Patent Application
20140267958
The present application claims priority from Japanese application JP2013-49077 filed on Mar. 12, 2013, the content of which is hereby incorporated by reference into this application.
1. Field of the Invention
The present invention relates to a display device.
2. Description of the Related Art
As a naked-eye stereoscopic display in which a two-dimensional display and a three-dimensional display are switched, a liquid crystal lens type has been proposed (JP 2010-224191A). The liquid crystal lens type that uses refractive index distribution generated by orientation distribution of liquid crystal has a characteristic of a high transmittance in the three-dimensional display compared with a liquid crystal barrier type.
A stereoscopic image is stereoscopically viewed by displaying a left-eye image only to the left eye and displaying a right-eye image only to the right eye. However, if the left-eye image inappropriately reaches the right eye or the right-eye image inappropriately reaches the left eye, crosstalk (double image) occurs, in which the stereoscopic view is not provided. In the liquid crystal lens type, the crosstalk easily occurs compared with the liquid crystal barrier type. Further, in order for liquid crystal cells to function as a lens, a cell gap is significantly wide (about 30 μm), which lengthens a response time. Furthermore, a columnar spacer is provided at the center of the lens so as not to influence the performance of the lens, which causes a problem that the columnar spacer is easily viewed particularly in the three-dimensional display.
The invention is to provide a technique capable of reducing crosstalk and a response time, and preventing a spacer from being easily viewed.
(1) According to an aspect of the invention, there is provided a display device including: a display panel that displays an image formed by a plurality of pixels; a liquid crystal lens panel for a naked-eye stereoscopic view; and a plurality of spacers, in which the liquid crystal lens panel includes a first substrate, a second substrate, a liquid crystal material disposed in a cell gap between the first substrate and the second substrate, a first electrode formed on a first inner surface of the first substrate that faces the liquid crystal material, a second electrode formed on a second inner surface of the second substrate that faces the liquid crystal material, a first polarizing plate arranged on a side of the first substrate opposite to the liquid crystal material, and a second polarizing plate arranged on a side of the second substrate opposite to the liquid crystal material, the first polarizing plate and the second polarizing plate are arranged in a crossed-Nicol manner, the liquid crystal material is arranged in a state where orientation of liquid crystal molecules is twisted so that incident light that passes through the first polarizing plate and is polarized passes through the second polarizing plate while being rotated, one of the first electrode and the second electrode includes a plurality of stripe electrodes that extend in a first direction and are arranged at intervals in a second direction intersecting with the first direction so that the adjacent stripe electrodes are arranged in parallel, the other one of the first electrode and the second electrode is arranged to face the plurality of stripe electrodes, the liquid crystal material is driven in a twisted nematic mode in which, while the liquid crystal molecules lose on each of the stripe electrodes, rotary power toward a direction along an electric field by a voltage applied between the plurality of stripe electrodes and the second electrode, the plurality of pixels are arranged in a plurality of rows so that each row extends along the first direction, and the plurality of spacers are arranged on the plurality of stripe electrodes to maintain the cell gap. According to this aspect of the invention, when the liquid crystal lens panel is not driven, since the polarized light that is incident onto the liquid crystal material through the first polarizing plate is rotated in the liquid crystal material and passes through the second polarizing plate, a two-dimensional display can be achieved. In a three-dimensional display, since the liquid crystal molecules lose rotary power on the stripe electrodes, the light becomes dark without passage on the stripe electrodes. Thus, even though the width of the stripe electrodes is increased, it is possible to reduce a crosstalk component. Since it is possible to increase the width of the stripe electrodes, it is possible to reduce the interval between the adjacent stripe electrodes. Accordingly, it is possible to reduce the cell gap. As the cell gap is reduced, it is possible to decrease a response time of the liquid crystal lens panel.
(2) In the display device according to (1), the plurality of spacers may be arranged so as not to be protruded on the plurality of stripe electrodes.
(3) In the display device according to (2), a distance d of the cell gap and the interval s between the adjacent stripe electrodes may satisfy the relation of 3.5≦s/d≦7. The present inventors found that when the distance d of the cell gap and the interval s between the adjacent stripe electrodes satisfy the relation of 3.5≦s/d≦7, it is possible to reduce crosstalk.
(4) In the display device according to (3), a pitch P2 of the adjacent spacers in the second direction and a pitch Q of the adjacent stripe electrodes may satisfy the relation of P2=nQ (n is a natural number).
(5) In the display device according to (4), a pitch P1 of the adjacent spacers in the first direction and the pitch Q of the adjacent stripe electrodes may satisfy the relation of P1=mQ (m is a natural number).
(6) In the display device according to any one of (1) to (5), the liquid crystal lens panel may further include a first orientation film formed on the first inner surface of the first substrate to cover the first electrode, and a second orientation film formed on the second inner surface of the second substrate to cover the second electrode.
(7) In the display device according to (6), an angle formed by a rubbing direction of the first orientation film and a rubbing direction of the second orientation film may be 90 degrees.
(8) In the display device according to (6) or (7), a permissible value of a transmission axis of the first polarizing plate may be 80 to 90 degrees, and the rubbing direction of the first orientation film may be 80 to 90 degrees with respect to the first direction.
(9) In the display device according to any one of (1) to (8), the width of each of the stripe electrodes may be wider than the thickness of the liquid crystal material.
(10) In the display device according to anyone of (1) to (9), the plurality of stripe electrodes may be a plurality of first stripe electrodes included in the first electrode, the second electrode may include a plurality of second stripe electrodes, each of the spacers may include a first spacer and a second spacer that are arranged to be overlapped, the first spacer may be arranged on the first stripe electrode, the second spacer may be arranged on the second stripe electrode, a cross section of the first spacer may be a rectangular shape, in which short sides thereof are parallel to the first stripe electrode, a cross section of the second spacer may be a rectangular shape, which is a shape obtained by rotating the first spacer by 90 degrees, and the first spacer and the second spacer may overlap each other in a cross shape.
(11) The display device according to (10) may further include: a first auxiliary electrode provided between the adjacent first stripe electrodes, and a second auxiliary electrode provided between the adjacent second stripe electrodes.
Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings.
As shown in
On the inner surface of the first substrate 32, a first orientation film 46 is formed to cover the first electrode 40. The first orientation film 46 is rubbed so that liquid crystal molecules are orientated approximately in parallel to the incident polarization direction. A rubbing angle is 80 to 90 degrees with respect to the stripe electrodes 42 of the first electrode 40. That is, a rubbing direction of the first orientation film 46 is 80 to 90 degrees with respect to the first direction (Y direction).
The incident polarization direction to the liquid crystal lens panel 30 (transmission axis direction of the first polarizing plate 22) forms an angle of 0 to 10 degrees with respect to a long side of the liquid crystal lens panel 30 (X direction). If the incident polarizing direction to the liquid crystal lens panel 30 coincides with linear polarization in a desired direction, the display mode of the display panel 10 is not limited. If the polarization direction is different from the linear polarization in the desired direction, a phase difference member may be provided between the first polarizing plate 22 and the liquid crystal material 33 so that the polarization direction coincides with the linear polarization in the desired direction.
The relation of angles between a transmission axis of the first polarizing plate 22 and the second polarizing plate 36 and orientation directions of the first orientation film 46 and a second orientation film 48 will be described with reference to
When the display panel 10 is in the IPS mode of a mono-domain, the transmission axis angle α1 is preferably 1 to 10 degrees, and more preferably 3 to 8 degrees.
If the rubbing angle β1 is equal to the transmission axis angle α1, even though linearly polarized light that passes through the first polarizing plate 22 is incident onto the liquid crystal material 33, the linearly polarized light does not become elliptically polarized light, and is incident onto the liquid crystal material 33 as the linearly polarized light is. Thus, it is preferable that the rubbing angle β1 matches with the transmission axis angle α1, which is preferably 1 to 10 degrees, and more preferably 3 to 8 degrees. Here, since the convergency of the liquid crystal lens is superior as the rubbing angle β1 becomes smaller, the rubbing angle β1 may be set to 0 degree.
The rubbing angle β2 is expressed as β2=β1+γ(≠0), twisted nematic orientation is applied to the liquid crystal material 33. That is, since the rubbing angle β1 is different from the rubbing angle β2, the liquid crystal material 33 is twisted. The incident light is optically rotated along a twist angle, and a polarization plane of the linearly polarized light advances while being rotated.
To reduce crosstalk in the three-dimensional display, γ=90° is preferably used.
If the transmission axis angle α2 is equal to the rubbing angle β2, it is possible to maximize the intensity of light passing through the second polarizing plate 36, which is preferable. That is, it is more preferable that α1=β2 and β2=α2=β1+90°.
If the transmission axis angle α2 is set to 70 to 90 degrees, it is possible to view a bright three-dimensional image and a bright two-dimensional image even using polarizing sunglasses. If the transmission axis angle α2 is set to about 30 to about 60 degrees, and preferably 45 degrees, it is possible to view a display even using the polarizing sunglasses, and to view an image using the polarizing sunglasses even when the display is rotated by 90 degrees to be vertical.
If the display panel 10 is in the IPS mode of the multi-domain, the transmission axis angle α1 is set to 0 degree. It is preferable that the rubbing angle β1 be equal to the transmission axis angle α1, that is, β1 be 0 degree. Here, the rubbing angle β1 may be set to 1 to 10 degrees, or 1 to 3 degrees. By setting β2=α2, it is possible to maximize the intensity of light passing through the second polarizing plate 36. Accordingly, it is more preferable that α1=β1=0° and β2=α2=90°. Here, to view the image even using the polarizing sunglasses, β2=β1+γ and 30°≦γ≦60° may be used.
In the following description, the case of α1=β1=0° and β2=α2=90° will be described.
The spacers 50 are formed in a columnar shape, and are arranged between the first substrate 32 and the second substrate 34. Across section (cross section orthogonal to a height direction) of the spacers 50 may be a circle or a quadrangle. Each spacer 50 stands up straight so that change in the shape of the cross section is small from the bottom to the top and a wall surface thereof is approximately vertical, which is preferable in view of reducing light scattering.
A pitch P1 of the adjacent spacers 50 in the first direction (Y direction) and a pitch Q of the adjacent stripe electrodes 42 satisfy the relation of P1=mQ (m is a natural number).
A pitch P2 of the adjacent spacers 50 in the second direction (X direction) and the pitch Q of the adjacent stripe electrodes 42 satisfy the relation of P2=nQ (n is a natural number).
The spacers 50 may be formed by photolithography using an ultraviolet curing resin, or may be formed by screen-printing, ink jet printing or the like. A transparent material is preferably used for the spacers 50, but the spacers 50 may be colored in black. The spacers 50 are arranged with a small density in a range where the strength capable of maintaining the cell gap is obtained.
The spacers 50 are preferably formed on the first substrate 32 on which the stripe electrodes 42 are formed so that the spacers 50 can be positioned to match with the stripe electrodes 42 in formation, but may be formed on the second substrate 34. When the spacers 50 are formed on the second substrate 34, the rubbing direction of the second orientation film 48 becomes approximately parallel to the extending direction of the stripe electrodes 42 of the first substrate 32, and a rubbing error due to the spacers 50 occurs in the length direction of the stripe electrodes 42, to thereby achieve an effect that the stripe electrodes 42 in the three-dimensional display hide the rubbing error portion to be hardly viewed.
As a modification example, the plural spacers may be arranged in irregular pitches. Further, bead spacers may be used as the spacers 50. The bead spacers may be regularly arranged on the stripe electrode 42, or may be irregularly arranged thereon.
As shown in
The liquid crystal lens panel 30 includes the liquid crystal material 33. The liquid crystal material 33 is provided in the cell gap between the first substrate 32 and the second substrate 34. The liquid crystal material 33 is provided in a state where orientation of liquid crystal molecules is twisted, in which polarized light incident through the first polarizing plate 22 is rotated and then passes through the second polarizing plate 36.
In (A) of
The present embodiment may be applied to a multi-viewpoint case, but a two-viewpoint case will be described hereinafter. In the two-viewpoint case, a right-eye pixel 24 and a left-eye pixel 24 are adjacently arranged. The right-eye pixel 24 and the left-eye pixel 24 are separated from each other according to a lens effect due to refractive index distribution of the liquid crystal material 33 for image formation, to thereby obtain the three-dimensional display. A light beam output from the right-eye pixel 24 arranged on the left side in (A) of
In (B) of
In (C) of
The liquid crystal material 33 is driven in a twisted nematic manner by a voltage (AC drive voltage) applied between the plural stripe electrodes 42 and the second electrode 54. If the voltage is applied, the liquid crystal molecules lose rotary power in a direction along an electric field on each of the stripe electrodes 42, but form a refractive index distribution of a lenticular lens in a region between the adjacent stripe electrodes 42. The lenticular lens is formed to have a cylindrical lens where a cylindrical axis is arranged in the first direction. The cylindrical lens faces at least two rows of pixels 24 of the display panel 10. The cylindrical lens has an effective refractive index for emitting light from the at least two rows of pixels 24 facing each other through the second polarizing plate 36 and then causing the light to advance in separating directions from each other.
According to the present embodiment, if the liquid crystal lens panel 30 is not driven, since the polarized light that is incident onto the liquid crystal material 33 through the first polarizing plate 22 rotates in the liquid crystal material 33 and passes through the second polarizing plate 36, the two-dimensional display is achievable. In the three-dimensional display, since the liquid crystal molecules lose rotary power on the stripe electrodes 42, the light becomes dark without passage on the stripe electrode 42. Thus, even though the width of the stripe electrodes 42 is increased, it is possible to reduce a crosstalk component. Since it is possible to increase the width of the stripe electrodes 42, it is possible to reduce an interval s between the adjacent stripe electrodes 42. Thus, it is possible to reduce the width of the cylindrical lens, and also to reduce the height, thereby reducing the cell gap. As the cell gap is reduced, it is possible to achieve a quick response of the liquid crystal lens panel 30.
A first electrode 140 of a first substrate 132 shown in
A second electrode 154 of a second substrate 134 shown in
The first spacer 150a and the second spacer 150b are provided so as not to be protruded from both of the first stripe electrode 142a and the second stripe electrode 142b. Since the first spacer 150a and the second spacer 150b are dividedly provided in the first substrate 132 and the second substrate 134, respectively, it is possible to increase the aspect ratio, compared with a case where the first spacer 150a and the second spacer 150b are integrally provided. If the aspect ratios are the same, it is possible to reduce an installation area of the first spacer 150a and the second spacer 150b. Since each of the first spacer 150a and the second spacer 150b has a height corresponding to ½ of the total height of the both spacers, it is possible to reduce each installation area to ¼ to the minimum. Since the installation area and volume are reduced, light scattering is decreased, and thus, it is possible to achieve the effect that the first spacer 150a and the second spacer 150b are not easily viewed. With the reduced height, the first spacer 150a and the second spacer 150b are easily formed.
When the second substrate 134 is bonded to the first substrate 132, the first spacer 150a and the second spacer 150b overlap each other to maintain the cell gap. The first spacer 150a and the second spacer 150b overlap each other in a cross shape, and thus, a position shift is allowed to some extent. Thus, it is possible to moderate the overlap accuracy of the first substrate 132 and the second substrate 134. The first spacer 150a and the second spacer 150b preferably extend to be perpendicular to the lengths of the first stripe electrode 142a and the second stripe electrode 142b, respectively.
When the first stripe electrode 142a is operated to form a cylindrical lens arranged in the X direction, an alternating voltage is applied between the second stripe electrode 142b, the second auxiliary electrode 156b and the first auxiliary electrode 156a, and the first stripe electrode 142a, using the second stripe electrode 142b, the second auxiliary electrode 156b and the first auxiliary electrode 156a as a common electric potential.
When the second stripe electrode 142b is operated to form a cylindrical lines parallel to the Y direction, an alternating voltage is applied between the first stripe electrode 142a, the second auxiliary electrode 156b and the first auxiliary electrode 156a, and the second stripe electrode 142b, using the first stripe electrode 142a, the second auxiliary electrode 156b and the first auxiliary electrode 156a as a common electric potential.
While there have been described what are at present considered to be certain embodiments of the invention, it is understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications to fall within the true spirit and scope of the invention.
Next, the relation of a distance d of the cell gap and the interval s of the adjacent stripe electrodes 42 will be described with reference to
This range was calculated by calculating s/d with respect to crosstalk by simulation. The simulation was performed by calculating s/d by light beam tracing software using a calculation result of liquid crystal orientation. In the calculation, the pitch p (
In the present example, it is possible to increase the width of the stripe electrodes 42, and thus, it is possible to reduce s, to thus reduce the cell gap d without degrading the quality of the three-dimensional display. By reducing the cell gap d, it is possible to reduce a response time of the liquid crystal lens panel 30, to thereby easily manufacture the liquid crystal lens panel 30, which enhances reliability.
When q is a liquid crystal lens pitch, p is the pitch of the pixels 24 (
When the refractive index distribution having the shape of the ideal quadratic function is obtained, if the cell gap is determined so as to satisfy the following expression (1), it is possible to reduce crosstalk, and to enlarge a three-dimensional display area.
d=n
1
s
2/8ΔnG (1)
Here, d represents the cell gap of the liquid crystal lens, n1 represents the refractive index (for example, 1.5 in a glass substrate) of the first substrate 32, Δn represents refractive index anisotropy of the liquid crystal material 33, G represents a gap between the pixels 24 and the liquid crystal material 33 (see
Further, between the gap G between the pixels 24 and the liquid crystal material 33, and an optimal viewpoint distance D (not shown), the relation of expression (2) is established.
G=n
1
pD/E (2)
Here, p represents the pitch of the pixels 24, and E represents the interocular distance (about 65 mm in an average adult). From the expression (1), the following expression is obtained.
s/d=8ΔnG/n1s
Accordingly, to make s/d constant while reducing s, it is necessary to reduce the refractive index anisotropy Δn of the liquid crystal material 33 or the gap G. From the expression (2), to reduce G, it is necessary to reduce the optimal viewpoint distance D or the pitch p of the pixels 24.
As described above, it can be understood that it is possible to use the liquid crystal material 33 having a small refractive index anisotropy Δn by making s/d constant and reducing s. For example, in the liquid crystal lens panel 30 in the related art, if the liquid crystal lens pitch is about 160 μm, the width of the stripe electrodes 42 is 10 μm (s=150 μm), and the cell gap is 30 μm, the refractive index anisotropy Δn of the liquid crystal material 33 is 0.2. On the other hand, in this example, if the width of the stripe electrodes 42 is 30 μm (s=130 μm), it is possible to use the liquid crystal material 33 of Δn=0.17, and if the width of the stripe electrodes 42 is 50 μm (s=110 μm), it is possible to use the liquid crystal material 33 of Δn=0.15. Since the refractive index anisotropy Δn is small, the liquid crystal material 33 has high reliability.
Further, since it is possible to reduce the gap G between the pixels 24 and the liquid crystal material 33, it is possible to reduce the optimal viewpoint distance D without degrading the quality of the three-dimensional display. The present embodiment may also be applied to the high-accuracy display panel 10 with a small pitch of the pixels 24 without degrading the quality of the three-dimensional display.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-049077 | Mar 2013 | JP | national |
