart of FIG. 5 is specifically exemplified.

(1) 0.29 shape ≦ _h a _/ w a <0.31 when the lens unit 52, r / _{w a} and γ may if they meet any of the following conditions.
(1a) 0 <r / w _a ≦ 0.23 and 31.57 ≦ γ ≦ 39.63
(1b) 0.44 ≦ r / w _a ≦ 0.48 and 51.66 ≦ γ ≦ 54.72
(1c) 0.52 ≦ r / w _a ≦ 0.56 and 58.03 ≦ γ ≦ 61.59
(1d) 0.60 ≦ r / w _a ≦ 0.79 and 65.41 ≦ γ ≦ 85.24

(2) 0.27 shape ≦ _h a _/ w a <0.29 when the lens unit 52, r / _{w a} and γ may if they meet any of the following conditions.
(2a) 0 <r / w _a ≦ 0.290 and 29.83 ≦ γ ≦ 39.70
(2b) 0.513 ≦ r / w _a ≦ 0.848 and 52.84 ≦ γ ≦ 84.90

(3) the shape of _{_{0.25 ≦ h a / w a <}} 0.27 when the lens unit 52, r / _{w a} and γ may if they meet any of the following conditions.
(3a) 0 <r / w _a ≦ 0.361 and 28.03 ≦ γ ≦ 39.79
(3b) 0.601 ≦ r / w _a ≦ 0.913 and 54.24 ≦ γ ≦ 84.51

(4) The shape of _{_{0.23 ≦ h a / w a <}} 0.25 when the lens unit 52, r / _{w a} and γ may if they meet any of the following conditions.
(4a) 0 <r / w _a ≦ 0.443 and 26.17 ≦ γ ≦ 39.89
(4b) 0.755 ≦ r / w _a ≦ 0.990 and 60.24 ≦ γ ≦ 84.05

(5) 0.21 shape ≦ _h a _/ w a <0.23 when the lens unit 52, r / _{w a} and γ may if they meet one of the following conditions.
(5a) 0 <r / w _a ≦ 0.597 and 24.25 ≦ γ ≦ 42.85
(5b) 0.881 ≦ r / w _a ≦ 1.080 and 62.98 ≦ γ ≦ 83.52

(6) 0.19 shape ≦ _h a _/ w a <0.21 when the lens unit 52, r / _{w a} and γ may if they meet one of the following conditions.
(6a) 0 <r / w _a ≦ 0.719 and 22.27 ≦ γ ≦ 43.32
(6b) 0.969 ≦ r / w _a ≦ 1.031 and 60.71 ≦ γ ≦ 66.44
(6c) 1.094 ≦ r / w _a ≦ 1.188 and 72.70 ≦ γ ≦ 82.87

(7) 0.17 shape ≦ _h a _/ w a <0.19 when the lens unit 52, r / _{w a} and γ may if they meet one of the following conditions.
(7a) 0 <r / w _a ≦ 0.868 and 20.23 ≦ γ ≦ 43.90
(7b) 1.215 ≦ r / w _a ≦ 1.285 and 70.93 ≦ γ ≦ 78.28

(8) When 0.15 ≦ h _a / w _a <0.17 If the shape of the lens portion 52 satisfies 0.586 ≦ r / w ≦ 1.133 and 27.14 ≦ γ ≦ 49.42 Good.

(9) When 0.13 ≦ h _a / w _a <0.15 The shape of the lens portion 52 satisfies 0.938 ≦ r / w _a ≦ 1.473 and 30.57 ≦ γ ≦ 58.14. Just do it.

(10) When 0.11 ≦ h _a / w _a <0.13 The shape of the lens portion 52 satisfies 1.302 ≦ r / w _a ≦ 1.719 and 32.70 ≦ γ ≦ 54.09. Just do it.

(11) When 0.09 ≦ h _a / w _a <0.11 The shape of the lens portion 52 satisfies 1.813 ≦ r / w _a ≦ 2.063 and 36.17 ≦ γ ≦ 49.07. Just do it.

Curvature radius w _a of the tip portion 52a represents the curvature of the tip portion 52a of the top portion of the lens portion 52. For example, as shown in FIG. 4, the radius of curvature of the distal end portion 52a is a radius of a circle when a circle that is in contact with the distal end portion 52a (a circle indicated by a broken line in FIG. 4) is assumed. The bottom angle is an angle formed between the tangential plane P of the lens unit 52 and the back surface 51b at the intersection of the contour line of the lens unit 52 and the back surface 51b in a cross section passing through the central axis C. The bottom angle γ corresponds to a contact angle when the lens unit 52 is regarded as a droplet. The bottom of the tip 52a is also the bottom of the lens 52. Thus, the bottom angle is also the skirt angle.

Width _{w a} is a 5μm to 1mm, preferably is 10μm or more 500μm or less. The lens unit 52 having such a size is a so-called microlens.

4, since the structure of the section including the center axis C of the lens unit 52 are shown, the width w _a is the maximum width corresponding lens portion 52. h _a is the thickness at the position of the tip portion 52a of the lens unit 52. Therefore, the aspect ratio [h _a / w _a ] is the thickness (or height) of the lens part 52 at the position of the tip part 52a with respect to the maximum width of the lens part 52, that is, the [thickness at the tip part position]. ] / [Maximum lens width]. Normally, the thickness of the lens portion 52 at the position of the tip portion 52a is the maximum, and therefore the thickness of the lens portion 52 at the position of the tip portion 52a is also the maximum thickness of the lens portion 52. The ratio described in (II) corresponds to the ratio between the radius of curvature r and the maximum width of the lens portion 52, that is, [curvature radius] / [maximum width of the lens portion].

The material of the lens part 52 may be the same material as that of the main body part 51. The material of the lens part 52 may be different from the material of the main body part 51 as long as it is a transparent material.

The main body 51 of the light guide plate 50 configured as described above may be a single-layer plate-like body made of a single translucent material, or layers made of different translucent materials are laminated. A plate-like body having a multilayer structure may be used. When the material of the lens part 52 is the same as that of the main body part 51, the light guide plate 50 is a plate-like body made of a single translucent material.

Furthermore, when a translucent resin material is used as the translucent material constituting the main body 51 and the lens unit 52, an ultraviolet absorber, an antistatic agent, an antioxidant, a processing stabilizer, Additives such as flame retardants and lubricants may be added. These additives may be used alone or in combination of two or more. In the form in which the ultraviolet absorber is added to the light guide plate 50, the light guide plate 50 can be prevented from being deteriorated by the ultraviolet rays when the light output from the light source unit 60 includes a lot of ultraviolet rays. It is preferable to add an ultraviolet absorber to the.

Examples of UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, cyanoacrylate UV absorbers, malonic acid ester UV absorbers, oxalic anilide UV absorbers, and triazine UV absorbers. Can be mentioned. Preferred examples of the ultraviolet absorber are a benzotriazole ultraviolet absorber and a triazine ultraviolet absorber.

The translucent resin material is usually used without adding a light diffusing agent as an additive, but within a range that does not depart from the spirit of the present invention, that is, in a slight amount that does not impair the purpose of the present invention. If present, a light diffusing agent may be added to the translucent resin material.

As the light diffusing agent, a powder having a refractive index different from that of the transparent material as described above, which mainly forms the light guide plate 50, specifically, the main body 51 and the lens 52, is used. Used by dispersing in. As the light diffusing agent, for example, organic particles such as styrene resin particles and methacrylic resin particles, and inorganic particles such as potassium carbonate particles and silica particles are used, and the particle diameter is usually 0.8 μm to 50 μm.

The exit surface 51a is preferably flat. However, the emission surface 51a may have a slight surface layer diffusion function in order to reduce moire.

The light guide plate 50 including the lens unit 52 can be manufactured by ink jet printing (ink jet method), photopolymer method, extrusion molding, injection molding, or the like.

When manufacturing the light guide plate 50 using inkjet printing (inkjet method) or photopolymer method, an ultraviolet curable resin can be used as the material of the lens portion 52. In this case, an acrylic ultraviolet curable resin can be used as the ultraviolet curable resin.

An example of a method for manufacturing the light guide plate 50 in the case where inkjet printing is used with the material of the lens portion 52 as an acrylic ultraviolet curable resin will be described. In this case, the main body 51 as a plate-like body is formed by extrusion molding or injection molding. Next, an ultraviolet curable resin is dropped (printed) onto the surface to be the back surface 51b of the main body 51 while operating the ink jet head. Next, the ultraviolet curable resin is irradiated with ultraviolet rays to cure the ultraviolet curable resin, so that the dropped ultraviolet curable resin becomes the lens portion 52.

An example of the ultraviolet curable resin when the lens portion 52 is formed from an ultraviolet curable resin is, for example, an acrylic ultraviolet curable resin.

Here, the manufacturing method by ink jet printing is exemplified, but as described above, the light guide plate 50 in which the lens portion 52 is directly formed may be manufactured by extrusion molding, injection molding, or the like. In this case, the material of the lens part 52 is the same as the material of the main body part 51.

Next, the effects of the light guide plate 50 are applied as a part of the surface light source device 30 as shown in FIG. 1 and the light guide plate 50 is applied to the transmissive image display device 10. A case will be described as an example. FIG. 6 is a partially enlarged view of the transmissive image display apparatus 10 shown in FIG. In FIG. 6, the side surface 50a (side surface 51c) side is shown enlarged in FIG.

When the point light source 61 included in the light source unit 60 emits light, the light from the point light source 61 enters the light guide plate 50 from the side surface 50 a of the light guide plate 50 facing the point light source 61. The light incident on the light guide plate 50 propagates in the light guide plate 50 while being totally reflected in the light guide plate 50. When light propagating in the light guide plate 50 enters the lens unit 52, the light is reflected in the lens unit 52 under conditions other than the total reflection condition. Therefore, the reflected light is emitted from the emission surface 51a.

Since the lens unit 52 has a shape in which the light quantity ratio Q is larger than 0.252%, the emission angle θ _o of the light emitted from the emission surface 51a is about 30 °, more specifically, 25 ° to 35 °. It tends to be in the range below °. As a result, the brightness of light emitted to the transmissive image display unit 20 through the prism plate 40 is improved.

This point will be described by taking as an example the case of a light guide plate 80 in which white dots 81 are formed on the back surface 51b instead of the lens portion 52. FIG. 7 is a schematic diagram showing an example of the configuration of the light guide plate 80 in which a plurality of white dots 81 are formed on the back surface 51b. In FIG. 7, the point light source 61 and the prism plate 40 are also shown for the sake of explanation. The configuration of the light guide plate 80 is the same as that of the light guide plate 50 except that white dots 81 are formed on the back surface 51b instead of the lens portion 52. Elements of the light guide plate 80 that are the same as those of the light guide plate 50 are denoted by the same reference numerals.

Also in the case of the light guide plate 80, the light output from the point light source 61 and entering the light guide plate 80 propagates in the light guide plate 80 while being totally reflected in the light guide plate 80. When the light propagating in the light guide plate 80 is reflected at the position of the white dot 81, the light reflected under conditions other than the total reflection condition is also generated. Therefore, the light reflected by the white dots 81 is emitted from the emission surface 51a. At this time, as shown in FIG. 8, the emission angle θ _o tends to be around 60 °. Figure 8 is a graph showing the results of measuring the intensity distribution of the emitted light with respect to emission angle theta _o. The horizontal axis of FIG. 8 is the outgoing angle θ _o of the outgoing light from the outgoing face 51a, and the vertical axis is the luminous intensity (cd). Light emitted from the light guide plate 80 is incident on the prism plate 40 at approximately the same angle and the emission angle theta _o. Therefore, the outgoing light emitted at the outgoing angle θ _o of about 60 ° enters the prism plate 40 at the incident angle θ _i of about 60 °.

However, when the light incident on the prism plate 40 when the incident angle θ _i is around 60 ° is emitted from the prism portion 41, it is likely to be emitted in a direction away from the Z direction as shown in FIG. As a result, the light incident on the transmissive image display unit 20 tends to be reduced.

On the other hand, in the light guide plate 50, light is easily emitted at an emission angle θ _o within a range of 30 ° ± 5 ° (that is, 25 ° or more and 35 ° or less). In this case, light enters the prism plate 40 at an incident angle θ _i of 30 ° ± 5 °. If the incident angle theta _i vicinity 30 ° of the light into the prism plate 40, the light emitted from the prism unit 41, as shown in FIG. 6, likely to be emitted in the thickness direction (Z-direction). In other words, more light emitted from the light guide plate 50 is collected in the front direction, which is the thickness direction.

Of the pair of

side surfaces

42a and 42b constituting the prism portion 41, light emitted from one surface 42a is emitted in the plate thickness direction, while light emitted from the other surface 42b is emitted in the plate thickness direction. You may be away from However, since the light is easily emitted from the one side surface 42a in the thickness direction, the amount of light emitted toward the transmissive image display unit 20 is larger than when the incident angle θ _i is about 60 °. Therefore, the brightness in the front direction is improved, and as a result, a brighter image can be displayed on the transmissive image display unit 20.

Next, when the lens unit 52 satisfies the conditions shown in FIG. 5, the point that the outgoing light having the outgoing angle θ _o near 30 ° is increased will be described based on the simulation result.

FIG. 9 is a schematic diagram showing a simulation model. For convenience of explanation, components corresponding to components shown in FIG. 1 is described are denoted by the M as a light guide plate 50 _M. Simulation, together with the side surface ₅₀ M a of the light guide plate 50 _M, 50 _M each point light source ₆₁ M on the side of b, 61 _M are arranged as shown in FIG. 9, below the light guide plate 50 _M in the reflection sheet is disposed model as a reflective portion 70 _M, was performed using a ray tracing method. The point

light sources

61 _M and 61 _M are disposed on the sides of the side surface 50 _M a and the side surface 50 _M b. The point

light sources

61 _M and 61 _M are located in the center of the short side direction in the short side direction of the light guide plate 50 _M.

The simulation conditions are as follows.
-Constituent material of light guide plate 50 _M : main body 51 _M and lens portion 52 _M both assume PMMA (refractive index: 1.49)-shape of light guide plate 50 _M in plan view (shape viewed from plate thickness direction): Rectangular / light guide plate 50 _M long side length W1: 500mm
· Light guide plate 50 _M , short side length W2: 20 mm
-Main body 51 _M thickness t: 4 mm
The distance between the lens portion 52 _M of the light guide plate 50 _M and the tip 52 _M a of the _M and the reflection portion 70 _M : 0.1 mm
Reflector 70 _M : Assuming a mirror (100% reflectance) Point light source 61 _M : Point light source, assuming isotropic emission Wavelength of light emitted from point light source 61 _M : Assuming 550 nm _-Distance between point light source 61 _M and light guide plate 50 _M : 0.1 mm
Incidentally, assuming periodic boundary conditions in the body portion 51 side 51 of _M _M e and side 51 _M f. That was a return to all light in the side surface 51 _M e and side 51 _M f is reflected guided plate 50.

In the simulation, the cross-sectional configuration of the lens unit 52 _M containing the center axis C of the lens unit 52 _M as shown in FIG. 4, the contour of the lens portion 52 _M is represented by conic. Specifically, as shown in FIG. 10, uv coordinate system is set, the cross-sectional shape of the lens portion 52 _M is defined by the conic v (u) represented by the formula (1). uv coordinate system v axis corresponds to the center axis C of the lens unit 52 _M in FIG. The u axis corresponds to the X direction shown in FIG.

In the formula (1), k _a is a parameter indicating the kurtosis how conic represented by the formula (1) represents the kurtosis how tip 52 M _a of the lens portion 52 _M. For example, when _{k a} is 0, the outer shape of the lens unit 52 _M becomes parabolic, when _{k a} is 1, the outer shape of the lens unit 52 _M becomes prism shape, when _{k a} is -1, the lens portion 52 _M The outer shape is a shape obtained by cutting an ellipse in half.

In the simulation model, a plurality of lens portions 52 _M to the rear 51 _M b of the main body portion 51 _M are arranged at regular intervals. Specifically, a square lattice having a plurality of square are arrayed is set to the back 51 M _b, one lens portion 52 _M in each square there is arranged in the structural units of the square lattice. Square lens unit 52 _M occupancy for the structural units of the lattice (coverage of the lens unit 52 _M for constituting units) was 78.5%. The length of one side of the square, which is a structural unit of the square lattice, was 500 μm.

In the simulation, first, the lens unit 52 _M having a contour defined by the formula (1) is designed. Relative designed lens portion 52 light guide plate 50 having a _M _M, assuming that the light from the point light sources 61 _M incident, emitting position of the light in the central portion of the emission surface 51 M _a of the light guide plate 50 _M Assuming that the point p is as follows, the radiance of the emitted light when the light is emitted from the point p was calculated.

Then, set the local xyz coordinate system shown in shown in FIG. 3 (b) and (c), the light quantity _{Q 1} and the light quantity _{Q 2} is calculated. In the simulation, for comparison with the experimental results for comparison described later, the range of 0 ° ≦ θ ≦ 90 ° and 0 ° ≦ φ ≦ 360 ° (z of the spherical surfaces of the unit sphere shown in FIG. 3B) The radiance of the emitted light emitted to the hemisphere in the region of ≧ 0 was calculated at a plurality of points on the hemisphere. Thereafter, based on the calculated radiance, the total radiant flux of the entire hemisphere and the radiant flux of a predetermined region were calculated.

The plurality of points at which the radiance is calculated are set in increments of 5 ° in the θ direction and in increments of 10 ° in the φ direction so as to include points within a predetermined region. Calculation of total radiant flux and radiant flux from radiance was carried out as follows.

That is, the radiance at each calculation point was converted into a radiant flux per unit solid angle. 1 / 4π was set as the unit solid angle. Next, each radiant flux was converted into a radiant flux per surface element on the unit sphere. Thereafter, the total radiant flux was calculated by numerically integrating the radiant flux per surface element on the unit sphere over the entire hemisphere. The radiant flux was calculated by numerically integrating the radiant flux per surface element on the unit spherical surface in the range of 25 ° ≦ θ ≦ 35 ° and −5 ° ≦ φ ≦ 5 °. In the simulation, a radiant flux that is a physical quantity is calculated, and the radiant flux corresponds to a so-called psychophysical quantity of light flux (amount of light per unit time). Therefore, the ratio of the radiant flux in the predetermined area to the calculated total radiant flux corresponds to the ratio of the luminous flux (light quantity per unit time) in the predetermined area to the total luminous flux (total light quantity per unit time). Therefore, the [radiant flux in a predetermined area] / [total radiant flux] was set to the light quantity ratio Q.

By changing k _a and h _a / w _a , the above simulation was performed on the set shapes of the plurality of lens portions 52 _M , and the light amount ratio Q was calculated.

For comparison, a light quantity ratio Q based on actual measurement values was obtained using a light guide plate 80 provided with white dots 81. In an experiment for comparison (hereinafter referred to as “comparison experiment”), the backlight unit used in “UN46B8000” manufactured by Samsung Electronics Co., Ltd. is taken out, and the light guide plate of the backlight unit is used as the light guide plate 80. Used. And while using the light-guide plate 80 and the light source of a backlight unit, and providing the silver vapor deposition reflective film in the back side of the light-guide plate 80, the structure similar to the structure of FIG. 9 was implement | achieved. The light guide plate 80 used for the comparison experiment was provided with white dots 81. In the comparative experiment, as in the simulation model shown in FIG. 9, white light is supplied from the side surface of the light guide plate 80 into the light guide plate 80, and a predetermined position (the center of the light guide plate 80 is centered). The luminance from the position) was measured. The measurement was performed using a luminance meter (“Color luminance meter BM-5AS” manufactured by TOPCOM). Specifically, the luminance was measured at each of a plurality of measurement points in the hemisphere corresponding to the region of z ≧ 0 in the spherical surface shown in FIG. The plurality of measurement points were set so as to correspond to the simulation radiance calculation points.

Based on the measured luminance, the total luminous flux and the luminous flux in a predetermined area were calculated in the same manner as in the simulation. That is, the luminance at each measurement point was converted into a luminous flux per unit solid angle. 1 / 4π was set as the unit solid angle. Next, each light beam was converted into a light beam per surface element on the unit spherical surface. Thereafter, the total luminous flux was calculated by numerically integrating the luminous flux per surface element on the unit sphere over the entire hemisphere. The luminous flux per predetermined area was calculated by numerically integrating the luminous flux per surface element on the unit spherical surface in the range of 25 ° ≦ θ ≦ 35 ° and −5 ° ≦ φ ≦ 5 °. Since light beams corresponding to the amount of light per unit time, the total luminous flux corresponding to the quantity Q _1, light flux of a predetermined region corresponding to the light quantity Q _2. Therefore, by dividing the light quantity Q ₂ in the amount of light Q _1, the light quantity ratio Q was calculated. The light quantity ratio Q when the white dots 81 were provided was 0.252%.

The simulation results are as shown in the charts shown in FIGS. 11 and FIG. 12 is a table showing the relationship between k _a and aspect ratio [h _{a /} w _{_a]} a de defined by the lens shape and the light quantity ratio Q in the formula (1). 11 _{k a} is shows the range of 0 to 0.9, FIG. 12, _{k a} indicates a and -0.1 below the range of -0.9.

11 and 12, it is shown that the larger the light quantity ratio Q is, the more light is emitted in the vicinity of the emission angle 30 °. In other words, towards the light quantity ratio Q is large, when combined with the prism plate 40 _M, so that the attained brightness improvement.

13 and 14, _{k a} and aspect ratio shown in FIGS. 11 and 12 _[h _a / _w a] a tip portion 52 to the width _{w a} of the lens shape determined de _M a width _{w a} radius of curvature r of is a table showing the ratio [r / w _a] against. Further, FIGS. 15 and 16 is a chart of the bottom angle of the lens shape determined out with k _a and an aspect ratio shown in FIGS. 11 and _{_{12 [h a / w a]}} .

In the charts shown in FIGS. 11 and 12, the light quantity ratio Q that is larger than the value (0.252%) of the light quantity ratio Q calculated for the white dot 81 is underlined. 13 and 15 corresponding to FIG. 11 and FIGS. 14 and 16 corresponding to FIG. 12, the front end portion 52a with respect to the width w _a of the lens portion 52 realizing the light quantity ratio Q underlined in FIGS. Is underlined with the radius of curvature [r / w _a ] and the bottom angle γ.

Accordingly, in FIGS. 11 to 16, in the lens portion 52 defined by the underlined portion h _a / w _a , the radius of curvature [r / w _a ] with respect to the width w _a, and the bottom portion angle γ, white dots 81 are formed. A larger light quantity ratio Q can be realized in the case of the light guide plate 80 provided.

The aspect ratio [h _a / w _a ], the radius of curvature [r / w _a ] with respect to the width w _a, and the bottom angle γ that define the shape of the lens portion 52 _M at the underlined portion in FIGS. Is within the range shown in the chart shown in FIG.

Therefore, as shown in FIG. _5, h _{a /} w _{_a,} the light guide plate 50 includes a lens portion 52 defined by combinations shown in r / w and gamma, 35 ° or less emission angle theta _o is 25 ° or more It becomes easy to become. Therefore, as described above, by employing the light guide plate 50 according to the present embodiment, the transmissive image display unit 20 can be illuminated with higher luminance in the transmissive image display device 10 including the prism plate 40. As a result, the luminance of the image displayed on the transmissive image display unit 20 is improved.

The embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.

In the above embodiment, the plurality of lens portions 52 formed on the back surface 51b have been described as having a shape such that the light quantity ratio Q is greater than 0.252%. However, at least half or more of the lens units formed on the back surface 51b may be the lens unit 52 described in the above embodiment. In other words, among the plurality of lens portions formed on the back surface 51b, half of the first lens portion as the lens portion 52 and the other half do not satisfy the conditions described in the above embodiment. You may comprise from a lens part. The ratio of the number of first lens portions as the lens portions 52 to the number of the second lens portions may be 6: 4.

As illustrated in FIG. 4, the shape of the lens unit 52 has a shape in which the angle formed between the tangential plane of the lens unit 52 and the back surface 51 b monotonously decreases from the bottom side to the front end side of the lens unit 52. Is preferred. However, the lens unit 52 has a shape defined by a combination indicated by h _a / w _a , r / w, and γ shown in FIG. 5, and the light quantity ratio Q becomes larger than 0.252%. If it has such a shape, it does not need to be monotonously decreasing toward the front end portion 52a side of the angle formed between the tangential plane of the lens portion 52 and the back surface 51b.

Furthermore, the number of light source units 60 is not limited to two. For example, the light source unit 60 may be three or more. In this case, for example, the light source unit 60 may be further provided on at least one of the side surfaces 51e and 51f of the main body unit 51. One light source unit 60 may be provided for the light guide plate. In this case, the light source unit 60 is disposed on one of the side surface 51c and the side surface 51d shown in FIG.

In the transmissive image display device 10 shown in FIG. 1, another optical member may be disposed between the light guide plate 50 and the prism plate 40 as long as the object of the present invention is not impaired. Another optical member may be disposed between the transmissive image display unit 10. Another example of the optical member provided between the light guide plate 50 and the prism plate 40 is a light diffusion sheet or a microlens sheet having a light diffusion characteristic that does not impair the object of the present invention. Examples of other optical members provided between the prism plate 40 and the transmissive image display unit 10 are a reflective polarization separation sheet, a light diffusion sheet, or a microlens sheet.

DESCRIPTION OF SYMBOLS 10 ... Transmission-type image display apparatus, 20 ... Transmission-type image display part, 30 ... Surface light source device, 40 ... Prism plate, 40a ... Front surface (one side of a prism plate), 40b ... Back surface (surface on the opposite side to one side of a prism plate) , 41... Prism portion, 50... Light guide plate, 51... Body portion, 51 a... Exit surface (first surface), 51 b... Back surface (second surface), 51 c. (Incident surface), 52... Lens portion, 52a... Tip portion, 52b.

Claims

A prism plate having a plurality of prism portions formed on one side, each of the plurality of prism portions extending in one direction, and the plurality of prism portions being substantially orthogonal to the extending direction of the prism portion. A light guide plate provided on the back side opposite to the one side with respect to the prism plates arranged in parallel in a direction,
A first surface located on the prism portion side, a second surface located on the opposite side of the first surface, and an incident surface intersecting the first and second surfaces and receiving light. A plate-like main body having
A plurality of lens portions formed on the second surface and convex to the opposite side of the first surface;
With
Each of the plurality of lens portions is
It has an outer shape such that the ratio of the second light quantity to the first light quantity of the emitted light that is incident from the incident surface and emitted from the first surface is greater than 0.252%,
The first light amount is an amount per unit time of all emitted light emitted from one point of the first surface,
The second light amount is an amount of emitted light emitted from the one point to a predetermined area,
The predetermined region has an angle range with respect to the normal line of the first surface of 25 ° or more and 35 ° or less, and around the normal line of ± 5 ° with respect to a direction substantially orthogonal to the extending direction of the prism portion. Having an angular width of,
Light guide plate.
A prism plate having a plurality of prism portions formed on one side, each of the plurality of prism portions extending in one direction, and the plurality of prism portions being substantially orthogonal to the extending direction of the prism portion. A surface light source device that supplies light to a surface opposite to the one surface of the prism plate arranged in parallel in a direction,
A first surface located on the prism portion side, a second surface located on the opposite side of the first surface, and an incident surface intersecting the first and second surfaces and receiving light. A light guide plate having a plate-like main body portion and a plurality of lens portions formed on the second surface and convex to the opposite side of the first surface;
A light source unit disposed on the side of the incident surface of the light guide plate and supplying light to the incident surface;
With
Each of the plurality of lens portions is
It has an outer shape such that the ratio of the second light quantity to the first light quantity of the emitted light that is incident from the incident surface and emitted from the first surface is greater than 0.252%,
The first light amount is an amount per unit time of all emitted light emitted from one point of the first surface,
The second light amount is an amount per unit time of emitted light emitted from the one point to a predetermined region,
The predetermined region has an angle range with respect to the normal line of the first surface of 25 ° or more and 35 ° or less, and around the normal line of ± 5 ° with respect to a direction substantially orthogonal to the extending direction of the prism portion. Having an angular width of,
Surface light source device.
A prism plate having a plurality of prism portions formed on one side, each of the plurality of prism portions extending in one direction, and the plurality of prism portions being substantially orthogonal to the extending direction of the prism portion. A prism plate arranged in parallel in the direction to
A light guide plate provided on a back surface side opposite to the one surface with respect to the prism plate, a first surface located on the prism portion side and a second surface located on the opposite side to the first surface. And a plate-shaped main body having an incident surface that intersects the first and second surfaces and is incident with light, and the first surface. A light guide plate having a plurality of lens portions that are convex on the opposite side, and
A light source unit provided on a side of the incident surface of the light guide plate and supplying light to the incident surface;
A transmissive image display unit that is provided on the one side of the prism plate and is illuminated by light emitted from the prism plate to display an image;
With
Each of the plurality of lens portions is
It has an outer shape such that the ratio of the second light quantity to the first light quantity of the emitted light that is incident from the incident surface and emitted from the first surface is greater than 0.252%,
The first light amount is an amount per unit time of all emitted light emitted from one point of the first surface,
The second light amount is an amount per unit time of emitted light emitted from the one point to a predetermined region,
The predetermined region has an angle range with respect to the normal line of the first surface of 25 ° or more and 35 ° or less, and around the normal line of ± 5 ° with respect to a direction substantially orthogonal to the extending direction of the prism portion. Having an angular width of,
Transmission type image display device.