JP2013174695A - Liquid crystal lens and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal lens and a display device comprising the liquid crystal lens which are capable of reducing meanders of disclination.SOLUTION: A liquid crystal lens L comprises: a first substrate 1 having a plurality of first electrodes 5a and a plurality of second electrodes 6a; a second substrate 2 having a counter electrode 8; and a liquid crystal layer. The first electrodes 5a and second electrodes 6a extend along the Y-axis and are spaced and alternately disposed in the direction along the X-axis. k33/k11 is 1.28 or less.

Description

  Embodiments described herein relate generally to a liquid crystal lens and a display device.

  In recent years, various techniques for displaying a stereoscopic image have been proposed. There has also been proposed a liquid crystal display device that enables a stereoscopic image to be viewed with the naked eye. As a typical method for forming the stereoscopic image, a parallax barrier method and a lenticular lens method can be given. In the lenticular lens method, an image with parallax can be displayed on each of the right eye and the left eye by installing a kamaboko type resin microlens on the display surface.

  In addition, as a method for forming the stereoscopic image, a liquid crystal lens method may be used. In the liquid crystal lens system, a liquid crystal panel (liquid crystal lens) in which a liquid crystal layer has a refractive index distribution similar to that of the resin lens can be used instead of the resin lens. When the liquid crystal lens method is used, it is possible to switch between planar image display (2D) and stereoscopic image display (3D) according to the voltage applied to the liquid crystal lens.

JP 2008-139793 A JP 2010-224191 A JP 2011-145697 A

  In the liquid crystal lens system, by controlling the refractive index distribution of the liquid crystal layer by the applied voltage, a part of the image on the same screen can be selectively projected. In order to control the refractive index distribution of the liquid crystal layer of the liquid crystal lens in the same manner as the lens, a comb-like electrode structure is formed on one of a pair of opposed substrates, and a planarized electrode layer is formed on the other.

  In the comb-like electrode structure, the ground electrode and the power supply electrode are arranged side by side. The ground electrode has the same potential as the opposing flat electrode layer. The power supply electrode is set to a potential different from that of the ground electrode and the electrode layer. When a voltage is applied to the liquid crystal lens and the power supply electrode is set to a potential different from that of the ground electrode and the opposed flat electrode layer, a refractive index distribution with a power supply electrode as the lens end is obtained.

  By the way, since the liquid crystal molecules on the power supply electrode are affected by a non-uniform electric field, discontinuity of director alignment is likely to occur. The discontinuity of director orientation is called disclination. At this time, it becomes a problem that the disclination takes a meandering shape on the power supply electrode. Specifically, if the disclination has a meandering shape, random scattering of incident light occurs and the visibility of the liquid crystal cell is greatly deteriorated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a liquid crystal lens capable of reducing the meandering of the disclination and a display device including the liquid crystal lens.

The liquid crystal lens according to one embodiment
A first substrate having a plurality of first electrodes and a plurality of second electrodes that extend along the Y axis and are alternately arranged with a gap in the direction along the X axis perpendicular to the Y axis. When,
A second substrate having a counter electrode disposed opposite to the plurality of first electrodes and the plurality of second electrodes;
A liquid crystal layer sandwiched between the first substrate and the second substrate,
When the splay elastic constant of the liquid crystal used for the liquid crystal layer is k11 and the bend elastic constant of the liquid crystal is k33, k33 / k11 is 1.28 or less.

In addition, a display device according to an embodiment includes:
A first substrate having a plurality of first electrodes and a plurality of second electrodes that extend along the Y axis and are alternately arranged with a gap in the direction along the X axis perpendicular to the Y axis. And a second substrate having a counter electrode disposed opposite to the plurality of first electrodes and the plurality of second electrodes, and a liquid crystal layer sandwiched between the first substrate and the second substrate. A lens,
A display panel disposed opposite to the first substrate of the liquid crystal lens,
When the splay elastic constant of the liquid crystal used for the liquid crystal layer is k11 and the bend elastic constant of the liquid crystal is k33, k33 / k11 is 1.28 or less.

FIG. 1 is a schematic cross-sectional view showing a liquid crystal display device according to an embodiment. FIG. 2 is a plan view showing the liquid crystal display panel shown in FIG. FIG. 3 is a cross-sectional view showing the liquid crystal display panel. FIG. 4 is a circuit diagram showing a part of the array substrate shown in FIGS. FIG. 5 is a plan view showing the liquid crystal lens shown in FIG. FIG. 6 is a cross-sectional view showing a part of the liquid crystal lens, and shows a liquid crystal layer in a state where no voltage is applied. FIG. 7 is a cross-sectional view showing a part of the liquid crystal lens, and shows the liquid crystal layer in a state where a voltage is applied. FIG. 8 is a graph showing changes in the degree of the meandering region of disclination with respect to the elastic constant ratio of the liquid crystal of the liquid crystal lens in Examples 1 and 2 and Comparative Examples 1 and 2 according to the embodiment. . FIG. 9 shows a change in the degree of the meandering generation region of the disclination with respect to the ratio between the elastic constant ratio and the dielectric constant ratio of the liquid crystal of the liquid crystal lens in Examples 1 and 2 and Comparative Examples 1 and 2 according to the embodiment. FIG.

Hereinafter, a liquid crystal display device according to an embodiment will be described in detail with reference to the drawings.
As shown in FIG. 1, the liquid crystal display device includes a liquid crystal display panel P as a display panel, a liquid crystal lens L that transmits an image displayed by the liquid crystal display panel to form a planar image or a stereoscopic image, and a control unit C. (Drive unit). An image displayed by the liquid crystal display device is switched to a flat (2D) image or a stereoscopic (3D) image by the liquid crystal lens L.

  As shown in FIGS. 1 to 4, the liquid crystal display panel P includes an array substrate 10, a counter substrate 20, a liquid crystal layer 30, a first polarizing unit 60, and a second polarizing unit 70 having a display surface S. It has. The array substrate 10 and the counter substrate 20 are each formed in a rectangular shape. The array substrate 10 is formed to have a size larger than that of the counter substrate 20.

  The array substrate 10 and the counter substrate 20 are arranged so that three sides almost overlap each other. On the remaining side of the array substrate 10, the array substrate 10 extends outward from the counter substrate 20. More specifically, the array substrate 10 and the counter substrate 20 are arranged so as to substantially overlap in the direction along the X axis. In the direction along the Y axis perpendicular to the X axis, the array substrate 10 extends outward from the counter substrate 20. The liquid crystal display panel P has a rectangular display region R that overlaps the array substrate 10 and the counter substrate 20.

  The array substrate 10 has a rectangular glass substrate 11 as a transparent insulating substrate. The glass substrate 11 has an extending portion 11 a that is detached from the counter substrate 20. A drive circuit 90 is mounted on the extending portion 11a.

  In the display region R, a plurality of pixels PX are provided on the glass substrate 11. The pixels PX are arranged in a matrix along the X axis and the Y axis along the display surface S. The pixel PX has red, green, and blue sub-pixels 14 arranged on the X axis. Note that the display surface S overlaps the display region R.

  In the display region R, a plurality of signal lines 15 and a plurality of scanning lines 16 are provided in a grid pattern on the glass substrate 11. The signal line 15 extends in the direction along the Y axis, and the scanning line 16 extends in the direction along the X axis. Two adjacent signal lines 15 and two adjacent scanning lines 16 define a sub-pixel 14.

  A TFT (thin film transistor) 17 as a switching element is provided in the vicinity of the intersection of the signal line 15 and the scanning line 16. Although not shown, the TFT 17 includes a gate electrode in which a part of the scanning line 16 is extended, a semiconductor layer facing the gate electrode through a gate insulating film, a source electrode connected to one region of the semiconductor layer, and a channel It has a drain electrode connected to the other region of the layer. The source electrode of the TFT 17 is connected to the signal line 15, and the drain electrode of the TFT 17 is connected to a pixel electrode 18 described later.

  A plurality of pixel electrodes 18 are formed in a matrix on the glass substrate 11. The pixel electrode 18 is formed of a transparent conductive film such as ITO (indium tin oxide). The pixel electrode 18 is surrounded by two adjacent signal lines 15 and two adjacent scanning lines 16. Formed in the region. Each subpixel 14 includes a TFT 17 and a pixel electrode 18 and the like electrically connected to the TFT.

  Although not all illustrated, a plurality of columnar spacers SS are formed as a plurality of spacers on the glass substrate 11 on which the TFT 17 and the pixel electrodes 18 are formed. An alignment film 19 is formed on the glass substrate 11 and the pixel electrode 18 so as to overlap the entire display region R.

  The counter substrate 20 has a rectangular glass substrate 21 as a transparent insulating substrate.

In the display region R, the color filter 50 is provided on the glass substrate 21. The color filter 50 includes a light shielding portion 51, a peripheral light shielding portion 52, and a plurality of colored layers 53, 54, and 55 of red, green, and blue.

  The light shielding portion 51 is formed in a lattice shape and overlaps the signal line 15 and the scanning line 16. The peripheral light-shielding part 52 is formed in a rectangular frame shape and is formed over the entire periphery of the display region R. The peripheral light shielding portion 52 contributes to shielding light leaking from the outside of the display region R.

The colored layers 53, 54, and 55 are formed on the glass substrate 21, the light shielding part 51, and the peripheral light shielding part 52. The colored layers 53, 54, and 55 are adjacent to each other in the direction along the X axis, and are arranged alternately. The colored layers 53, 54, and 55 are each formed in a stripe shape, extend in the direction along the Y axis, and overlap the subpixels 14 arranged along the Y axis. The peripheral portions of the colored layers 53, 54, and 55 overlap the light shielding portion 51 and the peripheral light shielding portion 52.
On the color filter 50, the counter electrode 22 is formed of a transparent conductive film such as ITO. An alignment film 23 is formed on the counter electrode 22.

  The array substrate 10 and the counter substrate 20 are arranged to face each other with a predetermined gap by columnar spacers SS. The array substrate 10 and the counter substrate 20 are joined to each other by a sealing material 31 disposed on the peripheral portions of both substrates outside the display region R.

  The liquid crystal layer 30 is sandwiched between the array substrate 10 and the counter substrate 20 and surrounded by a sealing material 31. A liquid crystal injection port 32 formed in a part of the sealing material 31 is sealed with a sealing material 33.

  The first polarizing unit 60 is disposed on the outer surface of the glass substrate 11. The second polarizing unit 70 is disposed on the outer surface of the glass substrate 21. As described above, the display surface S is formed on the outer surface of the second polarizing unit 70. The display surface S includes a display area R for displaying an image.

  As shown in FIGS. 1, 5 and 6, the liquid crystal lens L can be rephrased as a refractive index control liquid crystal panel. The liquid crystal lens L includes a first substrate 1, a second substrate 2, and a liquid crystal layer 3.

  The first substrate 1 has a glass substrate 1s as a transparent insulating substrate and a first pattern 1p formed on the glass substrate 1s. The first pattern 1 p includes a ground electrode 5, a power supply electrode 6, and an alignment film (first alignment film) 7.

  The ground electrode 5 is formed in a comb shape and is located in the display region R. The ground electrode 5 is formed of a transparent conductive film such as ITO. The ground electrode 5 has a plurality of first electrodes 5 a located in the display region R. The first electrodes 5a extend along the Y axis and are arranged with a gap in the direction along the X axis. A part of the ground electrode 5 is located outside the display region R. The ground electrode 5 has a terminal portion 5p positioned away from the display region R. Here, the terminal portion 5 p is located outside the region facing the second substrate 2.

  The power supply electrode 6 is formed in a comb shape and is positioned in the display region R. The power supply electrode 6 has a plurality of second electrodes 6 a located in the display region R. The second electrodes 6a extend along the Y axis and are arranged with a gap in the direction along the X axis. The first electrode 5a and the second electrode 6a are alternately arranged with a gap in the direction along the X axis. A part of the power supply electrode 6 is located outside the display region R. The power supply electrode 6 has a terminal portion 6p positioned away from the display region R. Here, the terminal portion 6 p is located outside the region facing the second substrate 2.

  The alignment film 7 is formed on the glass substrate 1 s, the ground electrode 5 and the power electrode 6. The alignment film 7 is disposed on the surface facing the second substrate 2. The alignment film 7 is rubbed in a first direction d1 parallel to the X axis.

  The second substrate 2 has a glass substrate 2s as a transparent insulating substrate and a second pattern 2p formed on the glass substrate 2s. The second pattern 2 p includes a counter electrode 8 and an alignment film (second alignment film) 9.

  The counter electrode 8 is disposed to face the first electrode 5a and the second electrode 6a. The counter electrode 8 is a solid electrode and is formed over the entire display region R. The counter electrode 8 is formed of a transparent conductive film such as ITO. A part of the counter electrode 8 is located outside the display region R, specifically, located outside the region facing the first substrate 1.

  The alignment film 9 is formed on the glass substrate 2s and the counter electrode 8. The alignment film 9 is disposed on the surface facing the first substrate 1. The alignment film 9 is rubbed in a second direction d2 that is parallel to the X axis and that is opposite to the first direction d1. The rubbing direction in the alignment film 7 and the rubbing direction in the alignment film 9 are antiparallel.

  The liquid crystal layer 3 is sandwiched between the first substrate 1 and the second substrate 2. The liquid crystal layer 3 is flat. The liquid crystal layer 3 uses Np liquid crystal (positive nematic liquid crystal) and adopts homogeneous alignment in which the liquid crystal molecules LM are initially aligned substantially parallel to the X axis.

  As shown in FIG. 1, the second polarizing unit 70 of the liquid crystal display panel P is disposed to face the first substrate 1 of the liquid crystal lens L. The liquid crystal lens L is affixed to the liquid crystal display panel P using an adhesive material (not shown).

  The pitch of the first electrode 5a and the second electrode 6a is not limited to a specific value and can be variously modified. For example, one or a plurality of pixels PX are opposed to a region between a pair of second electrodes 6a adjacent in the X-axis direction.

  Although not shown, a backlight unit is provided on the outer surface side of the first polarizing unit 60 of the liquid crystal display panel P as necessary. The backlight emitted from the backlight unit passes through the liquid crystal display panel P and the liquid crystal lens L in order.

  The control unit C is electrically connected to the liquid crystal display panel P and the liquid crystal lens L. In the liquid crystal display panel P, a control signal is given from the control unit C to the drive circuit 90. Thereby, the liquid crystal display panel P displays an image.

  In the liquid crystal lens L, the control unit C is electrically connected to the terminal unit 5p, the terminal unit 6p, and the counter electrode 8. The control unit C switches the liquid crystal lens L between the first state and the second state.

  As shown in FIGS. 1 and 6, when the control unit C switches the liquid crystal lens L to the first state, in detail, the plurality of first electrodes 5a, the plurality of second electrodes 6a, and the counter electrode 8 are all set to the same potential. Set. Here, the first electrode 5a, the second electrode 6a, and the counter electrode 8 are set to, for example, the ground potential (GND).

  In this first state, no potential difference is generated between the first electrode 5a, the second electrode 6a, and the counter electrode 8, so that no voltage is applied to the liquid crystal layer 3, and the alignment state of the liquid crystal molecules LM does not change. For this reason, in the first state, the liquid crystal layer 3 can have a uniform refractive index in the direction along the X axis and the Y axis (display surface S). The liquid crystal lens L transmits an image displayed by the liquid crystal display panel P to form a planar image.

  As shown in FIGS. 1 and 7, when the control unit C switches the liquid crystal lens L to the second state, in detail, the plurality of first electrodes 5a and the counter electrode 8 are set to the same potential, and the plurality of second electrodes 6a. Is set to a potential different from that of the plurality of first electrodes 5 a and the counter electrode 8. Here, the first electrode 5a and the counter electrode 8 are set to a ground potential, for example, and the second electrode 6a is set to a potential higher than the ground potential or a potential lower than the ground potential.

  In this second state, a potential difference is generated between the first electrode 5a and the second electrode 6a, and between the second electrode 6a and the counter electrode 8, so that a voltage is applied to the liquid crystal layer 3 and the liquid crystal molecules LM. The orientation state of changes. For this reason, in the second state, the liquid crystal layer 3 can have a uniform refractive index in the direction along the Y axis, and the liquid crystal layer 3 can have a refractive index distribution in the direction along the X axis.

  The refractive index distribution of the liquid crystal layer 3 of the liquid crystal lens L has a plurality of convex portions (the periphery is opposed to the second electrode 6a, a plurality are arranged at a predetermined pitch along the X axis, and each extend along the X axis. The refractive index distribution is the same as that of a lens having a plurality of convex portions. The liquid crystal lens L transmits an image displayed on the liquid crystal display panel P to form a stereoscopic image.

Next, Example 1 and Example 2, and Comparative Example 1 and Comparative Example 2 of the liquid crystal display device according to the above-described embodiment will be described.
Here, the splay elastic constant of the liquid crystal used for the liquid crystal layer 3 of the liquid crystal lens L is k11, the bend elastic constant of the liquid crystal is k33, and the elastic constant ratio of the liquid crystal is k33 / k11. Further, the dielectric anisotropy of the liquid crystal is Δε, the dielectric constant in the direction perpendicular to the major axis of the liquid crystal molecules of the liquid crystal is ε _⊥ , the dielectric constant ratio of the liquid crystal is Δε / ε _、, and the elastic constant ratio of the liquid crystal and the ratio of the dielectric constant ratio (k33 / k11) / (Δε / ε ⊥).

Example 1
In Example 1, k11 = 14.1, k33 = 16.2, Δε = 7, a ε _⊥ = 3.7. As shown in FIG. 8, k33 / k11 = 1.15. As shown in FIG. 9, (k33 / k11) / (Δε / _ε⊥ ) = 0.61. Here, when the inventors of the present application observed the disclination generated in the region overlapping the second electrode 6a, the disclination appears parallel to the second electrode 6a, and a meandering shape is seen over the entire area. There wasn't.

  Here, the case where there is no disclination meandering is a case where the disclination line is a straight line. The case where there is meandering of the disclination is a case where there is even one node in the disclination line. It can be said that there is meandering when the disclination is formed by two or more straight lines and the straight lines are joined by nodes and have a zigzag shape.

(Example 2)
In the second embodiment, Np liquid crystal different from the first embodiment is used for the liquid crystal layer 3. k11 = 14.7, k33 = 18.8, Δε = 7.5, and ε _⊥ = 3.8. As shown in FIG. 8, k33 / k11 = 1.28. As shown in FIG. 9, (k33 / k11) / (Δε / _ε⊥ ) = 0.65. Here, when the inventors of the present application observed the disclination generated in the region overlapping the second electrode 6a, the meandering shape of the disclination was not found in almost the entire region of the liquid crystal layer 3, but the minimum region It was seen in. The area where there was no meandering of the disclination was 80% with respect to the number of the second electrodes 6a.

(Comparative Example 1)
In Comparative Example 1, Np liquid crystal different from those in Examples 1 and 2 is used for the liquid crystal layer 3. k11 = 14.4, k33 = 22.4, Δε = 7.6, and ε _⊥ = 3.8. As shown in FIG. 8, k33 / k11 = 1.56. As shown in FIG. 9, a (k33 / k11) / (Δε / ε ⊥) = 0.78. Here, when the inventors of the present application observed the disclination generated in the region overlapping the second electrode 6 a, the meandering shape of the disclination was found in most of the liquid crystal layer 3.

(Comparative Example 2)
In Comparative Example 2, Np liquid crystals different from those in Examples 1 and 2 and Comparative Example 1 are used for the liquid crystal layer 3. k11 = 12.2, k33 = 19.3, Δε = 6.9, is a ε _⊥ = 3.8. As shown in FIG. 8, k33 / k11 = 1.58. As shown in FIG. 9, a (k33 / k11) / (Δε / ε ⊥) = 0.87. Here, when the inventors of the present application observed the disclination generated in the region overlapping the second electrode 6 a, the meandering shape of the disclination occurred over the entire liquid crystal layer 3.

  According to the liquid crystal lens L and the liquid crystal display device including the liquid crystal lens L according to the embodiment configured as described above, the liquid crystal lens L includes a plurality of first electrodes 5a and a plurality of second electrodes 6a. One substrate 1, a second substrate 2 having a counter electrode 8, and a liquid crystal layer 3 are provided. By switching the liquid crystal lens L to the first state or the second state, it is possible to switch to planar (2D) image display or stereoscopic (3D) image display.

In the said Example 1 and 2, k33 / k11 is 1.28 or less. The steepness of an index of the liquid crystal response (k33 / k11) / (Δε / ε ⊥) is 0.65 or less. In this case, even when the liquid crystal lens L is switched to the second state corresponding to the stereoscopic image display, the meandering shape of the disclination does not occur in almost the entire area of the liquid crystal layer 3. The area where no disclination meanders is 80% or more of the number of second electrodes 6a. For this reason, the liquid crystal lens L can show favorable visibility.

  As described above, it is possible to obtain the liquid crystal lens L that can reduce the meandering of the disclination. And the liquid crystal display device excellent in the quality of both a planar image display and a three-dimensional image display can be obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

For example, in the liquid crystal lens L, the first substrate 1 side faces the liquid crystal display panel P, but the second substrate 2 side may face the liquid crystal display panel P.
The embodiment of the present invention is not limited to the liquid crystal display device, can be variously modified, and can be applied to various display devices. If the display device includes a liquid crystal lens and a display panel other than the liquid crystal display panel, the above-described effects can be obtained.

  L ... Liquid crystal lens, 1 ... First substrate, 2 ... Second substrate, 3 ... Liquid crystal layer, 5a ... First electrode, 6a ... Second electrode, 7 ... Alignment film, 8 ... Counter electrode, 9 ... Alignment film, LM Liquid crystal molecules, P ... Liquid crystal display panel, 10 ... Array substrate, 20 ... Counter substrate, 30 ... Liquid crystal layer, PX ... Pixel, 14 ... Sub-pixel, S ... Display surface, R ... Display area, C ... Control unit, d1 ... 1st direction, d2 ... 2nd direction.

Claims (6)

A first substrate having a plurality of first electrodes and a plurality of second electrodes that extend along the Y axis and are alternately arranged with a gap in the direction along the X axis perpendicular to the Y axis. When,
A second substrate having a counter electrode disposed opposite to the plurality of first electrodes and the plurality of second electrodes;
A liquid crystal layer sandwiched between the first substrate and the second substrate,
A liquid crystal lens in which k33 / k11 is 1.28 or less, where k11 is a splay elastic constant of liquid crystal used in the liquid crystal layer and k33 is a bend elastic constant of the liquid crystal. The dielectric anisotropy of the liquid crystal [Delta] [epsilon], when the vertical direction of the dielectric constant epsilon _⊥ to the long axis of the liquid crystal molecules of the liquid crystal, (k33 / k11) / ( Δε / ε ⊥) in 0.65 The liquid crystal lens according to claim 1.   2. The liquid crystal lens according to claim 1, wherein the liquid crystal layer uses a positive nematic liquid crystal and adopts a homogeneous alignment in which liquid crystal molecules are initially aligned substantially parallel to the X axis. The first substrate further includes a first alignment film disposed on a surface facing the second substrate and rubbed in a first direction parallel to the X axis,
The second substrate further includes a second alignment film disposed on a surface facing the first substrate and rubbed in a second direction parallel to the X axis and opposite to the first direction. The liquid crystal lens according to claim 3. A liquid crystal lens according to any one of claims 1 to 4,
A display panel disposed opposite to the first substrate of the liquid crystal lens.   A first state in which all of the plurality of first electrodes, the plurality of second electrodes, and the counter electrode are set to the same potential, and the liquid crystal layer has a uniform refractive index in the direction along the X axis and the Y axis, respectively. The plurality of first electrodes and the counter electrode are set to the same potential, the plurality of second electrodes are set to a potential different from that of the plurality of first electrodes and the counter electrode, and in the direction along the Y axis, 6. The apparatus according to claim 5, further comprising: a control unit that switches between a second state in which the liquid crystal layer has a uniform refractive index and the liquid crystal layer has a refractive index distribution in a direction along the X axis. The display device described.

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