KR101428571B1 - Liquid Crystal Lens - Google Patents

Abstract

The present invention provides a liquid crystal display comprising: a first substrate; A first electrode formed on the entire side surface of the first substrate; A first alignment layer formed on the first electrode; A second substrate facing the first substrate and spaced apart from the first substrate; A plurality of second electrodes formed on the second substrate with a first spacing distance; A plurality of third electrodes overlapping the plurality of second electrodes with an insulating film interposed therebetween and having a second spacing distance from each other; A second alignment layer formed on the entire surface of the plurality of third electrodes and oriented in a direction perpendicular to the longitudinal direction of the plurality of third electrodes; And a liquid crystal layer formed between the first and second alignment layers.

Liquid crystal lens, side field, orientation film, rubbing direction, birefringence

Description

Liquid Crystal Lens

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal lens, and more particularly, to a liquid crystal lens characterized in that 3D performance is improved by minimizing the influence of a lateral electric field of a liquid crystal lens using a vertical electric field.

Generally, a liquid crystal display device is composed of two opposing electrodes and a liquid crystal layer formed therebetween. The liquid crystal molecules of the liquid crystal layer are driven by an electric field generated by applying a voltage to the two electrodes. The liquid crystal molecules have a polarization property and an optical anisotropy. The polarization property means that when the liquid crystal molecules are placed in the electric field, the charges in the liquid crystal molecules collide with both sides of the liquid crystal molecules, and the molecular alignment direction changes according to the electric field. Refers to changing the path of the emitted light and the polarization state differently depending on the incident direction or polarization state of the incident light due to the elongated structure of the liquid crystal molecules and the aforementioned molecular arrangement direction.

Accordingly, the liquid crystal layer exhibits a difference in transmittance due to the voltage applied to the two electrodes, and the image can be displayed by varying the difference between the pixels.

Recently, a liquid crystal lens has been proposed in which the liquid crystal layer serves as a lens by taking advantage of the properties of such liquid crystal molecules.

That is, the lens controls the path of the incident light by using the refractive index difference between the material constituting the lens and the air, and positions the liquid crystal layer in different electric fields by applying different voltages to the liquid crystal layers The incident light incident on the liquid crystal layer experiences a different phase change according to the position, and as a result, the liquid crystal layer can control the path of the incident light like an actual lens.

Such a liquid crystal lens will be described with reference to the drawings.

1A and 1B are a perspective view and a cross-sectional view of a general liquid crystal lens, respectively.

1A and 1B, a typical liquid crystal lens 10 includes first and second substrates 20 and 30 facing each other and a liquid crystal layer (not shown) formed between the first and second substrates 20 and 30 40 and first and second alignment layers 23, 33 formed on the upper and lower surfaces of the liquid crystal layer 40, respectively. A first electrode 22 and a first alignment layer 23 are sequentially formed on the entire inner surface of the first substrate 20 and spaced apart from each other by a distance d from the inner surface of the second substrate 30 A second electrode 32 is formed and the second alignment layer 33 is formed below the second electrode.

When a voltage is applied to the first and second electrodes 22 and 32 with respect to the liquid crystal lens 10 having such a configuration, an electric field E is formed between the two electrodes 22 and 32, Since the two electrodes 32 are not formed on the entire inner surface of the second substrate 30 but have a separate shape, a complete vertical electric field is not formed. That is, an electric field substantially perpendicular to the first and second substrates 20 and 30 is generated in a region distant from the separation section 32a of the second electrode 32, An electric field inclined to the first and second substrates 20 and 30 is generated in an area close to the separation section 32a.

Accordingly, the electric field generated by the first and second electrodes 22 and 32 varies in intensity and direction according to the distance from the separation section 32a of the second electrode 32, and as a result, The liquid crystal layer 40 also changes the phase of the incident light differently according to the distance from the separation section 32a of the first and second electrodes 22 and 32. [

FIG. 2 is a graph showing the phase change of incident light when light passes through the liquid crystal lens of FIGS. 1A and 1B. FIG. 2 also shows the phase change when light passes through an actual lens for comparison.

2, the first, second, and third curves 40a, 40b, and 40c are curves showing the phase changes of light passing through the liquid crystal lenses of different configurations, and the fourth curve 40d is a curve It is a curve showing the phase change of the light passing through the lens. As can be seen from the first, second and third curves 40a, 40b and 40c, the phase change of the light passing through the liquid crystal lens is different from the phase difference of the second electrode (32 in Figs. 1A and 1B) Symmetrical from left to right about the center 32a of FIG. 1B.

For example, the first, second, and third curves 40a, 40b, and 40c can be used to change the distance between the second electrode (32 in FIGS. 1A and 1B) Curves. Even if the separation distance (Figs. 1A and 1B, d) is appropriately adjusted, there is a limit, so that the same result as the actual lens can not be obtained. That is, the first and second curves 40a and 40b have less phase change than the fourth curve 40d as a whole, while the third curve 40c has a larger phase change than the fourth curve 40d as a whole.

This result is attributable to the fact that the phase change control variable of the liquid crystal lens is small. The reason why the phase change can be controlled in the liquid crystal lens is that the distance between the second electrode (32 in Figs. 1A and 1B) d and the voltage applied to the second electrode (32 in Figs. 1A and 1B), it is difficult to obtain the same curve as the phase change in the actual lens even if it is properly adjusted.

Accordingly, it is an object of the present invention to provide a liquid crystal lens capable of more freely controlling a phase change by driving a liquid crystal layer using three electrodes.

Another object of the present invention is to prevent crosstalk by optimizing the alignment direction of the first and second alignment layers which are involved in the initial alignment state of the liquid crystal molecules in the liquid crystal layer and the degree of change due to the applied electric field.

A liquid crystal lens according to the present invention includes: a first substrate; A first electrode formed on the entire side surface of the first substrate; A first alignment layer formed on the first electrode; A second substrate facing the first substrate and spaced apart from the first substrate; A plurality of second electrodes formed on the second substrate with a first spacing distance; A plurality of third electrodes overlapping the plurality of second electrodes with an insulating film interposed therebetween and having a second spacing distance from each other; A second alignment layer formed on the entire surface of the plurality of third electrodes and oriented in a direction perpendicular to the longitudinal direction of the plurality of third electrodes; And a liquid crystal layer formed between the first and second orientation films, wherein each of the plurality of second electrodes and the plurality of third electrodes is a stripe type.

At this time, the plurality of second electrodes and the plurality of third electrodes are integrally formed.

And the first separation distance is smaller than the second separation distance.

The liquid crystal lens according to the present invention is a liquid crystal lens in which three electrodes are used to generate an electric field, the liquid crystal layer is driven by such an electric field, and further, the two electrodes formed on the same substrate overlap each other, It is possible to realize a liquid crystal lens that substantially plays the same role as the optical lens.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

3 is a cross-sectional view schematically showing a liquid crystal lens according to an embodiment of the present invention.

As shown in the figure, the liquid crystal lens 110 according to the first embodiment of the present invention includes first and second substrates 120 and 130 spaced apart from each other and first and second substrates 120 and 130 And a liquid crystal layer 140 formed thereon.

A first electrode 122 is formed on the inner surface of the first substrate 120 and a first alignment layer 124 is formed on the first electrode 122.

On the inner surface of the second substrate 130, a second electrode 132 having a first opening having a width corresponding to the first spacing distance d1 is formed around the center of the second substrate 130 And an insulating layer 134 is formed under the second electrode 132. A third electrode 136 is formed under the insulating layer 134 and has a second opening having a width corresponding to the second spacing distance d2 with respect to the center of the second substrate 130, A second alignment layer 138 is formed on the entire surface of the lower portion of the third electrode 136.

At this time, the second and third electrodes 132 and 136 are electrically insulated from each other by the insulating layer 134, and are disposed so as to partially overlap each other.

A liquid crystal layer 140 is formed between the first and second alignment layers 124 and 138. In this embodiment, the second alignment layer 138 is formed in contact with the third electrode 136 However, as a modification thereof, a protective layer (not shown) made of an insulating material may be further formed between the third electrode 136 and the second alignment layer 138. Also, the first, second, and third electrodes 122, 132, and 136 may be made of a transparent conductive material.

The second and third electrodes 132 and 136 are not shown in the drawing. However, in a region where the lens region of the second substrate 130, that is, the liquid crystal layer 140, is formed in a plan view, When the plurality of second electrodes 132 are formed, the plurality of second electrodes 132 are integrally connected at their one ends, and the third electrodes 136 are formed in the same manner as the second electrodes 132 And when they are constituted by a plurality of units, they can be formed integrally with one end connected to each other.

In the liquid crystal lens 110 having such a structure, an electric field is generated by first, second and third voltages respectively applied to the first, second and third electrodes 122, 132 and 136, (140) is driven. In this case, the magnitude and direction of the generated electric field are controlled by the magnitude of the first, second and third voltages and the first and second separation distances d1 and d2. Can be generated more finely.

The magnitude of the magnitude and direction of the electric field generated at this time is a diversity of the phase change curve in the liquid crystal layer 140. The first, second, and third voltages and the first and second separation distances d1 and d2, So that a phase change curve substantially identical to that of the actual lens can be realized. That is, in the liquid crystal lens 110 according to the embodiment of the present invention, the refractive index of the liquid crystal layer 140 is finely adjusted by the electric field generated by the generated electric field, and accordingly, the fine phase in which the incident light passing through the liquid crystal layer 140 The change exhibits a light path change effect similar to that of an actual lens.

If electrodes facing each other are formed on the first and second substrates 120 and 130, a vertical electric field is formed. At the same time, different voltages are applied to the second substrate 130, A side surface electric field is locally generated at the boundary between the second and third electrodes 132 and 136. The second and third electrodes 132,

The side electric field thus generated affects the phase change of the liquid crystal layer 140 so that a part of the incident light incident on the liquid crystal layer 140 does not proceed to the optical path for serving as an actual lens, Furthermore, a crosstalk phenomenon occurs at the boundary of the second and third electrodes 132 and 136 which overlap each other. At this time, the crosstalk phenomenon occurring at the boundary between the two electrodes 132 and 136 to which different voltages are applied on one substrate (the second substrate 130) may be further reduced in accordance with the alignment direction of the second alignment film 138 It will be greatly affected.

More specifically, in the case of a liquid crystal lens using a vertical electric field, rubbing is performed on an alignment film formed on the substrate in a diagonal direction with respect to a substrate having a rectangular shape, and two or more electrodes are formed on one substrate The rubbing proceeds in the longitudinal direction of the two electrodes.

FIGS. 4A and 4B are plan views showing a part of a liquid crystal lens according to a comparative example of the present invention, wherein two electrodes having different voltages are formed on one substrate and rubbed in the longitudinal direction of the two electrodes Is a partial plan view schematically showing the state of the liquid crystal upon voltage on / off when an orientation film is formed.

When two electrodes 232 and 236 having a voltage difference are formed in one substrate 230 and the surface of the alignment film (not shown) is rubbed in the longitudinal direction of the two electrodes 232 and 236, The liquid crystal layer does not act as a lens when the power supply is turned off so that there is no effect. However, as shown in FIG. 4B, when the voltage is applied to the liquid crystal lens 210 , The side surface between the second and third electrodes 232 and 236 to which the different voltages are applied in addition to the vertical electric field E1, more precisely, the third electrode 232, which overlaps the second electrode 232, The second electrode 232 and the third electrode 236 have a horizontal component oriented toward the side of the second electrode 232 from the side of the third electrode 236 with respect to both sides of the second electrode 232 and the third electrode 236 A side electric field E2 is generated. The side electric field E2 thus generated is absorbed by the liquid crystal molecules in the liquid crystal layer corresponding to the region overlapping these electrodes 232 and 236 by reaction of energizing energy which is a force for restricting the liquid crystal molecules 241 of the alignment film (Not shown) to generate a twist component as well as a tilt component. In the absence of the energizing energy, the long axis of the liquid crystal molecules 241 is twisted by 90 degrees in the direction parallel to the side electric field E2. However, due to the energizing energy of the surface of the alignment layer (not shown) 241 have a long axis and a predetermined angle with respect to the direction of the side electric field E1. When linearly polarized light is incident on the liquid crystal layer in a state where an undesired twist component is generated when the liquid crystal molecules 241 located at the boundary of the second and third electrodes 232 and 236 are partially driven by the electric field, Light is transmitted through two separate lights along the crystal axis of the liquid crystal molecules 241 having the twist component in the boundary region between the second and third electrodes 232 and 236, and the different refractive indexes are felt.

의 굴절율을 느끼며 진행하고, 상기 액정분자의 단축방향으로는 n₂ = n₀의 굴절율을 느끼며 진행하게 된다.FIG. 5 is a graph showing a state in which liquid crystal molecules twisted by a side electric field are viewed from a position perpendicular to a substrate surface when a voltage is applied to the liquid crystal lens according to a comparative example, and a state of polarization of linearly polarized light incident on the liquid crystal layer FIG. If the angle of tilt of the long axis of the liquid crystal molecule from the alignment layer is?, The refractive index of the liquid crystal molecule in the long axis direction is n _e , and the refractive index in the short axis direction is n _o , the liquid crystal layer has linearly polarized light in the longitudinal direction of the electrode The incident light passes through the liquid crystal layer, and in the major axis direction of the twisted liquid crystal molecules, n ₁ =

Exposed to the progress of the refractive index, and a minor axis direction of the liquid crystal molecules to proceed exposed to the index of refraction of n ₂ = n _0.

Since the light having the refractive index of n ₂ always spatially feels n ₀ , the liquid crystal lens passes through the liquid crystal layer and does not change the refractive index As a result, light that can not be controlled as a result, i.e., light having an ideal optical path, is obtained. The light having such an abnormal optical path causes crosstalk.

Therefore, in the embodiment of the present invention, most notably, in the second alignment film formed on the second substrate on which the second and third electrodes are formed, the rubbing direction is perpendicular to the longitudinal direction of the second and third electrodes Direction, that is, a direction parallel to the direction of the electric field formed between the third electrode and the second electrode overlapping with the third electrode.

FIGS. 6A and 6B are plan views showing a part of a liquid crystal lens according to an embodiment of the present invention. In FIG. 6A and FIG. 6B, two electrodes having different voltages are formed on one substrate, In the case where an alignment film is formed, which is rubbed in the width direction of the liquid crystal layer, is a partial plan view schematically showing the liquid crystal state at the time of voltage on / off.

In an embodiment of the present invention including an alignment film rubbed in a direction perpendicular to the longitudinal direction of the second and third electrodes, that is, in the same direction as the width direction of the electrodes, first, referring to FIG. 6A, As shown in the drawing, the liquid crystal molecules 341 in the layer are arranged in a direction perpendicular to the longitudinal direction of the second and third electrodes 332 and 336, that is, in a direction parallel to the side electric field (E2 in FIG. 6B) A first electrode (not shown) formed on a first substrate (not shown) and a second electrode (not shown) formed on a second substrate (not shown), as shown in FIG. 6B, The side electric field E2 between the second and third electrodes 332 and 336 formed on the second substrate 330 is the same as the perpendicular electric field E1 between the second and third electrodes 332 and 336 formed on the second substrate 330. [ . In this case, in the case of the liquid crystal lens 310 according to the embodiment of the present invention, the liquid crystal molecules 341 in the liquid crystal layer (not shown) are aligned in the rubbing direction of the alignment film (not shown) 332, and 336, the twist of the liquid crystal molecules is not generated, and only the tilt angle is changed by the vertical electric field E1.

Therefore, when the linearly polarized light that horizontally vibrates in this state enters the liquid crystal layer, the linearly polarized light does not feel the short / short axis division of the liquid crystal molecules, and only the effective refractive index due to the tilt angle is felt. Accordingly, since the light traveling through the liquid crystal layer (not shown) does not feel two refractive indices, it is not birefringent and only reflects the refractive index in one direction. As a result, when the refractive index of the liquid crystal layer The generation of light having an abnormal light path is prevented.

In this case, when the tilt angle changed by the vertical electric field E1 generated by the voltage applied with the linearly polarized light is?, The tilt angle changed by the linear electric field E1 generated by the linearly polarized light source passing through the liquid crystal layer (not shown) The refractive index n is expressed by the following equation.

On the other hand, when light is incident on the liquid crystal lens according to the comparative example, the light is affected by the side electric field generated at the side surfaces of the second electrode and the third electrode. In the vicinity of the boundary between the second electrode and the third electrode When the birefringence occurs, the phase change curve at the boundary between the two electrodes is distorted as compared with the actual lens. However, in the liquid crystal lens according to the embodiment of the present invention, when light is incident on the liquid crystal layer, Distortion does not occur in the vicinity of the boundary, and even in the boundary region between the two electrodes, a phase change similar to that of an actual lens is generated, so that excellent lens characteristics are obtained.

The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

1A and 1B are a perspective view and a cross-sectional view of a typical liquid crystal lens, respectively.

FIG. 2 is a graph showing a phase change of an incident light when light passes through the liquid crystal lens of FIGS. 1A and 1B. FIG.

3 is a plan view schematically showing a liquid crystal lens according to an embodiment of the present invention.

FIGS. 4A and 4B are plan views showing a part of a liquid crystal lens according to a comparative example of the present invention, wherein two electrodes having different voltages are formed on one substrate and rubbed in the longitudinal direction of the two electrodes And some plan views schematically showing states of liquid crystals at voltage on / off when an orientation film is formed.

5 is a view showing a state in which liquid crystal molecules twisted by a side electric field are viewed from a vertical position on a substrate surface when a voltage is applied to the liquid crystal lens according to a comparative example and a polarization state of linearly polarized light incident on the liquid crystal layer .

FIGS. 6A and 6B are plan views showing a part of a liquid crystal lens according to an embodiment of the present invention. In FIG. 6A and FIG. 6B, two electrodes having different voltages are formed on one substrate, And the liquid crystal layer is rubbed in the width direction of the liquid crystal layer. In the case where the alignment layer is formed, the planar view schematically shows the state of the liquid crystal at the time of voltage on / off.

Description of the Related Art

310: liquid crystal lens 330: second substrate

332: second electrode 336: third electrode

341: liquid crystal molecule E1: vertical electric field

E2: Side field

Claims (4)

A first substrate; A first electrode formed on the entire side surface of the first substrate; A first alignment layer formed on the first electrode; A second substrate facing the first substrate and spaced apart from the first substrate; A plurality of second electrodes formed on the second substrate with a first spacing distance; A plurality of third electrodes overlapping the plurality of second electrodes with an insulating film interposed therebetween and having a second spacing distance from each other; A second alignment layer formed on the entire surface of the plurality of third electrodes and oriented in a direction perpendicular to the longitudinal direction of the plurality of third electrodes; The liquid crystal layer formed between the first and second alignment layers Wherein the plurality of second electrodes and the plurality of third electrodes are each of a stripe type. delete The method according to claim 1, Wherein the plurality of second electrodes and the plurality of third electrodes are integrally formed. The method according to claim 1, Wherein the first spacing distance is smaller than the second spacing distance.

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