JP4194067B2 - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of attaining bright display at high contrast without leakage of light at a black display even when a user views the image in an oblique direction. SOLUTION: Polymer walls 23 are formed in a grid and projected from a substrate 2 with a prescribed height to a liquid crystal layer side 4 in a couple of substrates 2, 3 and divide the liquid crystal layer 4 into a plurality of liquid crystal areas 4a laid out in a grid. Each of the walls 23 has a flat part 23b raised from the face of the substrate 2 by a prescribed height and slope parts 23a tilted at a prescribed tilt angle from the edge of the flat part 23b and reaching the face of the substrate 2. The flat part 23b is formed to have a translucency and each slope 23a is formed to have a shading property.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device in which viewing angle characteristics are improved by axially symmetric alignment of liquid crystal molecules.
[0002]
[Prior art]
Recently, TN (twisted nematic) type and STN (super twisted nematic) type liquid crystal display devices using a nematic liquid crystal material have been widely used. This type of liquid crystal display device has a common problem that the viewing angle is narrow, and technical development for improving this problem is underway.
[0003]
As one of the techniques for improving the viewing angle of the TN type liquid crystal display devices proposed so far, the so-called ASM (axially aligned micro-cell) mode technique in which liquid crystal molecules are axially symmetrically aligned for each pixel region. There is. The liquid crystal display device using ASM mode technology has liquid crystal molecules that are axially symmetrically aligned in each pixel region, so that the refractive index of the liquid crystal material is anisotropic regardless of the azimuth angle direction. And a wide viewing angle characteristic with little change in contrast can be realized.
[0004]
This ASM mode technique is disclosed in, for example, Japanese Patent Laid-Open No. 10-186330. In this publication, a lattice-like convex portion (polymer wall) made of a dielectric or the like is formed on a support substrate such as glass, and the lattice-like convex portion is a liquid crystal molecule having negative dielectric anisotropy. It is described that the lattice-shaped convex portions generate an axially symmetric alignment regulating force with respect to the liquid crystal molecules.
[0005]
Japanese Patent Application Laid-Open No. 11-271716 discloses a light leakage at the time of black display by making the cross-sectional shape of the convex portion formed in a lattice shape into a forward taper shape in which the width gradually decreases toward the tip side. A technique for improving contrast by eliminating the above has been disclosed. Japanese Patent Laid-Open No. 2000-19522 also discloses that a liquid crystal molecule on a polymer wall contributes to display by forming a grid-like convex portion (polymer wall) using a transparent dielectric, A technique for improving the brightness of the image is disclosed.
[0006]
[Problems to be solved by the invention]
In the structure of the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 11-271718, light leakage during black display can be sufficiently prevented, but a light-shielding polymer wall exists in the picture element region. However, there is a problem that the aperture ratio decreases and the display brightness becomes dark.
[0007]
In addition, in the liquid crystal display device disclosed in Japanese Patent Laid-Open No. 2000-19522, the brightness of display can be improved by making the cross-sectional shape of the polymer wall formed of a transparent dielectric into a forward tapered shape. In addition, it is possible to sufficiently suppress light leakage during black display from the front direction. However, even in this case, there is a problem that slight light leakage is observed when viewed from an oblique direction.
[0008]
Therefore, in the liquid crystal display device described above, it is impossible to achieve further improvement in display performance while achieving both improvement in display brightness and prevention of light leakage during black display.
[0009]
The present invention has been made in view of the above problems, and improves the brightness of display, and even when observed from an oblique direction, there is no light leakage during black display, and a bright display with high contrast is possible. An object of the present invention is to provide a liquid crystal display device having a wide viewing angle characteristic.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, a liquid crystal display device of the present invention is a liquid crystal formed by a pair of substrates arranged opposite to each other and a liquid crystal molecule having negative dielectric anisotropy provided between the pair of substrates. A polymer wall that is formed in a lattice shape protruding to a predetermined thickness on at least one liquid crystal layer side of the pair of substrates and divides the liquid crystal layer into a plurality of lattice-like liquid crystal regions; A liquid crystal display device having a vertical alignment layer formed on a surface of the pair of substrates in contact with the liquid crystal layer and vertically aligning liquid crystal molecules of the liquid crystal layer with respect to the surface, A flat portion projecting at a certain height with respect to the surface of the one substrate, and an inclined portion that is inclined from the edge of the flat portion at a constant inclination angle and reaches the surface of the one substrate. The flat portion is formed to have a light transmitting property, and the inclined portion is formed to have a light shielding property. And it is characterized in that is.
[0011]
In the liquid crystal display device of the present invention, it is preferable that the flat portion and the inclined portion of the polymer wall are made of a light-transmitting material, and the light shielding material is coated on the surface of the inclined portion.
[0012]
In the liquid crystal display device of the present invention, the optical density of the inclined portion of the polymer wall is preferably 1 or more.
[0013]
In the liquid crystal display device of the present invention, the polymer wall has an area formed so as to have a light-shielding property at an edge portion between the flat portion and the inclined portion than a region formed so as to have a light-transmitting property. However, it is preferable that the first substrate is formed to be thicker from the surface.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the liquid crystal display device of the present invention will be described with reference to the drawings.
[0015]
(Embodiment 1)
FIG. 1 is a cross-sectional view schematically showing a liquid crystal display device 1 according to the first embodiment.
[0016]
The liquid crystal display device 1 has a pair of substrate portions 2 and 3 arranged so as to be parallel to each other, and a liquid crystal having a negative dielectric anisotropy is interposed between the pair of substrate portions 2 and 3. A liquid crystal layer 4 is formed by filling molecules (not shown).
[0017]
The first substrate unit 2 includes a transparent glass substrate 21, and a plurality of first transparent electrodes 22 are formed on the surface of the glass substrate 21 facing the liquid crystal layer 4 by indium tin oxide (ITO). ) Or the like.
[0018]
On the glass substrate 21, polymer walls 23 projecting to a predetermined height are provided in a lattice shape. The polymer wall 23 has a constant thickness on the glass substrate 21 and is transparently formed of a transparent resin material or the like, and a resin material having a light shielding property on both sides of the flat portion 23b. And an inclined portion 23a formed. The inclined portion 23a is inclined so as to become thinner gradually as the distance from the flat portion 23b increases.
[0019]
The polymer wall 23 surrounds the liquid crystal molecules of the liquid crystal layer 4 on the glass substrate 21 for each of the plurality of liquid crystal regions 4a, and has an action of orienting the liquid crystal molecules separated into the respective liquid crystal regions 4a. is doing. In order to generate a sufficient axially symmetric alignment regulating force for the liquid crystal molecules in the liquid crystal region 4a, the height of the polymer wall 23 may be 0.5 μm or more. In the first embodiment, the height of the polymer wall 23 is set to 1.0 μm in consideration of the manufacturing margin. Further, the inclination angle of the inclined portion 23 a of the polymer wall 23 was formed so as to have an angle of 3 degrees to 45 degrees with respect to the glass substrate 21. If the range of the inclination angle of the inclined portion 23a is such a range, the disorder of alignment of liquid crystal molecules is not observed in the vicinity of the boundary portion between the inclined portion 23a of the polymer wall 23 and the first transparent electrode 22.
[0020]
A plurality of columnar protrusions 24 are provided in a discrete state on the flat portion 23 b of the polymer wall 23. Each columnar protrusion 24 is formed at a predetermined height in a portion corresponding to a region on the glass substrate 21 where the first transparent electrode 22 is not formed. In the first embodiment, each columnar protrusion 24 is formed to have a height of 5 μm.
[0021]
The liquid crystal molecules of the liquid crystal layer 4 are formed on the first transparent electrode 22 and the polymer wall 23 and the columnar protrusion 24 provided on the first substrate unit 2 so as to cover at least the first transparent electrode 22 and the polymer wall 23. A vertical alignment film 25 is provided for aligning in the vertical direction with respect to each surface.
[0022]
The second substrate unit 3 has a glass substrate 31, and on the surface of the glass substrate 31 facing the liquid crystal layer 4, a second transparent electrode 32 is transparent such as indium tin oxide (ITO). It is formed of a conductive member. On the second transparent electrode 32, a vertical alignment film 33 for aligning the liquid crystal molecules of the liquid crystal layer 4 perpendicularly to the surface of the second substrate unit 3 is provided so as to cover the entire surface.
[0023]
The first substrate portion 2 and the second substrate portion 3 having the above structure are bonded together, and a liquid crystal material having negative dielectric anisotropy is injected into the gap between the pair of substrate portions 2 and 3 by a vacuum injection method. A liquid crystal layer 4 is formed. The thickness (liquid crystal cell gap) of the liquid crystal layer 4 is defined by the sum of the height of the polymer wall 23 of the first substrate portion 2 and the height of the columnar protrusion 24. The height of the columnar protrusions 24 (5 μm) is sufficiently high with respect to the height of the polymer wall 23 (1.0 μm), so that liquid crystal molecules are also arranged on the polymer wall 23. It has become.
[0024]
Known electrode configurations and driving methods can be used for the configuration of the first transparent electrode 22 and the second transparent electrode 32 for driving the liquid crystal layer 4a and the driving method thereof. For example, an active matrix type or a simple matrix type can be applied. Further, in place of such an active matrix type, a plasma address type can be applied by replacing either the first transparent electrode 22 or the second transparent electrode 32 with a plasma discharge channel. is there.
[0025]
Further, in the above configuration, the first substrate unit 2 and the second substrate unit 3 may be interchanged with respect to the applied electrode configuration and driving method. For example, a polymer is formed on the surface of the second substrate unit 3. The wall 23 and the columnar protrusion 24 may be provided.
[0026]
In the liquid crystal display device according to the first embodiment, the liquid crystal molecules on the flat portion 23b formed transparent in the polymer wall 23 can contribute to switching, so that the aperture ratio is improved and a bright display is realized. be able to.
[0027]
On the other hand, when no voltage is applied, the liquid crystal molecules of the liquid crystal layer 4 are aligned perpendicularly to the surfaces of the first transparent electrode 22 and the polymer wall 23 by the alignment regulating force of the vertical alignment film 25, and black. Display state. In this case, in the inclined portion 23 a of the polymer wall 23, as shown in FIG. 2, each liquid crystal molecule 40 of the liquid crystal layer 4 is shifted from the normal direction with respect to the surface of the first substrate portion 2. However, in the liquid crystal display device according to the first embodiment, the inclined portion 23a of the polymer wall 23 has a light-shielding property, although it is easy to cause light leakage at the inclined portion 23a particularly at an oblique viewing angle. Because it is formed so as not to transmit light, no light leakage is observed.
[0028]
In this case, light leakage from the inclined portion 23a can be sufficiently suppressed if the optical density (OD) value expressed by the following equation (1) is 1 or more. As such a light-shielding material, a resin black matrix material used for forming the color filter portion can be used.
[0029]
Optical density (OD value) = − log 10 (transmittance) (1)
(Embodiment 2)
Since the liquid crystal display device of the second embodiment has substantially the same configuration as that of the liquid crystal display device of the first embodiment shown in FIG. 1, only different configurations will be described below.
[0030]
FIG. 3 is a cross-sectional view illustrating a schematic configuration of the polymer wall portion of the liquid crystal display device according to the second embodiment.
[0031]
The polymer wall 23 of the liquid crystal display device includes a flat portion 23b whose height from the first transparent electrode 22 is constant, and an inclined portion provided on both sides of the flat portion 23b. 23a is transparently provided by a transparent resin member or the like. The inclined portion 23a is formed so as to become thinner at a constant inclination angle in order as the distance from the flat portion 23b increases. A light-shielding resin material 26 is provided over the entire surface of the inclined portion 23a on the inclined portion 23a formed to be transparent. The resin material 26 is also provided on the flat portion 23b so as to overlap only a small size portion in the vicinity of the inclined portion 23a in the flat portion 23b. The film thickness of the light shielding resin member 26 is set so that the optical density is 1 or more.
[0032]
In this case, the height h1 from the surface of the first transparent electrode 22 in the region where the light-shielding material 26 on the flat portion 23b of the polymer wall 23 is provided is such that the light-shielding material 26 on the flat portion 23b is provided. The height h <b> 2 from the surface of the first transparent electrode 22 in the unexposed area is higher, and the stepped portion 27 is formed.
[0033]
FIG. 4 is a plan view of the liquid crystal display device according to the second embodiment viewed from the second substrate unit 3 side.
[0034]
In the liquid crystal display device according to the second embodiment, the liquid crystal molecules of the liquid crystal layer 4 are axially symmetric by being surrounded by the polymer wall 23 in the liquid crystal region 4a as shown in FIG. Oriented. Further, the liquid crystal molecules existing on the flat portion 23b of the polymer wall 23 are axially symmetrically aligned by receiving the alignment regulating force from the axially symmetrical liquid crystal molecules in the liquid crystal region 4a.
[0035]
As a result, the inclined portion 23a of the polymer wall 23 has a light-shielding property, so that light leakage at the inclined portion 23a is prevented, particularly at an oblique viewing angle, and a high contrast ratio is realized. A liquid crystal display device having a wide viewing angle characteristic can be obtained.
[0036]
Further, in the liquid crystal display device according to the second embodiment, the step portion 27 is formed on the flat portion 23b of the polymer wall 23, so that the liquid crystal molecules existing on the flat portion 23b of the polymer wall 23 are stepped. In response to the orientation regulating force from the portion 27, a more stable axisymmetric orientation is achieved. As described above, in addition to the alignment regulating force generated when the polymer wall 23 surrounds the liquid crystal region 4a, the alignment regulating force is generated by the stepped portion 27 generated on the flat portion 23b, thereby making it more powerful and stable. Since an alignment regulating force can be obtained, a margin for manufacturing variations and the like can be increased.
[0037]
【The invention's effect】
The liquid crystal display device of the present invention is a polymer that is formed in a lattice shape projecting to a predetermined thickness on at least one liquid crystal layer side of a pair of substrates, and divides the liquid crystal layer into a plurality of lattice liquid crystal regions. The wall has a flat portion that protrudes at a certain height with respect to the surface of one substrate, and an inclined portion that inclines at a constant inclination angle from the edge of the flat portion and reaches the surface of one substrate. The flat portion is formed so as to have translucency, and the inclined portion is formed so as to have a light shielding property. This prevents light leakage from the inclined portion of the polymer wall that distributes the liquid crystal molecules in the liquid crystal layer in an oblique direction with respect to the surface of the substrate, even when observed from an oblique direction during black display. High contrast and bright display can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram for explaining an alignment state of liquid crystal molecules aligned perpendicular to the surface of a polymer wall.
FIG. 3 is a cross-sectional view schematically showing a main part of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 4 is a plan view schematically showing a liquid crystal display device according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 2 1st board | substrate part 3 2nd board | substrate part 4 Liquid crystal layer 21 Glass substrate 22 1st transparent electrode 23 Polymer wall 24 Columnar protrusion 25 Vertical alignment film 31 Glass substrate 32 2nd transparent electrode 33 Vertical alignment film

Claims (4)

A pair of first and second substrates disposed opposite to each other;
A liquid crystal layer provided between the first substrate and the second substrate and formed of liquid crystal molecules having negative dielectric anisotropy;
A plurality of first transparent electrodes provided on a surface of the first substrate facing the liquid crystal layer;
A second transparent electrode that is provided on a surface of the second substrate facing the liquid crystal layer and that drives the liquid crystal layer with each of the first transparent electrodes;
Projecting on the liquid crystal layer side to a predetermined thickness on the first transparent electrode or the second transparent electrode facing the liquid crystal layer driven by the first transparent electrode and the second transparent electrode formed in a lattice shape, and the polymer walls dividing each grid a plurality of liquid crystal regions the liquid crystal layer,
The first transparent electrode and the polymer wall, and are formed respectively on the surface in contact with the liquid crystal layer in the second transparent electrode, and a vertical alignment layer for aligning the vertical liquid crystal molecules of the liquid crystal layer with respect to said surface A liquid crystal display device,
The polymer wall, said flat portion of the first transparent electrode or the second transparent electrode protrudes a predetermined height, the first transparent tilted at a predetermined inclination angle from the edge of the flat portion An inclined portion reaching the electrode or the second transparent electrode , the flat portion is formed to have translucency, and the inclined portion is formed to have a light shielding property. Liquid crystal display device. Wherein the flat portion and the inclined portion of the polymer wall is formed of a translucent material, a light-shielding material on a surface of the inclined portion is coated, a liquid crystal display device according to claim 1. The liquid crystal display device according to claim 1, wherein an optical density of the inclined portion of the polymer wall is 1 or more. The polymer wall, at the edge of the flat portion and the inclined portion, formed region so as to have a light shielding property, than the formation region so as to have a light-transmitting property, the first transparent electrode Or the liquid crystal display device in any one of Claims 1-3 currently formed so that the thickness from the said 2nd electrode may become thick.

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