JP2013218070A - Liquid crystal lens and stereoscopic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal lens capable of obtaining an effective refractive index distribution even when the distance between pattern electrodes is long as compared with the thickness of a liquid crystal layer.SOLUTION: A liquid crystal lens 11 includes: an insulating first substrate 111; a first pattern electrode 113 which is formed on the first substrate 111 and in which conducting regions and non-conducting regions are formed repeatedly in a stripe manner in a first direction; an insulating second substrate 116 arranged so as to face the first substrate 111; a second pattern electrode 117 which is formed on the second substrate 116 and in which conducting regions and non-conducting regions are formed repeatedly in a stripe manner in the first direction; a liquid crystal layer 115 held between the first substrate 111 and the second substrate 116; and a control part 119 for controlling the electric potentials of the first pattern electrode 113 and the second pattern electrode 117 to perform mode switching among two or more modes.

Description

  The present invention relates to a liquid crystal lens and a stereoscopic display device.

  A multi-view stereoscopic display device regularly displays images taken from multiple directions. Therefore, the resolution decreases as the number of viewpoints increases. Accordingly, it is preferable that the two-dimensional display mode and the three-dimensional display mode are switchable, and that the resolution can be maintained in the two-dimensional display mode.

  As such a stereoscopic display device, a stereoscopic display device using a liquid crystal lens is known. The liquid crystal lens controls the orientation of the liquid crystal by a potential difference between the pattern electrode and the common electrode, and forms a refractive index distribution.

  Japanese Unexamined Patent Application Publication No. 2010-282090 (Patent Document 1) discloses a stereoscopic display device using a variable lens array element. This stereoscopic display device includes a display panel and a variable lens array element. The variable lens array element includes a first electrode and a second electrode facing the first electrode. The second electrode is formed smaller than the width of the sub-pixel of the display panel, and is provided at least for each horizontal array position of the sub-pixel. The variable lens array element changes the position and shape of the cylindrical lens in the horizontal direction at least in units of sub-pixels by independently controlling the voltage applied to each of the plurality of second electrodes.

JP 2010-282090 A

  However, in the liquid crystal lens, when the distance between the pattern electrodes is longer than the distance between the pattern electrode and the common electrode (which roughly matches the thickness of the liquid crystal layer), no electric field is applied to the central portion between the pattern electrodes. There's a problem. In this case, a potential gradient is not formed at the central portion. Therefore, an effective refractive index distribution cannot be obtained, and the function as a lens cannot be obtained.

  The variable lens array element disclosed in Patent Document 1 forms pattern electrodes in units of subpixels, and independently controls the voltage applied to each. As a result, the horizontal position and shape of the cylindrical lens are changed in units of subpixels. However, in order to form pattern electrodes in units of subpixels and independently control the voltage applied to each, a complicated manufacturing process is required. In addition, a signal generation circuit for generating various types of voltages is required.

  An object of the present invention is to provide a liquid crystal lens capable of obtaining an effective refractive index distribution even when the distance between pattern electrodes is longer than the thickness of the liquid crystal layer.

  The liquid crystal lens disclosed herein includes an insulating first substrate, a first pattern electrode formed on the first substrate by repeating a conductive portion and a non-conductive portion in a stripe shape along a first direction, And an insulating second substrate disposed opposite to the first substrate, and a conductive portion and a non-conductive portion formed in the second substrate in a striped manner along the first direction. A second pattern electrode; a liquid crystal layer sandwiched between the first substrate and the second substrate; and a controller that controls the potentials of the first pattern electrode and the second pattern electrode to switch between two or more modes. Is provided.

  According to the liquid crystal lens of the present invention, an effective refractive index distribution can be obtained even when the distance between the pattern electrodes is longer than the thickness of the liquid crystal layer.

FIG. 1 is an exploded perspective view showing a schematic configuration of a stereoscopic display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and schematically shows the configuration of the liquid crystal lens according to the first embodiment of the present invention. FIG. 3 is a perspective view illustrating a part of the first substrate and the second substrate extracted from the configuration of the liquid crystal lens according to the first embodiment. FIG. 4 is a schematic cross-sectional view in one mode of the liquid crystal lens according to the first embodiment. FIG. 5 is a schematic cross-sectional view in another mode of the liquid crystal lens according to the first embodiment. FIG. 6 is a schematic cross-sectional view of a liquid crystal lens according to a virtual comparative example. FIG. 7 is a schematic cross-sectional view showing a schematic configuration of a liquid crystal lens according to the second embodiment of the present invention. FIG. 8 is a schematic cross-sectional view for explaining the effect of the liquid crystal lens according to the second embodiment. FIG. 9 is a schematic cross-sectional view showing a schematic configuration of a liquid crystal lens according to the third embodiment of the present invention. FIG. 10 is a schematic cross-sectional view for explaining the operation of the liquid crystal lens according to the third embodiment. FIG. 11: is typical sectional drawing which shows schematic structure of the liquid crystal lens concerning the 4th Embodiment of this invention. FIG. 12 is a schematic cross-sectional view for explaining the operation of the liquid crystal lens according to the fourth embodiment. FIG. 13 is a diagram and a table showing the arrangement and potential of each component in the simulation performed to explain the effects of the embodiment. FIG. 14 is a graph showing a simulation result and a theoretical curve in the arrangement and potential of FIG. FIG. 15 is a diagram and a table showing the arrangement of components and potentials in a simulation carried out to explain the effects of the embodiment. FIG. 16 is a graph showing a simulation result and a theoretical curve in the arrangement and potential of FIG. FIG. 16 is a diagram and a table showing the arrangement of components and potentials in a simulation carried out to explain the effects of the embodiment. FIG. 18 is a graph showing a simulation result and a theoretical curve in the arrangement and potential of FIG. FIG. 19 is a diagram and a table showing the arrangement and potential of each component in a simulation performed to explain the effect of the embodiment. FIG. 20 is a graph showing a simulation result and a theoretical curve in the arrangement and potential of FIG. FIG. 21 is a graph showing the relationship between the number of potentials on the horizontal axis and the mean square of the difference from the theoretical curve on the vertical axis.

  A liquid crystal lens according to an embodiment of the present invention includes a first insulating substrate and a first substrate formed by repeating a conductive portion and a non-conductive portion in a stripe shape along a first direction. A conductive portion and a non-conductive portion are repeated in a striped pattern along the first direction on the second substrate, an insulating second substrate disposed opposite to the first substrate, and the first substrate. Two or more modes by controlling the potential of the second pattern electrode, the liquid crystal layer sandwiched between the first substrate and the second substrate, and the first pattern electrode and the second pattern electrode. A switching control unit (first configuration).

  According to said structure, the 1st pattern electrode and 2nd pattern electrode in which the electroconductive part and the nonelectroconductive part were repeated in stripe form were formed in both the 1st board | substrate and the 2nd board | substrate. This makes it easier to apply an electric field in the in-plane direction as compared with the case where a pattern electrode is formed on one of the first substrate and the second substrate and a uniform common electrode is formed on the other. The liquid crystal molecules in the liquid crystal layer are aligned according to the electric field to form a refractive index distribution. By applying an electric field in the in-plane direction, a continuous refractive index distribution is obtained. Thereby, good lens characteristics can be obtained.

  In the first configuration, it is preferable that the non-conductive portion of the first pattern electrode and the non-conductive portion of the second pattern electrode do not face each other (second configuration).

  According to said structure, in the substantially all area | region in which the 1st pattern electrode and the 2nd pattern electrode were formed, the electroconductive part is formed in at least one of the 1st pattern electrode and the 2nd pattern electrode. Thereby, a potential gradient is easily formed also in the non-conductive portion of the first pattern electrode and the non-conductive portion of the second pattern electrode. As a result, an electric field can be applied more effectively in the in-plane direction.

  In the first or second configuration, the width of the conductive portion of the first pattern electrode is larger than that of a portion where the potential difference between the first pattern electrode and the second pattern electrode is small in one of the modes. It is preferable that the first pattern electrode and the second pattern electrode are narrowly formed in a portion where the potential difference is large (third configuration).

  In an ideal gradient index lens (Gradient Index Lens, GRIN lens), the refractive index distribution is a quadratic curve. Therefore, the change in refractive index at the lens edge is steeper than the change in refractive index at the center of the lens. Therefore, in order to obtain lens characteristics close to an ideal GRIN lens, it is preferable to make the potential gradient at the lens end portion steeper than the potential gradient at the lens center. The width of the conductive portion of the first pattern electrode is set at a portion where the potential difference between the first pattern electrode and the second pattern electrode is large compared to a portion where the potential difference between the first pattern electrode and the second pattern electrode is small. By forming it narrow, the potential gradient at the end of the lens can be made steep.

  In any one of the first to third configurations, it is preferable that the control unit controls the potential of the first pattern electrode and the potential of the second pattern electrode to a total of four levels or more (fourth) Configuration).

  In any one of the first to fourth configurations, the liquid crystal molecules of the liquid crystal layer are aligned substantially parallel to the first substrate when no potential difference is generated between the first substrate and the second substrate. It may be possible (fifth configuration).

  In any one of the first to fourth configurations, the liquid crystal molecules of the liquid crystal layer are aligned substantially perpendicular to the first substrate when no potential difference is generated between the first substrate and the second substrate. It may also be possible (sixth configuration).

  In the fifth configuration, the liquid crystal molecules have an alignment direction on the first substrate side and an alignment direction on the second substrate side when no potential difference is generated between the first substrate and the second substrate. And may be substantially orthogonal (seventh configuration).

  In the seventh configuration, an angle formed between the alignment direction of the liquid crystal molecules on the first substrate side and the second direction may be about 45 ° (eighth configuration).

  The seventh or eighth configuration preferably further includes a polarizing plate disposed on the first substrate side and having a polarization axis substantially parallel to an alignment direction of the liquid crystal molecules on the first substrate side (ninth). Configuration).

  The seventh or eighth configuration preferably further includes a polarizing plate disposed on the second substrate side and having a polarization axis substantially parallel to an alignment direction of the liquid crystal molecules on the second substrate side (tenth embodiment). Configuration).

  According to the ninth or tenth configuration, when there is no potential difference between the first substrate and the second substrate, the alignment direction of the liquid crystal molecules is about 90 ° in a plane substantially parallel to the first substrate. Rotate. The polarization axis of the light incident on the liquid crystal layer rotates according to this and passes through the polarizing plate. On the other hand, when the liquid crystal molecules are aligned approximately perpendicular to the first substrate due to the potential difference between the first substrate and the second substrate, the polarization axis of the light incident on the liquid crystal layer does not rotate. Therefore, this light cannot pass through the polarizing plate. Accordingly, a virtual parallax barrier that blocks light at regular intervals can be formed. Crosstalk can be reduced by the parallax barrier.

  A stereoscopic display device according to an embodiment of the present invention includes a display device capable of displaying an image and the liquid crystal lens having any one of the first to tenth configurations (first configuration of the stereoscopic display device).

  In the first configuration of the stereoscopic display device, the liquid crystal lens may have the first substrate disposed on the display device side (second configuration of the stereoscopic display device).

  In the first configuration of the stereoscopic display device, the second substrate of the liquid crystal lens may be disposed on the display device side (third configuration of the stereoscopic display device).

[Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated. In addition, in order to make the explanation easy to understand, in the drawings referred to below, the configuration is shown in a simplified or schematic manner, or some components are omitted. Further, the dimensional ratio between the constituent members shown in each drawing does not necessarily indicate an actual dimensional ratio.

[Overall configuration]
FIG. 1 is an exploded perspective view showing a schematic configuration of a stereoscopic display device 1 according to an embodiment of the present invention. The stereoscopic display device 1 includes a liquid crystal lens 11, a phase difference plate 12, a spacer 13, a liquid crystal display 14, and a backlight 15.

  Both the liquid crystal lens 11 and the liquid crystal display 14 have a substantially rectangular plate shape in plan view, and the sizes of the main surfaces (surfaces having the largest area) are substantially equal to each other.

  The liquid crystal display 14 has a display area D1 for displaying an image and a non-display area P1 in which wiring and the like are arranged. In FIG. 1, the non-display area P1 is formed in a frame shape surrounding the display area D1, but the arrangement of the non-display area P1 is not limited to this. The liquid crystal lens 11 has a display area D that roughly corresponds to the display area D1, and a non-display area P that roughly corresponds to the non-display area P1.

  The liquid crystal lens 11 includes a pair of substrates and a liquid crystal layer sandwiched between the substrates, although a detailed configuration will be described later. The liquid crystal lens 11 changes the behavior of light passing through the liquid crystal layer by changing the orientation of the liquid crystal molecules in the liquid crystal layer.

  A phase difference plate 12 is disposed on the back surface of the liquid crystal lens 11. The phase difference plate 12 adjusts the polarization direction of light emitted from the liquid crystal display 14. The phase difference plate 12 may not be provided depending on the polarization direction of the light emitted from the liquid crystal display 14.

  A liquid crystal display 14 is disposed on the back surface of the phase difference plate 12 via a spacer 13. The liquid crystal display 14 includes an active matrix substrate, a color filter substrate disposed to face the active matrix substrate, and a liquid crystal layer sandwiched between the substrates. On the active matrix substrate, TFTs (Thin Film Transistors) and pixel electrodes are formed in a matrix. The liquid crystal display 14 changes the orientation of the liquid crystal molecules in the liquid crystal layer on an arbitrary pixel electrode by controlling the TFT. Thereby, the liquid crystal display 14 can display an arbitrary image.

  A backlight 15 is disposed on the back surface of the liquid crystal display 14. The backlight 15 irradiates the liquid crystal display 14 with light.

  The stereoscopic display device 1 switches between the two-dimensional display mode and the three-dimensional display mode by controlling the liquid crystal lens 11 and the liquid crystal display 14 in conjunction with each other.

  In the two-dimensional display mode, the liquid crystal display 14 displays a normal two-dimensional image. At this time, the liquid crystal molecules in the liquid crystal layer of the liquid crystal lens 11 are uniformly aligned, and light passing through the liquid crystal lens 11 travels almost as it is. As a result, a normal two-dimensional image is displayed on the stereoscopic display device 1.

  In the three-dimensional display mode, the liquid crystal display 14 regularly displays images taken from multiple directions. Correspondingly, the liquid crystal lens 11 regularly changes the orientation of the liquid crystal molecules in the liquid crystal layer. Accordingly, when the stereoscopic display device 1 is observed at an optimum position, different images reach the left and right eyes. That is, the stereoscopic display device 1 performs stereoscopic display by a so-called parallax method in the three-dimensional display mode.

  The schematic configuration of the stereoscopic display device 1 has been described above. Note that the stereoscopic display device 1 may include an arbitrary display device other than the liquid crystal display 14.

[First Embodiment]
Hereinafter, the configuration of the liquid crystal lens 11 will be described in detail. Hereinafter, as shown in FIG. 1, the long side direction of the liquid crystal lens 11 is referred to as the x direction, the short side direction is referred to as the y direction, and the thickness direction is referred to as the z direction.

  FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1 and schematically shows the configuration of the liquid crystal lens 11. The liquid crystal lens 11 includes a first substrate S1, a second substrate C1, a liquid crystal layer 115, and a control unit 119.

In the present embodiment, the liquid crystal molecules 115a constituting the liquid crystal layer 115 are those having positive dielectric anisotropy. The liquid crystal molecules 115a have birefringence. That is, the refractive index n _e for the light vibrating in parallel with the optical axis, the refractive index n _o for light oscillating perpendicularly to the optical axis are different. The liquid crystal molecules 115a are larger values of Δn ₌ n e -n _o is preferred.

  Ferroelectric liquid crystal may be used as the liquid crystal molecules 115a. Since the ferroelectric liquid crystal has a memory property, once it is aligned by applying an electric field, it is not necessary to continue applying an electric field in order to maintain the alignment. Therefore, power consumption can be reduced.

  The controller 119 controls the first substrate S1 and the second substrate C1, applies an electric field to the liquid crystal layer 115, and changes the alignment of the liquid crystal molecules 115a. For example, the control unit 119 is arranged in the non-display area P of the first substrate S1 or the second substrate C1. The controller 119 can be monolithically formed on these substrates by a semiconductor process. The control unit 119 can also be mounted on these substrates by COG (Chip On Glass) technology. The control unit 119 may be disposed other than the first substrate S1 and the second substrate C1. In this case, the control unit 119 is connected to these substrates via, for example, an FPC (Flexible Printed Circuit).

  FIG. 3 is a perspective view showing a part of the first substrate S 1 and the second substrate C 1 extracted from the configuration of the liquid crystal lens 11. As shown in FIGS. 2 and 3, the first substrate S <b> 1 includes a substrate 111, a first pattern electrode 113, and an alignment film 114. The second substrate C1 includes a substrate 116, a second pattern electrode 117, and an alignment film 118.

  The substrate 111 and the substrate 116 are light-transmitting and insulating. The substrate 111 and the substrate 116 are glass substrates, for example. The surfaces of the substrate 111 and the substrate 116 may be coated with a passivation film or the like.

  The first pattern electrode 113 is formed on the substrate 111 by repeating a conductive portion and a non-conductive portion in a stripe shape along the x direction. More specifically, the first pattern electrode 113 includes an electrode 113A and an electrode 113B that are formed at predetermined intervals along the x direction.

  The second pattern electrode 117 is formed on the substrate 116 by repeating a conductive portion and a non-conductive portion in a stripe shape along the x direction. More specifically, the first pattern electrode 117 includes electrodes 117A and electrodes 117B formed at a predetermined interval along the x direction.

  Each of the electrodes 113A, 113B, 117A, and 117B extends in the y direction and is formed in an elongated shape as shown in FIG. The electrodes 113A, 113B, 117A, and 117B are formed of a light-transmitting conductive material. The electrodes 113A, 113B, 117A, and 117B are, for example, ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). The electrodes 113A, 113B, 117A, and 117B are formed by, for example, CVD or sputtering, and are patterned by photolithography.

  The electrodes 113A, 113B, 117A, and 117B are connected to the control unit 119 via wiring not shown. The controller 119 independently controls the potentials of the electrodes 113A, 113B, 117A, and 117B. In FIG. 3, as an example of the applied voltage, the electrode 113A is controlled to the potential V1, the electrode 113B is controlled to the potential V2, the electrode 117A is controlled to the potential V3, and the electrode 117B is controlled to the potential V4.

  The alignment film 114 is formed to cover the substrate 111 and the electrodes 113A and 113B. The alignment film 118 is formed so as to cover the substrate 116 and the electrodes 117A and 117B. The alignment films 114 and 118 are made of polyimide, for example, and are formed by a printing method.

  In the present embodiment, the alignment films 114 and 118 are rubbed in substantially parallel to the x direction. Thus, when no potential difference is generated between the first substrate S1 and the second substrate C1, the liquid crystal molecules 115a are aligned in the x direction.

  The liquid crystal lens 11 is manufactured by superimposing the first substrate S1 and the second substrate C1, sealing the peripheral edge, and injecting liquid crystal into the gap.

  In the present embodiment, the electrode 113A and the electrode 117A are arranged with their center positions in the x direction aligned. On the other hand, the electrode 113B and the electrode 117B are arranged with their center positions in the x direction shifted.

  Next, the operation of the liquid crystal lens 11 will be described with reference to FIGS.

  FIG. 4 is a schematic cross-sectional view in one mode of the liquid crystal lens 11. In FIG. 4, the control unit 119 controls the potential of the electrode 113A to the potential V1, the potential of the electrode 113B to V2, the potential of the electrode 117A to V3, and the potential of the electrode 117B to V4.

  In the present embodiment, the potentials of the electrodes 113A, 113B, 117A, and 117B are controlled so that V1> V2> V4> V3.

  The liquid crystal molecules 115a are aligned so that the electric field generated by the potential difference between the first substrate S1 and the second substrate C1 is parallel to the molecular long axis. A potential difference (V1-V3) is generated between the electrode 113A and the electrode 117A. Thereby, the molecular long axis of the liquid crystal molecules 115a in the vicinity of the first electrode 113A is aligned in parallel with the z direction.

  In the present embodiment, the positions and widths of the electrodes 113A, 113B, 117A, and 117B, and the potential so that the potential difference between the first substrate S1 and the second substrate C1 is minimized at an intermediate position between the adjacent electrodes 113A. V1 to V4 are adjusted.

  Thereby, the alignment direction of the liquid crystal molecules 115a continuously changes from the z direction to the x direction along the x direction.

  The refractive index of the liquid crystal layer 115 changes according to the change in the alignment direction of the liquid crystal molecules 115a. Therefore, the liquid crystal layer 115 has a refractive index distribution in the x direction. The liquid crystal layer 115 can collect the light incident on the liquid crystal layer 115 by this refractive index distribution, as shown by a broken arrow in FIG. That is, the liquid crystal lens 11 functions as a GRIN lens in this mode.

  FIG. 5 is a schematic cross-sectional view of the liquid crystal lens 11 in another mode. In FIG. 5, the potential of the electrodes 113A, 113B, 117A, and 117B is controlled to V0 by the control unit 119. For this reason, no potential difference is generated between the first substrate S1 and the second substrate C1. The liquid crystal molecules 115a are aligned by the alignment films 114 and 118 so that the molecular long axis is parallel to the x direction.

  Since the liquid crystal molecules 115a are uniformly aligned, the refractive index of the liquid crystal layer 115 is also uniform. As indicated by broken arrows in FIG. 5, the light incident on the liquid crystal layer 115 passes almost as it is. That is, the liquid crystal lens 11 does not function as a GRIN lens in this operation mode.

  Thus, the liquid crystal lens 11 can switch the function as the GRIN lens by controlling the potentials of the electrodes 113A, 113B, 117A, and 117B by the control unit 119.

[Comparative example]
FIG. 6 is a schematic cross-sectional view of a liquid crystal lens 91 according to a virtual comparative example for explaining the effect of the present embodiment. The liquid crystal lens 91 includes a first substrate S9 instead of the first substrate S1, and a second substrate C9 instead of the second substrate C1.

  The first substrate S9 includes a pattern electrode 913 instead of the first pattern electrode 113 of the first substrate S1. The pattern electrode 913 is obtained by removing the electrode 113B from the configuration of the first pattern electrode 113.

  The second substrate C9 includes a common electrode 917 instead of the second pattern electrode 117 of the second substrate C1. The common electrode 917 is formed on the substrate 116 as a uniform film.

  In FIG. 6, the control unit 119 controls the potential of the electrode 113A to the potential V1, and the potential of the common electrode 917 to the ground potential (GND). A potential difference V1 is generated between the electrode 113A and the common electrode 917. Accordingly, the molecular long axis of the liquid crystal molecules 115a in the vicinity of the electrode 113A is aligned in parallel with the z direction.

  However, in the liquid crystal lens 91, no potential gradient is formed in an intermediate region between the adjacent electrodes 113A. In this region, the alignment direction of the liquid crystal molecules 115a hardly changes. Therefore, an effective refractive index distribution cannot be obtained, and good lens characteristics cannot be obtained.

  Such a problem occurs when the distance a between adjacent electrodes 113A is larger than the distance d between the electrode 113A and the common electrode 117. When the ratio a / d is approximately 7 or more, the liquid crystal lens 91 does not function as a GRIN lens.

  The effect of this embodiment will be described with reference to FIG. 4 again. In the present embodiment, pattern electrodes are formed not only on the first substrate S1 but also on the second substrate C1. As a result, an electric field is easily applied to the xy plane.

  The configuration and effects of the liquid crystal lens 11 according to the first embodiment have been described above. According to the present embodiment, good lens characteristics can be obtained even when the ratio a / d is large.

  In the present embodiment, the first pattern electrode 113 includes an electrode 113A and an electrode 113B, and the second pattern electrode 117 includes an electrode 117A and an electrode 117B. The electrodes 113A, 113B, 117A, and 117B are independently controlled by the control unit 119. However, it is arbitrary how many kinds of independent electrodes the first pattern electrode 113 and the second pattern electrode 117 include. For example, one or both of the first pattern electrode 113 and the second pattern electrode 117 may be composed of one type of electrode. Further, the first pattern electrode 113 and the second pattern electrode 117 may include three or more types of independent electrodes.

  However, as will be described later, it is preferable that the control unit 119 controls the potential of the electrode on the first substrate S1 side and the potential of the electrode on the second substrate C1 side to a total of four levels or more.

  In the present embodiment, the electrode 113A and the electrode 117A are arranged with their center positions in the x direction aligned. On the other hand, the electrode 113B and the electrode 117B are arranged with their center positions in the x direction shifted. However, this configuration is exemplary. The electrode 113A and the electrode 117A may be arranged with the center position in the x direction shifted, and the electrode 113B and the electrode 117B may be arranged with the center position in the x direction aligned.

  However, the number of electrodes required to form an electric field in the in-plane direction can be reduced by shifting the center positions of at least one set of electrodes.

  In the present embodiment, the potentials of the electrodes 113A, 113B, 117A, and 117B are controlled so that V1> V2> V4> V3. However, this is exemplary. The values of the potentials V1 to V4 and the positions and widths of the electrodes 113A, 113B, 117A, and 117B are adjusted according to the lens characteristics. This will be described later together with a specific example.

  The liquid crystal lens 11 may be configured such that in the stereoscopic display device 1 (FIG. 1), the first substrate S1 is disposed on the liquid crystal display 14 side, and the second substrate C1 is disposed on the liquid crystal display 14 side. It may be configured.

  The alignment films 114 and 118 of the liquid crystal lens 11 are rubbed in a direction (x direction) substantially perpendicular to the extending direction (y direction) of the electrodes 113A, 113B, 117A, and 117B. However, the direction of the rubbing treatment of the alignment film is arbitrary. For example, the alignment films 114 and 118 may be rubbed in parallel with the y direction.

[Second Embodiment]
The stereoscopic display device 1 may include any of liquid crystal lenses 21, 31 and 41 described below instead of the liquid crystal lens 11.

  FIG. 7 is a schematic cross-sectional view showing a schematic configuration of the liquid crystal lens 21 according to the second embodiment of the present invention. The liquid crystal lens 21 includes a first substrate S2 instead of the first substrate S1, and a second substrate C2 instead of the second substrate C1.

  The first substrate S2 includes a first pattern electrode 213 instead of the first pattern electrode 113 of the first substrate S1. The second substrate C2 includes a second pattern electrode 217 instead of the second pattern electrode 117 of the second substrate C1.

  Similarly to the first pattern electrode 113 and the second pattern electrode 117, the first pattern electrode 213 and the second pattern electrode 217 are formed by repeating a conductive portion and a non-conductive portion in a stripe shape along the x direction. Yes. The first pattern electrode 213 includes an electrode 213A and an electrode 213B, and the second pattern electrode 217 includes an electrode 217A and an electrode 217B.

  In the liquid crystal lens 21, the electrodes 213A, 213B, 217A, and 217B are formed to have different widths in the x direction.

  In the liquid crystal lens 21, the non-conductive portion of the first pattern electrode 213 and the non-conductive portion of the second pattern electrode 217 do not face each other, as indicated by a one-dot chain line in FIG. 7. That is, a conductive portion (at least one of the electrodes 213A, 213B, 217A, and 217B) is provided on at least one of the first substrate S2 and the second substrate C2 over the entire display area D (FIG. 1) of the liquid crystal lens 21. Is formed.

  Next, the effect of this embodiment is demonstrated using FIG. FIG. 8 is a schematic cross-sectional view for explaining the effect of the liquid crystal lens 21. FIG. 8 shows a case where the potentials of the electrodes 213A, 213B, 217A, and 217B are controlled to potentials V1 to V4, respectively. FIG. 8 also shows a schematic refractive index of the liquid crystal layer 115 along the x direction.

  Also in this embodiment, the function as the GRIN lens can be switched by controlling the potentials of the electrodes 213A, 213B, 217A, and 217B by the control unit 119, as in the first embodiment. In addition, the pattern electrode is formed not only on the first substrate S2 but also on the second substrate C2. As a result, an electric field is easily applied to the xy plane. Therefore, good lens characteristics can be obtained even when the ratio a / d is large.

  In the present embodiment, the non-conductive portion of the first pattern electrode 213 and the non-conductive portion of the second pattern electrode 217 do not face each other. As a result, an electric field is more easily applied in the xy plane. Therefore, the number of potentials necessary for obtaining an effective refractive index distribution can be further reduced.

  In an ideal GRIN lens, the refractive index distribution is a quadratic curve as shown in FIG. Therefore, the change in refractive index at the lens edge is steeper than the change in refractive index at the center of the lens. Therefore, in order to obtain lens characteristics close to an ideal GRIN lens, it is preferable to make the potential gradient at the lens end portion steeper than the potential gradient at the lens center.

  Therefore, the width of the first pattern electrode 213 or the second pattern electrode 217 in the x direction is the same as that of the first substrate S2 and the second substrate compared to the portion where the potential difference between the first substrate S2 and the second substrate C2 is relatively small. It is preferable that the gap is narrowly formed in a portion where the potential difference between the two substrates C2 is relatively large. For example, in the present embodiment, the width of the electrode 213A in the x direction is narrower than the width of the electrodes 213B, 217A, and 217B in the x direction.

  Also in the present embodiment, it is arbitrary how many kinds of independent electrodes each of the first pattern electrode 213 and the second pattern electrode 217 include. Further, the electrode 213A and the electrode 217A may be arranged with the center position in the x direction shifted, and the electrode 213B and the electrode 217B may be arranged with the center position in the x direction aligned.

[Third Embodiment]
FIG. 9 is a schematic cross-sectional view showing a schematic configuration of a liquid crystal lens 31 according to the third embodiment of the present invention. The liquid crystal lens 31 includes a first substrate S3, a second substrate C3, a liquid crystal layer 315, and a control unit 119.

  In this embodiment, as the liquid crystal molecules 315a constituting the liquid crystal layer 315, those having a negative dielectric anisotropy are used.

  The first substrate S3 is obtained by replacing the alignment film 114 of the first substrate S2 with an alignment film 314 for vertical alignment. The second substrate C3 is obtained by replacing the alignment film 118 of the second substrate C2 with an alignment film 318 for vertical alignment.

  By the alignment films 314 and 318, the liquid crystal molecules 315a are aligned so that the molecular major axis is parallel to the z-axis direction when no potential difference is generated between the first substrate S3 and the second substrate C3. Since the liquid crystal molecules 315a are uniformly aligned, the refractive index of the liquid crystal layer 315 is also uniform. Therefore, in this case, the liquid crystal lens 31 does not function as a GRIN lens.

  FIG. 10 is a schematic cross-sectional view for explaining the operation of the liquid crystal lens 31. In FIG. 10, the potentials of the electrodes 213A, 213B, 217A, and 217B are controlled by the control unit 119 to potentials V1 to V4, respectively.

  The liquid crystal molecules 315a having a negative dielectric anisotropy are aligned so that the electric field generated by the potential difference between the first substrate S3 and the second substrate C3 is perpendicular to the molecular major axis. A potential difference (V1−V3) is generated between the electrode 213A and the electrode 217A. Thereby, the molecular long axis of the liquid crystal molecules 315a in the vicinity of the electrode 213A is aligned perpendicular to the z direction.

  Also in this embodiment, the positions and widths of the electrodes 213A, 213B, 217A, and 217B, and the potential difference between the first substrate S3 and the second substrate C3 are minimized at an intermediate position between the adjacent electrodes 213A, and The potentials V1 to V4 are adjusted. As a result, the alignment direction of the liquid crystal molecules 315a continuously changes from the x direction to the z direction along the x direction.

  Therefore, the liquid crystal layer 315 has a refractive index distribution in the x direction. The liquid crystal layer 315 can collect the light incident on the liquid crystal layer 315 by this refractive index distribution, as indicated by a broken arrow in FIG. That is, the liquid crystal lens 31 functions as a GRIN lens.

  As described above, the liquid crystal lens 31 can also switch the function as the GRIN lens by controlling the potentials of the electrodes 213A, 213B, 217A, and 217B by the control unit 119, similarly to the liquid crystal lens 11.

  Further, similarly to the liquid crystal lens 11, the pattern electrode is formed not only on the first substrate S3 but also on the second substrate C3. As a result, an electric field is easily applied to the xy plane. Therefore, good lens characteristics can be obtained even when the ratio a / d is large.

  In this embodiment, alignment films 314 and 318 for vertical alignment are used. Therefore, it is not necessary to perform a rubbing process. As a result, the influence of asymmetry associated with the rubbing process can be eliminated.

[Fourth Embodiment]
FIG. 11 is a schematic cross-sectional view showing a schematic configuration of a liquid crystal lens 41 according to the fourth embodiment of the present invention. The liquid crystal lens 41 includes a first substrate S4, a second substrate C4, a liquid crystal layer 115, a control unit 119, and a polarizing plate 46.

  The first substrate S4 is obtained by replacing the alignment film 114 of the first substrate S2 with an alignment film 414. The alignment film 114 and the alignment film 414 have different rubbing directions. Similarly, the second substrate C4 is obtained by replacing the alignment film 118 of the second substrate C2 with an alignment film 418. The alignment film 118 and the alignment film 418 have different rubbing treatment directions.

  The alignment film 414 is rubbed in a direction that forms an angle of about 45 ° with the direction in which the electrode 113A extends (y direction). The alignment film 418 is rubbed in a direction substantially orthogonal to the rubbing process direction of the alignment film 414.

  Accordingly, the liquid crystal molecules 115a of the liquid crystal layer 115 are aligned as follows when no potential difference is generated between the first substrate S4 and the second substrate C4. That is, the liquid crystal molecules 115a are aligned along the rubbing process direction of the alignment film 414 on the first substrate S4 side, and are aligned along the rubbing process direction of the alignment film 418 on the second substrate C4 side. As a result, the alignment direction of the liquid crystal molecules 115a is rotated by 90 ° between the first substrate S4 side and the second substrate C4 side. That is, the liquid crystal layer 115 is a TN (Twisted Nematic) type liquid crystal.

  The liquid crystal lens 41 further includes a polarizing plate 46. The polarizing plate 46 is disposed on the main surface of the first substrate S4 opposite to the liquid crystal layer 115. The polarizing axis of the polarizing plate 46 is approximately coincident with the rubbing treatment direction of the alignment film 414.

  Next, the operation of the liquid crystal lens 41 will be described. First, the phase difference plate 12 (FIG. 1) matches the polarization direction of the light emitted from the liquid crystal display 14 with the direction of the rubbing treatment of the alignment film 418. The phase difference plate 12 may not be provided depending on the polarization direction of the light emitted from the liquid crystal display 14.

  When no potential difference is generated between the first substrate S4 and the second substrate C4, as described above, the alignment direction of the liquid crystal molecules 115a rotates as it advances in the z direction. On the other hand, the alignment direction of the liquid crystal molecules 115a is uniform in the xy plane.

  Since the alignment direction of the liquid crystal molecules 115a is uniform in the xy plane, the refractive index distribution is also uniform in the xy plane. Therefore, when there is no potential difference between the substrate S8 and the substrate C3, the liquid crystal lens 41 does not function as a GRIN lens.

  As shown in FIG. 11, the polarization axis of the light incident on the liquid crystal layer 115 changes by 90 ° in accordance with the change in the alignment direction of the liquid crystal molecules 115a. The polarizing axis of the polarizing plate 46 is approximately coincident with the rubbing treatment direction of the alignment film 414. Therefore, the light that has passed through the liquid crystal layer 115 can pass through the polarizing plate 46.

  FIG. 12 is a schematic cross-sectional view for explaining the operation of the liquid crystal lens 41. In FIG. 12, the potentials of the electrodes 213A, 213B, 217A, and 217B are controlled by the control unit 119 to potentials V1 to V4, respectively.

  A potential difference (V1−V3) is generated between the electrode 213A and the electrode 217A. Thereby, the molecular long axis of the liquid crystal molecules 115a in the vicinity of the electrode 213A is aligned in parallel with the z direction.

  Also in this embodiment, the positions and widths of the electrodes 213A, 213B, 217A, and 217B, and the potential difference between the first electrode S4 and the second substrate C4 are minimized at an intermediate position between the adjacent electrodes 213A, and The potentials V1 to V4 are adjusted. Thereby, the alignment direction of the liquid crystal molecules 115a continuously changes from the z direction to the x direction along the x direction.

  Therefore, the liquid crystal layer 115 has a refractive index distribution in the x direction. The liquid crystal layer 115 can collect the light incident on the liquid crystal layer 115 by this refractive index distribution, as indicated by a broken arrow in FIG. That is, the liquid crystal lens 41 functions as a GRIN lens.

  At this time, the light passing through the vicinity of the electrode 213A passes through the liquid crystal layer 115 without rotating the polarization axis. Therefore, this light cannot pass through the polarizing plate 46 as shown by the solid arrow in FIG. As a result, the liquid crystal lens 41 forms a virtual parallax barrier in the boundary region of the virtual lens.

  According to the present embodiment, the liquid crystal lens 41 has a function as a parallax barrier in addition to a function as a GRIN lens. Thereby, crosstalk in stereoscopic display can be reduced.

  As described above, the liquid crystal lens 41 can switch the functions of the GRIN lens and the parallax barrier by controlling the potentials of the electrodes 213A, 213B, 217A, and 217B by the control unit 119.

  Further, similarly to the liquid crystal lens 11, the pattern electrode is formed not only on the first substrate S4 but also on the second substrate C4. As a result, an electric field is easily applied to the xy plane. Therefore, good lens characteristics can be obtained even when the ratio a / d is large.

  In the present embodiment, the polarizing plate 46 is disposed on the first substrate S4 side. In this case, in the stereoscopic display device 1 (FIG. 1), the second substrate C4 is disposed on the liquid crystal display 14 side. The polarizing plate 46 may be disposed on the second substrate C4 side. In this case, in the stereoscopic display device 1, the first substrate S4 is disposed on the liquid crystal display 14 side.

  The alignment film 414 of the liquid crystal lens 41 is rubbed in a direction that forms an angle of 45 ° with the direction in which the electrode 113A extends (y direction). The alignment film 418 is rubbed in a direction orthogonal to the rubbing process direction of the alignment film 414. However, the direction of the rubbing treatment of the alignment films 414 and 418 only needs to intersect, and the others are arbitrary.

[Example of lens characteristics calculation]
Hereinafter, an example of calculating lens characteristics will be described with reference to FIGS. The lens characteristics were simulated by changing the number of potentials. FIG. 13, FIG. 15, FIG. 17, and FIG. 19 are diagrams and tables showing the arrangement and potential of each component in this simulation. FIG. 14, FIG. 16, FIG. 18, and FIG. 20 are graphs showing the results of this simulation. The horizontal axis indicates the distance (μm) from the lens center, and the vertical axis indicates the phase difference (wave number). ing.

  In FIG. 13, FIG. 15, FIG. 17, and FIG. 19, only relevant components are extracted and shown. The liquid crystal molecules of the liquid crystal layer were calculated as a configuration in which the liquid crystal molecules are aligned in the TN type when there is no potential difference between the first substrate 111 and the second substrate 116. In any case, the calculation was performed assuming that the distance a (pitch) between the electrodes was 700 μm. The distance d between the first substrate 111 and the second substrate 116 (approximately equal to the distance between the electrode of the first substrate 111 and the electrode of the second substrate 116) was calculated as 60 μm. The ratio a / d was 11.66, which was higher than 7.0.

  In FIG. 13, the electrode 213 </ b> A is disposed on the first substrate 111, and the common electrode 917 is disposed on the second substrate 116. Then, the potential gradient was formed by controlling the electrode 213A and the common electrode 917 to two levels of potentials V1 and V2, respectively. W1 is the half width of the electrode 213A, and G11 is the distance between the adjacent electrodes 213A. Thus, the calculation was performed by arranging the pattern electrode in which the conductive portion and the non-conductive portion are repeated in a stripe pattern on the first substrate 111 and the uniform common electrode 917 on the second substrate 116.

  FIG. 14 is a graph showing a simulation result P2 and a theoretical curve P0 when the potential is 2 levels. Since the ratio a / d exceeds 7.0, it can be seen that an effective refractive index distribution is not obtained near the center between the adjacent electrodes 213A. The root mean square of the difference between the simulation result P2 and the theoretical curve P0 was 1.88.

  In FIG. 15, the electrodes 213A and 213B are arranged on the first substrate 111, and the electrodes 217A and 217B are arranged on the second substrate 116. Then, the electrodes 213A, 213B, 217A, and 217B were controlled at four levels of potentials V1 to V4 to form a potential gradient. W1 is the half width of the electrode 213A, W2 is the width of the electrode 213B, W3 is the half width of the electrode 217A, and W4 is the width of the electrode 217B. G12 is the distance between the electrodes 213A and 213B, G22 is the distance between the adjacent electrodes 213B, and G34 is the distance between the electrodes 217A and 217B. Thus, the calculation was performed by arranging the pattern electrodes in which the conductive portions and the non-conductive portions are repeated in a striped pattern on both the first substrate 111 and the second substrate 116.

  FIG. 16 is a graph showing a simulation result P4 and a theoretical curve P0 when the potential is 4 levels. The mean square of the difference between the simulation result P4 and the theoretical curve P0 was 0.40.

In FIG. 17, the electrodes 213A, 213B, and 213C are arranged on the first substrate 111, and the electrodes 217A, 217B, and 217C are arranged on the second substrate 116. Then, the electrodes 213A, 213B, 213C, 217A, 217B, and 217C are connected to potentials V1 to V1.
A potential gradient was formed by controlling the potential at 6 levels of V6. W1 is the half width of the electrode 213A, W2 is the width of the electrode 213B, and W3 is the width of the electrode 213C. W4 is the half width of the electrode 217A, W5 is the width of the electrode 217B, and W6 is the width of the electrode 217C. G12 is the distance between the electrodes 213A and 213B, G23 is the distance between the electrodes 213B and 213C, and G33 is the distance between the adjacent electrodes 213C. G45 is the distance between the electrodes 217A and 217B, and G56 is the distance between the electrodes 217B and 217C. Thus, the calculation was performed by arranging the pattern electrodes in which the conductive portions and the non-conductive portions are repeated in a striped pattern on both the first substrate 111 and the second substrate 116.

  FIG. 18 is a graph showing a simulation result P6 and a theoretical curve P0 when the potential is 6 levels. The mean square of the difference between the simulation result P6 and the theoretical curve P0 was 0.21.

  In FIG. 19, the electrodes 213A, 213B, 213C, and 213D are arranged on the first substrate 111, and the electrodes 217A, 217B, 217C, and 217D are arranged on the second substrate 116. Then, the electrodes 213A, 213B, 213C, 213D, 217A, 217B, 217C, and 217D were controlled to have eight levels of potentials V1 to V8 to form a potential gradient. W1 is the half width of the electrode 213A, W2 is the width of the electrode 213B, W3 is the width of the electrode 213C, and W4 is the width of the electrode 213D. W5 is the half width of the electrode 217A, W6 is the width of the electrode 217B, W7 is the width of the electrode 217C, and W8 is the width of the electrode 217D. G12 is the distance between the electrodes 213A and 213B, G23 is the distance between the electrodes 213B and 213C, G34 is the distance between the electrodes 213C and 214D, and G44 is the distance between the adjacent electrodes 213D. . G56 is the distance between the electrodes 217A and 217B, G67 is the distance between the electrodes 217B and 217C, and G78 is the distance between the electrodes 217C and 217D. Thus, the calculation was performed by arranging the pattern electrodes in which the conductive portions and the non-conductive portions are repeated in a striped pattern on both the first substrate 111 and the second substrate 116.

  FIG. 20 is a graph showing a simulation result P8 and a theoretical curve P0 when the potential is 8 levels. The mean square of the difference between the simulation result P8 and the theoretical curve P0 was 0.13.

  FIG. 21 is a graph showing the relationship between the number of potentials on the horizontal axis and the mean square of the difference between the theoretical curve C0 and the vertical axis. As shown in FIG. 21, the difference from the theoretical curve C0 is abruptly reduced when the potential is 4 levels or more. Therefore, the number of potentials is preferably 4 levels or more.

[Other Embodiments]
As mentioned above, although embodiment about this invention was described, this invention is not limited to each above-mentioned embodiment, A various change or combination is possible within the scope of the invention.

  The present invention can be industrially used as a liquid crystal lens and a stereoscopic display device.

DESCRIPTION OF SYMBOLS 1 3D display device 11, 21, 31, 41, 91 Liquid crystal lens S1, S2, S3, S4, S9 1st board | substrate 111 Board | substrate 113,213 First pattern electrode 913 Pattern electrode 114,314,414 Alignment film 115,315 Liquid crystal Layers 115a, 315a Liquid crystal molecules C1, C2, C3, C4, C9 Second substrate 116 Substrate 117, 217 Second pattern electrode 917 Common electrode 118, 318, 418 Alignment film 119 Controller 12 Phase difference plate 13 Spacer 14 Liquid crystal display 15 Backlight 46 Polarizing plate

Claims (13)

An insulating first substrate;
A first pattern electrode formed on the first substrate by repeating a conductive portion and a non-conductive portion in a stripe shape along a first direction;
An insulating second substrate disposed opposite to the first substrate;
A second pattern electrode formed by repeating conductive and non-conductive portions in a striped manner along the first direction on the second substrate;
A liquid crystal layer sandwiched between the first substrate and the second substrate;
A liquid crystal lens comprising: a control unit that controls potentials of the first pattern electrode and the second pattern electrode and switches between two or more modes.   The liquid crystal lens according to claim 1, wherein the non-conductive portion of the first pattern electrode and the non-conductive portion of the second pattern electrode are not opposed to each other.   The width of the conductive portion of the first pattern electrode is greater than that of a portion where the potential difference between the first pattern electrode and the second pattern electrode is small in one of the modes. The liquid crystal lens according to claim 1, wherein the liquid crystal lens is narrowly formed in a portion where a potential difference with the pattern electrode is large.   The liquid crystal lens according to claim 1, wherein the control unit controls the potential of the first pattern electrode and the potential of the second pattern electrode to a total of four levels or more.   The liquid crystal molecules of the liquid crystal layer are aligned approximately in parallel with the first substrate when no potential difference is generated between the first substrate and the second substrate. The liquid crystal lens described.   The liquid crystal molecules of the liquid crystal layer are aligned substantially perpendicularly to the first substrate when no potential difference is generated between the first substrate and the second substrate. The liquid crystal lens described.   In the liquid crystal molecules, when no potential difference is generated between the first substrate and the second substrate, the alignment direction on the first substrate side and the alignment direction on the second substrate side are substantially orthogonal to each other. Item 6. A liquid crystal lens according to Item 5.   The liquid crystal lens according to claim 7, wherein an angle formed between an alignment direction of the liquid crystal molecules on the first substrate side and the second direction is about 45 °.   The liquid crystal lens according to claim 7, further comprising a polarizing plate disposed on the first substrate side and having a polarization axis substantially parallel to an alignment direction of the liquid crystal molecules on the first substrate side.   The liquid crystal lens according to claim 7, further comprising a polarizing plate disposed on the second substrate side and having a polarization axis substantially parallel to an alignment direction of the liquid crystal molecules on the second substrate side. A display device capable of displaying images;
A three-dimensional display apparatus provided with the liquid-crystal lens as described in any one of Claims 1-10.   The stereoscopic display device according to claim 11, wherein the liquid crystal lens has the first substrate disposed on the display device side.   The stereoscopic display device according to claim 11, wherein the liquid crystal lens has the second substrate disposed on the display device side.

Images