JP2012009408A - Lighting unit equipped with concealment structure, lighting system, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concealment structure which makes the optical deflection element of a light guide plate invisible and improves front luminance.SOLUTION: The surface light source device 2 of a liquid crystal display device 1 makes light emitted from a light source 11 enter from an end face of a light guide plate 10 and deflects it to an emitting face by an optical deflection element 13. The optical deflection element 13 is arranged by a first pitch Pin a first direction q1 of the optical deflection face 12 and by a second pitch Pin a direction orthogonal to this. The concealment structure 3 has a plurality of first unit lenses 16 formed on the light emission face side 15a and a directional diffusion layer 17 having a function which diffuses more strongly to the second direction q2 than the first direction q1 formed on the light incident face side 15b. In the constitution of the concealment structure having no first unit lenses 16, when the angular distribution of intensity of light in which collimating light is made vertically enter from the light incident face side 15b and emitted from the light emission face side 15a is measured, the half-value angle of the angular distribution of the intensity of light to the second direction q2 is 3 degrees or more and less than 10 degrees.

Description

  The present invention relates to an illumination unit, an illumination device, and a display device that include a concealing structure mainly used for illumination optical path control.

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 used. 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 panel. A light diffusing plate is used between the image display element such as a liquid crystal panel and the 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 lighting device, a plurality of light sources such as cold cathode tubes and LEDs are arranged on an end face of a light-transmitting plate called a light guide plate. In general, a light deflection surface that efficiently guides incident light incident from the end surface of the light guide plate to the exit surface is formed on the surface opposite to the exit surface of the light guide plate (the surface facing the image display element). The light deflecting elements formed on the light deflecting surface include various light deflecting elements for efficiently leading to the exit surface, such as those printed with a white dot pattern or those provided with a lens shape. Proposed.

However, since the edge light system has a structure in which the light source is disposed only on the end face of a light-transmitting plate called a light guide plate, the number of light sources installed is limited. Therefore, as the liquid crystal display device becomes larger, it becomes difficult to brighten the entire display, and the role of the optical sheet for improving the brightness becomes important.

As means for improving the brightness of a liquid crystal display screen, a brightness enhancement film (BEF), which is a registered trademark of 3M Corporation of the United States, is widely used as a lens sheet.
18 and 19 show the brightness enhancement films described in Patent Documents 1 and 2 below. FIG. 18 schematically shows a surface light source 182, a BEF 185 as a brightness enhancement film on which light emitted from the surface light source 182 is incident, and a liquid crystal panel 184. As shown in FIG. 19, the BEF 185 is an optical film in which unit prisms 187 having a triangular cross section are periodically arranged in one direction on a transparent substrate 186. The unit prism 187 has a size (pitch) larger than the wavelength of light.

The BEF 185 collects light from “off-axis” and redirects this light “on-axis” or “recycle” toward the viewer. Can be made. That is, the BEF 185 can increase the on-axis luminance by reducing the off-axis luminance when using the liquid crystal display device (when observing). Here, “on the axis” is a direction that coincides with the visual direction F of the observer in FIGS. 14 and 15, and is generally on the normal direction side with respect to the display screen of the liquid crystal panel 184.

In addition, as shown in FIG. 20, when using a lens sheet 191 typified by BEF 185, a diffusion film 190 in which a diffusion filler is applied on a transparent substrate is disposed between the light guide plate 100 and the lens sheet 191. Accordingly, luminance unevenness of light emitted from the light guide plate 100 can be suppressed.

  Furthermore, when the diffusion film 190 is disposed between the lens sheet 191 and the liquid crystal panel 184, side lobes of emitted light caused by the prism sheet can be reduced, and lenses arranged regularly are arranged. Moire interference fringes generated between the liquid crystal pixels can be prevented.

Meanwhile, as described above, the light guide plate 100 used in the edge light system includes the light deflection surface 100b at a position facing the exit surface, and the light deflection surface 100b has a white dot pattern or a microlens (concave or convex). ) And other lens-shaped light deflection elements 102 are formed.

However, since any light deflection element 102 is formed of a reflective layer or a structure that is regularly or regularly arranged in a pseudo-random manner, a lens represented by the above-described BEF185 is used. There is a problem of interference with the sheet (moire interference fringes) and a problem that the unevenness of the light deflection surface 100b is visually recognized. A method using a diffusion film 190 as shown is common.

The BEF 185 is one of the most efficient lens sheets for improving the brightness in the front direction. However, in a medium or large-sized liquid crystal display device exceeding 20 inches, the display becomes dark only by the light condensing action of the BEF 185. End up. One method for further improving the front luminance is, for example, a method in which two BEF185s are arranged in a cross, but there is a problem that the viewing angle of the liquid crystal display device becomes extremely narrow. Compared to a notebook personal computer, a portable information terminal, or the like, a liquid crystal display device for television use requires a sufficient viewing angle, and particularly requires a sufficient viewing angle in the horizontal direction.

Therefore, in order to conceal the light deflection element 102 formed on the light deflection surface 100b, the diffusion sheet 190 having almost no light collecting action must be disposed, and the front luminance necessary for the liquid crystal display device is obtained. Therefore, there is a problem that it is not sufficient to use only one BEF185.

As a technique for improving the front luminance of an edge light type lighting device, Patent Document 5 discloses a means for arranging a lens sheet having a triangular prism shape in cross section and a lens sheet having an elliptical shape in cross section. Is disclosed. However, in order to conceal the light deflection element 102 formed on the light guide plate 100, it is necessary to dispose the diffusion film 190 between the light guide plate 100 and the elliptical lens sheet, and the triangular shape that provides the best brightness enhancement effect. As the prism lens sheet, for example, the above-described BEF 185 can improve the front luminance, but sidelobe light is generated. Therefore, a diffusion film 190 is disposed between the triangular prism lens sheet and the liquid crystal display element. There is a need to. Therefore, in the structure shown in Patent Document 5, two optical films, an elliptical lens sheet, and a triangular prism lens sheet, and four optical films are required, which increases costs.

Further, in Patent Document 6, an array-like optical element is formed on one surface, and the incident light on the optical sheet is controlled by an optical sheet having an anisotropic scattering function on the other surface. A surface light source device in which a diffusion sheet can be omitted is disclosed. That is, the light emitted from the light guide plate 100 is emitted with a light intensity bias toward the propagation axis direction in the light guide plate 100 (the forward direction in Patent Document 6). The diffusion sheet 190 can be omitted by controlling the emitted light by the anisotropic scattering function formed on the surface. That is, it aims at controlling the deviation of the emission angle of the emitted light intensity.
However, the light deflection elements 102 are formed in various arrangements at predetermined intervals. Examples of the various arrangements include a square arrangement, a rectangular arrangement, and a hexagonal arrangement. Therefore, on the exit surface 100a of the light guide plate 100, the exit angle and the exit intensity of the exit light differ depending on the relative position with the light deflection element 102. For this reason, luminance unevenness due to the light deflection element 102 occurs, and it is necessary to conceal this. Therefore, it is difficult to conceal the light deflection element 102 of the light guide plate 100 described above simply by controlling the emitted light having intensity bias in the forward direction. Furthermore, it is disclosed that the difference in half-value angle on one side of the emitted light when collimated light is incident on the anisotropic scattering function surface is 10 degrees or more, but anisotropic scattering in which the difference in half-value angle on one side is 10 degrees or more is disclosed. When it is formed on the back surface of the optical sheet, the front luminance is significantly reduced.

In Patent Document 7, as an optical sheet for concealing the light deflection element 102 of the light guide plate 100, a light deflection sheet having an optical structure on both sides of the sheet and one or both of them is an anisotropic lens is disclosed. ing. However, in the edge light system, the light incident on the surface of the prism sheet opposite to the surface on which the prism is formed is condensed by refraction, and the light incident on the surface of the prism sheet on which the prism is formed is reflected. Thus, Patent Document 7 relates to the latter system and cannot solve the problem of concealing the light deflection element 102 of the light guide plate 100 in the former system.

Japanese Patent Publication No. 1-378001 JP-A-6-102506 JP 10-506500 Gazette JP 2004-295080 A JP-A-8-146225 JP 2001-124909 A JP 2009-300098 A

  The present invention has been made to solve the above-described problems, and includes a concealing structure that conceals a light deflection element formed on a light deflection surface of a light guide plate and can improve front luminance. An object is to provide an illumination unit, an illumination device, and a display device using the illumination device.

An illumination unit according to the present invention includes a light source, an incident surface on which light emitted from the light source is incident, an emission surface that emits incident light to an observer side, and light deflection that guides the incident light to the emission surface. A surface light source device comprising: a light guide body including a surface; and a reflection sheet that reflects light emitted from a surface opposite to the light emission surface and guides the light to the light guide body; and the surface light source An illumination unit having a concealing structure on the light exit surface side of the apparatus, wherein the light guide guides light incident on the light guide to the light exit surface toward the light exit surface. The light deflection elements are arranged at substantially equal intervals in a first direction at a first pitch P1, and the first pitch in a second direction substantially orthogonal to the first direction. The concealment is arranged in a two-dimensional array arranged at substantially equal intervals with a second pitch P2 larger than P1. The structure is a member provided with a second main surface on the light incident surface side and a first main surface on the light emission surface side, and the second main surface is incident on the second main surface. A directional diffusion layer that diffuses light with a wider angular distribution in a second direction than the first direction, wherein a plurality of first unit lenses are formed on the first main surface, and the directivity In the configuration without the first unit lens of the concealing structure, the diffusion layer has the light intensity of the light emitted from the first main surface when collimated light is vertically incident from the second main surface side. An illumination unit including a concealing structure, wherein a half-value angle of an angular distribution in two directions is 3 degrees or more and less than 10 degrees.
According to the illumination unit including the concealing structure according to the present invention, when the illumination unit is viewed from the observation side, the light deflection surface of the light guide plate is formed by the directional diffusion layer and the first unit lens provided in the concealment structure. In addition to the fact that the image of the light deflection element formed on the surface is diffused, it cannot be visually recognized, and the front luminance can be improved.

In the illumination unit according to the present invention, the first unit lens is a lens in which a region including at least a vertex is formed by a curved surface.
According to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate is widened by the first unit lens and the directional diffusion layer, so that the light deflection element becomes invisible. Furthermore, the front luminance can also be improved.

In the illumination unit according to the present invention, the directional diffusion layer is formed by forming a plurality of second unit lenses each having a curved surface at least including a vertex.
According to the present invention, since the image of the light deflection element formed on the light deflection surface of the light guide plate is widened, the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

In the illumination unit according to the present invention, a plurality of first unit lenses arranged in parallel to each other are formed at substantially equal intervals on the first main surface, and the first unit lenses extend in the second direction. It consists of a uniaxial lens.
According to the present invention, since the image of the light deflection element formed on the light deflection surface of the light guide plate is widened, the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

In the illumination unit according to the present invention, a plurality of second unit lenses arranged in parallel with each other are formed on the second main surface, and the second unit lens is formed of a uniaxial lens extending in the first direction. It is characterized by that.
According to the present invention, since the image of the light deflection element formed on the light deflection surface of the light guide plate is widened, the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

を満たし、かつ、

で定義される値 Ｄ が、１．５以上５以下であることを特徴とする。
本発明による隠蔽構造体を備えた照明ユニットによれば、導光板の光偏向面に形成される光偏向要素の像が広がることで、光偏向要素が視認できなくなる。さらに、正面輝度も向上させることができる。 In the lighting unit according to the present invention,
When the end of the first unit lens is 0, the displacement measured in the first direction is x, the cross-sectional height of the first unit lens is f (x), and the pitch is Q1, f (x) is

And satisfy

The value D defined by is characterized by being 1.5 or more and 5 or less.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

の範囲で規定されることを特徴とする。
本発明による隠蔽構造体を備えた照明ユニットによれば、導光板の光偏向面に形成される光偏向要素の像が広がることで、光偏向要素が視認できなくなる。さらに、正面輝度も向上させることができる。 Moreover, the lighting unit according to the present invention comprises:
The absolute value of the differential df (x) / dx of f (x) at the point where the displacement x is 0 is

It is specified in the range of
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

の範囲で規定されることを特徴とする。
本発明による隠蔽構造体を備えた照明ユニットによれば、導光板の光偏向面に形成される光偏向要素の像が広がることで、光偏向要素が視認できなくなる。さらに、正面輝度も向上させることができる。 Moreover, the lighting unit according to the present invention comprises:
When the displacement x where R (x) is the maximum value is x0, the absolute value of the differential df (x) / dx of f (x) when the displacement x is x0 is

It is specified in the range of
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

In the illumination unit according to the present invention, when the height of the second unit lens is H2 and the pitch is Q2, the aspect ratio is a numerical value defined by the following formula (H2 / Q2) × 100. The aspect ratio of the second unit lens is 4 or more and 10 or less at any position on the two principal surfaces.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

Moreover, the lighting unit according to the present invention comprises:
The second unit lens is formed by a first surface formed in a region including the apex, and a second surface formed in a region including the end, and the first unit and the second surface In the boundary portion, the tilt angle changes discontinuously, and the tilt angle at an arbitrary point on the second surface is larger than the tilt angle at an arbitrary point on the first surface.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

The lighting device according to the present invention comprises:
The second main surface of the concealing structure is substantially rectangular, and an end side of the second main surface parallel to the first direction and an end of the second main surface parallel to the second direction. An imaginary coordinate axis having an origin at an arbitrary point of intersection with the side is set, an axis parallel to the first direction is set as an X axis, and an axis parallel to the second direction is set as a Y axis. The length of the end side of the second main surface parallel to the first direction is W1, the length of the end side of the second main surface parallel to the second direction is W2, and the concealing structure In the configuration without the first unit lens of the body, the first main surface when collimated light is vertically incident from the second main surface side to arbitrary coordinates (X, Y) on the second main surface If the half-value angle (deg) of the angle distribution in the second direction of the light intensity of the emitted light from Φ is Φ (X, Y), and X0 is an arbitrary constant between 0 and W1, 0 when the is continuously changed from W2 / 2, wherein the half-value angle in X = X0 Φ (X0, Y) decreases monotonically.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

The lighting device according to the present invention comprises:
When the aspect ratio of the second unit lens on the coordinate (X, Y) or nearest to the coordinate (X, Y) is Ω (X, Y), Y is changed from 0 to W2 / 2. The aspect ratio Ω (X0, Y) at X = X0 monotonously decreases when it is continuously changed.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

The lighting device according to the present invention comprises:
A plurality of the second unit lenses are arranged so as to be spaced apart from each other so that a flat portion is formed therebetween, and are on the coordinates (X, Y) or nearest to the coordinates (X, Y) Is Δ (X, Y), the width Δ (X0, Y) of the flat portion at X = X0 monotonously increases when Y is continuously changed from 0 to W2 / 2. Features.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

The lighting device according to the present invention comprises:
The light guide includes one incident surface on which light emitted from the light source is incident, and the one incident surface is parallel to the first direction, and the second main surface of the concealing structure. Of the intersections between the end of the surface parallel to the first direction and the end of the second main surface parallel to the second direction, an arbitrary intersection on the side close to the one incident surface If a virtual coordinate axis is set as the origin, the axis parallel to the first direction is taken as the X axis, and the axis parallel to the second direction is taken as the Y axis, Y is continuously changed from 0 to W2. In this case, the half-value angle Φ (X0, Y) at X = X0 monotonously decreases.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

The lighting device according to the present invention comprises:
When Y is continuously changed from 0 to W2, the aspect ratio Ω (X0, Y) at X = X0 monotonously decreases.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

The lighting device according to the present invention comprises:
When Y is continuously changed from 0 to W2, the flat portion width Δ (X0, Y) at X = X0 monotonously increases.
According to the illumination unit including the concealing structure according to the present invention, the image of the light deflection element formed on the light deflection surface of the light guide plate spreads, so that the light deflection element cannot be visually recognized. Furthermore, the front luminance can also be improved.

The illuminating device by this invention is equipped with the illuminating unit described in any one mentioned above, and the condensing sheet | seat which condenses the light radiate | emitted from this illuminating unit, It is characterized by the above-mentioned.
The front luminance is further improved by condensing the light emitted from the concealing structure by the prism of the condensing sheet.

In addition, the illumination device according to the present invention includes a polarization separation sheet that polarizes light emitted from the illumination unit.
When the polarization separation sheet is provided, the light emitted from the illumination unit can be polarized.

A display device according to the present invention includes any one of the illumination devices described above and an image display element that defines a display image.
According to the display device of the present invention, when viewed from the observation side, the light emitted from the surface light source device is concealed so that the light deflection element formed on the light deflection surface of the light guide plate cannot be visually recognized by the concealment structure. At the same time, the front luminance can be improved.

  According to the illumination unit, the illumination device, and the display device using the illumination device according to the present invention, the light deflection element formed on the light deflection surface of the light guide plate is visually recognized by the concealment structure when viewed from the observation side. Therefore, the front luminance can be increased.

1 is a liquid crystal display device including an illumination unit including a concealing structure according to an embodiment of the present invention. It is principal part explanatory drawing showing the light deflection | deviation element arranged on the light deflection surface of a light-guide plate. It is a figure showing the 2nd main surface of a concealment structure. (A) It is a perspective view which shows an example of a concealment structure. (B) It is sectional drawing when a concealment structure is cut | disconnected in parallel with a 1st direction. (C) It is sectional drawing when a concealment structure is cut | disconnected in parallel with a 2nd direction. It is a figure showing sectional direction when a concealment structure is cut | disconnected in a 1st direction, and the advancing direction of a light ray. (A) It is a figure which shows the image which the light deflection | deviation element of the light-guide plate spread linearly with the 1st unit lens of the concealment structure. (B) It is a figure which shows the image which the light deflection | deviation element of the light-guide plate spread in planar shape by the 1st unit lens and 2nd unit lens of a concealment structure. (A) It is a schematic diagram which shows the breadth of an emitted light when collimated light injects into a directional diffusion layer. (B) It is a figure which shows angle distribution of the light intensity of an emitted light when collimated light injects into a directional diffusion layer. (A) A graph showing the cross-sectional height f (x) of the first unit lens 16. (B) The gradient of f (x) is a graph showing the absolute value of df (x) / dx. (C) It is a graph showing the curvature radius R (x). It is a figure showing the advancing direction of a light ray when the aspect ratio of a 2nd unit lens is high. It is a figure showing an example of the 2nd unit lens. (A) It is a figure showing the example of the pattern of the light deflection | deviation element of the light-guide plate by which the light source is arrange | positioned at four end surfaces. (B) It is a figure showing the example of the pattern of the light deflection | deviation element of the light-guide plate by which the light source is arrange | positioned at two end surfaces. (C) It is a figure showing the example of the pattern of the light deflection | deviation element of the light-guide plate by which the light source is arrange | positioned at one end surface. It is a figure showing an example of a half value angle. (A) It is a perspective view which shows the concealment structure from which the aspect-ratio of a 2nd unit lens changes. (B) It is sectional drawing which cut | disconnected the concealment structure body along the straight line LM. (A) It is a perspective view which shows the concealment structure body from which the width | variety of the flat part between 2nd unit lenses changes. (B) It is sectional drawing which cut | disconnected the concealment structure body along the straight line LM. It is a figure showing an example of a half value angle. (A) It is a perspective view which shows the concealment structure from which the aspect-ratio of a 2nd unit lens changes. (B) It is sectional drawing which cut | disconnected the concealment structure body along the straight line LN. (A) It is a perspective view which shows the concealment structure body from which the width | variety of the flat part between 2nd unit lenses changes. (B) It is sectional drawing which cut | disconnected the concealment structure body along the straight line LN. It is principal part sectional drawing which shows the arrangement configuration of the liquid crystal display device containing BEF by a prior art. It is a perspective view of BEF shown in FIG. This is a conventional liquid crystal display device comprising a combination of a diffusion sheet and BEF.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view of an essential part showing a liquid crystal display device 1 for displaying a liquid crystal image as a display device according to an embodiment of the present invention. The liquid crystal display device 1 includes a surface light source device 2 that emits light from a light source 11, a concealing structure 3 made of a lens sheet, a prism sheet 4 as a condensing sheet for increasing luminance, and a polarization separation sheet 5 For example, an image display element 6 that displays a liquid crystal image as a liquid crystal display element is sequentially provided in the light traveling direction. The front side of the image display element 6 in the light traveling direction is the visual direction F.
In these liquid crystal display devices 1, the surface light source device 2 and the concealment structure 3 constitute an illumination unit 7, and the illumination unit 7, the prism sheet 4, and the polarization separation sheet 5 constitute an illumination device 8. In FIG. 1, the reduced size of each component does not match the actual one.

In the surface light source device 2, for example, a light source 11 is disposed on an end surface 10 a in the thickness direction of a light guide plate 10 having a flat plate shape, and a reflector 9 is provided on the back side of the light guide plate 10. Therefore, the illumination unit 7 employs an edge light system.
For example, a point light source is used as the light source 11. For example, an LED is used as the point light source, and a white LED, RGB-LED, organic EL light source, or the like can be employed as the LED. Alternatively, the light source 11 may be a fluorescent tube typified by CCFL. Although FIG. 1 shows an example in which the light source 11 is disposed on the two end faces 10a in the thickness direction of the light guide plate 10, the present invention is not limited thereto, and the light source 11 may be disposed only on one end face 10a. Each of the two end surfaces 10a may be disposed. The shape of the light guide plate 10 may be a wedge shape or the like instead of the flat plate shape.

A light deflection surface 12 is formed on the surface of the light guide plate 10 opposite to the exit surface 10b in the visual direction F. The light deflection surface 12 is formed with a light deflection element 13 that deflects light incident on the light guide plate 10 from the light source 11 toward the emission surface 10b. As the light deflection element 13, for example, white diffuse reflection dots are printed. Yes. As another example of the light deflection element 13, a structure such as a microlens shape or a prism shape may be used.

FIG. 2 is a diagram showing the light deflection surface 12 of the light guide plate 10 in the present embodiment, and the light deflection elements 13 are distributed on the light deflection surface 12. In FIG. 2, the shape of the light deflection element 13 is shown as a circle. However, the shape is not limited to this, and a shape such as an elliptical shape or a prism shape may be employed.
A first direction q1 and a second direction q2 perpendicular to each other are virtually indicated by broken lines on the light deflection surface 12. The light deflection elements 13 are provided at the intersections of the first and second directions q1 and q2, and are arranged with a pitch P1 in the first direction q1 and a pitch larger than the pitch P1 in the second direction. The two-dimensional arrangement arranged in P2. Here, the first direction q1 and the second direction q2 can be arbitrarily selected with respect to the vertical visual field and the horizontal visual field which are the vertical and horizontal directions orthogonal to each other of the liquid crystal display device 1. In the example shown in FIG. 2, it is assumed that the first direction q1 coincides with the horizontal visual field and the second direction q2 coincides with the vertical visual field.
FIG. 2 shows an example of the light deflection surface 12 in which the first direction q1 and the second direction q2 are orthogonal to each other, but not limited to this, the first direction q1 and the second direction q2 are inclined and intersect with each other. In some cases, the light deflection surface 12 may be formed.

  The concealment structure 3 shown in FIG. 1 has a base 15 and its light incident surface as a second main surface 15b, and its light exit surface as a first main surface 15a. A directional diffusion layer 17 is formed on the second main surface 15b to diffuse light incident on the second main surface 15b with a wider angular distribution in the second direction q2 than in the first direction q1. A plurality of first unit lenses 16 are formed on the first major surface 15a.

FIG. 3 is a diagram in the case where the second main surface 15b of the concealing structure 3 is a substantially quadrangular shape. If each vertex of the quadrangle is O1, O2, O3, O4, an arbitrary one of the vertices is used as the origin. A virtual coordinate axis is set (O1 is the origin in FIG. 3). A coordinate axis parallel to the first direction q1 is an X axis, and a coordinate axis parallel to the second direction q2 is a Y axis. Furthermore, an arbitrary point on the edge O1O2 of the second principal surface 15b is L (X0, 0), and a virtual straight line drawn through the point L and parallel to the second direction q2 is defined as the edge O3O4. The intersection point is N (X0, W2), and the midpoint of the straight line LN is M (X0, W2 / 2). W1 is the length of the edge parallel to the first direction q1, W2 is the length of the edge parallel to the second direction q2, and K1 and K2 are the edge O1O4 and the edge, respectively. This is the midpoint of O2O3.

FIG. 4A is a view of the concealment structure 3 viewed from above. Here, the first unit lens 16 is a lenticular lens, the directional diffusion layer 17 is also a lenticular lens, and the first unit lens 16 and the lenticular lens of the directional diffusion layer 17 are orthogonal to each other. Show.

4B is a cross-sectional view when the concealment structure 3 is cut along the first direction q1, and FIG. 4C is a cross-sectional view when it is cut along the second direction q2. .
As the first unit lens 16, in addition to the lenticular lens, a prism having a curved vertex or side surface, a cross lenticular lens in which the lenticular lens intersects in two directions within the surface, or a micro array arranged two-dimensionally within the surface. An example is a lens.
As the directional diffusion layer 17, in addition to the lenticular lens, the two-dimensionally arranged elliptical microlens, the linear concavo-convex structure formed with a fine pitch such as a hairline, and the corrugations arranged in parallel to each other Examples thereof include a concavo-convex structure and a layer in which needle-like fillers are coated so that the fillers are aligned in one direction.

As shown in FIG. 5, the first unit lens 16 is formed in a curved surface shape in which, for example, a rounded top portion and curved side surfaces on both sides thereof are smoothly connected in a cross-sectional view. The tangent angle of the top portion T1 of the first unit lens 16 is 0 degree, the angle of the tangent line to the first main surface 15a at the end E1 of the first unit lens 16 is α1, and the first main surface 15a from the top portion is α1. As a result, the tangent angle α gradually increases.
Accordingly, in a state where the directional diffusion layer 17 is not formed on the second main surface 15b of the concealing structure 3 in which a large number of the first unit lenses 16 are arranged on the first main surface 15a, the Lambert is approximately formed from the second main surface 15b side. When the point light source is installed so as to emit light, the oblique light K emitted from the point light source is raised in the front direction due to refraction at the surface of the first lens 16, and the first main part of the concealing structure 3. When the point light source is observed from the surface 15a side, the point light source is visually recognized as a linear light source. Here, the light emitted from the light exit surface 10b of the light guide plate 10 out of the light whose path is changed in all directions by the light deflection element 13 formed on the light deflection surface 12 of the light guide plate 10 is distributed. Although the distribution is different from Lambertian light, it can be treated as synonymous with a point light source.

That is, for example, when each of the circular light deflection elements 13 as shown in FIG. 2 is viewed as a point light source, the concealing structure 3 in which the first unit lens 16 is disposed is arranged on the light emitting surface 10b side of the light guide plate 10. When viewed from the first main surface 15a side, the circular light deflection element 13 appears to expand linearly in the first direction q1 as shown in FIG. 6 (a). The light deflection elements 13 spreading linearly in the first direction q1 are overlapped with the light deflection elements 13 repeatedly arranged at the pitch P1 in the first direction q1, and as a result, the pitch P2 / 2 is observed as a linear stripe pattern arranged at equal intervals.

In order to conceal such a linear stripe pattern, the directional diffusion layer 17 that diffuses in the second main surface 15b of the concealing structure 3 with a wider angular distribution in the second direction q2 than in the first direction q1. Is formed. The light incident on the second main surface 15b is diffused in the second direction q2 by the directional diffusion layer 17, and further diffused in the first direction q1 by the first unit lens 16 formed on the first main surface 15a. Thus, the image of the light deflection element 13 spreads two-dimensionally and the light deflection element 13 is not visually recognized. The directional diffusion layer 17 does not necessarily have to diffuse light in the first direction q1. This is because even if the light is diffused in the first direction q1, it is the same as the light diffusion direction of the first unit lens 16, so that the light deflection element 13 spreads linearly and does not greatly contribute to concealment. When the image of the light deflection element 13 spreads two-dimensionally as shown in FIG. 6B, the linear stripe pattern observed in FIG. 6A is hidden and the light deflection element 13 is visually recognized. Disappear.

Here, the diffusion action required for the directional diffusion layer 17 will be described with reference to FIGS. 7A and 7B.
The directional diffusion layer 17 is formed on the second main surface 15b of the concealing structure 3, and the first main surface 15a is a flat surface, that is, without the first unit lens 16, from the second main surface 15b side. When the collimated light G is incident on the second main surface 15b perpendicularly, the light emitted from the first main surface 15a is diffused with a wider angular distribution in the second direction q2 than in the first direction q1. FIG. 7A schematically shows a state in which the collimated light G perpendicularly incident on the coordinates (X, Y) of the second main surface 15b is spread and emitted from the first main surface 15a in the second direction q2. FIG. 6 shows a case where the directional diffusion layer 17 is a lenticular lens (second unit lens). In this figure, the pitch of the second unit lens 17 is drawn larger than the spot size of the collimated light G for easy understanding, but actually the second unit lens 17 is larger than the spot size of the collimated light G. It is assumed that the pitch of is small.
FIG. 7B shows an angular distribution of the intensity of light emitted from the first major surface 15a. The curve of the angular distribution of the light intensity in the plane including the vertical axis q3 and the first direction q1 of the first main surface 15a is 31a, and the vertical axis q3 and the second direction q2 of the first main surface 15a. If the curve of the angular distribution of the light intensity in the plane including is 31b, the curve 31b is wider than the curve 31a. The illustrated angle θa is the half-value angle of the curve 31a (the angle at which the light intensity is halved relative to the light intensity in the vertical direction q3), and the angle θb is the half-value angle of the curve 31b.

When the collimated light G is incident on an arbitrary coordinate (X, Y) on the second main surface 15b, if the half-value angle θb of the emitted light is within the range of 3 degrees or more and less than 10 degrees, it is arranged on the light guide plate. All the light deflection elements 13 are not visible. Furthermore, the front luminance of the illumination unit 7, the illumination device 8, and the liquid crystal display device 1 incorporating the concealing structure 3 can be increased by 3% or more compared to the case where the concealing structure 3 is replaced with a diffusion sheet. When the unit 7, the illumination device 8, and the liquid crystal display device 1 are viewed from the visual direction F side, it can be confirmed that they become brighter visually than when the diffusion sheet is placed.
A diffusion sheet here refers to the sheet | seat which coated the binder resin which disperse | distributed transparent beads on the surface of a film-form base material. For example, BS 912 manufactured by Eiwa Co., Ltd. is an example.
When the half-value angle θb is 10 degrees or more, the increase rate of the front luminance of the concealment structure 3 compared to the diffusion sheet is less than 3%, and the front luminance is lowered. However, the light deflection element 13 is not visually recognized.
When the half-value angle θb is less than 3 degrees, the front luminance is increased by 3% or more compared to the diffusion sheet and the front luminance is high, but the light deflection element 13 is visually recognized.

図８（ａ）は、第一の単位レンズ１６の断面高さを表すグラフ、図８（ｂ）は断面高さ ｆ（ｘ） の微分値 ｄｆ（ｘ）／ｄｘ の絶対値を表すグラフ、図８（ｃ）は曲率半径Ｒ（ｘ）を表すグラフである。図８（ｃ）は、 ｄｆ（ｘ）／ｄｘ の絶対値の傾斜が最も緩やかになる点 ｘ を ｘ０ とすると、ｘ＝ｘ０ においてピークを有する曲線を形成する。曲率半径 Ｒ（ｘ） は、 ｄｆ（ｘ）／ｄｘ の微分値の逆数に比例するので、 ｄｆ（ｘ）／ｄｘ の傾斜が水平に近くなれば、上式の分母が０に近づき、曲率半径 Ｒ（ｘ） は ｘ＝ｘ０ で強度の強いピークを形成する。 As described above, the shape of the first unit lens 16 is described so that the front luminance increases and the light deflection element 13 cannot be visually recognized. As shown in FIG. 4B, the cross section of the first unit lens 16 when the end E1 of the first unit lens 16 is 0 and the displacement measured along the first direction q1 is x. When the height is f (x), the radius of curvature R (x) of f (x) at the point x is expressed by the following equation.

FIG. 8A is a graph showing the cross-sectional height of the first unit lens 16, and FIG. 8B is a graph showing the absolute value of the differential value df (x) / dx of the cross-sectional height f (x). FIG. 8C is a graph showing the radius of curvature R (x). FIG. 8C forms a curve having a peak at x = x0 where x0 is the point x where the slope of the absolute value of df (x) / dx is the most gradual. Since the radius of curvature R (x) is proportional to the reciprocal of the differential value of df (x) / dx, if the slope of df (x) / dx is nearly horizontal, the denominator of the above equation approaches 0 and the radius of curvature is R (x) forms a strong peak at x = x0.

As the radius of curvature R (x) increases, the curved surface approaches a plane. Therefore, when R (x) forms a peak that rises sharply at x = x0, it indicates that the first unit lens 16 has a shape close to a plane at point x = x0. Conversely, when the peak of R (x) is gentle, it indicates that the first unit lens 16 is close to a cylindrical shape. If the first unit lens 16 is a complete cylinder, the radius of curvature R (x) is a constant value.

In order to prevent the light deflection element 13 from being visually recognized, it is preferable that the first unit lens 16 extends the light deflection element 13 linearly in the first direction q1. For example, if the first unit lens 16 has a cylindrical shape, the light incident on the first major surface 15a is evenly diffused, so that the first unit lens 16 can be linearly expanded in the first direction q1. However, in this case, the light incident on the first unit lens 16 is evenly diffused in all directions, so that the light condensing function is weakened and the front luminance is not increased.

When the radius of curvature R (x) of the first unit lens 16 forms a strong peak at the point x = x0, the curvature radius of the surface at x = x0 is large, so that the light incident in the vicinity of x = x0 The light can be condensed in a specific direction without being diffused, and the front luminance can be increased. However, if the first unit lens 16 condenses too much light, the light diffusing action is weakened, and the light deflection element 13 may be visually recognized.

ここで、 ｍａｘ は最大値、 ｍiｎ は最小値を表し、 Ｒ（ｘ）は曲率半径で、Ｒ（ｘ）の平均値は下式で定義する。

Ｄ は、曲率半径 Ｒ（ｘ） のコントラストを表す値である。 Ｄ が大きい場合は、曲率半径Ｒ（ｘ） が ｘ＝ｘ０ で強度の大きなピークを形成し、 Ｄ が小さい場合は Ｒ（ｘ） がなだらかなピークを形成する。 Ｄ がゼロになる場合、曲率半径 Ｒ（ｘ）は ｘ によらずに一定値となり、これはレンズが円筒形状である場合に相当する。従って、 Ｄ の値を大きくすれば、レンズの拡散作用を弱めて集光作用を強めることができる。Ｄ の値を小さくすれば、レンズの集光作用を弱めて拡散作用を強めることができる。 Here, the parameter D described by the following formula is defined.

Here, max represents a maximum value, min represents a minimum value, R (x) is a radius of curvature, and an average value of R (x) is defined by the following equation.

D is a value representing the contrast of the radius of curvature R (x). When D is large, the curvature radius R (x) is x = x0 and a strong peak is formed. When D is small, R (x) is a gentle peak. When D becomes zero, the radius of curvature R (x) becomes a constant value regardless of x, which corresponds to the case where the lens has a cylindrical shape. Therefore, if the value of D is increased, the diffusion effect of the lens can be weakened and the light condensing effect can be enhanced. If the value of D is reduced, the light condensing action of the lens can be weakened and the diffusing action can be enhanced.

When the value D defined in Paragraph 56 is in the range of 1.5 or more and 5 or less, the first unit lens 16 has both the condensing action and the diffusing action. Therefore, the first unit lens 16 is provided. The concealing structure 3 can exert a light collecting action and a diffusing action in a balanced manner. Therefore, the light deflection element 13 cannot be visually recognized. Furthermore, the front luminance of the illumination unit 7, the illumination device 8, and the liquid crystal display device 1 is increased by 3% or more compared to the case where the diffusion sheet is placed instead of the concealing structure 3.
When the value of D is larger than 5, the light deflection element 13 is visually recognized because the diffusing action of the first unit lens 16 is weak. Conversely, when the value of D is smaller than 1.5, the front unit luminance is less than 3% because the diffusing action of the first unit lens 16 is strong.

ｄｆ（ｘ）／ｄｘ（ｘ＝０） の絶対値が大きい方が、より斜めに進む光を視覚方向Ｆ側に立ち上げることができ、光偏向要素１３を広い範囲にわたって第一の方向ｑ１に線状に広げる。 ｄｆ（ｘ）／ｄｘ が １．４３ というのは、 ｆ（ｘ） の接線の傾き角度で表すと ５５ｄｅｇ になり、５５ｄｅｇ以上でなければ、線状の広がりが十分とは言えない。一方、 ｄｆ（ｘ）／ｄｘ の絶対値が ３．７３ というのは、角度で表すと ７５ｄｅｇ になり、７５ｄｅｇ以上では第一の単位レンズ１６を作製する際の金型の切削やレンズの成形が困難になる。そのため、 ｄｆ（ｘ）／ｄｘ（ｘ＝０） の絶対値の値は １．４３ から ３．７３ の範囲に含まれることが望ましい。 Furthermore, it is desirable that the absolute value of the differential df (x) / dx (x = 0) at the cross-section height f (x) at x = 0 is defined within the range of the following equation.

When the absolute value of df (x) / dx (x = 0) is larger, the light traveling more obliquely can be raised to the visual direction F side, and the light deflection element 13 is moved in the first direction q1 over a wide range. Spread it in a line. The fact that df (x) / dx is 1.43 is 55 deg when expressed by the inclination angle of the tangent line of f (x), and the linear spread is not sufficient unless it is 55 deg or more. On the other hand, the absolute value of df (x) / dx is 3.73, which is expressed as an angle of 75 deg. When the angle is 75 deg or more, cutting of the mold or molding of the lens when the first unit lens 16 is produced is performed. It becomes difficult. Therefore, the absolute value of df (x) / dx (x = 0) is preferably included in the range of 1.43 to 3.73.

ｄｆ（ｘ）／ｄｘ（ｘ＝ｘ０） の絶対値が ０．７０ の場合は、 ｆ（ｘ） のｘ＝ｘ０ での接線の傾き角度が ３５ｄeｇ に相当し、 ｄｆ（ｘ）／ｄｘ（ｘ＝ｘ０） の絶対値が １．４３ の場合は ５５ｄｅｇ に相当する。傾斜角度が ３５ｄｅｇ〜５５ｄｅｇ の場合に、隠蔽構造体３に入射した光が、視覚方向Ｆ側へ立ち上げられるので、隠蔽構造体３の正面輝度が上昇する。 In order to further enhance the light condensing action of the first unit lens 16, when the displacement x where the radius of curvature R (x) is the maximum value is x0, the absolute value of df (x) / dx when the displacement x is x0 is It should be specified in the range of the following formula.

When the absolute value of df (x) / dx (x = x0) is 0.70, the inclination angle of the tangent line at x = x0 of f (x) corresponds to 35 degg, and df (x) / dx (x = X0) is 1.43, it corresponds to 55 deg. When the inclination angle is 35 deg to 55 deg, the light incident on the obscuring structure 3 is raised to the visual direction F side, so that the front luminance of the obscuring structure 3 is increased.

Next, an optimum shape of the directional diffusion layer 17 that will increase the front luminance of the concealing structure 3 and make the light deflection element 13 invisible will be described.

As an example of the directional diffusion layer 17, the second unit lenses 17 extending in the first direction q <b> 1 and arranged in the second direction q <b> 2 are arranged on the second main surface 15 b of the concealing structure 3. In the second unit lens 17, a region including at least the vertex T1 is formed as a curved surface. When light is incident on such a second unit lens 17, the incident light is not diffused in the first direction q1, but is diffused in the second direction q2. Therefore, the image of the light deflection element 13 spreads linearly in the second direction q2.

The second unit lens 17 is combined with the first unit lens 16 to expand the image of the light deflection element 13 in a planar shape, so that the concealment structure 3 is not visually recognized. However, if the diffusing action by the second unit lens 17 is too strong, the front luminance of the concealing structure 3 cannot be increased. As shown in FIG. 9, when a cylindrical lens having a high aspect ratio is arranged on the second main surface 15b, a large amount of oblique light K is transmitted from the side surface of the cylindrical lens, and the transmitted oblique light is the first main surface. The light is refracted by the surface 15a and dissipated in a direction other than the visual direction F, and the front luminance cannot be increased.

In order for the front luminance of the hiding structure 3 to increase the front luminance by at least 3% or more as compared with the diffusion sheet, the second unit lens 17 has a half-value angle θb of 3 ° or more and less than 10 °. Set the aspect ratio. The aspect ratio is a value represented by the formula (h2 / Q2) × 100, where Q2 is the pitch of the second unit lens 17 and h2 is the height. When the half-value angle θb is less than 3 degrees, the light deflection element 13 is visually recognized because the diffusing action of the second unit lens 17 is weak. When the half-value angle θb is 10 degrees or more, the diffusion effect of the second unit lens 17 is too strong, and the front luminance cannot be increased by 3% or more.
The optimal aspect ratio range of the second unit lens 17 is 4 or more and 10 or less. When the aspect ratio is smaller than 4, the light deflection element 13 is visually recognized because the diffusion action of the second unit lens 17 is weak. When the aspect ratio is larger than 10, the diffusion effect of the second unit lens 17 is too strong, and the front luminance cannot be increased by 3% or more.

Examples of the curved shape of the second unit lens 17 include a curved surface whose cross-sectional shape is defined by a part of a circle or an ellipse, a polynomial function such as a quadratic function or a quartic function, or a trigonometric function. By setting the aspect ratio of these lenses within the above range, the front luminance of the obscuring structure 3 is increased and the light deflection element 13 is not visually recognized.

As another example of the shape of the second unit lens 17, as shown in FIG. 10, the first surface 17a formed in the region including the apex T2 and the second surface formed in the region including the end E2. The inclination angle is discontinuously changed at the boundary portion C between the first surface 17a and the second surface 17b, and the inclination angle at an arbitrary point on the second surface 17b is the first surface. The lens may be larger than the inclination angle of an arbitrary point 17a. Here, FIG. 10 shows the second main surface 15b side reversed from FIG. 4A in order to make the characteristics of the second unit lens 17 easy to understand.
Since the second surface 17b is a steep surface, the image of the light deflection element 13 can be widely spread in the second direction q2. On the other hand, since the first surface 17a is a gently inclined surface, the amount of light traveling straight in the visual direction F increases, and the front luminance can be increased. By adjusting the inclination angle of each of the two regions, the area ratio of the first surface 17a and the second surface 17b occupying the second unit lens 17, the condensing action and diffusion of the second unit lens 17 The strength of the action can be freely changed, the front luminance can be increased by 3% or more, and the light deflection element 13 can be prevented from being visually recognized.

By the way, it is preferable that the light deflection element 13 formed on the light guide plate 10 forms a pattern having a different radius depending on the position, rather than forming a uniform radius pattern regardless of the position from the end face 10a of the light guide plate 10. . When the radius of the light deflection element 13 is uniformly equal, light is scattered too much in the vicinity of the end surface 10a of the light guide plate 10 facing the light source 11, and the front luminance near the center portion of the light guide plate 10 is reduced. The light deflection element 13 having a small radius is formed so that light is not scattered much in the vicinity of 10a, and the light deflection element 13 is formed so that the radius increases as the distance from the end face 10a of the light guide plate 10 increases. By forming such a pattern of the light deflection element 13, it becomes easy for light to propagate to the center portion of the light guide plate, and the front luminance near the center portion of the light guide plate 10 can be increased.

FIGS. 11A to 11C show examples of arrangement patterns of the light sources 11 arranged facing the end face 10 a of the light guide plate 10 and the light deflection elements 13 arranged on the light deflection surface 12.
In FIG. 11A, the light sources 11 are arranged facing the four end surfaces 10a of the light guide plate 10, the pattern radius is maximized at the center of the light guide plate 10, and the pattern radius decreases as the end surface 10a is approached. It is a figure showing the arrangement pattern of such a light deflection element.
In FIG. 11B, the light source 11 is arranged facing the two end faces 10 a of the light guide plate 10, and the pattern radius increases as the distance from the light source 11 in the second direction q <b> 2 increases. It is a figure showing the arrangement pattern of the light deflection | deviation element 13 in which the radius of a pattern becomes the largest.
In FIG. 11C, the light source 11 is arranged facing one end surface 10 a of the light guide plate 10, and the radius of the pattern increases as the distance from the light source 11 in the second direction q <b> 2 is increased. 10a is a diagram showing an array pattern of the light deflection elements 13 in which the radius of the pattern is maximized in the vicinity of the end face 10a opposite to 10a.
In FIGS. 11B and 11C, the light deflection element 13 is depicted in the case where the radius of the pattern is constant in the first direction q1. However, if necessary, the pattern of the pattern in the first direction q1 is drawn. The radius may be changed.

Thus, when the radius of the light deflection element 13 changes depending on the distance from the end face 10a of the light guide plate 10, the intensity of diffusion of the directional diffusion layer 17 of the concealing structure 3 is also changed according to the distance from the end face 10a. Also good. For example, the intensity of diffusion of the directional diffusion layer 17 is changed so that the light deflection element 13 is diffused strongly at a small radius and the light deflection element 13 is weakly diffused at a radius. “Strong diffusion” described here represents a case where the angular distribution of the light intensity shown in FIG. 7B is wide, and “weak diffusion” represents a case where the angular distribution of the light intensity is narrow. In the portion where the radius of the light deflection element 13 is large, even if the diffusion of the directional diffusion layer 17 is weak, the images of the light deflection element 13 are likely to be overlapped. Therefore, the light deflection element 13 can be made sufficiently invisible. . If the diffusion of the directional diffusion layer 17 is weak, the front luminance can be increased accordingly. Thus, by changing the intensity of diffusion of the directional diffusion layer 17 in accordance with the radius of the light deflection element 17, the front luminance of the central portion of the light guide plate 10 by the concealing structure 3 is effectively increased. Can be made.

When the light source 11 is arranged facing the four end faces 10a as shown in FIG. 11A, or when the light source 11 is arranged facing the two end faces 10a as shown in FIG. 11B. The radius of the light deflection element 13 of the general light guide plate 10 is maximized at the center of the light guide plate 10. In this case, it is desirable to form the diffusion of the directional diffusion layer 17 of the concealing structure 3 so as to be the weakest at the center of the light guide plate 10.

In the configuration without the first unit lens 16 of the obscuring structure 3, when the collimated light G is irradiated from the second main surface 15 b side to the point (X0, Y) on the straight line LN, the first main surface 15 a Assuming that the half-value angle of the angular distribution of the light intensity of the emitted light in the second direction q2 is expressed by the function Φ (X0, Y), Φ is obtained when Y is continuously changed from 0 to W2 / 2. A directional diffusion layer 17 in which (X0, Y) monotonously decreases is formed on the second major surface 15b. Here, W2 is the width of the end parallel to the second direction q2 of the second main surface 15b, and X0 is an arbitrary point on the end O1O2 of the second main surface 15b. FIG. 12 is a graph showing an example of the function Φ (X0, Y), which monotonically decreases between Y = 0 and Y = W2 / 2, and has a minimum value at Y = W2 / 2.

As an example of the directional diffusion layer 17 in which the half-value angle Φ (X0, Y) monotonously decreases when Y is continuously changed from 0 to W2 / 2, a second unit lens in which the aspect ratio changes The method of forming 17 in the 2nd main surface 15b of the concealment structure 3 is mentioned. 13A and 13B, the aspect ratio in the vicinity of the edge O1O2 of the concealment structure 3 is the largest, the aspect ratio monotonously decreases as the distance from the edge O1O2 increases, and the aspect ratio in the vicinity of the center line K1K2 It is a figure which shows the concealment structure 3 which arranged the 2nd unit lens 17 so that it might become the minimum. FIG. 13A is an overhead view of the concealment structure 3 on the side including the end O1O2 in the concealment structure 3 cut into two along the middle line K1K2. FIG. 13B shows a cross-sectional view when the concealment structure 3 of FIG. 13A is cut along a straight line LM. When the aspect ratio of the second unit lens 17 ′ at the point (X0, Y) is Ω (X0, Y), Ω (X0, Y) is obtained when Y is continuously changed from 0 to W2 / 2. The second unit lenses 17 are arranged so as to monotonously decrease.

As another example of the directional diffusion layer 17 in which the half-value angle Φ (X0, Y) monotonously decreases when Y is continuously changed from 0 to W2 / 2, FIGS. ), A flat portion is formed between the adjacent second unit lenses 17, and the width of the flat portion is the smallest in the vicinity of the edge O1O2 of the concealing structure 3, and monotonously increases as the distance from the edge O1O2 increases. An example is a method in which the second unit lenses 17 are arranged so as to be maximum near the middle line K1K2. FIG. 14A is an overhead view of the concealment structure 3 on the side including the end O1O2 in the concealment structure 3 cut into two along the middle line K1K2. FIG. 14B shows a cross-sectional view when the concealment structure 3 of FIG. 14A is cut along a straight line LM. When the width of the flat part including or near the point (X0, Y) is Δ (X0, Y), Δ (X0, Y) changes Y continuously from 0 to W2 / 2. The second unit lenses 17 are arranged so as to increase monotonously.

FIG. 11C shows an example of the pattern of the light deflection element 13 when the light sources 11 are arranged to face one end face 10a. The light deflection element 13 has a radius so that the radius decreases as the distance from the light source 11 increases. Arrange the patterns. In this case, the diffusion of the directional diffusion layer 17 of the concealing structure 3 is preferably formed so as to be weak in the vicinity of the light source 11 and gradually increase as the distance from the light source 11 increases.

When the light source 11 is arranged on the side of the edge O1O2 of the obscuring structure 3, in the configuration without the first unit lens 16 of the obscuring structure 3, the collimated light G is pointed on the straight line LN from the second main surface 15b side. The half-value angle Φ (X0, Y) of the angle distribution in the second direction q2 of the light intensity of the light emitted from the first major surface 15a when irradiating (X0, Y) is Y from 0 to W2. A directional diffusion layer 17 that monotonously decreases when continuously changed is formed on the second main surface 15b. Here, W2 is the width of the end parallel to the second direction q2 of the second main surface 15b, and X0 is an arbitrary point on the end O1O2 of the second main surface 15b. FIG. 15 is a graph showing an example of the function Φ (X0, Y), and monotonically decreases between Y = 0 and Y = W2.

As an example of the directional diffusion layer 17 in which the half-value angle Φ (X0, Y) monotonously decreases when Y is continuously changed from 0 to W2, a second unit lens 17 having a change in aspect ratio is used. The method of forming in the 2nd main surface 15b of the concealment structure 3 is mentioned. 16A and 16B, the second unit lenses 17 are arranged so that the aspect ratio in the vicinity of the edge O1O2 of the concealing structure 3 is the largest, and the aspect ratio monotonously decreases as the distance from the edge O1O2 increases. It is a figure which shows the concealment structure. FIG. 16B shows a cross-sectional view when the concealment structure 3 of FIG. 16A is cut along a straight line LN. Assuming that the aspect ratio of the second unit lens 17 ′ at the point (X0, Y) is Ω (X0, Y), Ω (X0, Y) decreases monotonously when Y is continuously changed from 0 to W2. In this manner, the second unit lenses 17 are arranged.

FIGS. 17A and 17B show another example of the directional diffusion layer 17 in which the half-value angle Φ (X0, Y) monotonously decreases when Y is continuously changed from 0 to W2. As shown, a flat portion is formed between the adjacent second unit lenses 17, and the width of the flat portion is the smallest in the vicinity of the edge O1O2 of the concealing structure 3, and is increased monotonically as the distance from the edge O1O2 increases. A method of arranging the second unit lenses 17 may be mentioned. FIG. 17B shows a cross-sectional view when the concealment structure 3 of FIG. 17A is cut along a straight line LN. If the width of the flat part including or near the point (X0, Y) is Δ (X0, Y), Δ (X0, Y) is monotonous when Y is continuously changed from 0 to W2. The second unit lenses 17 are arranged so as to increase.

In order to prevent moiré caused by interference between the second unit lens 17 of the concealment structure 3 and the prisms 20 of the prism sheet 4 when the prism sheet 4 is placed on the concealment structure 3 as a brightness enhancement sheet, The pitch of the second unit lenses 17 is preferably as fine as possible compared to the pitch of the prism sheet 4. By making the arrangement pitch of the second unit lenses 17 fine, it is also possible to suppress moire due to interference between the second unit lenses 17 and the image display element 6.
Alternatively, the second unit lens 17 may be formed such that the pitch and / or height of the second unit lens 17 varies randomly. Thereby, moire due to interference between the hiding structure 3 and the prism sheet 4 or the image display element 6 can be suppressed.

When the prism sheet 4 is overlapped with the concealing structure 3 and used, the front luminance of the illumination unit 7 can be further increased as compared with the case where the concealing structure 3 is used alone.
The prism sheet 4 has a configuration in which a plurality of prisms 20 having, for example, a triangular section 20 extending in one direction are arranged in parallel on the base 19 (see FIG. 1). Here, consider a case where the prism 20 of the prism sheet 4 is arranged so that the direction of the prism 20 is orthogonal to the direction in which the first unit lens 16 extends.
In the following description, it is assumed that the prism sheet 4 is arranged in a direction in which the direction of the prism 20 coincides with the horizontal visual field direction of the illumination unit 7, and the direction parallel to the direction in which the prism 20 extends is the H direction (horizontal direction). A direction orthogonal to the direction is called a V direction (vertical direction).

The first unit lens 16 has a function of converging and condensing the angular distribution of light spreading in the H direction. The light transmitted through the first unit lens 16 in the obscuring structure 3 is emitted in the visual direction F with the angular distribution of the light in the V direction narrowed by the prism 20 of the prism sheet 4.

In particular, when a television is cited as a large-sized liquid crystal display device 1 having a size of 32 inches or more, a wide horizontal field of view is desired. The prism 20 having a triangular cross section narrows the field of view because of its strong light collecting effect. On the other hand, the first unit lens 16 has a diffusing action and a condensing action. Therefore, by arranging the prisms 20 so as to extend in the horizontal visual field direction, the vertical visual field becomes narrow, but the front luminance increases as compared with the case where the prisms 20 are not mounted.

For example, the prism 20 of the prism sheet 4 may have the same shape as the first unit lens 16 constituting the concealing structure 3 or may be a lens having a different shape. Alternatively, the prism 20 may be a lens that can obtain a condensing function without narrowing the field of view, such as a rounded triangular prism lens or a triangular prism lens having an apex angle of about 100 to 120 degrees.

The concealment structure 3 included in the illumination unit 7 according to the present embodiment includes a first unit lens 16 on the first main surface 15a of the base portion 15, a second unit lens 17 on the second main surface 15b, and a UV curable resin. Or PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), PAN (polyacrylonitrile copolymer), AS ( Acrylonitrile styrene copolymer) or the like can be integrally formed by an extrusion molding method, an injection molding method, or a hot press molding method well known in this technical field. Alternatively, the first unit lens 16 is obtained by pressing and extruding the resin material to be molded and the mold of the resin plate using a resin plate mold in which a lens shape is molded using a UV curable resin, a radiation curable resin, or the like. Alternatively, the second unit lens 17 may be molded.

The image display element 6 is preferably an element that displays an image by transmitting / blocking light in pixel units. If an image is displayed by transmitting / blocking light in pixel units, the illumination unit 7 according to the present embodiment improves the luminance in the visual direction F of the image transmitted through the image display element 6 and increases the light intensity. The viewing angle dependency is reduced. Further, the light deflection element 13 cannot be visually recognized, and an image with high image quality can be displayed.
The image display element 6 is preferably a liquid crystal display element. The liquid crystal display element will be described using the same reference numerals as those of the image display element 6. As shown in FIG. 1, the liquid crystal display element 6 is configured by laminating polarizing plates 23 and 23 before and after the liquid crystal panel 22. The liquid crystal display element 6 is a typical element that transmits / shields light in pixel units and displays an image. The liquid crystal display element 6 can improve image quality as compared with other display elements and can reduce manufacturing costs. it can.

  In addition to the television as the liquid crystal display device 1, the concealing structure 3 according to the present invention can be used for, for example, indoor or outdoor lighting applications. In particular, the illumination unit 7 incorporating the concealing structure 3 can emit light with high front luminance without unevenness in brightness, and can therefore illuminate a specific indoor or outdoor space uniformly and brightly.

In FIG. 1, light emitted from a light source 11 having a point light source made of, for example, an LED is incident on the light guide plate 10 through end faces in the thickness direction on two sides or four sides of the light guide plate 10 and arranged on the light deflection surface 12. For example, it goes to the light deflection element 13 made of, for example, white diffuse reflection dots.
The light deflection elements 13 on the light deflection surface 12 are two-dimensionally arranged at a pitch P1 in a first direction q1 that forms a horizontal direction and at a pitch P2 in a second direction q2 that forms a vertical direction. The light from the light source 11 is deflected by the light deflecting element 13 toward the exit surface 10 b of the light guide plate 10. As shown in FIG. 5, the light emitted from the light guide plate 10 enters the concealment structure 3 from the second main surface 15b, which is the incident surface, with an incident angle θ, for example.

  In the concealing structure 3, the first unit lens 16 is orthogonal to the first main surface 15a that is the exit surface of the base 15, and the second unit lens 17 is orthogonal to the second main surface 15b that is the entrance surface. For example, the second unit lenses 17 extend in parallel to the first direction q1 (H direction) in which the light deflection elements 13 are arranged, and are arranged in the second direction q2 (V direction). The first unit lens 16 extends in parallel with the second direction q2 (V direction) of the light deflection element 13 and is arranged in the first direction q1 (H direction). In the prism sheet 4 arranged on the light exit side of the concealing structure 3, the prism 20 extends in parallel with the first direction q1 (H direction) and is arranged in the second direction q2 (V direction). ing.

Therefore, the light is diffused in the second direction q2 by the second unit lens 17, and the first unit lens 16 condenses the light by converging the angular distribution of the light spread in the first direction q1, and further has a triangular cross section of the prism sheet. The light is condensed by the prism 20 and the front luminance is increased.
Moreover, the vertical field of view is narrowed by the first unit lens 16 and the prism lens 20 of the prism sheet 4, but the front luminance is increased, and the prism lens 20 of the prism sheet 4 does not extend in the second direction. A wide horizontal field of view can be secured. In particular, the large liquid crystal display device 1 is preferable because it is necessary to secure a wider field of view in the horizontal direction than in the vertical direction.

The light deflection element 13 disposed on the light deflection surface 12 of the light guide plate 10 has a pitch P2 in the second direction larger than the pitch P1 in the first direction q1. Since the extending direction of the first unit lens 16 coincides with the second direction q2 and the extending direction of the second unit lens 17 coincides with the first direction q1, the image of the light deflection element 13 is It spreads as a two-dimensional surface in the first direction and the second direction.
Therefore, when the image of the liquid crystal display element 6 is observed from the visual direction F in the liquid crystal display device 1, the image of the light deflection element 13 is not visually recognized.

As described above, according to the liquid crystal display device 1 including the illumination unit 7 and the illumination device 8 according to the present embodiment, the curvature radius R (x) that defines the first unit lens 16 in the concealment structure 3, and the cross section By setting the height differential value df (x) / dx within the optimum range and arranging the second unit lenses 17 having a half-value angle θb of 3 degrees or more and less than 10 degrees, the light deflection element 13 is visually recognized. Disappears, and the front brightness increases by 3% or more compared to the diffusion film.
When the image of the liquid crystal display element 6 is viewed from the visual direction F, the light deflecting element 13 formed on the light deflecting surface 12 of the light guide plate 10 is concealed by the concealing structure 3 so as to be concealed. While making it invisible, it is possible to widen the viewing angle in the horizontal direction and improve the front luminance.
In addition, the liquid crystal display element 6 is an element that transmits / shields light in pixel units and displays an image, and transmits / shields light in pixel units to display an image. The brightness of the transmitted image in the visual direction F is improved, and the viewing angle dependency of the light intensity is reduced. Further, the light deflection element 13 is not visually recognized, and an image with high image quality can be displayed.

Next, as examples of the present invention, the concealment structure 3 according to Examples 1 to 9 and the concealment structure 3 according to Comparative Examples 1 to 5 are manufactured, and each is incorporated into the illumination device 8 of the liquid crystal display device 1. The front luminance and the visibility of the light deflection element 13 were evaluated.

<Production of surface light source device 2>
The surface light source device 2 was produced as follows.
First, a 4 mm-thick light guide plate 10 was prepared, and LEDs were installed as light sources 11 on end faces 10 a in the thickness direction of the four sides of the light guide plate 10. White reflective ink was formed on the light deflection surface 12 of the light guide plate 10 by a printing method. The white reflective ink was regularly arranged on the light deflecting surface 12, and the size of the white reflecting ink was made smaller as it was closer to the end surface 10 a of the light guide plate 10 on which the light source 11 was installed, and larger as it was closer to the center of the light guide plate 10.
As shown in FIG. 2, the white reflective ink makes the first direction q1 coincide with the horizontal screen direction of the liquid crystal display device 1, the arrangement pitch P1 in the first direction q1 is about 1.45 mm, and the second The arrangement pitch P2 in the direction q2 was about 2.5 mm. And the surface light source device 2 was obtained by arrange | positioning the reflecting plate 9 in the back surface by the side of the light deflection surface 12 of the light-guide plate 10. FIG.

<Preparation of concealment structure 3 and prism sheet 4>
The concealment structure 3 and the prism sheet 4 in the illumination device 8 were produced by the method described below. Polycarbonate resin was used as a material for the hiding structure 3 and the prism sheet 4. Since the polycarbonate resin has a high refractive index of about 1.59, it is possible to obtain the concealment structure 3 having high front luminance and in which the light deflection element 13 is not visually recognized. The first unit lens 16 and the second unit lens 17 of the hiding structure 3 were formed by extrusion molding using a polycarbonate resin. The prism sheet 4 was also produced by the same method.
Specific configurations of the concealment structures 3 according to Examples 1 to 9 and Comparative Examples 1 to 5 will be described later.

<Production of lighting device 8>
The lighting device 8 was produced as follows.
First, the concealment structure 3 is arranged on the light emission surface side of the surface light source device 2 to produce the illumination unit 7. In the concealing structure 3, the direction in which the first unit lens 16 extends matches the second direction q2 in which the light deflection elements 13 of the light guide plate 10 are arranged. In addition, the direction in which the second unit lens 17 extends and the first direction q1 in which the light deflection elements 13 are arranged are matched.
Further, on the concealing structure 3, a prism sheet 4 in which prisms 20 having a triangular cross section having an apex angle of 90 ° are arranged as a light collecting sheet is disposed. The prism sheet 4 is arranged so that the extending direction of the prism 20 is perpendicular to the extending direction of the first unit lens 16 in the concealing structure 3, and further the DBEF (polarization separating / reflecting sheet 5) is provided thereon. The lighting device 8 was obtained by arranging 3M).

Next, concealment structures 3 according to Examples 1 to 9 and Comparative Examples 1 to 5 were produced as follows.
(Examples 1-2)
Two types of first unit lenses 16 having a pitch Q1 of 50 μm and D different in the following (a) and (b) are designed, and extend in parallel to the second direction q2 on the first main surface 15a. Two types of concealment structures 3 arranged in this way were produced.
A second unit lens 17 made of a part of a cylinder having a pitch Q2 of 20 μm and an aspect ratio of 6.0 extends parallel to the first direction q1 on the second main surface 15b of each concealing structure 3. Arranged as follows.
(A) D = 1.6 (Example 1)
(B) D = 4.8 (Example 2)

(Examples 3 to 4)
A first unit lens 16 having a pitch Q1 of 50 μm and a D of 4.8 is arranged on the first main surface 15a of the obscuring structure 3 so as to extend in parallel with the second direction q2, and the second On the main surface 15b, a second unit lens 17 made of a part of a cylinder having the following aspect ratios (c) and (d) and a pitch Q2 of 20 μm extends in parallel to the first direction q1. Two types of concealment structures 3 arranged as described above were produced.
(C) Aspect ratio = 5.1 (Example 3)
(D) Aspect ratio = 7.5 (Example 4)

(Examples 5-7)
A first unit lens 16 having a pitch Q1 of 50 μm and a D of 4.8 is arranged on the first main surface 15a of the concealing structure 3 so as to extend in parallel with the second direction q2, thereby concealing the concealing structure. On the second main surface 15b of the body 3, the pitch Q2 is 20 μm, the apex radius of curvature and the aspect ratio are the following (e), (f), (g), and the sectional height g (y) is: Three types of concealment structures 3 were produced in which the second unit lenses 17 represented by a quadratic function were arranged so as to extend parallel to the first direction q1. Here, y is the displacement measured along the second direction q2 with the end E2 of the second unit lens 17 being 0 as shown in FIG. 4C, and g (y) is the displacement y 2. This is the height of the second unit lens 17.
(E) Curvature radius = 60 μm Aspect ratio = 5.4 (Example 5)
(F) Curvature radius = 50 μm Aspect ratio = 6.4 (Example 6)
(G) Curvature radius = 40 μm Aspect ratio = 9.1 (Example 7)

(Examples 8 to 9)
A first unit lens 16 having a pitch Q1 of 50 μm and a D of 4.8 is arranged on the first main surface 15a of the obscuring structure 3 so as to extend in parallel with the second direction q2, and the second The main surface 15b has a pitch Q2 of 20 μm, a vertex radius of curvature and an aspect ratio of (h) and (i) below, and a sectional height g (y) expressed by a quartic function. Two types of concealment structures 3 in which the unit lenses 17 were arranged so as to extend parallel to the first direction q1 were produced.
(H) Curvature radius = 65 μm Aspect ratio = 6.4 (Example 8)
(I) Curvature radius = 52 μm Aspect ratio = 8.2 (Example 9)

(Comparative Examples 1-2)
Two types of first unit lenses 16 having a pitch Q1 of 50 μm and D different in (j) and (k) below are designed, and the first main lens 15a of the concealing structure 3 is arranged in the second direction q2. Two types of concealment structures 3 arranged so as to extend in parallel were produced. A second unit lens 17 made of a part of a cylinder having a pitch Q2 of 20 μm and an aspect ratio of 6.0 extends parallel to the first direction q1 on the second main surface 15b of each concealing structure 3. Was arranged as follows.
(J) D = 1.2 (Comparative Example 1)
(K) D = 6.1 (Comparative Example 2)

(Comparative Example 3)
A first unit lens 16 having a pitch Q1 of 50 μm and a D of 4.8 is arranged on the first main surface 15a of the obscuring structure 3 so as to extend in parallel with the second direction q2, and the second On the main surface 15b, a second unit lens 17 having a pitch Q2 of 20 μm, a part of a cylinder, and an aspect ratio of (l) below is extended in parallel to the first direction q1. Arranged.
(L) Aspect ratio = 11.0 (Comparative Example 3)

(Comparative Examples 4-5)
A first unit lens 16 having a pitch Q1 of 50 μm and a D of 4.8 is arranged on the first main surface 15a of the obscuring structure 3 so as to extend in parallel with the second direction q2, and the second The main surface 15b has a pitch Q2 of 20 μm, a vertex radius of curvature and an aspect ratio of (m) and (n) below, and a sectional height g (y) expressed by a quadratic function. Two types of concealment structures 3 in which the unit lenses 17 were arranged so as to extend parallel to the first direction q1 were produced.
(M) Curvature radius = 25 μm Aspect ratio = 12.7 (Comparative Example 4)
(N) Curvature radius = 130 μm Aspect ratio = 3.0 (Comparative Example 5)

<Evaluation of front brightness>
Next, as the illuminating device 8, the concealment structures 3 according to Comparative Examples 1 to 5 and Examples 1 to 9 are mounted on the surface light source device 2, respectively, and the prism sheet 4 is extended thereon in the direction in which the prism 20 having a triangular cross section extends. Are arranged so as to be parallel to the first direction q1, and the DBDF is placed thereon as the polarization separation sheet 5 to assemble the illumination devices 8 respectively.
And the front-side brightness | luminance was measured for every concealment structure 3 by Comparative Examples 1-5 and Examples 1-9. When measuring the front luminance, a spectral radiation luminance meter SR3 manufactured by TOPCON was used as a luminance measuring device.
In the evaluation, the front luminance was set to 1 when the concealment structure 3 was removed from the lighting device 8 and replaced with a diffusion sheet. The diffusion sheet used this time was a diffusion sheet BS912 manufactured by Ewa Corporation.

<Evaluation of concealment>
For the evaluation of the concealing property, the illumination device 8 is visually observed from the visual direction F, and it is confirmed whether or not the image of the white reflective ink as the light deflection element 13 provided on the light deflection surface 12 of the light guide plate 10 is visually recognized. I went there. When the image of the white reflective ink was visually recognized, it was evaluated as x, and when it was not visually recognized, it was evaluated as ◯.

<Evaluation of the diffusion angle of the second lens>
The second unit lens 17 of the concealment structure 3 produced in Comparative Examples 1 to 5 and Examples 1 to 9 is formed on the second main surface 15b, and a sheet in which the first main surface 15a is a flat surface is prepared. Using a goniophotometer, the half-value angle θb of the angular distribution in the second direction q2 of the light intensity of the light emitted from the first main surface 15a when collimated light is vertically incident from the second main surface 15b side is used. Measured. As the goniophotometer, an automatic variable angle photometer GP200 manufactured by Murakami Color Research Laboratory was used.

Table 1 shows the evaluation results of the front luminance and the concealing property of the lighting device 8 incorporating the concealing structure 3 in Comparative Examples 1 to 5 and Examples 1 to 9, and the measurement result of the half-value angle θb of the concealing structure 3.

From Example 1 and Example 2, when the value D 1 that defines the shape of the first unit lens 16 formed on the first major surface 15a is between 1.5 and 5, the front luminance is 3% compared to the diffusion film. As a result, it was confirmed that the light deflection element 13 was not visually recognized. When D 2 is smaller than 1.5 (Comparative Example 1), the light deflection element 13 is not visually recognized, but the front luminance is an increase of less than 3% compared to the diffusion film. When D was greater than 5 (Comparative Example 2), the front luminance increased by 3% or more compared to the diffusion film, but the light deflection element 13 was visually recognized.

From Example 3 to Example 9, when the half-value angle θb of the concealing structure 3 is in the range of 3 degrees or more and less than 10 degrees, the front luminance increases by 3% or more compared to the diffusion film, and the light deflection element 13 is visually recognized. It was confirmed that it was not.
When the half-value angle θb of the obscuring structure 3 was smaller than 3 degrees (Comparative Example 5), the front luminance increased by 3% or more as compared with the diffusion film, but the light deflection element 13 was visually recognized.
When the half-value angle θb of the obscuring structure 3 is 10 degrees or more (Comparative Example 3 and Comparative Example 4), the light deflection element 13 is not visually recognized, but the front luminance is increased by less than 3% compared to the diffusion film. .

From the measurement results of Examples 1 to 9 and Comparative Examples 1 to 5, the front luminance of the illuminating device 8 incorporating the concealment structure 3 in Examples 1 to 9 is higher than that of those incorporating Comparative Examples 1 to 5. Thus, the front luminance was increased by 3% or more compared to the diffusion sheet, and it was proved that the light deflection element 13 was not visually recognized.

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 Surface light source device 3 Concealment structure 4 Prism sheet 5 Polarization separation reflection sheet 6 Liquid crystal display element 7 Illumination unit,
8 Illuminating device 9 Reflecting plate 10 Light guide plate 10a End surface 11 Light source 12 Light deflecting surface 13 Light deflecting element 15 Base 15a First main surface 15b Second main surface 16 First unit lens 17 Second unit lens 17a First surface 17b Second surface 19 Base 20 Prism 22 Liquid crystal panel 23 Polarizing plate 100 Light guide plate 100a Emission surface 100b Light deflection surface 101 Light source 102 Light deflection element 182 Light source 184 Liquid crystal panel 185 BEF
186 Base material 187 Prism 190 Diffusion sheet 191 Lens sheet

Claims (19)

A light source;
A light guide including an incident surface on which light emitted from the light source is incident, an emission surface that emits incident light to an observer side, and a light deflection surface that guides the incident light to the emission surface;
A surface light source device including at least a reflection sheet that reflects light emitted from a surface opposite to the emission surface and guides the light to the light guide;
An illumination unit comprising a concealment structure on the light exit surface side of the surface light source device,
The light guide includes, on the light deflection surface, a light deflection element that guides light incident on the light guide to the exit surface side,
The light deflection elements are arranged at substantially equal intervals in the first direction at a first pitch P1,
In a second direction substantially orthogonal to the first direction, the two-dimensional array is arranged at substantially equal intervals with a second pitch P2 larger than the first pitch P1,
The concealing structure is a member having a second main surface on the light incident surface side and a first main surface on the light exit surface side,
The second main surface is a directional diffusion layer that diffuses light incident on the second main surface with a wider angular distribution in the second direction than in the first direction,
A plurality of first unit lenses are formed on the first main surface,
The directional diffusion layer has a light intensity of light emitted from the first main surface when collimated light is vertically incident from the second main surface side in the configuration without the first unit lens of the concealing structure. A lighting unit comprising a concealing structure, wherein a half-value angle of an angle distribution in the second direction is not less than 3 degrees and less than 10 degrees. The illumination unit having a concealing structure according to claim 1, wherein the first unit lens is a lens in which a region including at least a vertex is formed by a curved surface. The concealing structure according to claim 1, wherein the directional diffusion layer is formed by forming a plurality of second unit lenses in which a region including at least a vertex is formed by a curved surface. Lighting unit with body. A plurality of first unit lenses arranged in parallel to each other are formed on the first main surface at substantially equal intervals, and the first unit lens is composed of a uniaxial lens extending in a second direction. An illumination unit comprising the concealing structure according to any one of claims 1 to 3. A plurality of second unit lenses arranged in parallel to each other are formed on the second main surface at substantially equal intervals, and the second unit lens is composed of a uniaxial lens extending in the first direction. An illumination unit comprising the concealing structure according to any one of claims 1 to 4. When the end of the first unit lens is 0, the displacement measured in the first direction is x, the cross-sectional height of the first unit lens is f (x), and the pitch is Q1, f ( x)

And the value D defined by the following three formulas is 1.5 or more and 5 or less, comprising the concealing structure according to any one of claims 1 to 5: Lighting unit.

The absolute value of the differential df (x) / dx of f (x) at the point where the displacement x is 0 is defined in the range of the following expression: A lighting unit comprising the concealing structure described in 1.

The absolute value of the differential df (x) / dx of f (x) when the displacement x at which R (x) is the maximum value is x0 is defined within the range of the following equation. An illumination unit comprising the concealing structure according to any one of claims 1 to 7.

  When the height of the second unit lens is H2 and the pitch is Q2, when the aspect ratio is a numerical value defined by the following formula (H2 / Q2) × 100, any position on the second main surface 9, wherein the aspect ratio of the second unit lens is 4 or more and 10 or less, the illumination unit including the concealing structure according to claim 1.   The second unit lens is formed by a first surface formed in a region including an apex and a second surface formed in a region including an end, and the first surface and the second surface. In the boundary portion, the inclination angle changes discontinuously, and the inclination angle of an arbitrary point on the second surface is larger than the inclination angle of an arbitrary point on the first surface, The lighting unit provided with the concealment structure in any one of Claims 1-9. The second main surface of the concealing structure is substantially rectangular, and an end side of the second main surface parallel to the first direction and an end of the second main surface parallel to the second direction. An imaginary coordinate axis having an origin at an arbitrary point of intersection with the side is set, an axis parallel to the first direction is set as an X axis, and an axis parallel to the second direction is set as a Y axis. ,
The length of the end parallel to the first direction of the second main surface is W1,
The length of the end parallel to the second direction of the second main surface is W2,
In the configuration without the first unit lens of the concealing structure, the first when the collimated light is perpendicularly incident on an arbitrary coordinate (X, Y) on the second main surface from the second main surface side. The half-value angle (deg) of the angular distribution in the second direction of the light intensity of the light emitted from one principal surface is Φ (X, Y),
If X0 is an arbitrary constant between 0 and W1,
11. The half-value angle Φ (X0, Y) at X = X0 monotonously decreases when Y is continuously changed from 0 to W2 / 2. A lighting unit comprising the concealing structure described in 1. When the aspect ratio of the second unit lens on the coordinates (X, Y) or closest to the coordinates (X, Y) is Ω (X, Y),
The concealment structure according to claim 11, wherein the aspect ratio Ω (X0, Y) at X = X0 monotonously decreases when Y is continuously changed from 0 to W2 / 2. Provided lighting unit. A plurality of the second unit lenses are arranged so as to be spaced apart from each other so that a flat portion is formed therebetween, and are on the coordinates (X, Y) or nearest to the coordinates (X, Y) Let Δ (X, Y) be the width of
13. The flat portion width Δ (X0, Y) at X = X0 monotonously increases when Y is continuously changed from 0 to W2 / 2. A lighting unit comprising the concealing structure according to any one of the above. The light guide includes a single incident surface on which light emitted from the light source is incident,
The one incident surface is parallel to the first direction,
Of the intersections between the end side of the second main surface of the concealing structure parallel to the first direction and the end side of the second main surface parallel to the second direction, the one incident surface A virtual coordinate axis with an arbitrary intersection on the side close to the origin as an origin, an axis parallel to the first direction as an X axis, and an axis parallel to the second direction as a Y axis,
11. The half-value angle Φ (X0, Y) at X = X0 monotonously decreases when Y is continuously changed from 0 to W2. 11. Lighting unit with a concealing structure. 15. The concealing structure according to claim 14, wherein the aspect ratio Ω (X0, Y) at X = X0 monotonously decreases when Y is continuously changed from 0 to W2. Lighting unit. The flat portion width Δ (X0, Y) at X = X0 monotonously increases when Y is continuously changed from 0 to W2. A lighting unit comprising the concealing structure described in 1.   The illuminating device containing the concealment structure of any one of Claims 1-16, and one or more brightness enhancement films.   The illuminating device containing the concealment structure of any one of Claims 1-17, and a reflective polarization separation sheet.   A display device comprising: the illumination device according to any one of claims 17 to 18; and an image display element that defines a display image.

Images