JP2013054961A - Light guide plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate configured to improve luminance in a front direction, and a plane light source device and a transmission type image display device each including the light guide plate.SOLUTION: The light guide plate 50 has an emitting surface 51a arranged at a prism plate 40 side, a back surface 51b which is the surface opposite to the emitting surface 51a and extends in an extension direction of a prism section 41, wherein a plurality of projected ridge sections 52 are arranged in parallel with a direction orthogonal to the extension direction, and an incident surface 51c crossing the emitting surface 51a and the back surface 51b. Each projected ridge section 52 has an outer form wherein a value obtained by multiplying a ratio of a luminous flux of emitting light in a predetermined direction from a specific point to a luminous flux of emitting light in the whole direction from the specific point on the emitting surface 51a by light emission efficiency which is a ratio of an amount of emitted light from the emitting surface 51a to an amount of incident light to the incident surface 51c is greater than 1.055%. The predetermined direction is a direction wherein an angle to the normal of the emitting surface 51a is approximately 30° in a surface orthogonal to the extension direction of the prism section 41.

Description

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

  2. Description of the Related Art A transmissive image display device such as a liquid crystal display device generally includes a surface light source device that is disposed on the back side of a transmissive image display unit such as a liquid crystal display panel and 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. On the back side of the light guide plate, a plurality of lenticular lenses for reflecting light extend in a direction orthogonal to the incident direction of light and are provided in parallel to each other (for example, see Patent Document 1). In this configuration, the light emitted from the light source enters the light guide plate from the side surface of the light guide plate facing the light source, and propagates while totally reflecting inside the light guide plate. Since a plurality of lenticular lenses are formed on the back side of the light guide plate, the light reflected by the lenticular lens is emitted from the exit surface of the light guide plate on the transmissive image display unit side.

  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 2007-31325 A

  However, when the prism plate having the prism portion formed on the surface opposite to the surface facing the light guide plate as described above is disposed with respect to the light guide plate having the lenticular lens on the back side (reflection surface side), In some cases, the luminance in the front direction cannot be sufficiently improved.

  SUMMARY OF THE INVENTION 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 in which a plurality of prism portions extending in one direction are formed on one side, and the plurality of prism portions are arranged in parallel in a direction substantially orthogonal to the extending direction of the prism portions. A light guide plate provided on the back side opposite to one side with respect to the arranged prism plate, a first surface located on the prism plate side and a surface opposite to the first surface A second surface on which a plurality of ridges extending in a direction substantially parallel to the extending direction of the prism portion and arranged in parallel in a direction substantially orthogonal to the extending direction are formed; Each of the plurality of protrusions is incident on the incident surface and is emitted from the first surface. The value obtained by multiplying the ratio of the second luminous flux to the luminous flux by the light emission efficiency of the light emitted from the first surface is 1.055%. The first luminous flux is the total luminous flux of light emitted from one point on the first surface in all directions, and the second luminous flux is in a predetermined direction from one point. It is a light flux per unit solid angle of the emitted light, and the predetermined direction is a direction in which the angle with respect to the normal of the first surface is approximately 30 ° in a plane substantially orthogonal to the extending direction of the prism portion. Efficiency is the amount of light emitted from the first surface relative to the amount of light incident on the incident surface.

  The surface light source device according to the present invention is a prism plate in which a plurality of prism portions extending in one direction are formed on one side, and the plurality of prism portions are in a direction substantially orthogonal to the extending direction of the prism portions. A surface light source device that supplies light to a back surface opposite to one surface of a prism plate arranged in parallel, wherein the first surface located on the prism plate side is a surface opposite to the first surface. A second surface on which a plurality of ridges extending in a direction substantially parallel to the extending direction of the prism portion and arranged in parallel in a direction substantially orthogonal to the extending direction are formed; A light guide plate having an incident surface on which light is incident, and a light source unit that is disposed to face the incident surface of the light guide plate and supplies light to the incident surface. And each of the plurality of ridges is applied to the first light flux of the light incident from the incident surface and emitted from the first surface. And the ratio of the second light flux to be multiplied by the light emission efficiency of the light emitted from the first surface is greater than 1.055%. 1 is a total luminous flux of light emitted from one point on one surface in all directions, and the second luminous flux is a luminous flux per unit solid angle of light emitted from one point in a predetermined direction, and the predetermined direction is a prism. The angle with respect to the normal of the first surface is approximately 30 ° in a plane substantially orthogonal to the extending direction of the part, and the emission efficiency is emitted from the first surface with respect to the amount of light incident on the incident surface. Is the amount of light.

  The transmissive image display device according to the present invention is a prism plate in which a plurality of prism portions extending in one direction are formed on one side, and the plurality of prism portions are substantially orthogonal to the extending direction of the prism portions. A prism plate arranged in parallel in the direction, and a light guide plate provided on the back side opposite to the one side with respect to the prism plate, the first surface located on the prism plate side being opposite to the first surface A second surface having a plurality of ridges formed in parallel in a direction substantially orthogonal to the extending direction and extending in a direction substantially parallel to the extending direction of the prism portion. The light guide plate intersects the first and second surfaces and has an incident surface on which light is incident, and is disposed to face the incident surface of the light guide plate. A light source unit for supplying light and light emitted from the prism plate on one side of the prism plate And a transmissive image display unit that displays an image more illuminated, and each of the plurality of ridges is a second light flux with respect to the first light flux of light incident from the incident surface and emitted from the first surface. And a ratio obtained by multiplying the light output efficiency of the light emitted from the first surface by more than 1.055%, and the first light flux on the first surface The total luminous flux of light emitted from one point in all directions, the second luminous flux is a luminous flux per unit solid angle of light emitted from one point in a predetermined direction, and the predetermined direction is the extending direction of the prism portion The angle with respect to the normal of the first surface is approximately 30 ° in a plane substantially orthogonal to the plane, and the emission efficiency is the amount of light emitted from the first surface with respect to the amount of light incident on the incident surface. is there.

  Hereinafter, the surface of the prism plate that faces the light guide plate (the surface opposite to the one surface) is also 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 totally reflecting inside the light guide plate. When light propagating in the light guide plate is incident on the ridges provided on the second surface, the light is reflected by the ridges under conditions different from the total reflection conditions. Therefore, the light reflected by the ridge is emitted from the first surface of the light guide plate. Since each of the plurality of ridges formed on the second surface is formed in a shape that satisfies the above conditions, the first surface is in a predetermined direction (in a plane substantially orthogonal to the extending direction of the prism portion). The ratio of the light emitted in the direction in which the angle with respect to the normal of the first surface is approximately 30 ° is high. 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 light emitted from the first surface to the prism plate tends to be about 30 °. 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.

  In the light guide plate, the surface light source device, and the transmissive image display device according to the present invention, the ridges formed on the second surface of the light guide plate can be lenticular lenses.

  According to the present invention, it is possible 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.

It is a schematic diagram which shows schematic structure of the transmissive image display apparatus to which one Embodiment of the light-guide plate which concerns on this invention is applied. It is drawing for demonstrating the shape of a protruding item | line part, Drawing which shows the setting state of the local coordinate system on an output surface, and the definition method of the angle from the z-axis and x-axis in this coordinate system is demonstrated. FIG. It is drawing for demonstrating the example of the external shape of a protruding item | line part. It is a graph which shows the conditions which prescribe | regulate the external shape of a protruding item | line part. FIG. 2 is a partially enlarged view of the transmissive image display device shown in FIG. 1. It is a schematic diagram which shows an example of a structure of the light-guide plate in which the several white dot was formed in the back surface. It is a graph which shows the measurement result of the intensity distribution of the emitted light with respect to outgoing angle (theta) _o . It is a schematic diagram which shows a simulation model. It is drawing which shows the external shape of the protruding item | line part used for simulation. It is a graph which shows the relationship between the external shape of the protruding item | line part used for simulation, and the light emission efficiency in a predetermined direction. It is a graph which shows the relationship between the external shape of the protruding item | line part used for simulation, and the light emission efficiency in a predetermined direction. It is a graph which shows the relationship between the external shape of the protruding item | line part used for simulation, and a light emission ratio. It is a graph which shows the relationship between the external shape of the protruding item | line part used for simulation, and a light emission ratio. It is a graph which shows the relationship between the external shape of the protruding item | line part used for simulation, and an effective light emission ratio. It is a graph which shows the relationship between the external shape of the protruding item | line part used for simulation, and an effective light emission ratio. Is a table showing the bottom angle of the k _a and aspect ratio [h _{a /} w _a] and de determined external shape of convex portions shown in FIG. 14. 16 is a chart showing the bottom angle of the outer shape of the ridge portion determined by k _a and the aspect ratio [h _a / w _a ] shown in FIG. 15. 15 is a chart showing a radius of curvature r with respect to the width w _a of the outer shape of the ridge portion determined by k _a and the aspect ratio [h _a / w _a ] shown in FIG. 14. Is a table showing the radius of curvature r for the k _a and aspect ratio [h _{a /} w _a] and de determined width w _a of the outer shape of the convex portion shown in FIG. 15. It is a graph which shows the conditions which prescribe | regulate the external shape of a protruding item | line part. It is a graph which shows the conditions which prescribe | regulate the external shape of a protruding item | line part. It is a graph which shows the conditions which prescribe | regulate the external shape of a protruding item | line part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. The dimensional ratios in the drawings do not necessarily match those described. Further, in the description, words indicating directions such as “up” and “down” are convenient words based on the state shown in the drawings.

  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 sectional configuration of the transmissive image display device 10 is shown in an exploded manner. Moreover, in FIG. 1, light is typically shown as light rays. The transmissive image display device 10 can be suitably used as a display device or a television device of a mobile phone or various electronic devices.

  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 to each other.

  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 (Thin Film Transistor) type liquid crystal cell, a STN (Super Twisted Nematic) type liquid crystal cell, and the like.

  The prism plate 40 is used to collect the 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. Examples of the planar view shape of the prism plate 40 include a substantially rectangular shape and a substantially square shape.

  The prism portion 41 extends in one direction (Y direction in FIG. 1). The plurality of prism parts 41 are arranged in parallel in a direction orthogonal to the extending direction of the prism parts 41. The shape of the cross section perpendicular 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 85 ° or greater and 95 ° 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). The example of the refractive index of a translucent material is 1.46-1.62, Preferably, it is 1.49-1.59. 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: 1.56-1.59), polystyrene resin (refractive index). Ratio: 1.59), AS resin (acrylonitrile-styrene copolymer resin) (refractive index: 1.56-1.59), acrylic ultraviolet curable resin (refractive index: 1.46-1.58), poly And methyl methacrylate (PMMA) (refractive index: 1.49). Note that a diffusing agent or the like may be added to the prism plate 40 as long as it does not depart from the spirit of the present invention. 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 depart from the spirit of the present invention. By making the back surface 40b the rough surface as 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 can 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 a thickness of 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 portions 60 and 60 disposed on the side surfaces 51c and 51d 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 (arranged in the Y direction in FIG. 1). 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 make light incident on the light guide plate 50 efficiently. 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 cold cathode fluorescent lamp (CCFL).

  The surface light source device 30 may include a reflection unit 70 located on the opposite side of the light transmission plate 50 from the transmissive image display unit 20. 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 unit 70 may be a sheet as shown in FIG. Further, the reflection unit 70 may be a bottom surface of the housing of the surface light source device 30 that houses the light guide plate 50 and that is mirror-finished.

  The light guide plate 50 is used to emit light emitted from the light source unit 60 to the transmissive image display unit 20. Examples of the planar view shape of the light guide plate 50 include a substantially rectangular shape and a substantially square shape.

  The light guide plate 50 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: 1.56-1.59), polystyrene resin (refractive index). Ratio: 1.59), AS resin (acrylonitrile-styrene copolymer resin) (refractive index: 1.56-1.59), acrylic ultraviolet curable resin (refractive index: 1.46-1.58), 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 light guide plate 50 is opposed to the prism plate 40 and is substantially flat and has a light exit surface (first surface) 51a and a back surface on which a plurality of ridges 52 described later are formed. (Second surface) 51b and four side surfaces 51c, 51d, 51e, 51f intersecting with the emission surface 51a and the back surface 51b. FIG. 1 shows two side surfaces (incident surfaces) 51c and side surfaces (incident surfaces) 51d that face each other in the X direction. The side surface 51 c and the side surface 51 d face the light source unit 60. In this case, the side surface 51c and the side surface 51d are incident surfaces on which light from the light source unit 60 is incident. Of the four side surfaces 51c, 51d, 51e, 51f of the light guide plate 50, the remaining two side surfaces 51e, 51f (see FIG. 2) face each other in the Y direction. In FIG. 1, as an example of the arrangement relationship between the side surface 51c and the side surface 51d and the emission surface 51a and the back surface 51b, the side surface 51c and the side surface 51d are substantially orthogonal to the emission surface 51a and the back surface 51b. In the present embodiment, it is assumed that the other side surfaces 51e and 51f of the light guide plate 50 are also orthogonal to the emission surface 51a and the back surface 51b.

  The plurality of ridges 52 extend along the Y direction and are arranged in parallel in the X direction. The cross-sectional shape orthogonal to the extending direction of the ridges 52 is substantially uniform. The bottom part 52b which is an end of two adjacent protruding item | line parts 52 exists in the same position in a X direction. Each ridge 52 is transparent, and is used to emit light propagating through the light guide plate 50 from the emission surface 51a side. The outer shape of each ridge 52 is a shape that exhibits optical performance as a lenticular lens.

  The outer shape of each ridge 52 will be described. When light is emitted from an arbitrary point (one point) p on the emission surface 51a, the ridge 52 has a ratio of the second luminous flux to the first luminous flux of the light emitted from the point p that is the emission position ( The outer shape is such that a value obtained by multiplying the ratio) by the output efficiency is greater than 1.055%. The point p can be a point (one point) at the center of the emission surface (first surface) 51a, that is, the center of the emission surface 51a.

  The “first light flux” is the total light flux of light (emitted light) emitted from the point p in all directions (omnidirectional) outside the light guide plate 50. The “second light flux” is a light flux per unit solid angle of emitted light from the point p in a predetermined direction. In this embodiment, the “unit solid angle” is ¼π. The “predetermined direction” is a direction in which an angle with respect to the normal line of the emission surface 51a is about 30 ° in a plane orthogonal to the Y direction. “Emission efficiency” is the ratio of the amount of all light emitted from the emission surface 51 a to the amount of light incident on the side surfaces 51 c and 51 d as the incidence surfaces, that is, the amount of light incident on the light guide plate 50.

  This will be described more specifically with reference to FIG. FIG. 2 is a drawing for explaining the outer shape of the ridge portion 52. FIG. 2A is a diagram showing a local coordinate system setting state on the emission surface 51a. FIG. 2B 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.

  As shown in FIG. 2A, 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 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 FIG. 2B.

As shown in FIG. 2B, the angle (declination) formed between the direction of the emitted light from the point p and the z-axis is θ, and the angle (declination) formed between the direction of the emitted light and the x-axis. Is φ. In this setting, the predetermined direction is a direction of θ = 30 ° in the xz plane (in a plane substantially orthogonal to the extending direction of the prism portion 41). In other words, the predetermined direction is a direction defined by θ = 30 ° and φ = 0 °. However, the predetermined direction may be a direction within a range where θ and φ satisfy θ = 30 ° ± 5 ° and φ = 0 ± 5 °, respectively. Let Φ _{1 be} the total luminous flux of the outgoing light from the point p in all directions, and let Φ _{2 be} the luminous flux per unit solid angle of the outgoing light in the predetermined direction. The ratio of the luminous flux Φ ₂ to the total luminous flux Φ ₁ is the light emission ratio in a predetermined direction. Hereinafter, the “light emission ratio in a predetermined direction” is also simply referred to as “light emission ratio”. When this light emission ratio is R, R = Φ ₂ / Φ ₁ . The amount of light incident on the light guide plate 50 and Q _1, the amount of all of the light emitted from the emitting surface 51a and Q _2. When the light emitting efficiency E, is _{E = Q} 2 / Q _1.

At this time, the outer shape of the ridge 52 is
1.055 (%) <R × E × 100 (= R _E )
It is a shape satisfying. In the following description, also referred to as effective light emitting proportion R _E.

  FIG. 3 is a diagram for explaining an example of the outer shape of the ridge portion 52, and is a schematic diagram of a cross-sectional configuration of the light guide plate 50 including the ridge portion 52.

  The top of the ridge 52 is referred to as the tip 52 a of the ridge 52, and the bottom of the ridge 52 is referred to as the bottom 52 b of the ridge 52. In the present embodiment, the outer shape of the ridge portion 52 has an outer shape in which a cross-sectional shape orthogonal to the extending direction is substantially symmetric with respect to the center line C as shown in FIG. Further, the ridge 52 has an outer shape such that the angle formed between the tangential plane contacting the ridge 52 and the back surface 51b monotonously decreases from the bottom 52b side to the tip 52a side of the ridge 52. ing.

  With reference to FIG. 3, various examples of the outer shape of the ridge portion 52 will be described. Here, the reference plane 51 is defined for convenience of explanation. That is, the reference plane 51 is a plane parallel to a line connecting the bottoms 52b (indicated by a two-dot chain line in FIG. 3) in the cross section of the ridge 52 as shown in FIG. Is defined as a plane that forms In the present embodiment, the exit surface 51a (see FIG. 1) of the light guide plate 50 and the reference surface 51 are parallel to each other.

The outer shape of the ridge portion 52 in which the effective light emission ratio R _E (%) satisfies the above range can be a shape defined by any of the combinations in the chart shown in FIG. Hereinafter, the aspect ratio [h _a / w _a ], the radius of curvature [r / w _a ] and the bottom angle γ shown in FIG. 4 will be described.

(I) Aspect ratio [h _a / w _a ]
Aspect ratio _{[h a} / _w a], in FIG. 3, the width of the convex portion 52 _{w a} ([mu] m), the maximum height of the convex portion 52 (the distance between the reference plane 51 and the distal end portion 52a) When h _a (μm), it is the ratio of the maximum height h _a to the width w _a .

(II) Curvature radius relative to width [r / w _a ]
The radius of curvature [r / w _a ] with respect to the width refers to the width w _a when the width of the ridge 52 is w _a (μm) and the radius of curvature of the tip 52a of the ridge 52 is r (μm). It is the ratio of the radius of curvature r. The curvature radius r of the tip 52a represents the degree of bending of the tip 52a as the top of the ridge 52. For example, as shown in FIG. 3, the radius of curvature r of the tip 52a is a radius of a circle assuming a circle (circle indicated by a broken line in FIG. 3) in contact with the tip 52a.

(III) Bottom angle γ
The bottom angle γ is an angle formed between the tangent plane P of the ridge 52 and the reference plane 51 at the intersection of the contour line of the ridge 52 and the reference plane 51 in a cross section orthogonal to the extending direction. It is. Further, the bottom of the tip 52a is also the bottom of the ridge 52. Thus, the bottom angle γ is also the skirt angle.

Hereinafter, the conditions of the outer shape that the ridges 52 satisfy according to the case classification based on the aspect ratio [h _a / w _a ] shown in the chart of FIG. 4 will be specifically exemplified.

_{(1) 0.09 ≦ h a /} w a <0.11 where the outer shape of the convex portion 52, r / _{w a} and gamma (°) is a satisfying shape follows.
1.8125 ≦ r / w _a ≦ 1.9375 and 36.17 ≦ γ ≦ 41.83

_{(2) 0.11 ≦ h a /} w a <0.13 where the outer shape of the convex portion 52, r / _{w a} and gamma (°) has a shape which satisfies either of the following conditions.
(2A) 0.0521 ≦ r / w _a ≦ 0.7813 and 13.80 ≦ γ ≦ 21.03
(2B) 1.3021 ≦ r / w _a ≦ 1.6146 and 32.70 ≦ γ ≦ 47.01
(2C) 1.8229 ≦ r / w _a ≦ 2.0313 and 62.69 ≦ γ ≦ 83.66

(3) 0.13 external shape of ≦ _h a _/ w a <0.15 where ridges 52, r / _{w a} and gamma (°) has a shape which satisfies either of the following conditions.
(3A) 0.0446 ≦ r / w _a ≦ 0.4911 and 15.99 ≦ γ ≦ 21.14
(3B) 1.0268 ≦ r / w _a ≦ 1.2054 and 33.44 ≦ γ ≦ 40.84
(3C) 1.4732 ≦ r / w _a ≦ 1.7411 and 58.14 ≦ γ ≦ 84.64

(4) 0.15 outer shape of ≦ _h a _/ w a <0.17 where ridges 52, r / _{w a} and gamma (°) has a shape which satisfies either of the following conditions.
(4A) 0.0391 ≦ r / w _a ≦ 0.3516 and 18.14 ≦ γ ≦ 22.45
(4B) 0.7422 ≦ r / w _a ≦ 0.9766 and 31.41 ≦ γ ≦ 40.55
(4C) 1.2109 ≦ r / w _a ≦ 1.5234 and 55.00 ≦ γ ≦ 85.36

(5) 0.17 outer shape of ≦ _h a _/ w a <0.19 where ridges 52, r / _{w a} and gamma (°) has a shape which satisfies either of the following conditions.
(5A) 0.0347 ≦ r / w _a ≦ 0.2431 and 20.23 ≦ γ ≦ 23.59
(5B) 0.5903 ≦ r / w _a ≦ 0.7986 and 32.09 ≦ γ ≦ 40.32
(5C) 1.0070 ≦ r / w _a ≦ 1.3542 and 52.71 ≦ γ ≦ 85.90

The outer shape of _{(6) 0.19 ≦ h a /} w a <0.21 where ridges 52, r / _{w a} and gamma (°) has a shape which satisfies either of the following conditions.
(6A) 0.0313 ≦ r / w _a ≦ 0.0938 and 22.27 ≦ γ ≦ 23.40
(6B) 0.4688 ≦ r / w _a ≦ 0.5938 and 32.65 ≦ γ ≦ 37.34
(6C) 0.7813 ≦ r / w _a ≦ 1.2188 and 49.91 ≦ γ ≦ 86.33

(7) 0.21 outer shape of ≦ _h a _/ w a <0.23 when ridge 52, r / _{w a} and gamma (°) has a shape which satisfies either of the following conditions.
(7A) 0.3125 ≦ r / w _a ≦ 0.4830 and 31.28 ≦ γ ≦ 37.46
(7B) 0.7102 ≦ r / w _a ≦ 1.180 and 49.61 ≦ γ ≦ 86.68

(8) 0.23 outer shape of ≦ _h a _/ w a <0.25 where ridges 52, r / _{w a} and gamma (°) has a shape which satisfies either of the following conditions.
(8A) 0.1823 ≦ r / w _a ≦ 0.3906 and 30.21 ≦ γ ≦ 37.55
(8B) 0.5469 ≦ r / w _a ≦ 1.0156 and 45.34 ≦ γ ≦ 86.96

_{(9) 0.25 ≦ h a /} w a <0.27 where the outer shape of the convex portion 52, r / _{w a} and gamma (°) is a satisfying shape follows.
0.0240 ≦ r / w _a ≦ 0.9375 and 28.03 ≦ γ ≦ 87.20

_{(10) 0.27 ≦ h a /} w a <0.29 where the outer shape of the convex portion 52, r / _{w a} and gamma (°) is a satisfying shape follows.
0.0223 ≦ r / w _a ≦ 0.8705 and 29.83 ≦ γ ≦ 87.41

The outer shape of the _{(11) 0.29 ≦ h a /} w a <0.31 where ridges 52, r / _{w a} and gamma (°) is a satisfying shape follows.
(11A) 0.0208 ≦ r / w _a ≦ 0.8125 and 31.57 ≦ γ ≦ 87.59

_{(12) 0.31 ≦ h a /} w a <0.33 where the outer shape of the convex portion 52, r / _{w a} and gamma (°) is a satisfying shape follows.
0.0195 ≦ r / w _a ≦ 0.7617 and 33.24 ≦ γ ≦ 87.74

The outer shape of _{(13) 0.33 ≦ h a /} w a <0.35 where ridges 52, r / _{w a} and gamma (°) is a satisfying shape follows.
(13A) 0.0184 ≦ r / w _a ≦ 0.7169 and 34.86 ≦ γ ≦ 87.87

The outer shape of _{(14) 0.35 ≦ h a /} w a <0.37 where ridges 52, r / _{w a} and gamma (°) is a satisfying shape follows.
0.0174 ≦ r / w _a ≦ 0.6771 and 36.41 ≦ γ ≦ 87.99

_{(15) 0.37 ≦ h a /} w a <0.39 where the outer shape of the convex portion 52, r / _{w a} and gamma (°) is a satisfying shape follows.
0.0164 ≦ r / w _a ≦ 0.6414 and 37.90 ≦ γ ≦ 88.10

_{(16) 0.39 ≦ h a /} w a <0.41 where the outer shape of the convex portion 52, r / _{w a} and gamma (°) is a satisfying shape follows.
(16A) 0.0156 ≦ r / w _a ≦ 0.6094 and 39.33 ≦ γ ≦ 88.20

An example of the width w _a is 10 μm or more and 2 mm or less, preferably 20 μm or more and 1 mm or less, and more preferably 50 μm or more and 600 μm or less.

FIG. 3 shows a cross-sectional configuration orthogonal to the extending direction of the ridges 52. The width w _a corresponds to the maximum width of the ridge portion 52. Also, _{h a} is the thickness at the position of the tip portion 52a of the ridge portion 52. Therefore, the aspect ratio [h _a / w _a ] is the thickness (or height) of the ridge 52 at the position of the tip 52a with respect to the maximum width of the ridge 52, that is, [the position at the tip]. Corresponds to [Thickness] / [Maximum width of ridges]. Usually, since the thickness of the convex part 52 in the position of the front-end | tip part 52a is the maximum, the thickness of the convex part 52 in the position of the front-end | tip part 52a is also the maximum thickness of the convex part 52. The ratio described in the above (II) corresponds to the ratio between the radius of curvature r and the maximum width of the ridge 52, that is, [curvature radius] / [maximum width of the ridge].

  The light guide plate 50 having the above-described configuration may be a single-layer plate-like body made of a single translucent material, or a multi-layer plate in which layers made of different translucent materials are laminated. It may be a body.

  Further, when a translucent resin material is used as the translucent material constituting the light guide plate 50, an ultraviolet absorber, an antistatic agent, an antioxidant, a processing stabilizer, a flame retardant, a lubricant, etc. are added to the translucent resin material. These additives can also be added. These additives can be used alone or in combination of two or more. Note that it is preferable that an ultraviolet absorber is added to the light guide plate 50 because deterioration of the light guide plate 50 due to ultraviolet rays can be prevented when the light output from the light source unit 60 contains a lot of ultraviolet rays.

  Examples of UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, cyanoacrylate UV absorbers, malonic ester UV absorbers, oxalic anilide UV absorbers, and triazine UV absorbers. Preferred are benzotriazole ultraviolet absorbers and triazine ultraviolet absorbers.

  The translucent resin material is usually used without adding a light diffusing agent as an additive, but may be added with a light diffusing agent as long as it is a slight amount that does not depart from the spirit of the present invention.

  As the light diffusing agent, normally, a powder having a refractive index different from that of the above-described translucent material (or transparent material) mainly constituting the light guide plate 50 is used, and this is dispersed in the translucent material. Used. As such a 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.

  Moreover, it is preferable that the output surface 51a is flat. However, the emission surface 51a may have a slight surface layer diffusion to reduce moire.

  The light guide plate 50 provided with the ridges 52 can be manufactured by, for example, a method of scraping a plate material made of a translucent material (or a transparent material). Moreover, when using a transparent resin material as a translucent material, it can manufacture by normal methods, such as an injection molding method, an extrusion molding method, a photopolymer method, a press molding method, for example. Further, when the light guide plate 50 is manufactured using the photopolymer method, an ultraviolet curable resin can be used as the material of the ridge portion 52, and an acrylic ultraviolet curable resin is used as the ultraviolet curable resin. Can do.

  Next, the operation and effect of the light guide plate 50 will be described by taking as an example a case where the light guide plate 50 is applied to the transmissive image display device 10 as a part of the surface light source device 30 as shown in FIG. FIG. 5 is a partially enlarged view of the transmissive image display apparatus 10 shown in FIG. In FIG. 5, the 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 51 c of the light guide plate 50 facing the point light source 61. The light incident on the light guide plate 50 propagates while being totally reflected in the light guide plate 50. When light propagating in the light guide plate 50 enters the ridge 52, the light is reflected in the ridge 52 under conditions other than the total reflection condition. Therefore, the reflected light is emitted from the emission surface 51a.

Since the protrusion 52 has a shape in which the effective light emission ratio R _E (%) is greater than 1.055%, the ratio of light emitted from the emission surface 51a at an emission angle θ _o of about 30 ° is higher. Become. As a result, the brightness of light incident on the transmissive image display unit 20 through the prism plate 40 is improved.

  This 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 ridges 52. FIG. 6 is a schematic diagram illustrating 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. 6, 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 the configuration of the light guide plate 50 except that white dots 81 are formed on the back surface 51b instead of the ridges 52. In the light guide plate 80, the same elements 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 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. 7, the emission angle θ _o tends to be around 60 °. FIG. 7 is a graph showing the measurement result of the intensity distribution of the outgoing light with respect to the outgoing angle θ _o of the light from the light guide plate 80. The horizontal axis in FIG. 7 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. Accordingly, 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 at an incident angle θ _i near 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 that effectively enters the transmissive image display unit 20 from the front direction tends to be reduced.

On the other hand, in the light guide plate 50, the ratio of light emitted at an emission angle θ _o within a range of 30 ° ± 5 ° (that is, 25 ° to 35 °) is high. In this case, more light is incident on the prism plate 40 at an incident angle θ _i of 30 ° ± 5 °. When the incident angle θ _i to the prism plate 40 is around 30 °, the light emitted from the prism portion 41 is likely to be emitted in the plate thickness direction (Z direction) as shown in FIG. In other words, more light emitted from the light guide plate 50 is collected in the front direction, which is the thickness direction. Therefore, the ratio of the light emitted toward the transmissive image display unit 20 increases. As a result, the luminance in the front direction is improved, and a brighter image can be displayed on the transmissive image display unit 20.

Next, when the outer shape of the ridge 52 satisfies the condition shown in FIG. 4, a description will be given based on the simulation result about the point that the outgoing light having the outgoing angle θ _o near 30 ° increases. However, the present invention is not limited to these simulations.

FIG. 8 is a schematic diagram showing a simulation model. For convenience of explanation, the components corresponding to the components shown in FIG. 1, described are denoted by the M as a light guide plate 50 _M. Simulation, the placing side _{51 M} c, ₅₁ M d each point light source ₆₁ at a position opposed to M, 61 _M of the light guide plate 50 _M as shown in FIG. 8, reflected downward of the light guide plate 50 _M in models where the reflection sheet is arranged as a part 70 _M, it was performed using the ray tracing method. Further, the point light sources 61 _M and 61 _M are located in the center portion in the short side direction in the short side direction of the light guide plate 50 _M.

The simulation conditions are as follows.
· The light guide plate 50 _M of the material: PMMA (refractive index: 1.49) assumptions, the light guide plate 50 _M of the plan view shape (shape viewed from a thickness direction): the length of the longer sides of the rectangular-light guide plate 50 _M W1: 540mm
· Light guide plate 50 _M , short side length W2: 20 mm
-Light guide plate 50 _M thickness t: 4 mm
The distance between-the ridge 52 _M of the light guide plate 50 _M and tip 52 _M a and the reflecting 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 a side 51 _M e and side 51 _M f in the periodic boundary conditions of the light guide plate 50 _M. That was a return to all light in the side surface 51 _M e and 51 _M f is reflected guided plate 50. Thus, by providing periodic boundary conditions in the short-side direction of the light guide plate 50 _M (Y direction), the length of the short side direction is the simulation that assumes a substantially infinite light guide plate become. The thickness t of the light guide plate 50 _M shall not include the thickness of the convex portion 52 _M.

In the simulation, the cross-sectional configuration of the convex portion 52 _M orthogonal to the extending direction as shown in FIG. 3, showing the contour of the convex portion 52 _M in conic. Specifically, as shown in FIG. 9, set the uv coordinate system, the cross-sectional shape of the convex portion 52 _M defined by a conic v (u) represented by the formula (1). v axis of the uv coordinate system corresponds to the center line C of the ridges 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 ridge portions 52 _M. For example, when _{k a} is 0, the outer shape of the convex portion 52 _M becomes parabolic, when _{k a} is 1, the outer shape of the convex portion 52 _M becomes prism shape, when _{k a} is -1, ridges The outer shape of 52 _M is a shape obtained by cutting an ellipse in half.

In the simulation model, with a plurality of ridges 52 _M in 100% coverage on the back 51 _M b side of the light guide plate 50 _M. That is, as shown in FIG. 8, the rear surface 51 M _b side of the light guide plate 50 _M, ridges 52 _M which are adjacent to each other in the long side direction (X direction) are arranged without a gap, the adjacent projections position of the parts 52 _M edge a is the bottom 52 b _M of match each other. The maximum width of the convex portion 52 _M is 500 [mu] m.

In the simulation, it was first designed ridges 52 _M having an outer shape defined by Equation (1). Against the light guide plate 50 _M having a convex portion 52 _M designed, 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 point p as

  Then, the local xyz coordinate system shown in FIG. 2A (or FIG. 2B) is set, the total radiant flux from the point p, θ = 30 ° and φ = 0 ° from the point p. The radiant flux per unit solid angle of the emitted light emitted in the direction (hereinafter referred to as a predetermined direction) was calculated. Specifically, in the simulation, in order to compare with a comparative experiment to be described later, the range of 0 ° ≦ θ ≦ 90 ° and 0 ° ≦ φ ≦ 360 ° (z in the spherical surface of the unit sphere shown in FIG. 2B). 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 per unit solid angle in a predetermined direction were calculated.

  The plurality of points for calculating the radiance were set in increments of 5 ° in the θ direction and in increments of 10 ° in the φ direction so as to include points in a predetermined direction. The total radiant flux and radiant flux were calculated from the radiance as follows.

  That is, first, the radiance at each calculation point was converted into a radiant flux per unit solid angle. The unit solid angle was set to 1 / 4π. Next, each radiant flux was converted into a radiant flux per surface element on the unit spherical surface. Thereafter, the total radiant flux was calculated by numerically integrating the radiant flux per surface element on the unit sphere over the entire hemisphere. For the radiant flux per unit solid angle with respect to a predetermined direction, a conversion value at a calculation point in the predetermined direction was used. In the simulation, the radiant flux is calculated as a physical quantity, but the radiant flux corresponds to a so-called psychophysical quantity of light flux (light quantity per unit time). Therefore, the ratio of the radiant flux per unit solid angle in a predetermined direction to the calculated total radiant flux, that is, [radiant flux per unit solid angle] / [total radiant flux] is the light emission ratio (light emission in a predetermined direction). Ratio) corresponds to R.

To obtain a light output efficiency E by calculating the ratio of the amount of all of the light emitted from the emitting surface 51 M _a to the amount of light incident on the light guide plate 50 _M.

By changing k _a and h _a / w _a , the above-described simulation is performed on the set shapes of the plurality of ridges 52 _M , respectively, and the light emission ratio R and the light emission efficiency E are respectively calculated. to obtain an effective light emission ratio R _E for each simulation result.

For comparison, to obtain a useful light emission rate R _E based on the measured value using the light guide plate 80 having a white dot 81. In an experiment for comparison (hereinafter referred to as “comparison experiment”), the backlight unit used in “UN46B8000” manufactured by Samsung Electronics Co., Ltd. was taken out, and the light guide plate of the backlight unit was used as the light guide plate 80. . Then, by using the light guide plate 80 and the light source of the backlight unit, a silver vapor deposition reflective film is provided on the back side of the light guide plate 80, thereby realizing the same configuration as the configuration of FIG. 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. 8, white light is supplied from the side surface of the light guide plate 80 into the light guide plate 80, and a predetermined position on the light exit surface 51 a (the center position of the light guide plate 80). ) 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 a hemisphere corresponding to z ≧ 0 among the spherical surfaces shown in FIG. The plurality of measurement points were set so as to correspond to the calculation points of the radiance of the simulation.

The measured luminance was converted into luminous intensity, that is, light flux per unit solid angle. As the unit solid angle, 1 / 4π set in the luminance meter was adopted. Next, the luminous flux (luminous intensity) per unit solid angle was converted to the luminous flux 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. As the luminous flux per unit solid angle in the predetermined direction, the luminous flux per unit solid angle converted based on the luminance of the measurement point located in the predetermined direction was adopted. The light emission ratio (light emission ratio in a predetermined direction) R was calculated by dividing the light flux Φ ₁ per unit solid angle with respect to the predetermined direction by the total light flux Φ ₂ .

The light emission efficiency of the light guide plate 80 having white dots 81 formed by screen printing is known as 80%. Therefore, in the comparative experiment, the light emission efficiency of the light guide plate 80 is assumed to be 80%. The light emission ratio R of the calculated predetermined direction, by multiplying 80% is assumed light output efficiency E, was calculated effective light emission ratio R _E in comparative experiment. As a result, the obtained value of the effective light emission rate _{R E} was 1.055%.

The simulation results are as shown in the charts shown in FIGS. 10 and 11 are diagrams showing the external shape of the convex portion defined out with k _a and aspect ratio in equation _{(1) [h a / w} a], the relationship between the light output efficiency E. 10 _{k a} indicates the range of 0.1 or more and 0.9 or less. 11, _{k a} indicates a and 0 below the range of -0.9. The light emission efficiency E shown in FIG. 10 and FIG. 11 is shown as a percentage.

12 and FIG. 13 is a table showing the relationship between the lens shape defined out with k _a and aspect ratio in equation _{(1) [h a / w} a], the light emitting ratio R for a given direction. 12 _{k a} indicates the range of 0.1 or more and 0.9 or less. 13, _{k a} indicates a and 0 below the range of -0.9. In FIGS. 12 and 13, the light emission ratio R is shown as a percentage, as in FIGS. 10 and 11.

14 and 15 are diagrams showing a lens shape defined out with _{k a} and aspect ratio in equation _{(1) [h a / w} a], the relationship between the effective light emitting ratio _{R E.} 14 _{k a} indicates the range of 0.1 or more and 0.9 or less. 15, _{k a} indicates a and 0 below the range of -0.9. The value of each cell in the chart shown in FIG. 14 is based on the value of the corresponding cell in the chart shown in FIG. 10 and FIG. Similarly, the value of each cell in the chart shown in FIG. 15 is based on the value of the corresponding cell in the chart shown in FIG. 11 and FIG.

16 and 17 are charts showing the bottom angle γ of k _a and aspect ratio [h a _{/ w a]} and de determined ridge of the outer shape shown in FIGS. 14 and 15. 18 and 19, the curvature of the width of the tip portion 52 _M a to the width _{w a} of the _{k a} and aspect ratio _{[h a} / _w a] and de determined ridge of the outer shape shown in FIGS. 14 and 15 is a table showing the radius [r / _{w a].}

In the charts shown in FIG. 14 and FIG. 15, the effective light emission rate R _E that is larger than the value (1.055%) of the effective light emission rate R _E in the comparative experiment is hatched. Effective light emission ratio R _E is a larger indicates that often light emitted near the output angle 30 °. That is, the effective light emission ratio R _E is a larger, when combined with the prism plate 40 _M, attained brightness improvement. Therefore, in the charts shown in FIGS. 14 and 15, the light guide plate 50 _M having the ridge portion having the outer shape corresponding to the hatched portion (cell) is more prismatic than the light guide plate 80 of the comparative experiment. when combined with the plate 40 _M, so that the attained brightness improvement.

Further, in the diagram shown in FIGS. 14 and 15, in addition to the above hatching, depending on the value of the effective light emission rate R _E, as shown below, not underlined, wavy underline, the double underline, and thick lines underlined I am doing.
Compare corresponding to the effective light emitting ratio _{R E} value (1.055%) greater than less than 1.2 times (less than 1.055% greater than 1.266%) and a convex portion 52 _M outer shape in the experiment The effective light emission ratio R _E is only hatched and not underlined.
Compare ridges 52 _M contour of which is a 1.2 times or more than 1.5 times (less than 1.266% or more 1.583%) of the value of the effective light emission ratio _{R E} in the experiment (1.055%) the effective light emission rate R _E corresponding to the shape, wavy underline addition to hatching.
Compare ridges 52 _M contour of which is 1.5 times to 2.0 times less (less than 1.583% or more 2.110%) of the value of the effective light emission ratio _{R E} in the experiment (1.055%) the effective light emission rate R _E corresponding to the shape, double underline is added to the hatching.
The value of the effective light emission ratio _{R E} in Comparative Experiment (1.055%) of 2.0 times or more (2.110% or higher) and a convex portion 52 the effective light emitting rate corresponding to the outer shape of the _{M R E} Is underlined with bold lines in addition to hatching.

  16 to 19, the same processing (hatching, no underline, wavy underline, double underline, and bold underline display) is performed on the cells corresponding to FIGS. 14 and 15.

In FIG. 14 to FIG. 19, a cell with hatching is considered. The aspect ratio of the convex portion 52 _M corresponding to these cells [h _{a /} w _a], the curvature radius [r / w _a] and bottom angle γ with respect to the width, in the range of chart shown in FIG. Therefore, in the light guide plate 50 including the ridges 52 defined by the combination of the aspect ratio [h _a / w _a ], the radius of curvature [r / w _a ] and the bottom angle γ shown in FIG. A large proportion of light is emitted in the vicinity of 30 °. Therefore, by employing the light guide plate 50 in 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 brightness of the image displayed on the transmissive image display unit 20 can be improved.

Next, in FIG. 14 to FIG. 19, a cell with hatching and a wavy underline is considered. Aspect ratio corresponding to the cell in which hatching and wavy underlined [h a _{/ w a],} electrical with a curvature radius [r / w _a] and ridges 52 _M defined by the combination of the bottom angle γ with respect to the width in light plate is valid light 1.2 times the value of the emission rate _{R E (1.055%) (1.266} %) than in the comparative experiment, compared with the light guide plate of comparative experiment, emitted near the output angle 30 ° The proportion of light that is emitted increases. For this reason, the combination of the aspect ratio [h _a / w _a ], the radius of curvature [r / w _a ], and the bottom angle γ corresponding to the hatched and wavy underlined cells is the effective light emission ratio in the comparative experiment. be preferred than the combination shown in FIG. 4 becomes larger than the value of R _E (1.055%). When the combination of the aspect ratio [h _a / w _a ], the curvature radius [r / w _a ] with respect to the width, and the bottom angle γ of the ridges 52 _M corresponding to these cells is calculated, the range of the chart shown in FIG. Inside.

Next, in FIG. 14 to FIG. 19, a cell with hatching and double underlining is considered. A light guide plate having a ridge defined by a combination of an aspect ratio [h _a / w _a ], _a radius of curvature [r / w _a ], and a bottom angle γ corresponding to a hatched and double-underlined cell So valid light 1.5 times the value of the emission rate _{R E (1.055%) (1.583} %) than in the comparative experiment, compared with the light guide plate of comparative experiment is emitted near the output angle 30 ° The ratio of light to be increased further. For this reason, the combination of the aspect ratio [h _a / w _a ], the radius of curvature [r / w _a ], and the bottom angle γ corresponding to the hatched and double underlined cells is the effective light emission in the comparative experiment. ratio 1.2 times the value of _{R E} (1.055%) can be said to be preferred over the combination shown in Figure 20 as a (1.266%) or more. When the combination of the aspect ratio [h _a / w _a ], the radius of curvature [r / w _a ] and the bottom angle γ of the ridges 52 _M corresponding to these cells is calculated, the range of the chart shown in FIG. Inside.

Next, in FIG. 14 to FIG. 19, cells with hatching and bold underline are considered. In a light guide plate having a ridge defined by a combination of an aspect ratio [h _a / w _a ], _a radius of curvature [r / w _a ], and a bottom angle γ corresponding to a cell with hatching and a thick underline , 2.0 times the value of the effective light emission ratio _{R E} in Comparative experiment (1.055%) becomes (2.110%) or more, compared with the light guide plate of Comparative experiment, are emitted near the output angle 30 ° The proportion of light is further increased. Therefore, the combination of the aspect ratio [h _a / w _a ], the radius of curvature [r / w _a ] and the bottom angle γ corresponding to the hatched and bold underlined cells is the effective light emission ratio in the comparative experiment. half times the value of R _E (1.055%) can be said to be preferred over the combination shown in FIG. 21 which is (1.583%) or more. When the combination of the aspect ratio [h _a / w _a ], the curvature radius [r / w _a ] with respect to the width, and the bottom angle γ of the ridges 52 _M corresponding to these cells is calculated, the range of the chart shown in FIG. Inside.

  In addition, the light guide plate 50 including the ridge portion 52 defined by the combination illustrated in FIG. 4 includes the light guide plate including the ridge portion defined by the combination illustrated in FIGS. 20, 21, and 22. . Further, the light guide plate 50 including the ridges 52 defined by the combinations illustrated in FIG. 20 includes a light guide plate including the ridges defined by the combinations illustrated in FIGS. 21 and 22. Further, the light guide plate 50 including the ridges 52 defined by the combination illustrated in FIG. 21 includes a light guide plate including the ridges defined by the combination illustrated in FIG. 22.

  Although the embodiments of the present invention have been described above, 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.

Further, as illustrated in FIG. 3, the shape of the ridge portion 52 is such that the angle formed between the tangent plane of the ridge portion 52 and the back surface 51 b monotonously decreases from the bottom side to the tip side of the ridge portion 52. It preferably has a shape. However, ridge 52, such as by having a shape defined by the combinations shown in _{h a / w a, r /} w and γ shown in FIG. 4, the effective light emission ratio _{R E} is 1.055% As long as it has a shape that becomes larger, it does not have to be monotonously decreased toward the tip 52a side of the angle between the tangent plane of the ridge 52 and the back surface 51b.

  Moreover, about the arrangement | sequence of the protruding item | line part 52, as shown in FIG. 1 etc., the protruding item | line parts 52 adjacent to a long side direction are arrange | positioned without gap, and the bottom part 52b which is an end of the adjacent protruding item | line part 52 is shown. However, the present invention is not limited to this example. For example, the ridges 52 adjacent to each other in the long side direction may be arranged away from each other, and the distance (pitch) between the ridges 52 adjacent to each other in the long side direction changes in the long side direction. It may be arranged to do.

  Moreover, although the said embodiment demonstrated the light-guide plate 50 integrally formed including the protruding item | line part 52, the light-guide plate of this invention is not limited to this. For example, by using a photopolymer method, a protruding strip portion 52 that is a portion above the reference surface 51 may be formed on a plate-like main body portion that is a portion below the reference surface 51 shown in FIG. .

  Furthermore, the arrangement position of the light source unit 60 is not limited to two places. For example, the light source part 60 can also be arrange | positioned in three or more places. In this case, for example, it can further provide with respect to at least one of the side surfaces 51e and 51f which the light-guide plate 50 has. Moreover, the light source part 60 can also be arrange | positioned in one place. 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. A reflective tape such as a mirror tape or a white diffusion tape for preventing light leakage may be attached to the other side surface opposite to the one side surface on which light from the light source unit 60 is incident.

  Further, in the transmissive image display device 10 shown in FIG. 1, other optical members may be disposed between the light guide plate 50 and the prism plate 40 or transmitted to the prism plate 40 without departing from the spirit of the present invention. Another optical member may be arranged between the mold image display unit 20 and the like. An example of another 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 depart from the spirit of the present invention. Examples of other optical members provided between the prism plate 40 and the transmissive image display unit 20 include a reflective polarization separation sheet, a light diffusion sheet, a microlens sheet, a lenticular lens sheet, and a prism sheet. is there.

  DESCRIPTION OF SYMBOLS 10 ... Transmission type image display apparatus, 20 ... Transmission type image display part, 21 ... Liquid crystal cell, 22, 23 ... Polarizing plate, 30 ... Surface light source device, 40 ... Prism plate, 40a ... Surface (one side of prism plate), 40b ... back surface (surface opposite to one surface of the prism plate), 41 ... prism portion, 50 ... light guide plate, 51a ... exit surface (first surface), 51b ... back surface (second surface), 51c ... side surface (incident) Surface), 51d ... side surface (incident surface), 52 ... ridge, 52a ... tip, 52b ... bottom, 60 ... light source, 61 ... point light source, 70 ... reflector.

Claims (6)

The prism plate in which a plurality of prism portions extending in one direction are formed on one side, and the plurality of prism portions are arranged in parallel in a direction substantially orthogonal to the extending direction of the prism portions. In contrast, a light guide plate provided on the back side opposite to the one side,
A first surface located on the prism plate side;
A plurality of ridges that are opposite to the first surface, extend in a direction substantially parallel to the extending direction of the prism portion, and are arranged in parallel in a direction substantially orthogonal to the extending direction. A second surface on which is formed;
An incident surface intersecting the first and second surfaces and receiving light;
Have
Each of the plurality of ridges is
A value obtained by multiplying the ratio of the second luminous flux to the first luminous flux of the light incident from the incident surface and emitted from the first surface by the light emission efficiency of the light emitted from the first surface is 1. It has an outer shape that is larger than 0.055%,
The first light flux is a total light flux of light emitted from one point on the first surface in all directions,
The second light flux is a light flux per unit solid angle of light emitted from the one point in a predetermined direction,
The predetermined direction is a direction in which an angle with respect to the normal line of the first surface is approximately 30 ° within a plane substantially orthogonal to the extending direction of the prism portion,
The emission efficiency is the amount of light emitted from the first surface with respect to the amount of light incident on the incident surface.
Light guide plate. The ridge is a lenticular lens,
The light guide plate according to claim 1. The prism plate in which a plurality of prism portions extending in one direction are formed on one side, and the plurality of prism portions are arranged in parallel in a direction substantially orthogonal to the extending direction of the prism portions. A surface light source device for supplying light to a back surface opposite to the one side of
A first surface located on the prism plate side and a surface opposite to the first surface, extending in a direction substantially parallel to the extending direction of the prism portion and substantially extending in the extending direction. A second surface on which a plurality of ridges arranged in parallel in an orthogonal direction are formed; and an incident surface that intersects the first and second surfaces and is incident with light. A light guide plate,
A light source unit that is disposed to face the incident surface of the light guide plate and supplies light to the incident surface;
With
Each of the plurality of ridges is
A value obtained by multiplying the ratio of the second luminous flux to the first luminous flux of the light incident from the incident surface and emitted from the first surface by the light emission efficiency of the light emitted from the first surface is 1. It has an outer shape that is larger than 0.055%,
The first light flux is a total light flux of light emitted in all directions from one point on the first surface,
The second light flux is a light flux per unit solid angle of light emitted from the one point in a predetermined direction,
The predetermined direction is a direction in which an angle with respect to the normal line of the first surface is approximately 30 ° within a plane substantially orthogonal to the extending direction of the prism portion,
The emission efficiency is the amount of light emitted from the first surface with respect to the amount of light incident on the incident surface.
Surface light source device. The ridge is a lenticular lens,
The surface light source device according to claim 3. A prism plate in which a plurality of prism portions extending in one direction are formed on one side, and a plurality of the prism portions arranged in parallel in a direction substantially orthogonal to the extending direction of the prism portions; ,
A light guide plate provided on the back side opposite to the one side with respect to the prism plate; a first surface located on the prism plate side; and a surface opposite to the first surface; A second surface on which a plurality of ridges extending in a direction substantially parallel to the extending direction of the prism portion and arranged in parallel in a direction substantially orthogonal to the extending direction are formed; A light guide plate that intersects the second surface and has an incident surface on which light is incident;
A light source section that is disposed to face the incident surface of the light guide plate, and that supplies 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 ridges is
A value obtained by multiplying the ratio of the second luminous flux to the first luminous flux of the light incident from the incident surface and emitted from the first surface by the light emission efficiency of the light emitted from the first surface is 1. It has an outer shape that is larger than 0.055%,
The first light flux is a total light flux of light emitted from one point on the first surface in all directions,
The second light flux is a light flux per unit solid angle of light emitted from the one point in a predetermined direction,
The predetermined direction is a direction in which an angle with respect to the normal line of the first surface is approximately 30 ° within a plane substantially orthogonal to the extending direction of the prism portion,
The emission efficiency is the amount of light emitted from the first surface with respect to the amount of light incident on the incident surface.
Transmission type image display device. The ridge is a lenticular lens,
The transmissive image display apparatus according to claim 5.

Images