JP2013073736A - Light guide, lighting device having the same, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide with high luminance and effective for reduction of luminance unevenness, a lighting device, and a display device.SOLUTION: A light deflection surface 7a for entering light of a light source and an emitting surface 7b for emitting the reflected light are formed on the light guide 7 by making both surfaces face each other. Cylindrical light deflection elements 18 are extended in a direction parallel with an incident surface 7L wherein the light source faces the light deflection surface 7a, and a plurality of light deflection elements 18 are arranged in a direction orthogonal to the incident surface 7L. The light deflection elements 18 are arranged so as to make their intervals become a dense state from a thin state from a region approaching the incident surface 7L in the direction orthogonal to the incident surface 7L to a region separated from the incident surface 7L. Light confinement lens extended in a direction orthogonal to the incident surface 7L is arranged on the emitting surface 7b in a direction parallel with the incident surface 7L. The light confinement lens 19 is formed in an approximately convex curved shape by means of a first region 19a wherein the top is made of a flat surface section or a curved surface section and a pair of second regions 19b made of a tapered flat surface section.

Description

  The present invention relates to a light guide mainly used for illumination optical path control, and an illumination device and a display device including the light guide.

  In recent large-sized liquid crystal televisions, flat display panels, and the like, a direct type illumination device and an edge light illumination device are mainly employed as illumination means including a light source. In the direct type illumination device, a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) are regularly arranged as light sources on the back surface of the image display panel. A diffuser plate having a high light scattering property is used between an image display panel, for example, an image display element such as a liquid crystal panel, and a light source so that a cold cathode tube or LED as a light source is not visually recognized.

  On the other hand, in an edge light type illuminating device, a plurality of cold cathode tubes and LEDs as light sources are arranged on an end face of a translucent plate called a light guide plate. Generally, light deflection that efficiently guides incident light from the end face of the light guide plate to the exit surface on the surface (light deflection surface) opposite to the exit surface of the light guide plate (surface facing the image display element). Elements are arranged. At present, as the light deflection element formed on the light deflection surface, for example, white ink disclosed in Patent Document 1 is generally printed in a dot shape. However, since the light incident on the white dots is diffusely reflected almost omnidirectionally, the light extraction efficiency to the exit surface side of the light guide plate is low. Light absorption by white ink cannot be ignored.

  Therefore, recently, a method of forming a microlens on the light deflection surface of the light guide plate by an inkjet method, a method of forming a light deflection element by a laser ablation method, and the like have been proposed. Unlike the white ink, the microlens utilizes reflection, refraction, and transmission due to a difference in refractive index between the resin of the light guide plate and air, so that light absorption hardly occurs. Therefore, a light guide plate having a higher light extraction efficiency than that of white ink can be obtained.

  However, the formation of the light deflection element by the ink jet method or the laser ablation method is formed in a separate process after the light guide plate is formed into a flat plate, as in the case of printing with white ink, so the number of manufacturing steps is not reduced. This method of forming a light deflection element has a problem that the tact time is longer than the white ink printing process and the initial cost of the equipment is high, resulting in high costs.

  Therefore, for example, as disclosed in Patent Document 2, a method has been proposed in which a light guide plate is molded by an injection molding method or an extrusion molding method, and a light deflection element is directly shaped during extrusion. According to this method, since the light deflection element is formed simultaneously with the formation of the light guide plate, the number of processes is reduced, and the cost can be reduced.

  However, when producing light guide plates by injection molding, the larger the size, the higher the pressure required on the injection molding machine, making it suitable for making light guide plates for relatively small display devices such as mobile phones and laptop computers. However, it is difficult to apply to the production of a light guide plate for a large display device such as a television. On the other hand, the extrusion molding method is a manufacturing method suitable for producing a large-sized light guide plate. However, since roll-to-roll molding using a cylindrical roll mold is fundamental, there are the following problems. .

  The light guide plate disclosed in Patent Document 3 shows a light guide plate in which two types of prism grooves extending in one direction are arranged in parallel as an example of densely patterning light deflection elements in a one-dimensional direction on the back surface thereof. Yes. In such a light guide plate that is densely and densely patterned only in a one-dimensional direction, light incident from the side surface on which the light source is provided spreads in a fan shape within the light guide plate, and the influence of overlapping of the plurality of light sources or the left and right sides where no light source is provided Due to the influence of the reflection on the side surface and leakage light, a substantially triangular area with low luminance is generated as luminance unevenness at the left and right ends of the surface.

In order to reduce such luminance unevenness of illumination light in the light guide plate, it is necessary to form the dense patterning of the light deflection element not only in the one-dimensional direction of the back surface but also in two dimensions.
However, in the extrusion method using a roll mold, it is difficult to form the light deflection elements in a two-dimensional dense arrangement. If it is one direction, it is possible to pattern densely and densely in the width direction of the roll mold, but if the density is formed in the circumferential direction of the roll mold, the light deflection elements cannot be made seamless. In such a case, if the pattern width in the rotating direction of the light deflection element is not matched with the diameter of the roll mold, a blank space is generated during extrusion molding. However, the size of the television is, for example, 19 inches as a small size and 60 inches or more as a large size, and it is not realistic to prepare roll dies having different diameters for all sizes.

JP-A-1-241590 JP 2000-89033 A JP 2006-155994 A

  The present invention has been made in order to solve the above-described conventional problems, and is a high-intensity light guide effective for reducing luminance unevenness in an edge light type illumination device, and an illumination equipped with the light guide An object is to provide a device and a display device using the lighting device.

A light guide according to the present invention is a translucent light guide, and includes a first main surface, a second main surface facing the first main surface, and between the first main surface and the second main surface. And a light deflecting element for deflecting light incident from the light source toward the second main surface, and at least one of the second main surface facing the light source. A light confinement lens that extends in a direction perpendicular to the direction in which the side surfaces extend and restricts the optical path of light that is guided through the light guide is provided, and the light confinement lens has a region in which the lens shape includes the apex. And a second region having a tapered surface formed at both ends of the first region.
According to the present invention, the reflected light deflected and diffused by the light deflecting element can be diffused and emitted in the direction orthogonal to the extending direction by the light confinement lens, and the visibility of the light deflecting element can be reduced. . Moreover, the incident light is reflected by the light confinement lens and can be guided in the extending direction, so that it is possible to suppress the occurrence of dark portions on the side surface where the light source is not provided, thereby reducing luminance unevenness, and high-luminance emission. Light can be obtained.

Moreover, it is preferable that the angle θ formed by the second region of the optical confinement lens and the second main surface is not less than 55 degrees and not more than 70 degrees.
If the inclination angle θ is within this range, light that is refracted or reflected in the second region is emitted in an oblique direction, and the angle distribution is appropriately expanded, so that the viewing angle and the luminance can be effectively increased. On the other hand, when the inclination angle θ is less than 55 °, the amount of light emitted in the oblique direction is weak, so that the angle distribution does not spread sufficiently and the luminance does not increase so much. When the inclination angle θ exceeds 70 °, the amount of light totally reflected in the second region increases and the amount of light emitted in an oblique direction becomes too strong, so that the luminance in the front direction decreases.

In the optical confinement lens, when the distance from the second main surface to the first region is H1, the pitch of the optical confinement lens is P, and the angle between the second region and the second main surface is θ, the following ( It is preferable to satisfy 1).
Regarding the above formula (1), when the distance H1 is smaller than the lower limit value, the ratio of the first region to the total surface area of the light confinement lens is too large, and the light confinement effect is reduced, and dark portions S are formed on both sides of the light guide. May be visible. When H1 is larger than the upper limit, the proportion of the second region is too large, the light diffusing action in the first region becomes insufficient, and the light energy is locally concentrated to increase the brightness in a spot shape. May be visible.

The light deflection elements are arranged in parallel to the extending direction of the side surface facing the light source, and the distance between the light deflection elements changes from sparse to dense as the distance from the side surface increases in a direction orthogonal to the side surface facing the light source. It is preferable.
The dense pattern of the light deflection elements is arranged in a direction perpendicular to the side surface desired for the light source, so that the light incident from the light source is diffused in the direction perpendicular to the extending direction of the light deflection element and separated from the light source. By densely arranging the light deflection elements in the region, light can be efficiently diffused even in a region away from the light source, and uniform luminance can be realized over the entire light guide.

Further, the light deflection element is preferably in a cylindrical shape, a prism shape or a microdot shape in a sectional view concave shape or convex shape.
The light deflection element has a cylindrical shape, a prism shape, or a microdot shape, and may be formed continuously, or may be formed by being separated into dots. The reflected light has a relatively high luminance when formed in a concave section with respect to the light deflection surface, and a relatively high luminance can be obtained when formed in a continuous cylindrical shape or prism shape.

Further, the first region of the optical confinement lens may be a flat portion.
Further, it is preferable that the first region of the optical confinement lens is a curved surface portion, and a cross section obtained by cutting the first region in a direction orthogonal to the extending direction of the optical confinement lens has a quadratic function curve or an arc shape.
By forming the first region of the optical confinement lens with a flat surface portion or a curved surface portion, it is possible to obtain a diffusion effect of light emitted from the first region.

The first region of the optical confinement lens is a curved surface portion, and when the width of the first region is D and the height is H2, the aspect ratio defined by H2 ÷ D is 0.4 or less. Is preferred.
If the aspect ratio defined by H2 ÷ D is 0.4 or less, the light diffusion effect on the curved surface portion is high and hot spots are not visually recognized, but if it exceeds 0.4, it is emitted without being diffused by the curved surface portion. Since the amount of condensed light increases, the hot spot is visually recognized.

An illuminating device according to the present invention includes a light source, the light guide described in any of the above, and a reflection sheet disposed on a back surface on the first main surface side of the light guide. .
Further, according to the illumination device of the present invention, the light source in the edge light type illumination device is guided by the light that is guided through the light guide, reflected by the light deflection surface, refracted by the light confinement lens, and reflected and emitted. Therefore, it is possible to effectively reduce the luminance unevenness on the side surface without any defects and to obtain high-luminance illumination light without causing a dark portion.

It is preferable that an optical sheet having at least one of the functions of light scattering, refraction, absorption, and reflection is provided in front of the light guide in the light emission direction.
The light emitted from the light guide is further scattered, refracted, absorbed, and reflected by the optical sheet, thereby improving the light scattering and light collecting properties.

Further, it is preferable that a light collecting sheet having prisms arranged in front of the light emitting direction of the light guide is provided, and the extending direction of the light collecting sheet prism is parallel or orthogonal to the extending direction of the light confinement lens.
By transmitting through the prism sheet, it is possible to improve the light condensing property and obtain the light luminance.

A display device according to the present invention includes an image display element that defines a display image according to light transmission / shielding in pixel units, and the illumination device described in any of the above.
According to the display device of the present invention, it is possible to effectively reduce the uneven luminance of the side portion and to obtain a high-luminance display image by the light that is guided through the light guide and reflected and emitted.

In the light guide according to the present invention, a light deflecting element is provided on a first main surface that reflects incident light, and a light confinement lens is provided on a second main surface that emits reflected light. Since the first region having a flat portion or curved portion and the second region having a tapered portion are provided, the reflected light deflected and diffused by the light deflection element is orthogonal to the extending direction by the light confinement lens. In addition, the incident light is confined to the light confining lens and reflected in the extending direction while reflecting the light incident on the light confinement lens, thereby suppressing the occurrence of a dark portion on the side surface where the light source is not provided and diffusing the emitted light. Luminance unevenness can be reduced, and emission light with high luminance can be obtained. Further, it can be produced by, for example, an extrusion method using a roll mold, and the productivity is high.
In addition, according to the illumination device and the display device of the present invention, the uneven brightness on the side portion in the edge light type illumination device can be effectively reduced by the light that is reflected after being guided through the light guide and is emitted. Illuminating light and display images can be obtained.

It is a cross-sectional schematic diagram of the display apparatus containing the illuminating device provided with the light-guide plate by 1st embodiment of this invention. (A) is a perspective view of the light guide according to the first embodiment of the present invention, (b) is a partial cross-sectional view in a direction orthogonal to the longitudinal direction of the optical confinement lens, and (c) is in the longitudinal direction of the optical confinement lens. It is sectional drawing which follows. (A), (b) is a figure showing the shape of a confinement lens and the course of a light ray seen in the cross section orthogonal to the longitudinal direction of the confinement lens in the light guide by 1st embodiment. (A) is the top view explaining the light guide in the general light guide which does not have a light confinement lens, and the figure seen from the light source side, (b) is the light in the light guide by 1st embodiment of this invention. It is the top view explaining the light guide in a confinement lens, and the figure seen from the light source side. (A) is the top view which showed the luminance distribution in a general light guide with the shading. (B) is the top view which showed the luminance distribution in the light guide by 1st embodiment with the shading. It is an angle distribution map of the emitted light intensity of a light guide. It is a figure which shows the light guide by 2nd embodiment of this invention, (a) is a perspective view, (b) is sectional drawing of the direction orthogonal to the longitudinal direction of a light confinement lens, (c) is a light confinement lens It is sectional drawing of the direction along a longitudinal direction. It is a figure which shows the light guide by 3rd embodiment of this invention, (a) is a perspective view, (b) is sectional drawing of the direction orthogonal to the longitudinal direction of a light confinement lens, (c) is a light confinement lens It is sectional drawing of the direction along a longitudinal direction. It is a figure which shows the light guide by 4th embodiment of this invention, (a) is a perspective view, (b) is sectional drawing of the direction orthogonal to the longitudinal direction of a light confinement lens, (c) is a light confinement lens It is sectional drawing of the direction along a longitudinal direction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
A display device 1 shown in FIG. 1 includes an image display element 2 and an illumination device 3 arranged facing the light incident side of the image display element 2. The illumination device 3 includes a light guide 7 according to the first embodiment of the present invention. In addition, the reduced drawing of each site | part does not correspond with actual.
In the display device 1 shown in FIG. 1, the image display element 2 is a liquid crystal display element, for example, and includes a liquid crystal layer 9 sandwiched between two polarizing plates 10 and 11. A liquid crystal display element is a typical element that transmits / shields light in pixel units and displays an image, and can improve image quality and reduce manufacturing cost compared to other display elements. .

  Here, the image display element 2 is preferably an element that displays an image by transmitting / blocking light in pixel units. If the image is displayed by transmitting / blocking light in pixel units, the luminance in the observation direction F is improved by the illumination device 3 according to the present embodiment, and the viewing angle dependency of the light intensity is reduced. It is possible to display an image with high image quality by effectively using the light whose visibility of the light deflection element 18 described later is reduced.

  The illuminating device 3 includes a laminate in which the light guide 7, the diffusion sheet 8, the light collection sheet 20, and the diffusive optical sheet 28 are laminated in this order along the light traveling direction. The reflector 5 is provided on the surface. The light guide 7 has, for example, a rectangular plate shape, and the light source 6 is disposed on, for example, two opposing side surfaces 7m out of the four side surfaces 7m. Here, a side surface 7m on which the light source 6 faces is indicated by a reference numeral 7L as an incident surface. The illumination device 3 is arranged with the diffusive optical sheet 28 facing the image display element 2.

For example, a point light source is provided as the light source 6. Examples of the light source 6 include an LED (light emitting diode), and examples of the LED include a white LED and an RGB-LED composed of red, green, and blue chips that are the three primary colors of light. Alternatively, the light source 6 may be a fluorescent tube typified by CCFL (cold cathode tube).
Although FIG. 1 shows an example in which a plurality of light sources 6 are arranged on two light incident surfaces 7L facing each other, the light source 6 is not limited to this and may be arranged only on one light incident surface 7L. You may arrange | position at the four side surfaces 7L.
Further, the shape of the light guide 7 may be a wedge shape instead of the rectangular flat plate shape as shown in FIG.

The diffusion sheet 8 has a function of diffusing light emitted from the light guide 7. The condensing sheet 20 is a prism sheet formed by arranging the prisms 21 in one direction, and has a function of condensing the light diffused by the diffusion sheet 8 in the observation direction F. The diffusive optical sheet 28 diffuses the light collected by the light collecting sheet 20 again. The diffusive optical sheet 28 protects the light collecting sheet 20 and suppresses the generation of moire interference fringes due to interference between the light periodic structure formed on the light collecting sheet 20 and the image periodic structure of the image display element 2. can do. The diffusive optical sheet 28 may be configured to have a function of separating the polarization of the light collected by the light collecting sheet 20.
In addition, it is not necessary to arrange | position all these optical members in the light guide 7 as the illuminating device 3, and it can abbreviate | omit suitably.

Next, the light guide 7 will be described.
In the thickness direction of the light guide 7, the surface opposite to the diffusion sheet 8 (the reflection plate 5 side) is a light deflection surface 7 a as a first main surface that reflects light incident from the light source 6 toward the diffusion sheet 8. The surface in the light emission direction F facing the light deflection surface 7a is the emission surface 7b as the second main surface. An optical deflection element 18 for deflecting incident light from the light source 6 toward the exit surface 7b is arranged on the optical deflection surface 7a.
The light deflecting element 18 has, for example, a cylindrical shape, a prism shape, or a microlens shape having a concave or convex cross section, and may be continuously formed in a linear shape, or may be arranged separately in a dot shape. It may be. The amount of light deflected to the exit surface 7b side by the light deflection element 18 increases as the area occupied by the light deflection element 18 per unit area on the light deflection surface 7a increases.

In the present embodiment, as shown in FIGS. 2A and 2C, the light deflection element 18 is a concave portion having a cylindrical shape (a lenticular lens shape having a substantially semicircular or substantially semielliptical cross section) having a concave cross section. Are formed on the light deflecting surface 7a along the direction of the incident surface 7L of the light guide 7 and are arranged in parallel to each other.
A plurality of light deflection elements 18 are arranged in parallel to the light incident surface 7L facing the light source 6 (see FIG. 2B), and are arranged at intervals in a direction perpendicular to the light incident surface 7L. . In other words, the direction orthogonal to the incident surface 7L is also the optical axis direction of incident light incident from the incident surface 7L. As shown in FIG. 2C, the arrangement interval of the light deflection elements 18 is wide on the side close to the incident surface 7L provided with the light source 6, and gradually increases toward the far side. They are arranged with a dense pattern in a one-dimensional direction so that the interval is narrowed.
The closer to the incident surface 7L, the smaller the area occupied by the light deflection element 18 per unit area, and the closer the distance from the incident surface 7L, the larger the area occupied by the light deflection element 18 per unit area. That is.

On the exit surface 7b of the light guide 7, a light confinement lens 19 having a convex cross section is formed so as to protrude. The light confinement lenses 19 are formed to extend in a direction orthogonal to the incident surface 7L, and are arranged at a plurality of equal intervals along the incident surface 7L.
As shown in FIGS. 2B and 3, the optical confinement lens 19 has a first region 19 a formed in the top region including the apex of the lens in the cross-sectional shape in the direction orthogonal to the extending direction, and an exit surface. A substantially convex curved surface is formed by the second region 19b formed in the side region forming a tapered surface extending from 7b to both ends of the first region 19a. The first region 19a is formed by a flat surface portion or a curved surface portion, and is a convex curved surface in this embodiment. The second region 19b is constituted by, for example, a tapered plane.
The light confinement lenses 19 were arranged so as to extend in a direction parallel to the extending direction of the prism 21 of the light collecting sheet 20. Alternatively, the light confinement lens 19 may extend in a direction orthogonal to the extending direction of the prism 21 of the light collecting sheet 20.

Here, the configuration of the optical confinement lens 19 will be described with reference to FIG.
In the cross-sectional shape of the optical confinement lens 19 shown in FIGS. 3A and 3B, the inclination angle θ of the second region 19b with respect to the exit surface 7b of the light guide 7 is in the range of 55 ° to 70 °. Is desirable.
If the inclination angle θ is within this range, the angle distribution is appropriately expanded by the light Lb emitted in the oblique direction, so that the viewing angle and the luminance of the illumination device 3 can be effectively increased.

On the other hand, when the inclination angle θ is less than 55 °, the amount of light emitted in the oblique direction is weak, so the angle distribution is not sufficiently widened, and the luminance of the illumination device 3 does not increase so much.
When the inclination angle θ exceeds 70 °, the amount of light totally reflected by the second region 19b increases and the amount of Lb emitted in the oblique direction becomes too strong, so that the emitted light is stacked on the light guide 7. Further, the loss due to Fresnel reflection when light enters the diffusion sheet 8 or the light collecting sheet 20 is increased, and the luminance is decreased.
In the optical confinement lens 19, the first region 19 a and the second region 19 b that form the convex cross section are, for example, line symmetric with respect to the center line.

  When the first region 19a is a parallel plane portion, the pitch of the light confinement lens 19 is P, the distance of the virtual line O connecting both ends of the substantially arc-shaped first region 19a is D, and the first The distance between the virtual line O corresponding to the height of the two regions 19b and the exit surface 7b (the distance between the first region 19a and the exit surface 7b) is H1, and the distance between the virtual line O and the apex of the first region 19 Is set to H2, the relationship between the height H1 and angle θ of the second region 19b and the pitch P of the optical confinement lens 19 is preferably in the range indicated by the following equation (1).

In the above equation (1), the coefficient 0.3 on the left side and the coefficient 0.7 on the right side are experimentally obtained numerical values. If the coefficient is smaller than 0.3, the height of the confinement lens 19 is too low and the optical confinement action. Becomes insufficient, and the dark portion S is visually recognized on both sides of the light guide 7. On the other hand, if it is larger than 0.7, the light diffusion action by the first region 19a formed of the flat surface or the curved surface formed on the top of the confinement lens 19 becomes weak, so that a problem that the hot spot is visually recognized occurs.
Further, regarding the above formula (1), when the distance H1 is smaller than the lower limit value, the ratio of the first region 19a to the total surface area of the light confinement lens 19 is too large, and the light confinement effect is reduced. A dark part S, which will be described later, is visually recognized on both side parts (see FIG. 5A). When H1 is larger than the upper limit value, the proportion of the second region 19b is too large, the light diffusing action in the first region 19a becomes insufficient, the light is concentrated locally and the brightness increases in a spot shape. Spots will be visible.

Even when the first region 19a is a curved surface portion, the dark portion S and the hot spot reduction effect similar to those when the first region 19a is a plane portion can be exhibited within the range of the expression (1). In this case, H1 refers to the height from the exit surface 7b to both ends of the first region 19a.
Examples of the shape of the curved surface portion formed in the first region 19a include a quadratic function curve and an arc shape in a longitudinal section, but are not necessarily limited thereto. Based on FIG. 3, when the width of the curved surface portion of the first region 19a is D and the height is H2, the aspect ratio defined by H2 ÷ D is preferably within a range of 0.4 or less. . When the aspect ratio exceeds 0.4, the amount of light collected in the observation direction F without being diffused by the curved surface portion locally increases, so that a hot spot is visually recognized.

Next, the optical function by the structure which arranged the light confinement lens 19 in the output surface 7b of the light guide 7 is demonstrated with reference to FIG.4 and FIG.5.
FIG. 4A is a top view of a general light guide 7 ′ without the light confinement lens 19 and a view from the light source 6 side. In the absence of the light confinement lens 19, the light emitted from the light source 6 enters the light guide 7 through the facing incident surface 7 </ b> L, and guides the light guide 7 while spreading in a fan shape. Reflected and diffused in the direction of the side surface 7m.

  On the other hand, FIG. 4B is a top view of the light guide 7 according to the first embodiment provided with the light confinement lens 19 and a view seen from the light source 6 side. When the light confinement lens 19 is provided, the incident light is reflected by the light deflection surface 7a and spreads in the direction of the side surface 7m toward the opposite exit surface 7b, but the second region 19b formed of the inclined surface of the light confinement lens 19 or Since light is repeatedly reflected back in the first region 19a, light does not diffuse so much and is guided in the extending direction of the light confinement lens 19.

Next, the luminance distribution in the plan view of the light guide 7 will be described with reference to FIGS.
In the plan view of the light guide 7 shown in FIGS. 5A and 5B, a plurality of light sources 6 are respectively arranged facing the two incident surfaces 7 </ b> L facing each other with long sides. In the light deflecting surface 7a of the light guide 7, the cylindrical light deflecting elements 18 arranged in parallel to the incident surface 7L are sparser as the distance from the incident surface 7L is closer to each other, that is, from the incident surface 7L. The luminance distribution in the case where the light guides 7 are arranged so as to be closer to the center is shown. That is, the light deflection elements 18 are one-dimensional dense patterns arranged in a direction parallel to the incident surface 7L.
Further, the light guide 7 does not have to have uniform brightness on the entire exit surface 7b. For example, the light exiting surface 7b of the light guide 7 can form a sparse / dense pattern of the light deflection elements 18 in which the arrangement of the light deflection elements 18 at the center is dense so that the brightness is highest at the center.

In the exit surface 7b of a general light guide 7 ′ not provided with the light confinement lens 19 shown in FIG. 5A, the light deflection elements 18 are one-dimensional dense patterns arranged in parallel to the entrance surface 7L. In this case, there is a problem that a substantially triangular dark portion S is generated at both ends on the short side where the light source 6 is not disposed.
The reason for this is that, as shown in FIG. 4A, the light incident on the light guide 7 'from the light source 6 spreads in a fan shape and is guided and reflected by the light deflection element 18 on the light deflection surface 7a and emitted. Head to face 7b. At that time, due to the light incident on the light guide 7 ′ spreading in a fan shape, superimposition of the light guides from the plurality of light sources 6, light leakage from the side 7 m on the short side where the light sources 6 are not disposed, Then, the arrangement relationship of the plurality of light sources 6 and the like are related in a complex manner, and a triangular dark portion S is generated on the side surface 7m on the short side where the light source 6 of the emission surface 7b is not provided.
Therefore, normally, the light deflection element 18 is two-dimensional so that the dark portion S does not occur on both side surfaces 7m side of the emission surface 7b where the light source 6 is not present, and the central luminance of the emission surface 7b of the light guide 7 is increased. It is necessary to form with a dense pattern.

On the other hand, FIG. 5B is a diagram showing a luminance distribution when the light guide 7 according to the embodiment in which the light confinement lenses 19 (not shown) are arranged on the exit surface 7b as viewed from the exit surface 7b side.
Similarly, the light guide 7 is configured such that the light deflection elements 18 arranged on the light deflection surface 7a are arranged sparsely on the surface 7L side and densely arranged at the center of the light guide 7 to increase the luminance. ing. As shown in FIG. 4B, the light incident on the light guide 7 from the light source 6 is changed in the direction of the incident surface 7 </ b> L in the second regions 19 b on both sides so that it does not spread like a fan in the light confinement lens 19. Since the light is confined in the range of the light confinement lens 19 by repeating the reflection, there is little light leakage on the short side 7m side, high luminance is obtained in the extending direction of the incident surface 7L facing the light source 6, and there is no light source 6. A dark portion S as shown in FIG. 5A does not occur in the vicinity of both side surfaces 7m.

  In addition, it is desirable that the display device 1 using the light guide 7 according to the first embodiment has a higher luminance as the screen center. Since the light deflection elements 18 of the light deflection surface 7a of the light guide 7 having the light confinement lens 19 formed on the emission surface 7b are arranged in a one-dimensional dense pattern, the direction orthogonal to the incidence surface 7L on which light is incident. For example, as shown in FIG. 2, it is possible to increase the brightness at the center of the screen by appropriately adjusting the density pattern of the light deflection elements 18 so that the center is dense. However, the light deflection elements 18 have a cylindrical shape. Therefore, the brightness is substantially uniform in the direction parallel to the incident surface 7L (see FIG. 5B).

  Therefore, it is possible to adjust the current applied to the plurality of light sources 6 arranged along the incident surface 7L facing the light source 6 so that the luminance increases in the direction parallel to the incident surface 7L as the screen is centered. it can. For example, the amount of current applied to the light source 6 disposed in the central region in the longitudinal direction of the incident surface 7L may be increased, and the amount of current applied to the light source 6 may be gradually reduced toward both ends.

In this embodiment, the light guide 7 is made of, for example, an acrylic resin represented by PMMA (polymethyl methacrylate), PET (polyethylene terephthalate), PC (polycarbonate), COP (cycloolefin polymer), PAN (polyacrylonitrile). A transparent resin such as a copolymer) or AS (acrylonitrile styrene copolymer).
The light guide 7 is manufactured by using these materials by an extrusion molding method, an injection molding method, or a heat press molding method well known in the art, and the light deflection element 18 and the optical confinement lens. 19 is integrally formed.
Alternatively, after the parallel plate light guide 7 is formed by any of the above-described manufacturing methods, the light deflection element 18 and the light confinement lens 19 are formed using a printing method, a UV curable resin, a radiation curable resin, or the like. May be.

In the light guide 7 according to the present embodiment, it is desirable that the light deflection element 18 and the light confinement lens 19 are integrally formed by using the extrusion molding method among the manufacturing methods described above. As a result, the number of steps for producing the light guide 7 is reduced, and the mass productivity is high because it is formed by roll-to-roll.
In the light guide 7 according to the first embodiment, since the light deflection elements 18 formed on the light deflection surface 7a have a one-dimensional density pattern, the width direction of the roll mold matches the one-dimensional density direction. In addition, the light guide 7 can be formed in a roll-to-roll manner by disposing the roll mold in the circumferential direction at a substantially constant interval.
In the light guide 7, the light deflection element 18 and the light confinement lens 19 are formed at the same time. Therefore, even if the light deflection element 18 has a one-dimensional sparse / dense pattern, the triangular dark portion S shown in FIG. It is possible to obtain a light guide 7 that does not cause the occurrence of light.

The light guide 7 according to the present embodiment and the display device 1 on which the light guide 7 is mounted have the above-described configuration, and the operation thereof will be described next.
In the display device 1 according to the present embodiment shown in FIG. 1, light is projected from the light source 6 facing the incident surface 7 </ b> L having a long side facing the light guide 7, and the light is guided through the incident surface 7 </ b> L. Enter the body 7 and diffuse. The emitted light is reflected by a cylindrical light deflection element 18 arranged in a dense pattern on the light deflection surface 7a of the light guide 7 and diffused in a direction A perpendicular to the extending direction (see FIG. 2). It progresses while diffusing toward the exit surface 7b.
At that time, the light deflection elements 18 are arranged in parallel to the extending direction of the incident surface 7L and are sparsely spaced in a region close to the incident surface 7L in the orthogonal direction, and dense in a central region gradually separated from the incident surface 7L. Arranged at intervals. As shown in FIG. 5A, the light is guided so that the luminance in the central region in the direction orthogonal to the incident surface 7L is high and the luminance is relatively low in the region near the incident surface 7L.

A plurality of light confinement lenses 19 extend in the direction orthogonal to the extending direction of the light deflection element 18 on the exit surface 7b of the light guide 7 and are arranged in the direction of the side surface 7a.
As shown in FIG. 4B, the reflected light from the light deflecting element 18 incident on the light confinement lens 19 is not reflected outside the second region 19b facing inside the light confinement lens 19 and spreads outward. By traveling in the extending direction of 19, the light can be prevented from diffusing around.
As a result, the light source 6 of the light guide 7 is not provided, for example, the triangular dark portion S is not formed on both side surfaces 7m on the short side, and the overall brightness is high and the brightness at the center is higher than the surroundings. Can be set.

Further, in each light confinement lens 19, the first region 19a including the apex is formed by a flat surface portion or a curved surface portion, and a part of the reflected light from the light deflection element 18 is as shown in FIG. Then, it is directly incident on the first region 19a, diffused in the direction perpendicular to the direction in which the optical confinement lens 19 extends, and emitted.
As shown in FIG. 3B, the other part of the reflected light is reflected and diffused by the second region 19 b formed by the tapered surface of the flat portion of the light confinement lens 19. Here, a part of the light La is refracted and emitted in the observation direction F, and another part of the light Lb is refracted in the first region 19a after being reflected and emitted in an oblique direction, and the remaining part of the light. Lc is returned to the inside of the light guide 7 by total reflection.

As described above, the light confined in the first region 19a of the light confinement lens 19 and the light La and Lb refracted in the second region 19b and emitted obliquely are emitted in the extending direction of the light confinement lens 19. Spread in the orthogonal B direction.
Therefore, the angular distribution of the light emitted from the light guide 7 is reduced in the strong luminance peak in the 0 ° direction as seen in the case of the 90 ° prism, and forms a distribution shape that is moderately spread over a wide angle. (See FIG. 6).

Since the light confinement lens 19 is formed on the exit surface 7b of the light guide 7, the light traveling on the exit surface 7b is less likely to spread in a direction parallel to the entrance surface 7L. Therefore, for example, an LED is used as the light source 6. In this case, when the light guide 7 is observed from the observation direction F, bright and dark unevenness (hot spot) including a bright spot facing the LED and a dark spot between the LED and the LED may be observed. Such a hot spot causes a deterioration in the quality of the lighting device 3.
On the other hand, the light confinement lens 19 of the light guide 7 according to the present embodiment diffuses the light emitted from the light source 6 in a direction parallel to the incident surface 7L in the first region 19a formed by a flat surface or a curved surface. Therefore, hot spots can be effectively reduced.

Thus, the emitted light emitted from the light guide 7 is further diffused by passing through the diffusion sheet 8 and becomes more uniform light. Then, the diffused light is condensed in the observation direction F by transmitting through the condensing sheet 20, and the light collected by transmitting through the diffusive optical sheet 28 is diffused again.
Then, the diffused light is transmitted through the image display element 2 so that the transmitted image can be observed from the observation direction F side. The obtained transmission image has high brightness as a whole, and in particular, the brightness at the center can be set higher than that at the periphery, and since the dark portion S does not occur at both ends, the whole has high brightness and uniform brightness. A high-quality image with particularly high luminance at the center can be obtained.

Here, in order to raise the brightness | luminance of the illuminating device 3, the case where the condensing sheet | seat 20 which consists of a prism sheet is further overlapped and used for the light guide 7 is considered. At this time, it is assumed that the light collecting sheet 20 is arranged so that the direction in which the light confinement lens 19 of the light guide 7 extends and the direction in which the prism 21 of the light collecting sheet 20 extends are parallel to each other. At this time, if the angular distribution of the light emitted from the light guide 7 has a strong peak in the 0 ° direction, the light is returned to the light guide 7 side by total reflection on the prism surface of the light collecting sheet 20. Therefore, the brightness of the lighting device 3 cannot be sufficiently increased. In order to increase the luminance of the illuminating device 3, the angular distribution of light emitted from the light guide 7 needs to have a moderate spread.
In that respect, the light confinement lens 19 of the light guide 7 according to the present embodiment forms a distribution shape in which a strong peak in the 0 ° direction is relaxed and moderately spread over a wide angular distribution. The total reflection by 20 can be suppressed, and the luminance of the lighting device 3 can be effectively increased. The same applies when the diffusion sheet 8 is inserted between the light guide 7 and the light collecting sheet 20.

Next, a test example in which the luminance distribution by the light guide 7 according to this embodiment and a general conventional light guide is measured will be described.
Example a is a light guide 7 in which light confinement lenses 19 are arranged on the exit surface 7b according to the above-described embodiment, and Comparative Example b is a replacement of the light confinement lens 19 in Example a with a prism having an apex angle of 90 °. For the light guide, Comparative Example c, a light guide having an exit surface 7b on which the light confinement lens 19 is not formed was used. The cylindrical light deflecting elements 18 according to the above-described embodiment are provided in a sparse / dense pattern on the light deflecting surface 7a of each light guide 7.
And the light source 6 was arrange | positioned in a pair of long-side entrance plane 7L which opposes about each light guide, and angular distribution of each brightness | luminance was measured. The result is shown in FIG.

The angular distribution on the horizontal axis shown in FIG. 6 indicates the angular distribution of light spreading in the direction perpendicular to the extending direction of the optical confinement lens 19, and the vertical axis indicates the luminance.
In the embodiment a shown in FIG. 6, the first region 19a and the second region 19b of the optical confinement lens 19 are both constituted by a plane portion, the pitch P of the optical confinement lens 19 is 100 μm, the second region and the exit surface 7b. The angle θ is 65 °, and the distance H1 of the second region is 53.6 μm.
Comparative example b shows the angular distribution of a light guide having a prism with an apex angle of 90 °, which forms a steep high-brightness peak in the 0 ° direction and generates a side lobe at a position near ± 90 °. did. Comparative example c shows the angular distribution of the light guide 7 in which the optical confinement lens 19 is not formed. The luminance is small near 0 ° and does not form a strong peak at a specific angle, and the luminance is low over a wide angle. The distribution shape spreads.
From these results, the angular distribution of the light guide body 7 provided with the optical confinement lens 19 according to the present embodiment a has an intermediate distribution characteristic between the comparative examples b and c. For this reason, a balanced luminance distribution is obtained in which the central region has a moderately high luminance and the luminance is prevented from decreasing in the peripheral portion.

(1) As described above, according to the light guide 7 according to the present embodiment, since the light confinement lenses 19 are arranged on the exit surface 7b, a conventional light guide in which the exit surface is a flat plate or a prism is arranged. As compared with the above, a high luminance peak in the central region is relaxed and a decrease in luminance in the peripheral portion is suppressed, so that a moderately high luminance distribution can be obtained over a wide angular distribution.
(2) The light confinement is composed of a first region 19a having a flat surface or curved surface including an apex in the light guide 7, and a second region 19b having a tapered plan view formed at both ends of the first region 19a. By arranging the lenses 19, the emitted light is diffused and emitted in the first region 19 a and refracted and reflected in the second region 19 b to diffuse and emit the emitted light La and Lb in an oblique direction. The diffused light can be emitted in a direction orthogonal to the extending direction of the light confinement lens 19. In addition, the visibility of the light deflection element 18 can be reduced.

(3) Since the light confinement lens 19 extends in a direction orthogonal to the incident surface 7L facing the light source 6 and is arranged in a parallel direction, the reflected light from the light deflection surface 18 enters the light confinement lens 19. Then, since reflection is repeated in the second region 19b facing each other and travels in the extending direction of the lens 19, the reflected light can be prevented from diffusing to the surroundings, such as leaking outside from the side surface 7m without the light source 6, The dark portion S is not formed on the side surfaces 7m on both sides. Therefore, the brightness of the peripheral part is increased and high brightness is obtained as a whole.

(4) Moreover, since the light deflection element 18 is provided on the light deflection surface 7a facing the exit surface 7b of the light guide 7, incident light can be diffused and reflected to the exit surface 7b, thereby improving the diffusibility. . In particular, by arranging the light deflection elements 18 so as to extend in a direction orthogonal to the light confinement lens 19, light can be diffused in directions orthogonal to each other, and more uniform diffused light can be emitted.
Further, the light deflection elements 18 are arranged in parallel to the incident surface 7L facing the light source 6, and the light deflection elements 18 are spaced apart from each other in a region close to the light source 6 in a direction orthogonal to the incidence surface 7L. By arranging in a dense and dense pattern, the luminance of the central region can be set high.
In addition, according to the light guide 7 according to the present embodiment, the light emitted from the light source 6 is incident on the incident surface in the first region 19a formed by the light confinement lens 19 (and the light deflection element 18) as a flat surface or a curved surface. Since diffusion is performed in a direction parallel to 7L, hot spots can be effectively reduced.

Therefore, according to the illuminating device 3 according to the present embodiment, the illuminating device 3 can be obtained in which the dark portion S in the peripheral portion is eliminated by the light guide 7 according to the present embodiment, and the entire central portion has higher luminance.
Further, according to the display device 1 according to the present embodiment, the high-luminance illumination device 3 is transmitted through the image display element 2, so that the central portion has high luminance and the decrease in luminance in the peripheral portion is suppressed, and a dark portion S or the like is generated. A high-brightness image can be obtained.

It should be noted that the present invention is not limited to the above-described embodiment, and appropriate changes and substitutions can be made without departing from the spirit of the present invention. In the following, other embodiments and the like will be described using the same reference numerals for members, parts, and the like that are the same as or similar to the above-described embodiments.
Next, a light guide 7A according to a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment described above, the configuration in which the light deflection element 18 has a concave cylindrical shape has been described, but the present invention is not limited to such a configuration. 7A to 7C show a light guide 7A according to the second embodiment.

In the light guide 7A according to the second embodiment, the light polarization element 18A has a convex cylindrical shape protruding outward from the light deflection surface 7a. In the light deflecting element 18A having the convex cylindrical shape, the effect of deflecting light toward the exit surface 7b is lower than that of the concave cylindrical light deflecting element 18. Therefore, it is necessary to arrange a larger number of light deflection elements 18A in this light deflection element 18A than the concave cylindrical light deflection element 18 is.
In this case, in the second embodiment, the number of the light deflection elements 18A arranged at positions close to the incident surface 7L facing the light source 6 is increased and the arrangement interval is reduced, so that the light deflection element serving as a pseudo light source This is desirable because the effect of preventing see-through of 18A (the concealing property of the light deflection element 18A) is enhanced and the observation becomes more difficult to see.

Next, a light guide 7B according to a third embodiment of the present invention will be described with reference to FIG.
In the light guide 7C according to the third embodiment, the light deflection elements 18B arranged on the light deflection surface 7a have a concave microdot shape, that is, a substantially hemispherical or semi-elliptical recess. The light deflection elements 18B are arranged at a substantially constant interval in a direction parallel to the incident surface 7L. In a direction orthogonal to the incident surface 7L, the light deflection elements 18B are arranged at a sparser interval as the position is closer to the incident surface 7L, and at a denser interval as it is farther away. This is a structure of a one-dimensional sparse pattern array.
Also in the light guide 7B having such a configuration, the same effects as those of the light guide 7 according to the first embodiment can be obtained.

Next, a light guide 7C according to a fourth embodiment of the present invention will be described with reference to FIG.
In the light guide 7C according to the fourth embodiment, the light deflection elements 18B arranged on the light deflection surface 7a have a convex microdot shape, that is, a substantially hemispherical or semi-elliptical convex portion. The light deflecting elements 18C are arranged at a substantially constant interval in a direction parallel to the incident surface 7L. In a direction orthogonal to the incident surface 7L, the light deflecting elements 18C are arranged at a sparser interval as the position is closer to the incident surface 7L, and at a denser interval as it is farther away. This is a one-dimensional sparse / dense pattern array structure.

Here, in the third and fourth embodiments, the light deflection elements 18 (18B, 18C) on the light deflection surfaces 7a of the light guides 7B, 7C are substantially in a direction parallel to the light incident surface 7L. Although formed at a constant interval, the interval may be changed in the direction orthogonal to the incident surface 7L depending on the distance from the incident surface 7L.
For example, on the light deflecting surface 7a, the light deflecting elements 18 (18B, 18C) are arranged at regular intervals that are sparse in the direction parallel to the incident surface 7L, and are arranged more densely apart in the direction orthogonal to the incident surface 7L. For this reason, the light incident surface 7L may be arranged at a constant interval in a direction parallel to the light incident surface 7L.
Alternatively, the light deflection elements 18 (18B, 18C) may be irregularly arranged. At this time, the light deflection elements 18 (18B, 18C) per unit area are disposed so that the ratio of the light deflection elements 18 (18B, 18C) per unit area in the direction parallel to the incident surface 7L is substantially constant, and in the direction orthogonal to the light incident surface 7L. It is desirable to have a sparse gradation pattern that is arranged sparsely as it is closer to 7L and denser as it is farther away.

In each of the above-described embodiments, the case where the light deflection element 18 has a concave or convex cylindrical shape or microdot shape has been described. However, the present invention is not limited to this. For example, it may be a concave or convex prism shape, or may be an elliptical micro dot or a pyramidal micro dot.
In addition, the second region 19b of the optical confinement lens 19 is a tapered surface composed of a flat portion, but the shape is not limited to the flat portion, and may be a curved surface such as a convex curved surface or a concave curved surface. Any shape can be used as long as the reflected light can be refracted or reflected to be emitted to the outside as diffused light.

  The embodiments of the light guide 7 (7A, 7B, 7C), the illumination device 3, and the display device 1 according to the present invention have been described above. However, the illumination device 3 according to the present invention is not applied only to the display device 1. Absent. That is, it goes without saying that the illumination device 3 having a function of efficiently collecting the light emitted from the light source 6 can be used for, for example, an illumination device.

Examples of the present invention will be described in detail below, but the present invention is not limited to the following examples.
Two types of light guide 7 and lighting device 3 shown below were produced.
The first light guide 7 is a rectangular parallelepiped of 310 mm × 520 mm in 23 inch size, and has a thickness of 2 mm. The side surface 7m of the two short sides (310 mm side) of the light guide 7 was used as the incident surface 7L facing the light source 6.
The light deflecting element 18 formed on the light deflecting surface 7a of the light guide 7 has a concave microlens shape as shown in FIG. 8, and the area occupied by the microlens 18 is reduced in the region close to the incident surface 7L, so that the light is incident. A one-dimensional dense / dense pattern was formed so that the area occupied by the microlens 18 increased as the distance from the surface 7L increased.
That is, the microlenses 18 are arranged most densely in the central region in the direction orthogonal to the incident surface 7L of the light guide 7. The microlens 18 had a diameter of about 70 μm and a height of about 15 μm.
The diffusing sheet 8 and the prism sheet 20 were placed in this order in the light emission direction of the light guide 7 to produce the lighting device 3. The prism sheet 20 was installed so that the direction in which the prism with an apex angle of 90 ° extends was parallel to the long side (520 mm side).

  Examples in which an optical confinement lens 19 having the following dimensions was formed on the exit surface 7b of the light guide 7 were designated as Examples 1-9. The first region 19a of each light confinement lens 19 was a flat portion. The optical confinement lens 19 was formed so that its extending direction was parallel to the long side (520 mm side), and the unit lens pitch P was set to 100 μm.

Example 1 θ = 55 °, H1 = 21.5 μm
(Example 2) θ = 55 °, H1 = 35.7 μm
Example 3 θ = 55 °, H1 = 49.0 μm
(Example 4) θ = 65 °, H1 = 32.5 μm
(Example 5) θ = 65 °, H1 = 53.6 μm
(Example 6) θ = 65 °, H1 = 75.0 μm
Example 7 θ = 70 °, H1 = 41.5 μm
Example 8 θ = 70 °, H1 = 68.7 μm
Example 9 θ = 70 °, H1 = 96.0 μm

  As the 2nd light guide 7, what formed the light confinement lens 19 of the shape which has the following dimensions in the output surface 7b was made into Comparative Examples 1-4. The first region 19a of the optical confinement lens 19 is a flat portion. The optical confinement lens 19 was formed so that the extending direction was parallel to the long side (520 mm side), and the unit lens pitch P was 100 μm.

(Comparative Example 1) θ = 50 °, H1 = 29.8 μm
Comparative Example 2 θ = 75 °, H1 = 56.0 μm
Comparative Example 3 θ = 65 °, H1 = 20.0 μm
(Comparative example 4) θ = 65 °, H1 = 85.8 μm

  Examples 10 to 13 were obtained by forming the light confinement lens 19 having the following dimensions on the exit surface 7b of the first light guide 7. The first region 19a of the light confinement lens 19 is a curved surface portion. The curved surface portion has a shape defined by a quadratic function. The optical confinement lens 19 was formed so that the extending direction was parallel to the long side (520 mm side), and the unit lens pitch P was 100 μm.

Example 10 θ = 60 °, H1 = 43.3 μm, H2 = 20.0 μm
Example 11 θ = 60 °, H1 = 43.3 μm, H2 = 10.0 μm
(Example 12) θ = 65 °, H1 = 53.6 μm, H2 = 20.0 μm
(Example 13) θ = 65 °, H1 = 53.6 μm, H2 = 10.0 μm

(Comparative Example 5)
A prism having a pitch of 100 μm and an apex angle of 90 ° was formed on the exit surface 7b of the second light guide 7 so that the extending direction thereof was parallel to the long side (520 mm side).

The light guides 7 of Examples 1 to 13 and Comparative Examples 1 to 5 have a rectangular flat plate shape, and the two short side surfaces 7m facing each other are used as a light incident surface 7L, and a plurality of LEDs are used as the light source 6 facing the light incident surface 7L. Arranged.
The light guide 7 according to Examples 1 to 13 and Comparative Examples 1 to 5 is disposed in the lighting device 3, and the light reflecting sheet is white and has a reflectance of 98% on the back surface of the light guide 7 on the light deflection surface 7 a side. 5 was arranged. And the illuminating device 3 was each manufactured by laminating | stacking and arrange | positioning the diffusion sheet 8 and the prism sheet 20 in order on the emission surface 7b side of the light guide 7.

About the illuminating device 3 obtained by attaching the light guides 7 of Examples 1 to 13 and Comparative Examples 1 to 5, measurement of front luminance and evaluation of hot spot visibility and dark portion S visibility are as follows. Went like that.
In the measurement of the front luminance, the measurement was performed using a spectral luminance meter SR-3 manufactured by TOPCON. Moreover, evaluation of the visibility of a hot spot and the dark part S made the case where a hot spot and the dark part S were not visually recognized when visually observing the illuminating device 3 from the observation direction F, and made x when visually recognized.

  Table 1 shows the evaluation results of the front luminance, hot spot, and dark part S of the illumination devices 3 according to Examples 1 to 13 and Comparative Examples 1 to 5.

Here, the measured value of the front luminance is expressed as normalized front luminance (%) when the front luminance of Comparative Example 5 is set to 100.
As a result of the evaluation, it was confirmed that all of Examples 1 to 13 increased the front luminance as compared with Comparative Example 5. Here, an error range of the measuring instrument of ± 1% or more and an increase in front luminance was judged to have a front luminance improvement effect.
Furthermore, all Examples 1-13 confirmed that the hot spot and the dark part S were not visually recognized. On the other hand, in Comparative Examples 1 and 2, there was no effect of improving the front luminance, in Comparative Example 3, the dark portion S was exposed, and in Comparative Examples 4 and 5, a hot spot was generated.

DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Liquid crystal panel 3 Illumination apparatus 5 Reflection board (reflection sheet)
6 Light source 7, 7A, 7B, 7C Light guide 7a Light deflection surface 7b Emission surface 7m Side surface 7L Incident surface 8 Diffusion sheet,
9 Liquid crystal layer 10, 11 Polarizing plate 18, 18A, 18B, 18C Optical deflection element 19 Optical confinement lens,
19a 1st field 19b 2nd field 20 Condensing sheet (prism sheet)
28 Diffusing Optical Sheet S Dark Part

Claims (12)

A translucent light guide,
A first main surface, a second main surface facing the first main surface, and a side surface provided between the first main surface and the second main surface,
The first main surface is provided with a light deflection element that deflects light incident from a light source toward the second main surface,
On the second main surface, there is a light confinement lens that extends in a direction perpendicular to the extending direction of at least one of the side surfaces facing the light source and regulates an optical path of light guided inside the light guide. Provided,
The optical confinement lens includes a first region composed of a flat surface portion or a curved surface portion formed in a region including the apex, and a second region composed of tapered surfaces formed at both ends of the first region. A light guide characterized by comprising.   2. The light guide according to claim 1, wherein an angle θ formed by the second region of the light confinement lens and the second main surface is not less than 55 degrees and not more than 70 degrees. In the optical confinement lens, when the distance from the second main surface to the first region is H1, the pitch of the optical confinement lens is P, and the angle formed by the second region and the second main surface is θ. The light guide according to claim 1, wherein the following expression (1) is satisfied.
  The light deflection elements are arranged in parallel to the extending direction of the side surface facing the light source, and the distance between the light deflection elements changes from sparse to dense as the distance from the side surface increases in a direction orthogonal to the side surface facing the light source. The light guide according to any one of claims 1 to 3, wherein the light guide is formed.   5. The light guide according to claim 1, wherein the light deflecting element has a cylindrical shape, a prism shape, or a microdot shape that is concave or convex when viewed in cross section.   6. The light guide according to claim 1, wherein the first region of the optical confinement lens is a flat portion.   The first region of the optical confinement lens is a curved surface portion, and a cross section obtained by cutting the first region in a direction perpendicular to the extending direction of the optical confinement lens is a quadratic function curve or an arc shape. The light guide according to any one of claims 1 to 5.   When the first region of the optical confinement lens is a curved surface portion, and the width of the first region is D and the height is H2, the aspect ratio defined by H2 ÷ D is 0.4 or less. The light guide according to any one of claims 1 to 5 and 7. A light source;
A light guide according to any one of claims 1 to 8,
A lighting device comprising: a reflection sheet disposed on a back surface of the light guide on the first main surface side.   The lighting device according to claim 9, further comprising an optical sheet having at least one of light scattering, refraction, absorption, and reflection in front of the light guide in the light emission direction.   A light collecting sheet in which prisms are arranged in front of the light emitting direction of the light guide, the prism extending direction of the light collecting sheet being parallel or perpendicular to the light confining lens extending direction; The lighting device according to claim 9 or 10. An image display element that defines a display image according to light transmission / shielding in pixel units;
The lighting device according to any one of claims 9 to 11,
A display device comprising: