WO2013121771A1

WO2013121771A1 - Image display device

Info

Publication number: WO2013121771A1
Application number: PCT/JP2013/000745
Authority: WO
Inventors: 山口　博史
Original assignee: パナソニック株式会社
Priority date: 2012-02-13
Filing date: 2013-02-12
Publication date: 2013-08-22
Also published as: JP2015084005A

Abstract

The problem addressed by the present invention is to provide an image display device that can display excellent images. An image display device (1) that addresses this problem is provided with a light guide plate (6), light sources (2a, 2b), a directivity control sheet (3), and a liquid crystal panel (4). The light guide plate (6) has a substantially flat sheet shape and has a side surface as a light input surface and one main surface as a light output surface. The light of the light sources (2a, 2b) is incident to the input surfaces of the light guide plate (6). The directivity control sheet (3) has output light that has been output by the light guide plate (6) incident thereto, converts to prescribed light distribution characteristics, and outputs the light. The liquid crystal panel (4) is provided on the light output side of the directivity control sheet (3) and forms the light that is input into an image by spatial modulation according to an image signal. The directivity control sheet (3) has a prism array (31) on the light input surface. The prism array (31) is constituted by arranging a plurality of prisms having a substantially triangular shape in cross-section. Furthermore, an angle formed by a line bisecting the apex of a prism and a line normal to the bottom surface of the prism increases from the center to the edges of the directivity control sheet.

Description

Image display device

The present disclosure relates to an image display device such as a liquid crystal display.

Patent Document 1 uses a backlight capable of illuminating two types of light having different directivities, and alternately switches light having different directivities, and displays an image corresponding to left and right parallax in synchronization with the switching. Is disclosed. According to this method, stereoscopic display can be performed with the same resolution as that of two-dimensional display.

JP 2005-266293 A

The present disclosure provides an image display device capable of displaying a good image even on a relatively large screen.

The image display device according to the present disclosure includes a substantially flat light guide plate having a light incident surface as a side surface and a light exit surface as one of the main surfaces, a light source that emits light to the light incident surface of the light guide plate, and a light guide. A directivity control sheet that receives light emitted from the light plate, converts the incident light into a desired light distribution characteristic and emits the light, and is provided on the light output side of the directivity control sheet. And an image display panel that forms an image by spatial modulation. The directivity control sheet has a prism array on the light incident surface. The prism array is configured by arranging a plurality of prisms having a substantially triangular cross section. The angle formed by the bisector of the apex angle of the prism and the normal to the bottom surface of the prism increases from the central portion toward the end portion of the directivity control sheet.

The image display device according to the present disclosure is effective for displaying a good image even on a relatively large screen.

FIG. 1 is a schematic configuration diagram of an image display apparatus. FIG. 2 is an exploded perspective view of a part of the image display apparatus. FIG. 3 is a graph showing the intensity distribution with respect to the angle of light emitted from the light guide plate. FIG. 4 is a schematic enlarged view showing the shape of the central portion and the shape of the end portion of the directivity control sheet. FIG. 5 is a schematic diagram showing the shape of the central portion and the end portion of the directivity control sheet 3. FIG. 6 is a graph showing changes in the tilt angle of the prism. FIG. 7A is a schematic diagram showing ray tracing in the central portion, and FIG. 7B is a graph showing light distribution characteristics in the central portion. FIG. 8A is a schematic diagram showing the ray trajectory at the right end of the screen, and FIG. 8B is a graph showing the light distribution characteristic at the right end of the screen. FIG. 9A is a schematic diagram illustrating ray tracing of the comparative example, and FIG. 9B is a graph illustrating light distribution characteristics of the comparative example. FIG. 10 is a schematic diagram illustrating a modification of the directivity control sheet. FIG. 11 is a conceptual diagram for explaining light condensed on the left and right eyes of the viewer.

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

The inventor provides the accompanying drawings and the following description in order for those skilled in the art to fully understand the present disclosure, and is not intended to limit the subject matter described in the claims. Absent.

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of already well-known matters and repeated descriptions for substantially the same configuration may be omitted. This is to avoid the following description from becoming unnecessarily redundant and to facilitate understanding by those skilled in the art. Further, the drawings schematically show main components for easy understanding.

(Embodiment)
[1-1. Image display device]
FIG. 1 is a schematic sectional view of an image display device 1 according to the embodiment, and FIG. 2 is a perspective view. In FIG. 1, representative ray trajectories are also shown.

In the present embodiment, a three-dimensional orthogonal coordinate system is set for the image display device 1, and the direction is specified using the coordinate axes. As shown in FIGS. 1 and 2, the X-axis direction coincides with the left-right direction (horizontal direction) when the user faces the display surface of the image display panel 4. The Y-axis direction coincides with the vertical direction when the user faces the display surface of the liquid crystal panel 4. The Z-axis direction coincides with a direction perpendicular to the display surface of the liquid crystal panel 4. Here, “directly facing” means that, for example, when the character “A” is displayed on the display surface, the user faces the front of the display surface so that the user can see the character “A” from the correct direction. It means that it is located. 1 and 2 correspond to views seen from the upper side of the image display device 1. Therefore, the left side of FIGS. 1 and 2 is the right side of the display screen viewed from the viewer.

The image display device 1 mainly includes a light source switching type backlight 7 and a liquid crystal panel 4 that displays the right-eye image and the left-eye image while alternately switching them. Details of each component will be described below.

The backlight 7 includes

light sources

2 a and 2 b facing each other, a reflective film 5, and a light guide plate 6. The reflective film 5 is provided on the lower surface side (back surface side) of the light guide plate 6.

The

light sources

2a and 2b are disposed along each of the pair of side surfaces of the light guide plate 6 and face each other in the X-axis direction. The light source 2 a is disposed on the left side surface of the light guide plate 6, and the light source 2 b is disposed on the right side surface of the light guide plate 6. Each of the

light sources

2a and 2b has a plurality of LED elements arranged in the Y-axis direction. The

light sources

2a and 2b are alternately turned on and off in synchronization with switching between the left-eye image and the right-eye image displayed on the liquid crystal panel 4. That is, when the liquid crystal panel 4 displays the right-eye image, the light source 2a is turned on and the light source 2b is turned off. When the liquid crystal panel 4 displays the left-eye image, the light source 2a is turned off and the light source 2b is turned on. To do.

The light guide plate 6 has a substantially flat plate shape. The light guide plate 6 has a light incident surface on which light emitted from the

light sources

2a and 2b is incident and a light emission surface from which light incident from the side surface is emitted. The side surface of the light guide plate 6 corresponds to the light incident surface. Further, the upper surface (front surface) of the light guide plate 6 corresponds to a light emitting surface.

The light emitted from the

light sources

2 a and 2 b is incident from the side surface of the light guide plate 6. The light incident from the side surface of the light guide plate 6 propagates through the light guide plate 6 while repeating total reflection between the opposing main surfaces (upper surface and lower surface) of the light guide plate. A plurality of fine inclined surfaces are formed on the lower surface of the light guide plate 6, and the angle changes little by little during the propagation process, so that light rays that deviate from the total reflection condition are emitted from the light guide plate 6. By appropriately setting the angular distribution of these inclined surfaces, the intensity of light emitted from the light guide plate 6 is made uniform over the entire upper surface.

FIG. 3 is a graph showing the angular distribution of the light intensity of the light emitted from the light guide plate 6. The horizontal axis of the graph indicates the emission angle, and the vertical axis indicates the light intensity. The outgoing angle is expressed as an angle formed by outgoing light with respect to the normal line of the main surface of the light guide plate 6. The outgoing angle of 0 ° indicates that the outgoing direction of outgoing light is parallel to the ray of the main surface of the light guide plate. A plus sign on the horizontal axis indicates that the light guide plate 6 is inclined rightward from the normal line of the main surface of the light guide plate 6. A minus sign on the horizontal axis indicates that the light guide plate 6 is tilted leftward from the normal line of the main surface of the light guide plate 6.

As shown in FIG. 3, the light intensity of the light emitted from the light guide plate 6 has a distribution that peaks in the vicinity of ± 70 °. That is, a large amount of light emitted from the light guide plate 6 is emitted in an oblique direction inclined by + 70 ° or −70 ° with respect to the direction perpendicular to the display surface of the liquid crystal panel.

The reflective film 5 is provided on the lower surface side of the light guide plate 6. The light that has broken the total reflection angle of the inclined surface provided on the lower surface of the light guide plate 6 is reflected by the reflection film 5, enters the light guide plate 6 again, and finally exits from the upper surface. The light emitted from the light guide plate 6 enters the directivity control sheet 3.

The reflective film is composed of, for example, a film having silver deposited on the surface or a multilayer film that causes regular reflection.

[1-2. Directivity control sheet]
The light emitted from the light guide plate 6 enters the directivity control sheet 3. The directivity control sheet 3 converts the incident light into a desired light distribution characteristic and emits it. The directivity control sheet 3 converts light having directivity as shown in FIG. 3 into light having a direction toward the viewpoint of each of the left eye and right eye as a main directivity direction, and also having higher directivity. It has a function. Here, “light with higher directivity” means light having a higher peak of light intensity and a narrower half-width of the peak.

A prism array 31 is provided on the incident surface of the directivity control sheet 3, and a lenticular lens array 32 is provided on the exit surface side. The directivity control sheet 3 is formed, for example, by transferring a lens shape and a prism shape with a UV resin onto a base material made of a PET film.

The light emitted from the light guide plate 6 is reflected upward (in the positive direction of the Z axis) by the inclined surface of the prism array 31. Specifically, the prism array 31 totally reflects the light from the light guide plate 6 and converts the main directing direction. The light reflected upward is collected by the lenticular lens array 32. Specifically, the lenticular lens 32 sharpens the directivity by converging the incident light, and reduces crosstalk (interference between the image for the right eye and the image for the left eye) during stereoscopic display.

Details of the directivity control sheet 3 will be described with reference to FIG. FIG. 4A is a schematic enlarged view showing the shape of the central portion of the directivity control sheet 3, and FIG. 4B is a schematic enlarged view showing the shape of the end portion of the directivity control sheet 3.

The prism array 31 is composed of a plurality of prisms having a triangular cross section and ridge lines extending in the Y-axis direction. The lenticular lens 32 includes a plurality of cylindrical lenses that extend in the Y-axis direction and are arranged in parallel in the X-axis direction.

The pitch of the prism array 31, that is, the width of each prism is the same over the entire surface. The pitch of the lenticular lens array 32, that is, the width of each cylindrical lens is the same over the entire surface. In the present embodiment, the pitch of the lenticular lens array 32 is smaller than the pitch of the prism array 31. Accordingly, as will be described in detail later, as the distance from the central portion of the directivity control sheet 3 toward the side end portion increases, the positional relationship between the prism and the cylindrical lens shifts, and the cylindrical lens moves toward the central portion with respect to the prism. And shift.

In the central part of the directivity control sheet 3, the prism has a symmetrical isosceles triangle shape. That is, the bisector L1 of the apex angle of the vertex A1 of the central prism (hereinafter sometimes referred to as “line segment L1”) is substantially parallel to the Z axis. A surface formed by connecting the bottommost portions C of the concave portions of the prism is defined as a bottom surface B of the prism. When the normal line of the bottom surface B is the normal line M1, the normal line M1 and the line segment L1 are substantially parallel.

Further, in the central portion of the directivity control sheet 3, the prism and the cylindrical lens are opposed to each other. That is, the line segment L1 and the line segment N passing through the center of the cylindrical lens substantially coincide with each other.

The prisms other than the center of the directivity control sheet 3, that is, on the end side, are formed such that the apex angle bisector L <b> 2 (hereinafter sometimes referred to as a line segment L <b> 2) is inclined toward the center. . That is, the line segment L2 is inclined at a predetermined angle θ with respect to the normal line M2 of the bottom surface B. The inclination angle θ gradually changes from the central portion toward the end portion of the directivity control sheet 3. Specifically, the inclination angle θ increases from the central portion toward the end portion. That is, the inclination angle θ is larger as the distance from the center is larger.

Further, on the end side of the directivity control sheet 3, the cylindrical lens position with respect to the prism is shifted to the center side. This shift amount differs depending on the magnitude of the inclination angle θ. Specifically, the greater the inclination angle θ, the greater the shift amount.

As described above, in the directivity control sheet 3 of the present embodiment, the shape of the prism is different between the central portion and the end portion. However, the apex angle of the apex of the prism is constant in any region.

Since the apex angle of the prism is constant, it can be processed using a tool having the same shape when processing a die for transferring the prism. Therefore, the directivity control sheet 3 can be easily manufactured.

In the present embodiment, the shapes of the apex A and the bottom B of the prism are shown as acute angles. However, when the actual prism is strictly observed, it may be a curved surface with a slight curvature instead of an acute angle. In such a case, the extreme end portion of the curved surface may be regarded as a vertex.

Further, when the vertex A is a curved surface, a point that intersects when two sides (slopes) forming the prism are extended may be regarded as the vertex.

[1-3. Effect]
In an image display device capable of displaying a stereoscopic image, in order to realize a favorable stereoscopic display on the entire screen, right-eye illumination light is condensed on the right eye, and left-eye illumination light is emitted over the entire screen. It is necessary to focus on the left eye.

FIG. 11 is a conceptual diagram for explaining light condensed on the left and right eyes of the viewer. FIGS. 11A and 11B are schematic diagrams showing the relationship between a type 3 screen and viewers. FIG. 11C is a schematic diagram showing the relationship between the 10-inch screen and the viewer.

Here, the viewing distance, which is the distance from the viewer's eyes to the display screen, is 300 mm. The distance between the viewer's left and right eyes is 65 mm. This is the average left-right eye spacing for adults. Assume that the center position of the left and right eyes of the viewer is at a position passing through the center of the screen. Here, a perpendicular line that passes through the center of the screen and is perpendicular to the screen is defined as a reference axis X.

First, the light emitted from the center of the screen will be described.

As shown in FIG. 11A, the light emitted from the center of the screen reaches the left and right eyes with a spread of ± 6 ° with respect to the reference axis X. Since the viewer is viewing while facing the center of the screen, the central axis Xa of the light emitted from the center of the screen coincides with the reference axis X.

Next, the light emitted from the edge of the screen will be described.

As shown in FIG. 11B, the central axis Xb of the light emitted from the edge of the screen has an inclination of 6 ° with respect to the reference axis X. That is, in order to allow light emitted from the edge of the screen to reach the left and right eyes of the viewer, it is necessary to deflect the emission angle by 6 °.

Further, as shown in FIG. 11C, when the screen size is 10 type, the central axis Xc of the light emitted from the edge of the screen has an inclination of 20 ° with respect to the reference axis X. . That is, in order to make the light emitted from the edge of the screen reach the left and right eyes of the viewer, it is necessary to increase the light emission angle from the edge of the screen by 20 °.

In Japanese Patent Application Laid-Open No. 2006-266293, the pitch of the prism array and the lenticular lens array facing each other is slightly different, and the lenticular lens is arranged inward in the peripheral portion, thereby setting the light emission angle from the edge of the screen. Attempts to make it larger.

However, with this method, it has been the limit to increase the light emission direction (direction direction) by about 10 °. Therefore, the screen size of the stereoscopic image display apparatus that can be realized by this method is limited to about 5 inches, and there is a problem that it cannot cope with a large screen.

In contrast, the image display device 1 of the present embodiment includes a light guide plate 6,

light sources

2 a and 2 b, a directivity control sheet 3, and a liquid crystal panel 4. The light guide plate 6 has a substantially flat plate shape with a side surface serving as a light incident surface and a main one as a light emitting surface. The

light sources

2 a and 2 b make light incident on the incident surface of the light guide plate 6. The directivity control sheet 3 receives the emitted light emitted from the light guide plate 6, converts the light into a desired light distribution characteristic, and emits the light. The liquid crystal panel 4 is provided on the light output side of the directivity control sheet 3 and forms an image by spatially modulating incident light according to a video signal. The directivity control sheet 3 has a prism array 31 on the light incident surface. The prism array 31 is configured by arranging a plurality of prisms having a substantially triangular cross section. The angle formed between the bisector of the apex angle of the prism and the normal to the bottom surface of the prism gradually changes from the end of the directivity control sheet toward the center.

With such a configuration, even in a display device having a relatively large screen size, the light emitted from the left and right ends of the screen can be efficiently condensed on the left and right eyes of the viewer. As a result, the image display device 1 can perform better stereoscopic display than before.

(Other embodiments)
In the above-described embodiment, the case where stereoscopic image display is performed using the two

light sources

2a and 2b has been described as an example, but the present disclosure is not limited thereto. The light source may be arranged only on one side surface of the light guide plate 6 to display a two-dimensional image. In this case, it is expected that a bright image can be obtained with a small amount of light by collecting the light in the viewing direction. In the case of such a configuration, the shape of the prism array 31 of the directivity control sheet 3 can be appropriately designed as shown in FIG. As shown in FIG. 10, the shape of the central portion of the prism array 31 is not necessarily a symmetric shape (isosceles triangle). In short, the shape is gradually changed from the center to the end so that the light from the entire region is directed toward the viewpoint. For example, as shown in FIG. 10, the prism at the left end may have an isosceles triangle cross section, and the apex of the prism may shift to the right as it goes to the right end. In the configuration example of the directivity control sheet 3 illustrated in FIG. 10, the light condensing position is the left front of the directivity control sheet 3 (upper left in FIG. 10). When it is desired to collect light to the right front of the directivity control sheet 3, the shape of the prism is symmetrical to that of FIG. 10, that is, the prism at the right end is an isosceles triangle, and the apex of the prism increases toward the left end. What is necessary is just to comprise a prism array so that may shift to the left side. As described above, the asymmetric directivity control sheet 3 having a prism shape that is asymmetrical to the left and right is a case where the viewer's viewpoint position with respect to the image display device is shifted to a side portion from the center, such as an in-vehicle display. Available to:

In the above-described embodiment, the LED is described as an example of the light source, but the present disclosure is not limited to this. For example, a cold cathode tube or a laser diode may be used as the light source.

In the above-described embodiment, the light guide plate 6 is shared by the

light sources

2a and 2b. However, a light guide plate for the light source 2a and a light guide plate for the light source 2b are provided, and the two light guide plates are stacked. May be.

In the above embodiment, the directivity control sheet in which the prism array 31 and the lenticular lens array 32 are integrated has been described as an example, but the present disclosure is not limited thereto. You may provide separately the prism sheet in which the prism array was formed, and the lenticular lens array sheet in which the lenticular lens was formed. In this case, the prism sheet and the lenticular lens array sheet may be configured to have shapes corresponding to the prism array and the lenticular lens array of the directivity control sheet, respectively.

Furthermore, in the above-described embodiment, the stereoscopic image display device that displays the right-eye image and the left-eye image with parallax in a time-division manner is described as an example, but an image without parallax may be displayed. In this case, instead of blinking the

light sources

2a and 2b alternately, the light sources may be constantly lit. When displaying 2D images as well as 3D images, not only the energy is saved but also the contents displayed by the surrounding people can be viewed by reducing and projecting the image only near the viewer's eyes. Can be prevented and privacy protection can be improved.

Furthermore, in the above-described embodiment, the lenticular lens array 32 is provided on the exit surface side of the directivity control sheet 3, but the directivity control sheet 3 having only the prism array 31 is provided without providing the lenticular lens array 32. May be. In this case, the exit surface of the directivity control sheet 3 is formed flat. Even when the directivity control sheet 3 has only the prism array 31, the prism array 31 deflects the left and right light emitted from the light guide plate 6, thereby allowing the light emitted from the left and right ends of the screen to be viewed by the viewer's eyes. The light can be condensed at the position, and a bright image display device can be realized over the entire screen. However, when the lenticular lens array 32 is provided as in the above-described embodiment, the variation in the deflection angle of the light emitted from the side of the center of the screen can be reduced (that is, FIG. Since the dispersion of the light intensity distribution shown in b) can be reduced), a brighter image display device can be realized. Further, when the lenticular lens array 32 is provided, the crosstalk component of light emitted from the side of the center of the screen can be reduced, so that the image quality of the entire screen can be improved.

(Example)
Examples will be described below. In this example, simulation was performed on a directivity control sheet designed with a parallax of 6 °, assuming an optimal viewing distance of 300 mm and a screen size of 10 type.

FIG. 5 is a schematic diagram showing the shape and design data of the central part and the end part of the directivity control sheet 3. FIG. 6 is a graph showing changes in the inclination angle φ.

As shown in FIG. 5A, the cross-sectional shape of the prism is an isosceles triangle in the central portion of the directivity control sheet 3.

As shown in FIG. 5 (c), the apex angle θp of the prism was 60 °, and the same angle was used at the center and at the end of the directivity control sheet 3.

The prism pitch Pp was 0.1 mm, and the same pitch was used at the center and at the end of the directivity control sheet 3.

Pitch P _L of the lenticular lens is the same in the end in the central part of the directivity control sheet 3, shift amount for the prism of the lenticular lens element which is disposed outermost end (endmost eccentricity) [Delta] x is The thickness was set to 0.099967 mm so as to be 0.036 mm.

The thickness t from the bottom surface of the prism to the bottom surface of the lenticular lens was 0.121 mm.

The radius of curvature _RL of the lenticular lens was 0.091 mm, and the central portion and the end portion had the same radius of curvature.

As shown in FIG. 5B, the inclination angle φ of the prism disposed on the outermost side of the end portion of the directivity control sheet 3 was 9 °. The tilt angle φ is an angle formed by a bisector of the apex angle of the prism and a normal to the bottom surface of the prism.

Further, as shown in FIG. 6, the inclination angle φ of the prism was designed to gradually change between the central portion and the end portion of the directivity control sheet 3. The vertical axis in FIG. 6 indicates the inclination angle φ of the prism. The horizontal axis is the distance from the central part of the directivity control sheet 3 to a predetermined position, and is normalized by the length from the central part to the end part. The value on the horizontal axis is “0” at the center of the directivity control sheet 3, “1” at the rightmost end, and “−1” at the leftmost end.

As shown in FIG. 6, the prism inclination angle is changed linearly from the center to the end. The shift amount (eccentric amount) of the lenticular lens position is also changed linearly.

FIG. 7A is a ray tracing diagram at the central portion, and the representative ray from the light source 2a arranged on the right side as viewed from the observer is a broken line and the representative ray from the light source 2b arranged on the left side as seen from the observer. Is indicated by a solid line. FIG. 7B shows the light distribution characteristics at the center.

As shown in FIG. 7B, when the light source 2a was turned on (broken line), the light intensity distribution of the emitted light peaked at −6 ° which is the viewpoint direction of the right eye. When the light source 2b was turned on (solid line), the light intensity distribution of the emitted light peaked at + 6 ° which is the viewpoint direction of the left eye.

FIG. 8 (a) is a schematic diagram showing the ray trajectory at the right end of the screen, and FIG. 8 (b) is a graph showing the light distribution characteristics. As shown in FIG. 8A, the prism is designed so that the prism tilt angle (the angle formed by the bisector of the prism apex angle with respect to the prism bottom surface) is 9 ° at the right end.

Since the prism at the right end of the screen is inclined, as shown in FIG. 8A, the light (dashed line) from the light source 2a is deflected to the minus side (that is, toward the center of the screen). Further, the light beam (solid line) from the light source 2b is also deflected to the minus side. The cylindrical lens constituting the lenticular lens at the right end is shifted to the center by 36% with respect to the prism pitch. Thereby, the light reflected by the prism at the right end can be efficiently focused. As a result, the directivity of light at the right end can be increased.

As shown in FIG. 8B, when the light source 2a was turned on (broken line), the light intensity distribution of the emitted light peaked at minus 26 °, which is the viewpoint direction of the right eye. When the right light source 2b was turned on (solid line), the light intensity distribution of the emitted light peaked at minus 14 °, which is the viewpoint direction of the right eye. That is, the light for the right eye and the light for the left eye emitted from the right end portion was deflected by 20 ° minus side (screen center side). Since the deflection of the light emitted from the left end is the same except that it is opposite to the deflection direction of the light emitted from the right end, repeated description is omitted. Therefore, even with a 10-inch display, the light emitted from the left and right edges of the screen can be focused on the viewer's eyes, and the right and left of the viewer watching in the center of the screen The amount of light that reaches the eyes can be increased. Therefore, the image display device using the directivity control sheet 3 according to the embodiment can provide a bright image over the entire screen to the viewer.

(Comparative example)
Next, a comparative example will be described. As a comparative example, prisms having the same shape were used at any location. Further, the lenticular lens was shifted inward by 36% at the extreme end as in the example. A simulation was performed for such a directivity control sheet.

FIG. 9 (a) is a schematic diagram showing the ray trajectory at the end of the directivity control sheet of the comparative example, and FIG. 9 (b) shows its light distribution characteristics.

As shown in FIG. 9B, the directivity peak was confirmed, but the deflection angle with respect to the normal of the directivity control sheet was a small value of 10 °. Also, the symmetry of the light distribution characteristic of the right eye light and the light distribution characteristic of the left eye light is poor. Further, as shown in FIGS. 9A and 9B, the cylindrical lens adjacent to the cylindrical lens corresponding to the prism (the cylindrical lens to which light from the prism should originally enter) is transmitted to the cylindrical lens. Since a part of the light is incident and the condensing position of a part of the light is shifted, a lot of irregular unnecessary light is generated. As a result, as shown in FIG. 9B, a peak of unnecessary light occurs in the light intensity distribution.

In this state, the brightness of the left and right images is unbalanced and a good 3D display is not possible. Even if this state is allowed, if the deflection angle is about 10 °, it can only deal with a screen of about 5 inches at a viewing distance of 300 mm.

As described above, the embodiments have been described as examples of the technology in the present disclosure. For this purpose, the accompanying drawings and detailed description are provided.

Accordingly, among the components described in the accompanying drawings and the detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to illustrate the above technique. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

In addition, since the above-described embodiments are for illustrating the technique in the present disclosure, various modifications, replacements, additions, omissions, and the like can be made within the scope of the claims and the equivalents thereof.

The present disclosure is suitably used for an image display device such as a liquid crystal display.

DESCRIPTION OF SYMBOLS 1

Image display apparatus

2a, 2b Light source 3 Directionality control sheet 31 Prism array 32 Lenticular lens array 4 Liquid crystal panel 5 Reflective film 6 Light guide plate 7 Backlight

Claims

A substantially flat light guide plate having a side surface as a light incident surface and one of the main surfaces as a light exit surface;
A light source that emits light to the light incident surface of the light guide plate;
A directivity control sheet that receives light emitted from the light guide plate, converts the incident light into desired light distribution characteristics, and emits the light, and
An image display panel that is provided on the light output side of the directivity control sheet and that spatially modulates incident light according to a video signal to form an image;
The directivity control sheet has a prism array on the light incident surface,
The prism array is configured by arranging a plurality of prisms having a substantially triangular cross section,
The image display device, wherein an angle formed by a bisector of the apex angle of the prism and a normal line to the bottom surface of the prism increases from a central portion toward an end portion of the directivity control sheet.
The image display device according to claim 1, wherein apex angles of the plurality of prisms are constant.
A lenticular lens array composed of cylindrical lenses facing each prism is formed on the exit surface facing the entrance surface on which the prism array of the directivity control sheet is formed,
The lenticular lens array is configured by arranging a plurality of the cylindrical lenses,
The position in the arrangement direction of the cylindrical lenses corresponding to the prism is shifted to the center side according to the angle formed by the bisector of the apex angle of the prism and the normal to the bottom surface of the prism. The image display device according to claim 1.
The light source includes a first light source and a second light source that emit light to each of two opposing side surfaces of the light guide plate,
The first light source and the second light source alternately turn on and off repeatedly,
The image display device according to claim 1, wherein the image display panel switches a display image of the image display panel in synchronization with switching of turning on and off of the first light source and the second light source.