JP2007017575A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent reduction of luminance of a display image of an image display device also usable as a mirror. <P>SOLUTION: A shape of a projecting and recessed part provided on the boundary surface between first and second layers 2 and 3 of an optical switch 6 is formed in a tooth shape. Since the refractive indices of the first and the second layers 2 and 3 of the optical switch 6 are so constituted as to be nearly equal to each other, output light from a display part 5 is transmitted through the boundary surface between the first and the second layers 2 and 3 in a display mode. Thereby, a user can view display of the display part 5 via the optical switch 6. In a mirror mode, incident light from the front surface on the user side is totally reflected on the tooth-shaped boundary surface between the first and the second layers 2 and 3 of the optical switch 6, and returned to the user side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image display apparatus that also serves as a mirror and has two types of modes, a display mode and a mirror mode.

  In recent years, an image display device (hereinafter sometimes abbreviated as “display”) used in a mobile phone device or a portable information terminal device is used not only as an image display device but also as a mirror. What has been configured to do so has been proposed. That is, such an image display device has two types of modes, a display mode and a mirror mode, and is used as a mirror when not used as an image display device.

FIG. 16 is an explanatory diagram showing the concept of a display unit used in a conventional image display device that also serves as a mirror.
As shown in the figure, in the above-described image display device (hereinafter also referred to as “mirror combined display”), as the “first method”, on the front surface of the display unit as viewed from the user side, A half mirror is arranged so that the display part can be seen through the half mirror, and the optical characteristics of the half mirror (that is, from the darker side, the brighter side can be seen, but from the brighter side, the darker side cannot be seen. A method of switching between the display mode and the mirror mode by switching the display unit to on or off using a characteristic) is known.

This first method has an advantage that a mirror-use display can be realized with a simple configuration in which the half mirror is simply arranged on the front surface (user side) of the display.
Specific examples of the first method include, for example, a half mirror as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2003-58067) and Patent Document 2 (Utility Model Registration No. 3087539). There are those in which silver or the like is applied so that the transmittance and the reflectance are halved, that is, a general half mirror is used.

  Further, as disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2004-85590) and Patent Document 4 (Japanese Patent Laid-Open No. 2004-86145), specific polarized light is reflected on the half mirror, and the others are Some employ a polarizing plate that transmits light (a reflective polarizing plate).

FIG. 17 is an explanatory view showing another concept of a display unit used in a conventional image display device also serving as a mirror. FIG. 18 is an explanatory diagram showing the structure of a reflective liquid crystal panel used in an image display device that also serves as a conventional mirror.
As shown in FIGS. 17 and 18, the above-mentioned mirror-combined display has a reflection type liquid crystal panel having a transmission mode and a reflection mode on the front surface of the display unit as viewed from the user side as a “second method” ( Mode switching means), the display unit can be seen through the reflective liquid crystal panel, and the reflective liquid crystal panel is switched between the transmissive mode and the reflective mode to switch between the display mode and the mirror mode. Is also known.

As a specific example of the second method, for example, as disclosed in Patent Document 5 (Japanese Patent Laid-Open No. 2001-318374), an absorption-type polarizing plate, a control electrode, a glass substrate, and a liquid crystal shown in FIG. A reflective liquid crystal panel composed of a layer, a glass substrate, a control substrate, and a reflective polarizing plate is placed in front of the display unit, and this reflective liquid crystal panel is set to a transmission mode in the display mode and a reflection mode in the mirror mode. As a result, screen reflection due to external light in the display mode, which is a drawback of the first method described above, is suppressed.
JP 2003-58067 A Utility Model Registration No. 3087539 JP 2004-85590 A JP 2004-86145 A JP 2001-318374 A

  However, in the conventional image display device described in the above background art, in the case of the above-described first method, the reflection characteristics of the half mirror are constant regardless of the display mode and the mirror mode. There is a problem that the screen is reflected and the display quality of the image in the display mode is deteriorated.

  In the case of the second method described above, since a reflective liquid crystal panel that transmits only specific polarized light is used, a self-luminous display device such as electroluminescence (hereinafter referred to as EL) is adopted for the display unit. In this case, there is a problem that the light output from the display unit is attenuated by the reflective liquid crystal panel, the display image becomes dark, and the display quality is deteriorated. In order to compensate for the deterioration in display quality due to the decrease in the luminance of the display image, it is necessary to increase the luminance of the display unit, which increases the power consumption of the display.

  The present invention has been made in view of the above-described conventional problems, and in order to realize the combined use of a mirror, a transmission state and a reflection state using total reflection are provided on the user side of the display unit. An object of the present invention is to provide an image display device that can be used as a mirror and does not reduce the luminance of a display image by providing an optical switch that realizes switching between two modes.

  The present invention has been made in view of the problems of the conventional image display device described above, and an optical switch that changes optical characteristics between the display mode and the mirror mode is arranged on the front surface of the display panel as viewed from the user side. The optical switch includes a first layer having a first refractive index, a second layer having a second refractive index, and an electric field applied simultaneously to the first layer and the second layer. And an electrode for applying light, and an image display device characterized by changing a critical angle of light incident on the second layer from the first layer when an electric field is applied to the electrode It is.

  The image display device is characterized in that an unevenness is provided on a boundary surface between the first layer and the second layer of the optical switch.

  In the image display device, serrated irregularities are provided on a boundary surface between the first layer and the second layer of the optical switch.

  The image display device is characterized in that conical or pyramidal irregularities are provided on a boundary surface between the first layer and the second layer of the optical switch.

  The image display device is characterized in that a frustoconical shape or a truncated pyramid shape is provided on a boundary surface between the first layer and the second layer of the optical switch.

  The image display device is characterized in that hemispherical irregularities are provided on a boundary surface between the first layer and the second layer of the optical switch.

  Further, in the image display device, the sawtooth, the cone, the pyramid, the truncated cone, the truncated pyramid, or the truncated cone having the shape of the unevenness provided on the boundary surface between the first layer and the second layer of the optical switch, The angle of inclination of any one of the hemispheres (a part of the sphere cut out in a plane) (when the boundary surface between the first layer and the second layer of the optical switch is used as a reference surface, The size of the uneven surface provided on the boundary surface between the first layer and the second layer of the optical switch and the angle formed by the normal to the reference plane is set to be equal to or larger than the critical angle in the reflection mode of the optical switch. It is characterized by that.

  In the image display device, a width of one period of the serrated irregularities provided on a boundary surface between the first layer and the second layer of the optical switch is equivalent to one pixel of the display panel. It is shorter than the width.

  Furthermore, in the image display device, the cone, the pyramid, the truncated cone, the truncated pyramid, or the truncated pyramid having the shape of the unevenness provided on the boundary surface between the first layer and the second layer of the optical switch, The size of one bottom surface of the hemisphere is smaller than the size of one pixel of the display panel.

  As described above, according to the image display device of the present invention, an electric field is applied to an optical switch that realizes two modes of a transmissive state and a reflective state using total reflection instead of a reflective liquid crystal panel. And using a material whose refractive index changes (for example, lithium niobate (LiNbO3), lithium tantalate (LiTaO3), or liquid crystal), and this optical switch is arranged on the user side of the display unit Therefore, it is possible to increase the transmittance of the light output of the display unit in the display mode as compared with the conventional method, and the display quality is reduced due to the luminance decrease due to the attenuation of the light output of the display unit. There is an effect of reducing deterioration.

  In addition, since the attenuation of the light output of the display unit is reduced, it is not necessary to increase the display brightness in order to compensate for the deterioration in display quality in the display mode as in the past, and the power consumption of the display unit can be suppressed. effective.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an image display device according to an embodiment of the invention will be described in detail with reference to the drawings.

FIG. 1 is an external view showing the overall structure of a display unit of an image display apparatus according to an embodiment of the present invention.
In the figure, the display unit of the image display apparatus according to the present embodiment includes a display unit 5 (display panel according to claim 1) on which an image is displayed, and an optical switch 6 that switches light.
The optical switch 6 includes an upper electrode 1 for supplying power, a first layer 2 having a refractive index n1 stacked on the front surface of the display unit 5 described later, and a refractive index stacked below the first layer 2. An n2 second layer 3 and a lower electrode 4 for supplying power are provided.

  By applying an electric field between the electrode 1 and the electrode 2 of the optical switch 6, a critical angle θ (refracted) when light from a light source (not shown) enters the second layer 3 from the first layer 2. The angle at which the total reflection of light occurs at the boundary between media having different rates changes, and the display mode / mirror mode is switched.

(First configuration example of optical switch)
FIG. 2 is a schematic diagram showing an enlarged structure including the size of the optical switch (main part) shown in FIG.
In the structure of the optical switch 6 illustrated in the figure, the shape of the unevenness provided on the boundary surface between the first layer 2 and the second layer 3 of the optical switch 6 is a sawtooth shape. More specifically, the boundary surface between the first layer 2 and the second layer 3 constituting the optical switch 6 has a sawtooth structure in which the interval (distance) between the peaks or valleys is a (unit is omitted). It has become. In FIG. 2, the shape and size of the serrated irregularities of the optical switch 6 are enlarged.

FIG. 3 is a schematic diagram showing an optical path in the display mode of the optical switch shown in FIG.
In the display mode (transmission mode), the refractive index n1 of the first layer 2 constituting the optical switch 6 and the refractive index n2 of the second layer 3 are configured to be substantially the same. Output light from the display unit 5 (incident light on the second layer 3 side) passes through the boundary surface between the first layer 2 and the second layer 3. Therefore, the user can see the display on the display unit 5 through the optical switch 6.

FIG. 4 is a schematic diagram showing an optical path in the reflection mode of the optical switch shown in FIG.
As shown in the figure, at the time of reflection mode (hereinafter referred to as “mirror mode”), the user side at the serrated interface between the first layer 2 and the second layer 3 of the optical switch 6. Incident light from the front is totally reflected and returned to the user side.

  As shown in FIG. 4, in the mirror mode, when the inclination of each serrated surface is 45 degrees and light is incident from the front on the first layer 2 side, that is, the light is incident on the first layer 2 and the second layer. When the light is incident at an angle of 45 degrees (θ1 = 45 degrees = π / 4 radians) with respect to the boundary surface with respect to the boundary surface 3 and the angle of the valley is a right angle, the first constituting the optical switch 6 By changing the refractive index n1 of the layer 2 so as to satisfy the condition of n1 ≧ (n2 / sin (π / 4)), total reflection was performed twice at the boundary surface between the first layer 2 and the second layer 3. Then, it returns to the direction in which light entered. At this time, the optical switch 6 can be used as a mirror by setting the display unit 5 to a resting state (a state in which there is no output light from the display unit 5).

  In the case of this example, incident light on the first layer 2 side of the optical switch 6 in the mirror mode is reflected a plurality of times and then returns to the incident side. For this reason, unlike a normal mirror that returns light to the incident side by a single reflection, the positions of the incident point and the outgoing point are different. If the positions of the entrance point and the exit point are different, there is a possibility of causing a visually uncomfortable feeling. In order to avoid this problem, it is desirable that the interval “a” between the peaks or valleys of the sawtooth structure is set to such a length that the user cannot recognize the difference in position between the incident point and the exit point. More specifically, it is preferable that the distance a is equal to or less than the length of one side of one pixel of the display unit 5 of the image display device of the present invention.

(Second configuration example of optical switch)
FIG. 5 is a perspective view showing a structure as another example of the optical switch of the image display apparatus according to the embodiment of the present invention.
In the structure of the optical switch 6 illustrated in the figure, the shape of the unevenness provided on the boundary surface between the first layer 2 and the second layer 3 is a quadrangular pyramid. In FIG. 5, the shape and size of the quadrangular pyramid of the optical switch 6 are enlarged.

FIG. 6 is a schematic view showing an enlarged structure including the size of the optical switch (main part) shown in FIG.
In the display mode (the optical path is not shown), since the refractive index of the first layer 2 and the second layer 3 of the optical switch 6 is substantially the same, a structure in which the boundary surface is serrated (illustrated in FIG. 2). Similarly to the structure described above, output light from the display unit (light incident from the second layer 3 side) passes through the boundary surface between the first layer 2 and the second layer 3. Therefore, the user can see the display on the display unit 5 through the optical switch 6.

FIG. 7 is a schematic diagram showing an optical path in the mirror mode of the optical switch shown in FIG.
As shown in FIG. 7, in the mirror mode, when the inclination of each surface of the quadrangular pyramid is 45 degrees and light is incident from the front on the first layer 2 side, that is, the light is incident on the first layer 2 and the second layer. In the case where the light is incident at an angle of 45 degrees (θ1 = 45 degrees) with respect to the boundary surface with 3 and the valley angle is a right angle, the refractive index of the first layer 2 constituting the optical switch 6 By changing n1 so as to satisfy the condition of n1 ≧ (n2 / sin (π / 4)), light is totally reflected twice at the boundary surface between the first layer 2 and the second layer 3, and then light is incident. Return to the direction you did. At this time, the optical switch 6 can be used as a mirror by setting the display unit 5 to a resting state (a state in which there is no output light from the display unit 5).

  In the structure of the optical switch 6 illustrated in FIG. 5, since the four side surfaces of the quadrangular pyramid are used for reflection, compared to the structure (structure illustrated in FIG. 2) in which only two surfaces of the serrated irregularities are used for reflection, Light reflection efficiency is improved.

  In the case of this example, incident light on the first layer 2 side of the optical switch 6 returns to the incident side after being reflected a plurality of times in the mirror mode. For this reason, the positions of the incident point and the outgoing point are different from those of a normal mirror that returns light to the incident side by one reflection. If the positions of the entrance point and the exit point are different, there is a possibility of causing a visually uncomfortable feeling. In order to avoid this problem, it is desirable that the size of the bottom surface of the quadrangular pyramid (FIG. 6) is designed so that the user cannot recognize the difference in position between the incident point and the exit point. More specifically, it is desirable that the size of the bottom surface is equal to or smaller than the size of one pixel.

(Third configuration example of optical switch)
FIG. 8 is a perspective view showing a structure as another example of the optical switch of the image display device according to the embodiment of the present invention.
In the structure of the optical switch 6 illustrated in the figure, the shape of the unevenness provided on the boundary surface between the first layer 2 and the second layer 3 is a truncated cone. In FIG. 8, the shape and size of the truncated cone of the optical switch 6 are enlarged.

  FIG. 9 is a schematic diagram showing an enlarged structure including the size of the optical switch (main part) shown in FIG. FIG. 10 is a schematic diagram showing an optical path in the display mode of the optical switch shown in FIG.

  As shown in FIG. 10, in the display mode, the refractive index of the first layer 2 and the second layer 3 is substantially the same, so that the interface has a sawtooth shape (structure illustrated in FIG. 2) Similarly, output light from the display unit 5 (light incident from the second layer 3 side) passes through the boundary surface between the first layer 2 and the second layer 3. Therefore, the user can see the display on the display unit 5 via the optical switch 6.

FIG. 11 is a schematic diagram showing an optical path in the mirror mode of the optical switch shown in FIG.
As shown in FIG. 11, in the mirror mode, when the inclination of the side surface of the truncated cone is 60 degrees and light is incident from the front surface on the first layer 2 side, that is, the light is incident on the first layer 2 and the second layer 3. Is incident at an angle of 60 degrees (θ1 = 60 degrees = π / 3 radians), the refractive index n1 of the first layer 2 constituting the optical switch 6 is set to n1 ≧ (n2 / By changing so as to satisfy the condition of sin (π / 3)), the light is totally reflected three times at the boundary surface between the first layer 2 and the second layer 3 and then returns to the light incident direction. At this time, the optical switch 6 can be used as a mirror by setting the display unit 5 to a resting state (a state in which there is no output light from the display unit 5).

  In the structure of the optical switch 6 illustrated in FIG. 8, in order to return the light incident from the front on the first layer 2 side to the incident side through three reflections, the light incident from the front on the first layer 2 side is The critical angle tends to be larger than the above-described configuration example (FIGS. 2 and 5) that returns to the incident side through two reflections. The amount of change in the refractive index n1 of the first layer 2 constituting the optical switch (the amount of change between the display mode and the mirror mode) can be reduced. For this reason, the choice of the medium forming the first layer 2 of the optical switch 6 can be expanded.

  In this example, incident light to the first layer 2 side of the optical switch 6 returns to the incident side after being reflected a plurality of times in the mirror mode. For this reason, unlike a normal mirror that returns light to the incident side by a single reflection, the positions of the incident point and the outgoing point are different. If the positions of the entrance point and the exit point are different, there is a possibility of causing a visually uncomfortable feeling. In order to avoid this problem, it is desirable that the size of the bottom surface of the truncated cone (see FIG. 9) is designed so that the user cannot recognize the difference between the positions of the entrance point and the exit point. More specifically, it is desirable that the size of the bottom surface is equal to or smaller than the size of one pixel.

(Fourth configuration example of optical switch)
FIG. 12 is a perspective view showing a structure as another example of the optical switch of the image display device according to the embodiment of the present invention.
In the structure of the optical switch 6 illustrated in the figure, the shape of the unevenness provided on the boundary surface between the first layer 2 and the second layer 3 of the optical switch is a hemisphere. In FIG. 12, the shape and size of the hemisphere of the optical switch 6 are enlarged.

  FIG. 13 is a schematic diagram showing an enlarged structure including the size of the optical switch (main part) shown in FIG. FIG. 14 is a schematic diagram showing an optical path in the display mode of the optical switch shown in FIG.

In the display mode, the first layer 2 and the second layer 3 have substantially the same refractive index, so that the output light from the display unit 5 is similar to the structure in which the boundary surface is serrated (structure illustrated in FIG. 2). The (incident light on the second layer 3 side) passes through the boundary surface between the first layer 2 and the second layer 3. Therefore, the user can see the display on the display unit 5 via the optical switch 6.

FIG. 15 is a schematic diagram showing an optical path in the mirror mode of the optical switch shown in FIG.
As shown in the figure, in the mirror mode, the incident light on the first layer 2 side is totally reflected a plurality of times at the boundary surface between the first layer 2 and the second layer 3, and then returns to the light incident direction. It will be. At this time, the optical switch 6 can be used as a mirror by setting the display unit 5 to a resting state (a state in which there is no output light from the display unit 5).

  In this example, incident light to the first layer 2 side of the optical switch in the mirror mode is reflected a plurality of times and then returns to the incident side. Therefore, unlike a normal mirror that returns light to the incident side by a single reflection, the positions of the incident point and the outgoing point are different, and the positions of the incident point and the outgoing point are different visually. There is a possibility of causing a sense of incongruity. In order to avoid this problem, it is desirable that the size of the bottom surface of the hemisphere (FIG. 13) is designed to be such that the user cannot recognize the difference in position between the incident point and the outgoing point. More specifically, it is desirable that the size of the bottom surface is equal to or smaller than the size of one pixel.

  In each of the above-described configuration examples, the respective functions are described by giving the case where the magnitude of the refractive index n1 of the first layer 2 of the optical switch 6 changes in the display mode and the mirror mode. However, if the refractive indexes (n1, n2) of the first layer 2 and the second layer 3 of the optical switch 6 meet the conditions for the display mode and the mirror mode, respectively, the display mode and the mirror mode The portion where the refractive index changes with time is not necessarily limited to the medium of the first layer 2 alone. If necessary, the refractive index of the medium of the second layer 3 may be changed between the display mode and the mirror mode, or the refractive indexes of both the first layer 2 and the second layer 3 may be used. However, it may be configured to change between the display mode and the mirror mode.

It is an external view which shows the whole structure of the display part of the image display apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the enlarged structure including the size of the optical switch (main part) shown in FIG. It is a schematic diagram which shows the optical path at the time of the display mode of the optical switch shown in FIG. It is a schematic diagram which shows the optical path at the time of the reflection mode of the optical switch shown in FIG. It is a perspective view which shows the structure as another example of the optical switch of the image display apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the enlarged structure including the size of the optical switch (main part) shown in FIG. It is a schematic diagram which shows the optical path at the time of the mirror mode of the optical switch shown in FIG. It is a perspective view which shows the structure as another example of the optical switch of the image display apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the enlarged structure including the size of the optical switch (main part) shown in FIG. It is a schematic diagram which shows the optical path at the time of the display mode of the optical switch shown in FIG. It is a schematic diagram which shows the optical path at the time of the mirror mode of the optical switch shown in FIG. It is a perspective view which shows the structure as another example of the optical switch of the image display apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the enlarged structure including the size of the optical switch (main part) shown in FIG. It is a schematic diagram which shows the optical path at the time of the display mode of the optical switch shown in FIG. It is a schematic diagram which shows the optical path at the time of the mirror mode of the optical switch shown in FIG. It is explanatory drawing which shows the concept of the display part used with the image display apparatus used also as the conventional mirror. It is explanatory drawing which shows the other concept of the display part used with the image display apparatus which also used the conventional mirror. It is explanatory drawing which shows the structure of the reflection type liquid crystal panel used with the image display apparatus which also used the conventional mirror.

Explanation of symbols

1, 4 electrode 2 first layer 3 second layer 5 display unit 6 optical switch

Claims (9)

An image display device in which an optical switch that changes an optical characteristic between a display mode and a mirror mode is disposed on the front surface of a display panel viewed from a user side,
The optical switch includes a first layer having a first refractive index, a second layer having a second refractive index, and an electrode for simultaneously applying an electric field to the first layer and the second layer. ,
An image display device, wherein a critical angle of light incident on the second layer from the first layer is changed when an electric field is applied to the electrode.   The image display device according to claim 1, wherein unevenness is provided on a boundary surface between the first layer and the second layer of the optical switch.   The image display device according to claim 2, wherein sawtooth-shaped irregularities are provided on a boundary surface between the first layer and the second layer of the optical switch.   The image display device according to claim 2, wherein conical or pyramidal irregularities are provided on a boundary surface between the first layer and the second layer of the optical switch.   The image display device according to claim 2, wherein a conical or truncated pyramid-shaped unevenness is provided on a boundary surface between the first layer and the second layer of the optical switch.   The image display device according to claim 2, wherein a hemispherical unevenness is provided on a boundary surface between the first layer and the second layer of the optical switch.   The slope of any one of the sawtooth, the cone, the pyramid, the truncated cone, the truncated pyramid, or the hemisphere having the uneven shape provided on the boundary surface between the first layer and the second layer of the optical switch 7. The image display device according to claim 3, wherein a magnitude of a tilt angle of the surface is equal to or greater than a critical angle in a reflection mode of the optical switch.   A width of one period of the serrated irregularities provided on a boundary surface between the first layer and the second layer of the optical switch is shorter than a width of one pixel of the display panel. The image display device according to claim 3.   The bottom surface of any one of the cone, the pyramid, the truncated cone, the truncated pyramid, or the hemisphere having the shape of the unevenness provided at the boundary surface between the first layer and the second layer of the optical switch. The image display device according to claim 4, wherein the size of the image display device is smaller than the size of one pixel of the display panel.

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