JP3600531B2 - Liquid crystal display - Google Patents

Liquid crystal display Download PDF

Info

Publication number
JP3600531B2
JP3600531B2 JP2001038556A JP2001038556A JP3600531B2 JP 3600531 B2 JP3600531 B2 JP 3600531B2 JP 2001038556 A JP2001038556 A JP 2001038556A JP 2001038556 A JP2001038556 A JP 2001038556A JP 3600531 B2 JP3600531 B2 JP 3600531B2
Authority
JP
Japan
Prior art keywords
liquid crystal
layer
opening
crystal display
conductive layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
JP2001038556A
Other languages
Japanese (ja)
Other versions
JP2002055343A (en
Inventor
真澄 久保
和広 前川
明弘 山本
正悟 藤岡
貴志 越智
Original Assignee
シャープ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to JP2000049495 priority Critical
Priority to JP2000161588 priority
Priority to JP2000-161588 priority
Priority to JP2000-49495 priority
Application filed by シャープ株式会社 filed Critical シャープ株式会社
Priority to JP2001038556A priority patent/JP3600531B2/en
Priority claimed from US09/790,802 external-priority patent/US6924876B2/en
Publication of JP2002055343A publication Critical patent/JP2002055343A/en
Application granted granted Critical
Publication of JP3600531B2 publication Critical patent/JP3600531B2/en
Expired - Fee Related legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with high display quality. SOLUTION: The liquid crystal display device carries out a display by applying voltage to a liquid crystal layer, which is in a vertical alignment condition with no voltage application, with a first electrode and a second electrode. The first electrode has a lower conductive layer, a dielectric layer covering at least a part of the lower conductive layer 12 and an upper conductive layer 14 arranged on the liquid crystal layer side of the dielectric layer. The upper conductive layer has a first opening part. Furthermore, the lower conductive layer is arranged opposite to at least a part of the first opening part via the dielectric layer.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having characteristics of a wide viewing angle and performing high-quality display.
[0002]
[Prior art]
2. Description of the Related Art In recent years, a thin and lightweight liquid crystal display device has been used as a display device used for a display of a personal computer or a display unit of a portable information terminal device. However, the conventional twisted nematic (TN) and super twisted nematic (STN) liquid crystal display devices have a drawback of a narrow viewing angle, and various technical developments have been made to solve them. ing.
[0003]
As a typical technique for improving the viewing angle characteristics of a TN type or STN type liquid crystal display device, there is a method of adding an optical compensator. As another method, there is a lateral electric field method in which an electric field in a direction horizontal to the surface of the substrate is applied to the liquid crystal layer. This horizontal electric field type liquid crystal display device has been mass-produced in recent years and has been receiving attention. As another technique, there is a DAP (deformation of vertical aligned phase) in which a nematic liquid crystal material having negative dielectric anisotropy is used as a liquid crystal material and a vertical alignment film is used as an alignment film. This is one of the voltage controlled birefringence (ECB) methods, and controls the transmittance using the birefringence of liquid crystal molecules.
[0004]
[Problems to be solved by the invention]
However, although the in-plane switching method is one of the methods effective as a technique for widening the viewing angle, the production margin in the manufacturing process is significantly narrower than that of a normal TN type, so that stable production is difficult. is there. This is because unevenness in the gap between the substrates and deviation in the direction of the transmission axis (polarization axis) of the polarizing plate with respect to the alignment axis of the liquid crystal molecules greatly affects the display brightness and the contrast ratio. In order to achieve stable production, further technological development is required.
[0005]
Further, in order to perform uniform display without display unevenness in a DAP type liquid crystal display device, it is necessary to control the alignment. As a method of controlling the alignment, there is a method of performing an alignment treatment by rubbing the surface of the alignment film. However, when a rubbing treatment is performed on the vertical alignment film, rubbing streaks are easily generated in a display image, and thus the method is not suitable for mass production.
[0006]
On the other hand, as a method of controlling alignment without performing a rubbing process, a method of generating an oblique electric field by forming a slit (opening) in an electrode and controlling the orientation direction of liquid crystal molecules by the oblique electric field has been devised. (For example, JP-A-6-301036). However, as a result of the study by the present inventors, it has been found that this method has the following problems.
[0007]
If a configuration in which an oblique electric field is generated by forming a slit (opening) in the electrode is adopted, a sufficient voltage cannot be applied to the liquid crystal layer in a region corresponding to the slit formed in the electrode. There is a problem that the alignment of the liquid crystal molecules of the liquid crystal layer in the region corresponding to the slit cannot be sufficiently controlled, and a loss of transmittance occurs when a voltage is applied.
[0008]
The present invention has been made in order to solve the above problems, and has as its object to provide a liquid crystal display device having high display quality and a method of manufacturing the same.
[0009]
[Means for Solving the Problems]
A liquid crystal display device according to the present invention includes a first substrate, a second substrate, and a liquid crystal layer provided between the first substrate and the second substrate, wherein the first substrate has a liquid crystal layer side. And a plurality of picture element regions defined by a first electrode provided on the second substrate and a second electrode provided on the second substrate and facing the first electrode via the liquid crystal layer. Each liquid crystal layer in the region takes a vertical alignment state when no voltage is applied between the first electrode and the second electrode, and has a liquid crystal layer between the first electrode and the second electrode. Changes the alignment state according to the voltage applied to the first electrode, the first electrode, a lower conductive layer, a dielectric layer covering at least a part of the lower conductive layer, and a liquid crystal layer side of the dielectric layer And an upper conductive layer provided, wherein the upper conductive layer has at least one first opening, and Conductive layer includes the provided way through the dielectric layer to face at least a portion of said at least one first opening, by the above-described object is achieved. The upper conductive layer having the first opening generates an oblique electric field at the edge of the first opening and acts to radially tilt the liquid crystal molecules. Further, since an electric field is applied to the region facing the first opening by the lower conductive layer, the alignment of the liquid crystal molecules located on the first opening is stabilized.
[0010]
It is preferable that the lower conductive layer is provided in a region including a region facing the at least one first opening via the dielectric layer. An electric field can be effectively applied to the liquid crystal layer located on the first opening.
[0011]
The at least one first opening may be square or circular.
[0012]
The at least one first opening of the upper conductive layer is preferably a plurality of first openings. When a configuration having a plurality of first openings is employed, a stable radially inclined orientation can be formed over the entire picture element region. In addition, a decrease in response speed can be suppressed.
[0013]
It is preferable that the plurality of first openings of the upper conductive layer are regularly arranged. In particular, it is preferable to arrange the plurality of first openings so as to have rotational symmetry.
[0014]
The dielectric layer may have a recess or a hole in the at least one first opening. When a configuration having a concave portion or a hole in the dielectric layer is employed, a voltage drop due to the dielectric layer can be suppressed. In addition, the thickness of the liquid crystal layer can be adjusted.
[0015]
The lower conductive layer may have a second opening in a region facing the first opening. The second opening acts to stabilize the center of the radially tilted orientation of the liquid crystal layer in the first opening.
[0016]
One of the upper conductive layer and the lower conductive layer may be a transparent conductive layer, and the other may be a reflective conductive layer. In particular, if a configuration in which the upper conductive layer is a reflective electrode and the lower conductive layer is a transparent electrode is employed, it is possible to optimize the transmission mode display characteristics and the reflection mode display characteristics.
[0017]
The at least one first opening of the upper conductive layer is a plurality of first openings and is formed in the first electrode by a voltage applied between the first electrode and the second electrode. It is preferable that the liquid crystal layer in a region facing the plurality of first openings is formed with a plurality of liquid crystal domains each in a radially inclined alignment state.
[0018]
The second substrate has an alignment exhibiting an alignment control force that causes liquid crystal molecules in the at least one liquid crystal domain to be radially tilt-aligned at least in a voltage applied state in a region corresponding to at least one liquid crystal domain of the plurality of liquid crystal domains. It is good also as composition which further has a regulation structure.
[0019]
It is preferable that the alignment control structure is provided in a region corresponding to the vicinity of the center of the at least one liquid crystal domain.
[0020]
In the at least one liquid crystal domain, it is preferable that an alignment control direction by the alignment control structure matches a direction of the radial tilt alignment.
[0021]
The alignment control structure may be configured to exhibit an alignment control force for radially tilting the liquid crystal molecules even when no voltage is applied.
[0022]
The alignment control structure may be a protrusion protruding toward the liquid crystal layer of the second substrate.
[0023]
The alignment control structure may include a horizontal alignment surface provided on the liquid crystal layer side of the second substrate.
[0024]
The alignment control structure may be configured to exhibit an alignment control force for radially tilting the liquid crystal molecules only in a voltage application state.
[0025]
The alignment control structure may include an opening provided in the second electrode.
[0026]
The liquid crystal display may further include a pair of polarizing plates provided to face each other with the liquid crystal layer interposed therebetween, and the pair of polarizing plates may be arranged in a crossed Nicols state.
[0027]
The liquid crystal display further includes a pair of quarter-wave plates provided so as to face each other with the liquid crystal layer interposed therebetween, and each of the pair of quarter-wave plates includes the liquid crystal layer and the pair of polarizing plates. It is preferable to adopt a configuration arranged between them.
[0028]
The liquid crystal display further includes a pair of half-wave plates provided so as to face each other with the liquid crystal layer interposed therebetween, and each of the pair of half-wave plates includes the pair of polarizing plates and the pair of half-wave plates. It is further preferable to adopt a configuration arranged between each of the quarter-wave plates.
[0029]
It is preferable that the slow axes of the pair of quarter-wave plates are arranged to be orthogonal to each other.
[0030]
It is preferable that the slow axes of the pair of half-wave plates are arranged to be orthogonal to each other.
[0031]
It is preferable that each of the liquid crystal layers in the plurality of picture element regions be in a spiral alignment state by a voltage applied between the first electrode and the second electrode.
[0032]
Each of the liquid crystal layers in the plurality of picture element regions may include a minute region which takes a twist alignment state along the liquid crystal layer by a voltage applied between the first electrode and the second electrode. More preferred.
[0033]
The first substrate further includes an active element provided corresponding to each of the plurality of picture element areas, and the first electrode is provided for each of the plurality of picture element areas, and is switched by the active element. The second electrode may be at least one counter electrode facing the plurality of pixel electrodes. The counter electrode is typically a single electrode.
[0034]
Another liquid crystal display device according to the present invention includes a first substrate, a second substrate, and a liquid crystal layer provided between the first substrate and the second substrate. A plurality of picture element regions each defined by a first electrode provided on the layer side and a second electrode provided on the second substrate and facing the first electrode via the liquid crystal layer; The first electrode includes a lower conductive layer, a dielectric layer covering at least a part of the lower conductive layer, and an upper conductive layer provided on the liquid crystal layer side of the dielectric layer. In each of the pixel regions, the upper conductive layer has a plurality of openings and a solid portion, and the liquid crystal layer has a voltage applied between the first electrode and the second electrode. A vertical alignment state when no voltage is applied, and a voltage is applied between the first electrode and the second electrode An oblique electric field generated at an edge of the plurality of openings of the upper conductive layer forms a plurality of liquid crystal domains, each of which takes a radially inclined alignment state, in the plurality of openings or the solid portion, The liquid crystal display device has a configuration in which display is performed by changing the alignment state of the plurality of liquid crystal domains according to the applied voltage, thereby achieving the above object.
[0035]
Preferably, at least some of the plurality of openings have substantially the same shape and size, and form at least one unit cell arranged to have rotational symmetry.
[0036]
The shape of each of the at least some of the plurality of openings preferably has rotational symmetry.
[0037]
Each of the at least some of the plurality of openings may be substantially circular.
[0038]
The solid portion may include a plurality of unit solid portions each substantially surrounded by the at least one opening, and each of the plurality of unit solid portions may be substantially circular.
[0039]
In each of the plurality of picture element regions, the total area of the plurality of openings of the first electrode is preferably smaller than the area of the solid portion of the first electrode.
[0040]
A projection is further provided inside each of the plurality of openings, and a cross-sectional shape of the projection in an in-plane direction of the substrate is the same as a shape of the plurality of openings, and a side surface of the projection is The liquid crystal layer of the liquid crystal layer may have an alignment control force in the same direction as the alignment control direction by the oblique electric field.
[0041]
The first substrate further includes an active element provided corresponding to each of the plurality of picture element areas, and the first electrode is provided for each of the plurality of picture element areas, and is switched by the active element. The second electrode may be at least one counter electrode facing the plurality of pixel electrodes. The counter electrode is typically a single electrode.
[0042]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0043]
(Embodiment 1)
First, the electrode structure of the liquid crystal display device of the present invention and its operation will be described. Since the liquid crystal display device according to the present invention has excellent display characteristics, it is suitably used for an active matrix type liquid crystal display device. Hereinafter, an embodiment of the present invention will be described for an active matrix liquid crystal display device using a thin film transistor (TFT). The present invention is not limited to this, and can be applied to an active matrix liquid crystal display device and a simple matrix liquid crystal display device using MIM. In the following, embodiments of the present invention will be described by taking a transmissive liquid crystal display device as an example. However, the present invention is not limited to this, and is applicable to a reflective liquid crystal display device and a transflective liquid crystal display device described later. Can be applied.
[0044]
In the specification of the present application, a region of the liquid crystal display device corresponding to a "picture element" which is a minimum unit of display is referred to as a "picture element region". In the color liquid crystal display device, “picture elements” of R, G, and B correspond to one “pixel”. In an active matrix type liquid crystal display device, a picture element region defines a picture element region by a picture element electrode and a counter electrode facing the picture element electrode. In a simple matrix type liquid crystal display device, each region where a column electrode provided in a stripe shape and a row electrode provided orthogonal to the column electrode intersects each other defines a picture element region. Note that, in the configuration in which the black matrix is provided, strictly speaking, of the regions to which the voltage is applied according to the state to be displayed, the region corresponding to the opening of the black matrix corresponds to the pixel region. .
[0045]
FIG. 1 schematically shows a cross section of one picture element region of the liquid crystal display device 100 according to the embodiment of the present invention. Hereinafter, a color filter and a black matrix are omitted for simplicity of description. In the following drawings, components having substantially the same functions as those of the liquid crystal display device 100 are denoted by the same reference numerals, and the description thereof is omitted. Note that, for the sake of simplicity, FIG. 1 shows one picture element region of the liquid crystal display device 100, but as will be described in detail later, the liquid crystal display device according to the present invention has the electrode configuration shown in FIG. It is sufficient that at least one pixel is provided in one pixel region.
[0046]
The liquid crystal display device 100 is provided between an active matrix substrate (hereinafter, referred to as “TFT substrate”) 100a, a counter substrate (also referred to as “color filter substrate”) 100b, and the TFT substrate 100a and the counter substrate 100b. And a liquid crystal layer 30. The liquid crystal molecules 30a of the liquid crystal layer 30 have a negative dielectric anisotropy, and are formed by a vertical alignment layer (not shown) provided on the surface of the TFT substrate 100a and the counter substrate 100b on the liquid crystal layer 30 side. When no voltage is applied to the vertical alignment film, as shown in FIG. At this time, the liquid crystal layer 30 is said to be in a vertical alignment state. However, the liquid crystal molecules 30a of the liquid crystal layer 30 in the vertical alignment state may be slightly inclined from the normal of the surface of the vertical alignment film (the surface of the substrate) depending on the type of the vertical alignment film and the type of the liquid crystal material. In general, a state in which a liquid crystal molecular axis (also referred to as “axial direction”) is oriented at an angle of about 85 ° or more with respect to the surface of a vertical alignment film is called a vertical alignment state.
[0047]
The TFT substrate 100a of the liquid crystal display device 100 has a transparent substrate (for example, a glass substrate) 11 and picture element electrodes 15 formed on the surface thereof. The counter substrate 100b has a transparent substrate (for example, a glass substrate) 21 and a counter electrode 22 formed on the surface thereof. The alignment state of the liquid crystal layer 30 for each picture element region changes according to the voltage applied to the picture element electrode 15 and the counter electrode 22 arranged to face each other with the liquid crystal layer 30 interposed therebetween. Display is performed using a phenomenon in which the polarization state and amount of light transmitted through the liquid crystal layer 30 change with the change in the alignment state of the liquid crystal layer 30.
[0048]
The pixel electrode 15 included in the liquid crystal display device 100 includes a lower conductive layer 12, a dielectric layer 13 covering at least a part of the lower conductive layer 12, and an upper conductive layer 14 provided on the liquid crystal layer 30 side of the dielectric layer. And In the liquid crystal display device 100 shown in FIG. 1, the lower conductive layer 12 is formed in a region including the entire region on the substrate 11 facing the opening 14a (the area of the lower conductive layer 12> the area of the opening 14a). ).
[0049]
The configuration of the picture element electrode 15 in the liquid crystal display device of the present embodiment is not limited to the above example, and may be formed on the substrate 11 facing the opening 14a as in the liquid crystal display device 100 'shown in FIG. (The area of the lower conductive layer 12 = the area of the opening 14a). Further, as in a liquid crystal display device 100 ″ shown in FIG. 2B, the lower conductive layer 12 may be formed in a region on the substrate 11 facing the opening 14a (the area of the lower conductive layer 12 < Area of opening 14a). That is, the lower conductive layer 12 may be provided so as to face at least a part of the opening 14a via the dielectric layer 13. However, in the configuration in which the lower conductive layer 12 is formed in the opening 14a (FIG. 2B), any one of the lower conductive layer 12 and the upper conductive layer 14 is placed in a plane viewed from the normal direction of the substrate 11. In some cases, there is a region (gaps region) in which no liquid crystal exists, and a sufficient voltage may not be applied to the liquid crystal layer 30 in a region facing the gap region. Therefore, it is preferable that the width of the gap region (WS in FIG. 2B) is sufficiently reduced so as to stabilize the orientation of the liquid crystal layer 30. Preferably, the WS typically does not exceed about 4 μm.
[0050]
The picture element electrode 15 including the lower conductive layer 12 and the upper conductive layer 14 may be referred to as a “two-layer electrode”. “Lower layer” and “upper layer” are terms used to express the relative relationship between the two electrodes 12 and 14 with respect to the dielectric layer 13 and limit the spatial arrangement of the liquid crystal display device during use. is not. Further, the "two-layer structure electrode" does not exclude a configuration having an electrode other than the lower conductive layer 12 and the upper conductive layer 14, and has at least the lower conductive layer 12 and the upper conductive layer 14, which will be described below. Any configuration having an effect may be used. Further, the two-layer structure electrode does not need to be a picture element electrode in a TFT type liquid crystal display device, and can be applied to other types of liquid crystal display devices if a two-layer structure electrode is provided for each picture element region. Specifically, for example, if a column electrode (signal electrode) in a simple matrix type liquid crystal display device has a two-layer structure for each pixel region, the column electrode in the pixel region functions as a two-layer structure electrode. .
[0051]
Next, the operation of the liquid crystal display device having the two-layer structure electrode will be described with reference to FIGS. 1, 3 and 4 while comparing the operation of the liquid crystal display device with the electrode of another configuration.
[0052]
First, the operation of the liquid crystal display device 100 will be described with reference to FIG.
[0053]
FIG. 1A schematically illustrates an alignment state (OFF state) of the liquid crystal molecules 30a in the liquid crystal layer 30 to which no voltage is applied. FIG. 1B schematically shows a state in which the orientation of the liquid crystal molecules 30a has started to change in accordance with the voltage applied to the liquid crystal layer 30 (ON initial state). FIG. 1C schematically shows a state in which the orientation of the liquid crystal molecules 30a changed according to the applied voltage has reached a steady state. FIG. 1 shows an example in which the same voltage is applied to the lower conductive layer 12 and the upper conductive layer 14 constituting the pixel electrode 15 for simplicity. Curves EQ in FIGS. 1B and 1C show equipotential lines EQ.
[0054]
As shown in FIG. 1A, when the pixel electrode 15 and the counter electrode 22 are at the same potential (when no voltage is applied to the liquid crystal layer 30), the liquid crystal molecules 30a in the pixel region are It is oriented perpendicular to the surfaces of both substrates 11 and 21.
[0055]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by an equipotential line EQ (perpendicular to the electric force lines) EQ shown in FIG. 1B is formed. The liquid crystal layer 30 located between the upper conductive layer 14 and the counter electrode 22 of the pixel electrode 15 is represented by an equipotential line EQ parallel to the surfaces of the upper conductive layer 14 and the counter electrode 22. A uniform potential gradient is formed. A potential gradient corresponding to the potential difference between the lower conductive layer 12 and the counter electrode 22 is formed in the liquid crystal layer 30 located above the opening 14 a of the upper conductive layer 14. At this time, the potential gradient formed in the liquid crystal layer 30 is affected by the voltage drop (capacity division) by the dielectric layer 13, so that the equipotential lines EQ formed in the liquid crystal layer 30 pass through the opening 14a. A drop occurs in the corresponding region (a “valley” is formed in the equipotential line EQ). Part of the equipotential line EQ penetrating into the dielectric layer 13 in a region corresponding to the opening 14a indicates that a voltage drop (capacity division) is caused by the dielectric layer 13. . Since the lower conductive layer 12 is formed in a region facing the opening 14a via the dielectric layer 13, the upper conductive layer 14 and the counter electrode are also provided in the liquid crystal layer 30 located near the center of the opening 14a. A potential gradient represented by an equipotential line EQ parallel to the plane 22 is formed (the “valley bottom” of the equipotential line EQ). An oblique electric field represented by an inclined equipotential line EQ is formed in the liquid crystal layer 30 on the edge of the opening 14a (the inner periphery of the opening 14a including the boundary (extension) of the opening 14a) EG. .
[0056]
A torque acts on the liquid crystal molecules 30a having a negative dielectric anisotropy so as to orient the axis direction of the liquid crystal molecules 30a parallel to the equipotential line EQ (perpendicular to the lines of electric force). Therefore, the liquid crystal molecules 30a on the edge portion EG are clockwise in the right edge portion EG in the drawing and counterclockwise in the left edge portion EG in the drawing, as shown by the arrow in FIG. In the directions, they incline (rotate), and are oriented parallel to the equipotential lines EQ.
[0057]
Here, the change in the alignment of the liquid crystal molecules 30a will be described in detail with reference to FIG.
[0058]
When an electric field is generated in the liquid crystal layer 30, a torque acts on the liquid crystal molecules 30a having negative dielectric anisotropy so as to orient the axis of the liquid crystal molecules 30a in parallel with the equipotential line EQ. As shown in FIG. 5A, when an electric field represented by an equipotential line EQ perpendicular to the axial direction of the liquid crystal molecules 30a is generated, the liquid crystal molecules 30a are tilted clockwise or counterclockwise. Acts with equal probability of torque. Therefore, as will be described later with reference to FIG. 3, the liquid crystal molecules 30a receiving clockwise torque and the liquid crystal molecules 30a in counterclockwise The liquid crystal molecules 30a receiving the torque are mixed. As a result, the change to the alignment state according to the voltage applied to the liquid crystal layer 30 may not occur smoothly.
[0059]
As shown in FIG. 1B, at the edge EG of the opening 14a of the liquid crystal display device 100 according to the present invention, an electric field (oblique) represented by an equipotential line EQ inclined with respect to the axial direction of the liquid crystal molecules 30a. When an electric field is generated, as shown in FIG. 5B, the liquid crystal molecules 30a are inclined in a direction in which the amount of inclination for becoming parallel to the equipotential line EQ is small (counterclockwise in the illustrated example). Further, the liquid crystal molecules 30a located in a region where an electric field generated by an equipotential line EQ perpendicular to the axis direction of the liquid crystal molecules 30a is generated as shown in FIG. The liquid crystal molecules 30a are tilted in the same direction as the liquid crystal molecules 30a positioned on the tilted equipotential lines EQ so that the alignment with the liquid crystal molecules 30a positioned on the line EQ is continuous (matched). Here, “located on the equipotential line EQ” means “located in the electric field represented by the equipotential line EQ”.
[0060]
As described above, the change in the alignment starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses, and when the liquid crystal molecules reach a steady state, the alignment state is schematically shown in FIG. 1C. Since the liquid crystal molecules 30a located near the center of the opening 14a are almost equally affected by the orientation of the liquid crystal molecules 30a at the opposite edge portions EG of the opening 14a, the liquid crystal molecules 30a are perpendicular to the equipotential lines EQ. The liquid crystal molecules 30a in a region away from the center of the opening 14a maintain the alignment state, and are inclined under the influence of the alignment of the liquid crystal molecules 30a at the near edge EG, and are symmetric with respect to the center SA of the opening 14a. Form a tilted orientation. This alignment state is such that, when viewed from a direction perpendicular to the display surface of the liquid crystal display device 100 (a direction perpendicular to the surfaces of the substrates 11 and 21), the axial orientation of the liquid crystal molecules 30a is radially aligned with respect to the center of the opening 14a. (Not shown). Therefore, in the specification of the present application, such an orientation state is referred to as “radially inclined orientation”.
[0061]
In order to improve the viewing angle dependence of the liquid crystal display device in all directions, it is preferable that the orientation of liquid crystal molecules in each pixel region has a rotational symmetry about an axis in a direction perpendicular to the display surface, More preferably, it has axial symmetry. Therefore, it is preferable that the openings 14a are arranged so that the orientation of the liquid crystal layer 30 in the picture element region has rotational symmetry (or axial symmetry). When one opening 14a is formed for each picture element region, the opening 14a is preferably provided at the center of the picture element region. The shape of the opening 14a (shape in the layer plane of the liquid crystal layer 30) preferably has rotational symmetry (axial symmetry), and is preferably a regular polygon such as a square or a circle. The arrangement when a plurality of openings 14a are formed in the picture element region will be described later.
[0062]
As described with reference to FIGS. 1A to 1C, the liquid crystal display device 100 according to the present invention has the two-layer structure electrode 15 for each pixel region, and the liquid crystal layer in the pixel region. An electric field represented by an equipotential line EQ having an inclined region is generated in 30. The liquid crystal molecules 30a having a negative dielectric anisotropy in the liquid crystal layer 30 in the vertical alignment state when no voltage is applied change their alignment directions by using the change in the alignment of the liquid crystal molecules 30a positioned on the inclined equipotential lines EQ as a trigger. To form a stable radial tilted orientation. Of course, the liquid crystal display devices 100 'and 100''shown in FIGS. 2A and 2B operate similarly. However, in the configuration of FIG. 2B, if the gap region WS is too large (for example, if it exceeds about 5 μm), a sufficient voltage is not applied to the edge portion of the opening 14a, and a region that does not contribute to display is displayed. Sometimes it becomes.
[0063]
Next, the operation of the conventional typical liquid crystal display device 200 will be described with reference to FIG. FIGS. 3A to 3C schematically show one picture element region of the liquid crystal display device 200. FIG.
[0064]
The liquid crystal display device 200 has a picture element electrode 15A and a counter electrode 22 arranged to face each other. Each of the picture element electrode 15A and the counter electrode 22 is formed of a single conductive layer having no opening 14a.
[0065]
As shown in FIG. 3A, when no voltage is applied to the liquid crystal layer 30, the liquid crystal layer 30 assumes a vertical alignment state.
[0066]
The electric field generated by applying a voltage to the liquid crystal layer 30 is parallel to the surface of the pixel electrode 15A and the surface of the counter electrode 22 over the entire pixel region as shown in FIG. It is represented by an equipotential line EQ. At this time, the liquid crystal molecules 30a try to change the alignment direction so that the axis direction is parallel to the equipotential line EQ. However, in an electric field in which the axis direction of the liquid crystal molecules 30a is orthogonal to the equipotential line EQ. As shown in FIG. 5A, the direction in which the liquid crystal molecules 30a incline (rotate) is not uniquely determined. The liquid crystal molecules 30a typically start to tilt in various directions under the influence of the local difference in the surface state of the vertical alignment film. As a result, the alignment state of the liquid crystal molecules 30a differs between the plurality of picture element regions, and the display by the liquid crystal display device 200 becomes a rough display. Further, it takes a longer time for the alignment state of the liquid crystal layer 30 to reach the steady state shown in FIG. 3C than in the liquid crystal display device 100 of the present invention described above.
[0067]
That is, the liquid crystal display device 100 of the present invention is characterized by being capable of performing high-quality display without roughness and having a high response speed, as compared with the conventional liquid crystal display device 200.
[0068]
Next, the operation of the liquid crystal display device 300 having the opening 15b in the picture element electrode 15B will be described with reference to FIG. The picture element electrode 15B is constituted by a single electrode having an opening 15b, and differs from the picture element electrode 15 of the liquid crystal display device of the present invention in not having the lower conductive layer 12 (for example, see FIG. 1). . The liquid crystal display device 300 generates an oblique electric field in the liquid crystal layer 30 as in the liquid crystal display device disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Hei 6-301036, which has the opening 14a in the counter electrode.
[0069]
As shown in FIG. 4A, the liquid crystal layer 30 of the liquid crystal display device 300 assumes a vertical alignment state when no voltage is applied. The alignment state of the liquid crystal layer 30 when no voltage is applied is the same as that of the liquid crystal display device of the present invention (FIGS. 1 and 2) and the conventional typical liquid crystal display device (FIG. 3).
[0070]
When a voltage is applied to the liquid crystal layer 30, an electric field represented by an equipotential line EQ shown in FIG. 4B is generated. Since the picture element electrode 15B has an opening 15b like the picture element electrode 15 (for example, see FIG. 1) of the liquid crystal display device 100 of the present embodiment, equipotential lines generated in the liquid crystal layer 30 of the liquid crystal display device 200 are provided. The EQ drops in a region corresponding to the opening 15b, and an oblique electric field represented by an inclined equipotential line EQ is formed in the liquid crystal layer 30 on the edge EG of the opening 15b. However, the pixel electrode 15B is formed from a single conductive layer, and does not have a lower conductive layer (the same potential as the pixel electrode) in a region corresponding to the opening 15b, and thus is located on the opening 15b. In the liquid crystal layer 30, there is a region where an electric field is not generated (a region where the equipotential lines EQ are not drawn).
[0071]
The liquid crystal molecules 30a having a negative dielectric anisotropy placed under an electric field as described above behave as follows. First, as shown by the arrow in FIG. 4B, the liquid crystal molecules 30a on the edge portion EG of the opening 15b are clockwise in the right edge portion EG in the figure and leftward in the diagram. Then, they tilt (rotate) in the counterclockwise direction, and are oriented parallel to the equipotential lines EQ. This is the same behavior as the liquid crystal molecules 30a in the liquid crystal display device 100 of the present embodiment described with reference to FIG. 1B, and the tilt (rotation) direction of the liquid crystal molecules 30a near the edge EG is unambiguous. The orientation can be determined stably and the orientation can be changed stably.
[0072]
However, since no electric field is generated in the liquid crystal layer 30 located above the region of the opening 15b other than the edge EG, no torque for changing the alignment is generated. As a result, even if the alignment change of the liquid crystal layer 30 reaches a steady state after a sufficient time has elapsed, as shown in FIG. 4C, the liquid crystal layer 30 is located above the region excluding the edge EG of the opening 15b. The liquid crystal layer 30 remains in the vertical alignment state. Of course, under the influence of the change in the orientation of the liquid crystal molecules 30a in the vicinity of the edge EG, some of the liquid crystal molecules 30a change their orientation. It cannot change. The distance from the end of the opening 15b to the position of the liquid crystal molecules 30a depends on the thickness of the liquid crystal layer 30 and the physical properties of the liquid crystal material (magnitude of dielectric anisotropy, elastic modulus, etc.). If the distance between the regions where the conductive layers actually exist adjacent to each other via the opening 15b (also referred to as a “solid portion”) exceeds about 4 μm, the liquid crystal molecules near the center of the opening 15b 30a maintains the vertical alignment without changing the alignment by the electric field. Therefore, the region located on the opening 15b in the liquid crystal layer 30 of the liquid crystal display device 300 does not contribute to the display, so that the display quality is reduced. For example, in a normally black display mode, the effective aperture ratio decreases and the display luminance decreases.
[0073]
As described above, in the liquid crystal display device 300, the direction in which the orientation of the liquid crystal molecules 30a changes is uniquely determined by the oblique electric field formed by the pixel electrodes 15B having the openings 15b. Although the roughness of the display that occurs in the display device 200 can be prevented, the brightness is reduced. Since the liquid crystal display device 100 of the present embodiment includes the upper conductive layer 14 having the opening 14a and the lower electrode 12 provided so as to face the opening 14a, the liquid crystal layer 30 located on the opening 14a An electric field can be applied to almost all regions to contribute to display. Therefore, the liquid crystal display device 100 of the present embodiment can realize high-quality display with high luminance and no roughness.
[0074]
The shape (the shape viewed from the normal direction of the substrate) of the opening 14a of the upper conductive layer 14 of the two-layer structure electrode (picture element electrode) 15 included in the liquid crystal display device of the present embodiment will be described. The shape of the opening 14a may be a polygon, a circle or an ellipse.
[0075]
The display characteristics of a liquid crystal display device show azimuth dependence depending on the alignment state (optical anisotropy) of liquid crystal molecules. In order to reduce the azimuth angle dependency of the display characteristics, it is preferable that the liquid crystal molecules are aligned with equal probability for all azimuth angles. Further, it is more preferable that the liquid crystal molecules in each picture element region are oriented with equal probability for all azimuth angles. Therefore, it is preferable that the opening 14a has a shape such that the liquid crystal molecules in each picture element region are oriented with equal probability at all azimuth angles. Specifically, the shape of the opening 14a preferably has rotational symmetry with the center (normal direction) of the picture element region as the axis of symmetry. It is more preferred to have an axis of high rotational symmetry of two or more rotation axes.
[0076]
The alignment state of the liquid crystal molecules 30a when the shape of the opening 14a is a polygon will be described with reference to FIGS. 6 (a) to 6 (c). FIGS. 6A to 6C schematically show the alignment states of the liquid crystal molecules 30a as viewed from the normal direction of the substrate. In FIGS. 6B and 6C, which show the alignment state of the liquid crystal molecules 30a viewed from the normal direction of the substrate, the ends of the liquid crystal molecules 30a drawn in an elliptical shape are indicated by black ends. This indicates that the liquid crystal molecules 30a are inclined such that the end is closer to the substrate side where the two-layer electrode having the opening 14a is provided than the other end. The same applies to the following drawings.
[0077]
Here, a structure in which a rectangular opening 14a is formed corresponding to a rectangular (including a square and a rectangular) picture element region will be described as an example. A sectional view taken along line 1A-1A 'in FIG. 6A corresponds to FIG. 1A, and a sectional view taken along line 1B-1B' in FIG. 6B is shown in FIG. 6C, and a cross-sectional view taken along line 1C-1C ′ in FIG. 6C corresponds to FIG. This will be described with reference to FIGS. 1 (a) to 1 (c). Of course, the shape of the pixel region (pixel electrode 15) is not limited to this.
[0078]
When the pixel electrode 15 having the lower conductive layer 12 and the upper conductive layer 14 and the counter electrode 22 are at the same potential, that is, when no voltage is applied to the liquid crystal layer 30, the liquid crystal of the TFT substrate 100a and the counter substrate 100b The liquid crystal molecules 30a whose alignment direction is regulated by a vertical alignment layer (not shown) provided on the surface of the layer 30 have a vertical alignment state as shown in FIG.
[0079]
When an electric field is applied to the liquid crystal layer 30 and an electric field represented by the equipotential line EQ shown in FIG. 1A is generated, the liquid crystal molecules 30a having a negative dielectric anisotropy have an axial orientation of equipotential. A torque is generated so as to be parallel to the line EQ. As described with reference to FIGS. 5A and 5B, the liquid crystal molecules 30a under an electric field represented by an equipotential line EQ perpendicular to the molecular axis of the liquid crystal molecules 30a have tilted liquid crystal molecules 30a. Since the direction of (rotation) is not uniquely determined (FIG. 5 (a)), the change of the orientation (tilt or rotation) does not easily occur, whereas the orientation of the liquid crystal molecule 30a is inclined. Since the tilt (rotation) direction of the liquid crystal molecules 30a placed below the potential line EQ is uniquely determined, the alignment easily changes. In the structure shown in FIG. 6, the liquid crystal molecules 30a start to tilt from the four edges of the rectangular opening 14a of the upper conductive layer 14 in which the molecular axis of the liquid crystal molecules 30a is tilted with respect to the equipotential line EQ. Then, as described with reference to FIG. 5C, the surrounding liquid crystal molecules 30a are also tilted so as to match the alignment of the liquid crystal molecules 30a with the tilted edges of the openings 14a. As shown in ()), the axial orientation of the liquid crystal molecules 30a is stabilized (radial tilt alignment).
[0080]
As described above, if the opening 14a of the upper conductive layer 14 is not a slit shape (a shape in which the width (the direction orthogonal to the length) is extremely narrow with respect to the length) but a rectangular shape, the inside of the pixel region may be reduced. When the voltage is applied, the liquid crystal molecules 30a are inclined from the four edges of the opening 14a toward the center of the opening 14a, so that the alignment control force of the liquid crystal molecules 30a from the edges balances. The liquid crystal molecules 30a near the center of the aperture 14a maintain a state of being oriented perpendicular to the substrate surface, and the liquid crystal molecules 30a around the liquid crystal molecules 30a are continuously arranged radially around the liquid crystal molecule 30a near the center of the opening 14a. Thus, a state of being inclined gradually is obtained. As described above, when the liquid crystal molecules 30a take a radially inclined orientation for each picture element region, the existence probabilities of the liquid crystal molecules 30a in the respective axis directions become substantially equal in all the viewing angle directions (including the azimuth directions). In addition, it is possible to realize a high-quality display without roughness in any viewing angle direction.
[0081]
Further, when the shape of the opening 14a is a square having high rotational symmetry (having a four-time rotation axis), the center of the opening 14a is more symmetrical than a rectangle having a low rotational symmetry (having a two-time rotation axis). , The symmetry of the radially inclined alignment of the liquid crystal molecules 30a is increased, so that a favorable display with less roughness in the viewing angle direction can be realized. Although the shape of the opening 14a is rectangular, other polygons may be used as long as the liquid crystal molecules 30a inside the opening 14a have a stable radially inclined orientation when a voltage is applied. Is more preferable.
[0082]
The radial tilt alignment of the liquid crystal molecules 30a is more counterclockwise or clockwise as shown in FIGS. 8B and 8C than the simple radial tilt alignment as shown in FIG. The spiral radial oblique orientation is more stable. Here, the spiral alignment indicates an alignment state of liquid crystal molecules in a liquid crystal layer plane (substrate plane). The spiral alignment observed when a small amount of a chiral agent is added to a liquid crystal material is that the alignment direction of the liquid crystal molecules 30a almost changes spirally along the thickness direction of the liquid crystal layer 30 as in a normal twist alignment. When the orientation direction of the liquid crystal molecules 30a is viewed in a minute region, there is almost no change along the thickness direction of the liquid crystal layer 30. That is, the cross section at any position in the thickness direction of the liquid crystal layer 30 (cross section in a plane parallel to the layer surface) is in the same alignment state as in FIG. 8B or FIG. There is almost no twist deformation along the vertical direction. However, a certain amount of twist deformation occurs in the entire opening 14a.
[0083]
When a material obtained by adding a chiral agent to a nematic liquid crystal material having a negative dielectric anisotropy is used, as shown in FIGS. 7A and 7B, when a voltage is applied, the liquid crystal molecules 30a open the opening 14a. It takes a counterclockwise or clockwise spiral radially inclined orientation at the center. Whether clockwise or counterclockwise depends on the type of chiral agent used. Therefore, the liquid crystal layer 30 in the opening 14a is spirally and radially inclined when voltage is applied, so that the liquid crystal molecules 30a that are radially inclined are wound around the liquid crystal molecules 30a that stand perpendicular to the substrate surface. Since the direction can be made constant in all the openings 14a, uniform display without roughness can be achieved. Further, since the direction of winding around the liquid crystal molecules 30a standing perpendicular to the substrate surface is determined, the response speed when a voltage is applied to the liquid crystal layer 30 is also improved.
[0084]
Furthermore, when many chiral agents are added, even in the liquid crystal layer in the spiral alignment state, when attention is paid to the minute region, the alignment of the liquid crystal molecules 30a along the thickness direction of the liquid crystal layer 30 is changed as in the normal twist alignment. It changes spirally.
[0085]
In an alignment state in which the alignment of the liquid crystal molecules 30a does not change spirally along the thickness direction of the liquid crystal layer 30, the liquid crystal molecules 30a that are aligned in a direction perpendicular or parallel to the polarization axis of the polarizer are incident light. Since no phase difference is given to the incident light, incident light passing through the region in such an alignment state does not contribute to the transmittance. For example, when observing a picture element region in a white display state of a liquid crystal display device in which a polarizing plate is arranged in a crossed Nicol state, a cross quenching pattern is clearly observed at the center of a liquid crystal domain in a radially inclined alignment.
[0086]
On the other hand, in the alignment state in which the alignment of the liquid crystal molecules 30a changes spirally along the thickness direction of the liquid crystal layer 30, the liquid crystal molecules 30a that are aligned in a direction perpendicular or parallel to the polarization axis of the polarizing plate are also changed. In addition to giving a phase difference to the incident light, the optical rotation of the light can be used. Accordingly, the incident light passing through the region in such an alignment state also contributes to the transmittance, so that a liquid crystal display device capable of bright display can be obtained. For example, when observing a picture element region in a white display state of a liquid crystal display device in which a polarizing plate is arranged in a crossed Nicols state, the extinction pattern of a cross in the center of a liquid crystal domain in a radially inclined orientation becomes unclear, and the whole becomes brighter. Become. The twist angle of the liquid crystal layer is preferably about 90 degrees in order to efficiently improve the light use efficiency due to the optical rotation.
[0087]
The shape of the opening 14a is not limited to the polygon described above, and may be a circle or an ellipse.
[0088]
The alignment state of the liquid crystal molecules 30a when the shape of the opening 14a is circular will be described with reference to FIGS. 9 (a) to 9 (c). FIGS. 9A to 9C schematically show the alignment state of the liquid crystal molecules 30a as viewed from the normal direction of the substrate. Here, a structure in which a circular opening 14a is formed in a rectangular picture element region will be described as an example. A cross-sectional view along line 1A-1A 'in FIG. 9A corresponds to FIG. 1A, and a cross-sectional view along line 1B-1B' in FIG. 9B is FIG. 9C, and a sectional view taken along line 1C-1C 'in FIG. 9C corresponds to FIG. This will be described with reference to FIGS. 1 (a) to 1 (c).
[0089]
When the pixel electrode 15 having the lower conductive layer 12 and the upper conductive layer 14 and the counter electrode 22 are at the same potential, that is, when no voltage is applied to the liquid crystal layer 30, the liquid crystal of the TFT substrate 100a and the counter substrate 100b The liquid crystal molecules 30a whose alignment direction is regulated by a vertical alignment layer (not shown) provided on the surface of the layer 30 have a vertical alignment state as shown in FIG.
[0090]
When an electric field is applied to the liquid crystal layer 30 and an electric field represented by the equipotential line EQ shown in FIG. 1A is generated, the liquid crystal molecules 30a having a negative dielectric anisotropy have an axial orientation of equipotential. A torque is generated so as to be parallel to the line EQ. As described with reference to FIGS. 5A and 5B, the liquid crystal molecules 30a under an electric field represented by an equipotential line EQ perpendicular to the molecular axis of the liquid crystal molecules 30a have tilted liquid crystal molecules 30a. Since the direction of (rotation) is not uniquely determined (FIG. 5 (a)), the change of the orientation (tilt or rotation) does not easily occur, whereas the orientation of the liquid crystal molecule 30a is inclined. Since the tilt (rotation) direction of the liquid crystal molecules 30a placed below the potential line EQ is uniquely determined, the alignment easily changes. In the structure shown in FIG. 9, the liquid crystal molecules 30a start to tilt from the circumferential edge of the circular opening 14a of the upper conductive layer 14 in which the molecular axis of the liquid crystal molecules 30a is tilted with respect to the equipotential line EQ. Then, as described with reference to FIG. 5C, the surrounding liquid crystal molecules 30a are also inclined so as to match the orientation of the liquid crystal molecules 30a having the inclined edges of the openings 14a. In the state shown in (1), the axis direction of the liquid crystal molecules 30a is stabilized (radial tilt alignment).
[0091]
As described above, when the opening 14a of the upper conductive layer 14 has a circular shape, the liquid crystal molecules 30a in the pixel region move from the edge of the circumference of the opening 14a to the center of the opening 14a when a voltage is applied. Since the liquid crystal molecules 30a incline toward the center, the liquid crystal molecules 30a near the center of the opening 14a where the alignment control force of the liquid crystal molecules 30a from the edge balances maintain a state of being aligned perpendicular to the substrate surface. Liquid crystal molecules 30a are continuously inclined radially around the liquid crystal molecules 30a near the center of the opening 14a (radially inclined alignment). When the shape of the opening 14a is circular, the center of the radially inclined alignment (the position of the liquid crystal molecules 30a aligned perpendicular to the substrate surface) is more stably formed at the center of the opening 14a than in the case of the square. A high-quality display without roughness can be realized in all directions when a voltage is applied.
[0092]
The effect of stabilizing the center position of the radially tilted orientation, which is obtained when the shape of the opening 14a is circular, is that the rotation symmetry of the circle is high and the edge of the opening 14a that determines the direction in which the liquid crystal molecules 30a tilt. Are continuous. The effect of stabilizing the radially inclined orientation due to the continuous edge of the opening 14a can be obtained even if the shape of the opening 14a is an ellipse (an ellipse).
[0093]
Note that the radially inclined alignment of the liquid crystal molecules 30a is further stabilized by imparting a spiral alignment as described above with reference to FIG. Therefore, as shown in FIG. 10A and FIG. 10B, it is more preferable to form a counterclockwise or clockwise spiral radially inclined orientation around the opening 14a. In particular, when the area of the opening 14a is large and the distance from the side of the opening 14a to the center is long, the alignment of the liquid crystal molecules 30a located in the opening 14a becomes difficult to stabilize. Is preferred. For example, by adding a chiral agent to a liquid crystal material, a spiral alignment can be imparted to the radial alignment.
[0094]
[Configuration having a plurality of openings]
In the above description, the configuration and operation of the two-layer structure electrode having an opening are described by taking the configuration having one opening for each pixel region as an example, but a plurality of openings may be provided for each pixel region. . Hereinafter, a configuration using a two-layered pixel electrode having a plurality of openings for each pixel region will be described.
[0095]
When a plurality of openings are provided for each pixel region, each of the plurality of openings has a rotational symmetry as described above so that the liquid crystal molecules in the pixel region take a uniform orientation in all directions. It is preferable that the plurality of openings have a rotational symmetry. Hereinafter, the configuration and operation of a liquid crystal display device having a two-layered picture element electrode in which a plurality of openings are arranged in each picture element area so as to have rotational symmetry will be described.
[0096]
FIG. 11 schematically illustrates a cross-sectional structure of one pixel region of a liquid crystal display device 400 including a pixel electrode 15 having a plurality of openings 14a (including 14a1 and 14a2). The liquid crystal display device 400 has a TFT substrate 400a and a counter substrate 100b (substantially the same as the counter substrate 100b shown in FIG. 1).
[0097]
FIG. 11A schematically illustrates an alignment state (OFF state) of the liquid crystal molecules 30 a in the liquid crystal layer 30 to which no voltage is applied. FIG. 11B schematically shows a state in which the orientation of the liquid crystal molecules 30a has started to change in accordance with the voltage applied to the liquid crystal layer 30 (ON initial state). FIG. 11C schematically shows a state in which the orientation of the liquid crystal molecules 30a changed according to the applied voltage has reached a steady state. FIGS. 11A, 11B, and 11C show FIGS. 1A, 1B, and 1C for a liquid crystal display device 100 including a picture element electrode 15 having one opening 14a for each picture element area. (C) respectively. In FIG. 11, lower conductive layer 12 provided so as to face openings 14a1 and 14a2 via dielectric layer 13 overlaps openings 14a1 and 14a2, respectively, and also has openings 14a1 and 14a2. Although the example in which the lower conductive layer 12 is formed so as to be present also in the region between them (the region where the upper conductive layer 14 is present) is shown, the arrangement of the lower conductive layer 12 is not limited to this, and the openings 14a1 and 14a2 Thus, they may be arranged so as to have the arrangement relationship shown in FIGS. Further, the lower conductive layer 12 formed at a position opposite to the region where the conductive layer of the upper conductive layer 14 is present via the dielectric layer 13 does not substantially affect the electric field applied to the liquid crystal layer 30. It is not particularly necessary to perform patterning, but patterning may be performed.
[0098]
As shown in FIG. 11A, when the pixel electrode 15 and the counter electrode 22 are at the same potential (when no voltage is applied to the liquid crystal layer 30), the liquid crystal molecules 30a in the pixel region are It is oriented perpendicular to the surfaces of both substrates 11 and 21.
[0099]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by an equipotential line EQ shown in FIG. 11B is formed. The liquid crystal layer 30 located between the upper conductive layer 14 and the counter electrode 22 of the pixel electrode 15 is represented by an equipotential line EQ parallel to the surfaces of the upper conductive layer 14 and the counter electrode 22. A uniform potential gradient is formed. In the liquid crystal layer 30 located above the openings 14a1 and 14a2 of the upper conductive layer 14, a potential gradient corresponding to the potential difference between the lower conductive layer 12 and the counter electrode 22 is formed. At this time, since the potential gradient formed in the liquid crystal layer 30 is affected by the voltage drop due to the dielectric layer 13, the equipotential lines EQ formed in the liquid crystal layer 30 correspond to the openings 14a1 and 14a2. A drop occurs in the region (a plurality of “valleys” are formed on the equipotential line EQ). Since lower conductive layer 12 is formed in a region opposed to openings 14a1 and 14a2 with dielectric layer 13 interposed therebetween, liquid crystal layer 30 located near the center of each of openings 14a1 and 14a2 has an upper layer. A potential gradient represented by an equipotential line EQ parallel to the surfaces of the conductive layer 14 and the counter electrode 22 is formed (the “valley bottom” of the equipotential line EQ). An oblique electric field represented by an inclined equipotential line EQ is formed in the liquid crystal layer 30 on the edge portion (around the inside of the opening including the boundary (extension) of the opening) EG of the openings 14a1 and 14a2. .
[0100]
A torque acts on the liquid crystal molecules 30a having a negative dielectric anisotropy so as to orient the axis of the liquid crystal molecules 30a in parallel with the equipotential line EQ. Therefore, the liquid crystal molecules 30a on the edge portion EG are clockwise in the right edge portion EG in the drawing and counterclockwise in the left edge portion EG in the drawing, as shown by the arrow in FIG. In the directions, they incline (rotate), and are oriented parallel to the equipotential lines EQ.
[0101]
As shown in FIG. 11B, at the edge portions EG of the openings 14a1 and 14a2 of the liquid crystal display device 400 according to the present invention, the electric field represented by the equipotential line EQ inclined with respect to the axial direction of the liquid crystal molecules 30a. When the (oblique electric field) is generated, as shown in FIG. 5B, the liquid crystal molecules 30a are inclined in a direction in which the amount of inclination for becoming parallel to the equipotential line EQ is small (counterclockwise in the illustrated example). I do. Further, the liquid crystal molecules 30a located in a region where an electric field generated by an equipotential line EQ perpendicular to the axis direction of the liquid crystal molecules 30a is generated as shown in FIG. The liquid crystal molecules 30a are tilted in the same direction as the liquid crystal molecules 30a positioned on the tilted equipotential lines EQ so that the alignment with the liquid crystal molecules 30a positioned on the line EQ is continuous (matched).
[0102]
As described above, the change in the alignment starting from the liquid crystal molecules 30a located on the inclined equipotential line EQ progresses, and when the steady state is reached, the openings 14a1 and 14a1 are formed as schematically shown in FIG. A symmetric inclined orientation (radial inclined orientation) is formed with respect to each center SA of 14a2. Further, the liquid crystal molecules 30a on the region of the upper conductive layer 14 located between the two adjacent openings 14a1 and 14a2 are also arranged such that the alignment with the liquid crystal molecules 30a at the edges of the openings 14a1 and 14a2 is continuous. Obliquely oriented (to match). Since the liquid crystal molecules 30a on the portions located at the centers of the edges of the openings 14a1 and 14a2 are equally affected by the liquid crystal molecules 30a at the respective edges, the liquid crystal molecules 30a located at the center of the openings 14a1 and 14a2 Similar to 30a, the vertical alignment state is maintained. As a result, the liquid crystal layer on the upper conductive layer 14 between the two adjacent openings 14a1 and 14a2 is also in a radially inclined alignment state. However, the tilt direction of the liquid crystal molecules is different between the radial tilt orientation of the liquid crystal layer in the openings 14a1 and 14a2 and the radial tilt direction of the liquid crystal layer between the openings 14a1 and 14a2. Paying attention to the alignment near the liquid crystal molecules 30a located at the center of each of the radially tilted regions shown in FIG. 11C, a cone is formed in the openings 14a1 and 14a2 that expands toward the counter electrode. The liquid crystal molecules 30a are tilted so as to form a cone that spreads toward the upper conductive layer 14 between the openings. In addition, since any radial tilt alignment is formed so as to match the tilt alignment of the liquid crystal molecules 30a at the edge portion, the two radial tilt alignments are continuous with each other.
[0103]
As described above, when a voltage is applied to the liquid crystal layer 30, the liquid crystal molecules 30a begin to tilt from the liquid crystal molecules 30a on the edge portions EG of the plurality of openings 14a1 and 14a2 provided in the upper conductive layer 14, and then the liquid crystal molecules 30a in the peripheral region. Are tilted so as to match the tilt alignment of the liquid crystal molecules 30a on the edge portion EG, thereby forming a radial tilt alignment. Therefore, the larger the number of openings 14a formed in one picture element region, the larger the number of liquid crystal molecules 30a that start to tilt in response to an electric field, so that the radially inclined alignment is formed over the entire picture element region. The time required for the formation is reduced. That is, the response speed of the liquid crystal display device can be improved by increasing the number of openings 14a formed in the pixel electrode for each pixel region.
[0104]
By forming a plurality of openings 14a1 and 14a2 for each picture element region in this manner, a liquid crystal display device having a display quality excellent in omnidirectional viewing angle characteristics is realized, and the response characteristics of the liquid crystal display device are improved. Is also improved.
[0105]
Next, the relationship between the shape and relative arrangement of the plurality of openings 14a and the orientation of the liquid crystal molecules 30a will be described with reference to FIGS. A cross-sectional view taken along line 11A-11A 'in FIGS. 12A and 13A corresponds to FIG. 11A, and 11B-11B' in FIGS. 12B and 13B. A cross-sectional view taken along a line corresponds to FIG. 11B, and a cross-sectional view taken along a line 11C-11C ′ in FIGS. 12C and 13C corresponds to FIG. 11C.
[0106]
12 and 13 illustrate the rectangular pixel electrode 15 (pixel region), but the outer shape of the pixel electrode 15 (upper conductive layer 14) is not limited to this. Further, the liquid crystal display device according to the present invention is not limited to the one having one electrode configuration shown in FIG. 12 or FIG. A plurality may be provided in the element region. Further, there is no particular limitation on the relative positional relationship between the outer periphery of the pixel electrode 15 (upper conductive layer 14) and the opening 14a, and a part of the plurality of openings 14a defines the outer periphery of the upper conductive layer 14. Alternatively, they may be formed so as to overlap corners. This is the same for the liquid crystal display devices of other embodiments showing the picture element region having the plurality of openings 14a. The relative arrangement between the openings 14a, which is preferable for stabilizing the alignment of the liquid crystal molecules over the entire picture element region (and improving the response speed), will be described later.
[0107]
First, the shape of each opening 14a may be a polygon, a circle, or an ellipse as described above. In order to improve the viewing angle characteristics in all azimuthal directions of the liquid crystal display device 400 (eliminate the roughness of the display), it is preferable that each shape of the opening 14a has a high rotational symmetry. A regular polygon such as a square or a circle shown in FIG. 13 is preferable. Since the relationship between the shape of each opening 14a and the alignment state of the liquid crystal molecules 30a is as described above, the description is omitted here.
[0108]
In the configuration in which the plurality of openings 14a are formed, it is preferable that the relative arrangement of the plurality of openings 14a has rotational symmetry. For example, as shown in FIG. 12, when four square openings 14a are formed in the upper conductive layer 14 of the square (that is, when the picture element region is a square), the four openings 14a are The upper conductive layer 14 is preferably arranged to have rotational symmetry about the center SA. As shown in the figure, it is preferable to arrange the center SA of the square upper conductive layer 14 so as to be a rotation axis four times. With this arrangement, as shown in FIGS. 12B and 12C, when a voltage is applied to the liquid crystal layer 30, the regions having the radially inclined alignment formed around the respective openings 14a become: It has four-fold rotational symmetry about the center SA of the upper conductive layer 14. As a result, the viewing angle characteristics of the liquid crystal display device 400 are further uniformed in all azimuthal directions.
[0109]
FIG. 12 illustrates a configuration in which four apertures 14a are formed in one picture element region, but the number of apertures 14a is not limited to this. The number of openings 14a formed in one picture element region is determined in consideration of the size and shape of the picture element region, the size of the region where the radially inclined orientation is stably formed by one opening 14a, and the response speed. It is set appropriately. When a large number of openings 14a are formed in one picture element region, in order to improve the uniformity of viewing angle characteristics, the openings 14a are arranged so as to have rotational symmetry throughout the picture element region. However, depending on the shape of the pixel region, it may not be possible to arrange the pixel region so as to have rotational symmetry over the entire pixel region. It is preferable to arrange them so as to have rotational symmetry over as large an area as possible. For example, when the picture element region is a rectangle, the rectangle is divided into a plurality of squares, and a plurality of openings 14a are formed so as to have rotational symmetry with respect to each square, so that the viewing angle characteristics are sufficiently uniform. Can be obtained.
[0110]
FIG. 13 shows a configuration in which a circular opening 14a is provided instead of the square opening 14a shown in FIG.
[0111]
As described above with reference to FIG. 12, the viewing angle characteristics of the liquid crystal display device are further improved by arranging the four openings 14a such that the center SA of the upper conductive layer 14 becomes the rotation axis four times. be able to. In addition, the circular shape of the openings 14a has higher continuity of the alignment of the liquid crystal molecules 30a along the edges of the respective openings 14a than the polygon, so that the radially inclined alignment of the liquid crystal molecules 30a is higher. Stabilize. Further, in the configuration in which the plurality of openings 14a are provided, when the shape of the openings 14a is circular, continuity between the radially inclined orientations formed by the adjacent openings 14a is high, and the openings 14a are formed in the pixel region. The advantage is obtained that a plurality of radially inclined orientations are easily stabilized.
[0112]
For example, as shown in FIG. 14, even in a configuration in which four circular openings 14a are arranged such that their centers are located at the corners of a rectangle, the liquid crystal molecules 30a located on the diagonal of the rectangle are continuous. It is possible to form a proper tilt orientation. On the other hand, if the four openings 14a in FIG. 14 are square, the rectangular diagonal formed by connecting the centers of the openings 14a does not coincide with the square diagonal of the opening 14a. The alignment of the liquid crystal molecules 30a in the region surrounded by the four openings 14a is unlikely to be continuous. On the other hand, if the shape of the four openings 14a is a rectangle having a similar relationship to the rectangle formed by the centers of the four openings 14a, the above-described problem can be solved, but the four openings 14a are formed in the respective openings 14a. The continuity of the radially tilted orientation is reduced. Therefore, it is preferable to appropriately set the shape and arrangement of the opening 14a in consideration of the shape and size of the picture element region. FIG. 14 shows a state in which a voltage is applied to the liquid crystal layer, and a cross-sectional view taken along line 11C-11C ′ in FIG. 14 corresponds to FIG.
[0113]
Preferred examples of the arrangement of the openings in an electrode configuration having a plurality of openings for each picture element region (that is, a two-layer structure electrode in which a picture element electrode or a counter electrode has an opening) will be described in more detail.
[0114]
Another pattern of the upper conductive layer 14 of another liquid crystal display device 400A of the first embodiment will be described with reference to FIG. FIG. 15B is a cross-sectional view taken along the line 15B-15B ′ in FIG. 15A. The solid portion of the upper conductive layer 14 is denoted by reference numeral 14b, and the unit solid portion is denoted by reference numeral 14b. It is substantially the same as FIG. 11 (a) except that 14b 'is added.
[0115]
The upper conductive layer 14 included in the liquid crystal display device 400A has a plurality of openings 14a and a solid portion 14b. The opening 14a indicates a portion of the upper conductive layer 14 formed of a conductive film (for example, an ITO film) from which the conductive film has been removed, and the solid portion 14b indicates a portion where the conductive film exists (other than the opening 14a). Part). Although a plurality of openings 14a are formed for each pixel electrode, the solid portions 14b are basically formed of a single continuous conductive film.
[0116]
The plurality of openings 14a are arranged such that their centers form a square lattice, and are substantially surrounded by four openings 14a whose centers are located on four lattice points forming one unit lattice. The solid portion (referred to as a "unit solid portion") 14b 'has a substantially circular shape. Each of the openings 14a has a substantially star-shaped shape having four quarter-arc-shaped sides (edges) and having a rotation axis at its center four times. In order to stabilize the orientation over the entire picture element region, it is preferable to form a unit lattice up to the end of the upper conductive layer 14. Therefore, as shown in the drawing, the end of the upper conductive layer 14 is located at about one half of the opening 14a (the area corresponding to the side) and about one quarter of the opening 14a (the area corresponding to the corner). Preferably, it is patterned into a corresponding shape. A square (a set of square lattices) indicated by a solid line in FIG. 15A indicates a region (outer shape) corresponding to a conventional pixel electrode formed from a single conductive layer.
[0117]
The openings 14a located at the center of the picture element region have substantially the same shape and the same size. The unit solid portions 14b 'located in the unit lattice formed by the openings 14a are substantially circular, have substantially the same shape and the same size. The unit solid portions 14b ′ adjacent to each other are connected to each other, and constitute a solid portion 14b that functions substantially as a single conductive film.
[0118]
When a voltage is applied between the upper conductive layer 14 and the counter electrode 22 having the above-described configuration, a plurality of liquid crystal domains each having a radially tilted orientation are formed by an oblique electric field generated at the edge of the opening 14a. It is formed. One liquid crystal domain is formed in each of the regions corresponding to the openings 14a and the regions corresponding to the unit solid portions 14b 'in the unit cell.
[0119]
Here, the square upper conductive layer 14 is illustrated, but the shape of the pixel electrode 14 is not limited to this. Since the general shape of the upper conductive layer 14 is approximated to a rectangle (including a square and a rectangle), the openings 14a can be regularly arranged in a square lattice. Even if the upper conductive layer 14 has a shape other than a rectangular shape, the openings 14a are regularly (for example, in a square lattice shape as illustrated) so that liquid crystal domains are formed in all regions in the pixel region. If it arrange | positions, the effect of this invention can be acquired.
[0120]
The shape (shape viewed from the normal direction of the substrate) of the opening 14a of the upper conductive layer 14 included in the liquid crystal display device 400A of the present embodiment and the arrangement thereof will be described.
[0121]
The display characteristics of a liquid crystal display device show azimuth dependence depending on the alignment state (optical anisotropy) of liquid crystal molecules. In order to reduce the azimuth angle dependence of the display characteristics, it is preferable that the liquid crystal molecules are aligned with the same probability for all azimuth angles. Further, it is more preferable that the liquid crystal molecules in each picture element region are aligned with equal probability for all azimuth angles. Therefore, it is preferable that the opening 14a has a shape that forms a liquid crystal domain such that the liquid crystal molecules 30a in each picture element region are aligned with equal probability at all azimuth angles. . Specifically, the shape of the opening 14a preferably has a rotational symmetry (preferably a symmetry of two or more rotation axes) with the center (normal direction) as the axis of symmetry. It is preferable that the openings 14a are arranged so as to have rotational symmetry. Also, the shape of the unit solid portion 14b 'substantially surrounded by these openings preferably has rotational symmetry, and the unit solid portion 14b' is also arranged to have rotational symmetry. preferable.
[0122]
However, it is not always necessary that the openings 14a and the unit solid portions 14b 'are arranged so as to have rotational symmetry over the entire picture element region. For example, as shown in FIG. If the picture element region is constituted by a combination of these as the minimum unit, the liquid crystal molecules are substantially equal in all azimuthal angles over the entire picture element region. Can be oriented.
[0123]
FIG. 16 shows the alignment state of the liquid crystal molecules 30a when the substantially star-shaped openings 14a and the substantially circular unit solid portions 14b ′ having the rotational symmetry are arranged in a square lattice as shown in FIG. This will be described with reference to FIGS.
[0124]
FIGS. 16A to 16C schematically show the alignment state of the liquid crystal molecules 30a viewed from the normal direction of the substrate. In FIGS. 16B and 16C, which show the alignment state of the liquid crystal molecules 30a as viewed from the normal direction of the substrate, the ends of the liquid crystal molecules 30a drawn in an elliptical shape are indicated by black dots. This indicates that the liquid crystal molecules 30a are inclined such that the end is closer to the substrate side where the upper conductive layer 14 having the opening 14a is provided than the other end. The same applies to the following drawings. Here, one unit lattice (formed by the four openings 14a) in the picture element region shown in FIG. 15A will be described. Sectional views along diagonal lines in FIGS. 16A to 16C correspond to FIGS. 11A to 11C, respectively, and will be described with reference to these figures.
[0125]
When the upper conductive layer 14 and the counter electrode 22 have the same potential, that is, when no voltage is applied to the liquid crystal layer 30, the vertical alignment layer (provided on the liquid crystal layer 30 side surfaces of the TFT substrate 400 a and the counter substrate 100 b) The liquid crystal molecules 30a whose alignment direction is regulated by (not shown) take a vertical alignment state as shown in FIG.
[0126]
When an electric field is applied to the liquid crystal layer 30, the liquid crystal molecules 30a start to tilt from the edge of the opening 14a as shown in FIG. The surrounding liquid crystal molecules 30a are also inclined so as to match the orientation of the liquid crystal molecules 30a in which the edges of the opening 14a are inclined, and the axial azimuth of the liquid crystal molecules 30a in the state shown in FIG. Is stable (radial tilt orientation).
[0127]
As described above, when the opening 14a has a shape having rotational symmetry, the liquid crystal molecules 30a in the picture element region move from the edge of the opening 14a toward the center of the opening 14a when a voltage is applied. Are tilted, the liquid crystal molecules 30a near the center of the opening 14a where the alignment control force of the liquid crystal molecules 30a from the edge balances maintain a state of being aligned perpendicular to the substrate surface, and the surrounding liquid crystal molecules 30a A state in which the liquid crystal molecules 30a are continuously inclined radially around the liquid crystal molecules 30a near the center of the opening 14a is obtained.
[0128]
In addition, the liquid crystal molecules 30a in a region corresponding to the substantially circular unit solid portion 14b ′ surrounded by the four substantially star-shaped openings 14a arranged in a square lattice are also generated at the edge of the opening 14a. The liquid crystal molecules 30a are tilted so as to match the alignment of the liquid crystal molecules 30a tilted by the oblique electric field. The liquid crystal molecules 30a near the center of the unit solid portion 14b 'where the alignment control force of the liquid crystal molecules 30a from the edge portion is balanced maintain a state of being oriented perpendicular to the substrate surface, and the surrounding liquid crystal molecules 30a are A state in which the liquid crystal molecules 30a are continuously tilted radially around the liquid crystal molecules 30a near the center of the real part 14b 'is obtained.
[0129]
As described above, when the liquid crystal domains in which the liquid crystal molecules 30a take a radially inclined alignment are arranged in a square lattice pattern over the entire pixel region, the existence probability of the liquid crystal molecules 30a in each axis direction has a rotational symmetry. That is, it is possible to realize a high-quality display without roughness in all viewing angle directions. In order to reduce the viewing angle dependence of the liquid crystal domain having the radially inclined alignment, the liquid crystal domain preferably has high rotational symmetry (preferably two or more rotation axes, more preferably four or more rotation axes). In order to reduce the viewing angle dependence of the entire picture element region, a plurality of liquid crystal domains formed in the picture element region have high rotational symmetry (preferably two or more rotation axes, more preferably four or more rotation axes). It is preferable to form an array (for example, a square lattice) represented by a combination of units (for example, a unit lattice) having (preferably).
[0130]
FIG. 15A illustrates an example in which the opening 14a has a substantially star shape, the unit solid portion 14b ′ has a substantially circular shape, and these are arranged in a square lattice. The shape of the unit solid portion 14b 'and the arrangement thereof are not limited to the above example.
[0131]
FIGS. 17A and 17B are top views of upper conductive layers 14A and 14B having openings 14a and unit solid portions 14b 'of different shapes, respectively.
[0132]
The openings 14a and the unit solid portions 14b 'of the upper conductive layers 14A and 14B shown in FIGS. 17A and 17B respectively correspond to the openings 14a and the unit solid portions of the picture element electrodes shown in FIG. The real part 14b 'has a slightly distorted shape. The openings 14a and the unit solid portions 14b 'of the upper conductive layers 14A and 14B have a rotation axis twice (no rotation axis four times) and are regularly arranged so as to form a rectangular unit lattice. ing. Each of the openings 14a has a distorted star shape, and each of the unit solid portions 14b 'has a substantially elliptical shape (distorted circular shape). Even when the upper conductive layers 14A and 14B are used, a liquid crystal display device having high display quality and excellent viewing angle characteristics can be obtained.
[0133]
Further, upper conductive layers 14C and 14D as shown in FIGS. 18A and 18B, respectively, can also be used.
[0134]
Upper conductive layers 14C and 14D have substantially cross-shaped openings 14a arranged in a square lattice so that unit solid portions 14b 'are substantially square. Of course, these may be distorted and arranged so as to form a rectangular unit cell. As described above, even if the unit solid portions 14b 'of a substantially rectangular shape (rectangles include a square and a rectangle) are regularly arranged, a liquid crystal display device with high display quality and excellent viewing angle characteristics can be obtained. .
[0135]
However, the shape of the opening 14a and / or the unit solid portion 14b 'is more preferably circular or elliptical than rectangular, because the radially inclined orientation can be stabilized. This is presumably because the sides of the opening 14a change continuously (smoothly), so that the alignment direction of the liquid crystal molecules 30a also changes continuously (smoothly).
[0136]
From the viewpoint of the continuity of the alignment direction of the liquid crystal molecules 30a, the upper conductive layers 14E and 14F shown in FIGS. The upper conductive layer 14E shown in FIG. 19A is a modification of the upper conductive layer 14 shown in FIG. 15A, and has an opening 14a consisting of only four arcs. The upper conductive layer 14F shown in FIG. 19 (b) is a modification of the upper conductive layer 14D shown in FIG. 18 (b). It is formed from a combination of 1/1 arcs. The openings 14a and the unit solid portions 14b 'of the upper conductive layers 14E and 14F each have a rotation axis four times, and are arranged in a square lattice (having a rotation axis four times). However, as shown in FIGS. 17A and 17B, the shape of the unit solid portion 14b ′ of the opening 14a is distorted to have a shape having two rotation axes, and a rectangular lattice (two rotation axes) is used. ).
[0137]
In the above-described example, the substantially star-shaped or substantially cross-shaped opening 14a is formed, and the shape of the unit solid portion 14b 'is substantially circular, substantially elliptical, substantially square (rectangular), and substantially rectangular with corners. The configuration has been described. On the other hand, the relationship between the opening 14a and the unit solid portion 14b 'may be reversed from negative to positive. For example, FIG. 20 shows an upper conductive layer 14G having a pattern in which the opening 14a of the upper conductive layer 14 and the unit solid portion 14b 'shown in FIG. Thus, the upper conductive layer 14G having the negative-positive inverted pattern has substantially the same function as the upper conductive layer 14 shown in FIG. When both the opening 14a and the unit solid portion 14b 'are substantially square, as in the upper conductive layers 14H and 14I shown in FIGS. In some cases, the pattern becomes the same as the original pattern.
[0138]
As in the case of the pattern shown in FIG. 20, even when the pattern shown in FIG. 15A is inverted from negative to positive, the edge of the upper conductive layer 14 has a unit solid portion 14b 'having rotational symmetry. It is preferable to form a part (about one-half or about one-fourth) of the opening 14a so that is formed. By adopting such a pattern, the effect of the oblique electric field can be obtained at the edge of the pixel region as well as at the center of the pixel region, and a stable radially inclined orientation can be obtained over the entire pixel region. Can be realized.
[0139]
Next, the upper conductive layer shown in FIG. 20 having a pattern obtained by inverting the pattern of the upper conductive layer 14, the opening 14a of the upper conductive layer 14 and the unit solid portion 14b 'from negative to positive is shown in FIG. Using 14G as an example, which of the negative-positive patterns should be used will be described.
[0140]
Regardless of which negative-positive pattern is employed, the length of the side of the opening 14a is the same in both patterns. Therefore, there is no difference between these patterns in the function of generating an oblique electric field. However, the area ratio of the unit solid portion 14b '(the ratio to the total area of the upper conductive layer 14) may be different between the two. That is, the area of the solid portion 14b (the portion where the conductive film actually exists) that generates the electric field used for the liquid crystal molecules of the liquid crystal layer may be different.
[0141]
Since the voltage applied to the liquid crystal domain formed in the opening 14a is lower than the voltage applied to the liquid crystal domain formed in the solid portion 14b, for example, when a display in a normally black mode is performed. The liquid crystal domains formed in the openings 14a become dark. That is, as the area ratio of the opening 14a increases, the display luminance tends to decrease. Therefore, it is preferable that the area ratio of the solid portion 14b is high. Although the operation of the lower conductive layer is ignored here for simplicity, the two-layer structure electrode of the liquid crystal display device according to the present invention has a lower layer in a region corresponding to the opening 14 a of the upper conductive layer 14. It has a conductive layer (for example, the lower conductive layer 12 in FIG. 1). Accordingly, since the electric field from the lower conductive layer also acts on the liquid crystal layer 30 in the region corresponding to the opening 14a, the extent to which the display luminance decreases with the increase in the area ratio of the opening 14a is as shown in FIG. The number is smaller than that of the conventional liquid crystal display device 300 described with reference to FIGS.
[0142]
Which of the pattern in FIG. 15A and the pattern in FIG. 20 has a higher area ratio of the solid portion 14b depends on the pitch (size) of the unit cell.
[0143]
FIG. 22A shows a unit lattice of the pattern shown in FIG. 15A, and FIG. 22B shows a unit lattice of the pattern shown in FIG. 20 (however, the opening 14a is centered). Is shown. In FIG. 22 (b), a portion (branch portion extending from a circular portion in four directions) serving to connect the unit solid portions 14b 'to each other in FIG. 20 is omitted. The length (pitch) of one side of the square unit lattice is p, and the length of the gap (one side space) between the opening 14a or the unit solid part 14b 'and the unit lattice is s.
[0144]
Various upper conductive layers 14 having different values of the pitch p and the space s on one side were formed, and the stability of the radially inclined orientation was examined. As a result, first, by using the upper conductive layer 14 having the pattern shown in FIG. 22A (hereinafter, referred to as “positive pattern”), an oblique electric field necessary for obtaining a radially inclined orientation is generated. For this purpose, it has been found that the space s on one side is required to be about 2.75 μm or more. On the other hand, with respect to the upper conductive layer 14 having the pattern shown in FIG. 22B (hereinafter, referred to as a “negative pattern”), in order to generate an oblique electric field for obtaining a radially inclined orientation, the space s on one side is reduced. It was found that about 2.25 μm or more was required. Using the one-sided space s as the lower limit, the area ratio of the solid portion 14b when the value of the pitch p was changed was examined. The results are shown in Table 1 and FIG.
As can be seen from Table 1 and FIG. 22 (c), when the pitch p is about 25 μm or more, the positive (FIG. 22 (a)) pattern has a higher area ratio of the solid portion 14b and is shorter than about 25 μm. Then, the negative type (FIG. 22B) has a larger area ratio of the solid portion 14b. Therefore, from the viewpoint of the display luminance and the stability of the orientation, the pattern to be adopted changes when the pitch p is about 25 μm. For example, when three or less unit lattices are provided in the width direction of the upper conductive layer 14 having a width of 75 μm, the positive pattern shown in FIG. 22A is preferable, and when four or more unit lattices are provided. Is preferably a negative pattern shown in FIG. In the case other than the exemplified pattern, either the positive type or the negative type may be selected so that the area ratio of the solid portion 14b is increased.
[0145]
The number of unit cells is obtained as follows. The unit lattice size is calculated so that one or two or more integer unit lattices are arranged with respect to the width (horizontal or vertical) of the upper conductive layer 14, and a solid part is calculated for each unit lattice size. Calculate the area ratio and select the unit cell size that maximizes the solid area ratio. However, when the diameter of the unit solid portion 14b ′ is less than 15 μm in the case of the positive pattern and the diameter of the opening 14a is less than 15 μm in the case of the negative pattern, the alignment regulating force due to the oblique electric field is reduced, and It becomes difficult to obtain a radially inclined alignment. The lower limit of these diameters is when the thickness of the liquid crystal layer 30 is about 3 μm. If the thickness of the liquid crystal layer 30 is smaller than this, the diameters of the unit solid portion 14b ′ and the opening 14a are Even if the liquid crystal layer 30 is thicker than this lower limit, a stable radial tilt alignment can be obtained even if it is smaller than the lower limit, and the unit solid portions 14b 'and The lower limit of the diameter of the opening 14a is larger than the above lower limit. Further, in the liquid crystal display device of the present invention, since an electric field is applied by the lower conductive layer, a decrease in display quality is suppressed even if the diameter of the opening 14a is slightly larger than the above result.
[0146]
The configuration of the liquid crystal display device of Embodiment 1 described above can adopt the same configuration as a known vertical alignment type liquid crystal display device, except that the picture element electrode 15 is a two-layered electrode having an opening. It can be manufactured by a known manufacturing method. Here, a method for forming a pixel electrode having a two-layer structure will be described, and the others will be omitted. Here, for example, FIG. 1A is referred to again.
[0147]
Up to the step of depositing the transparent conductive layer (typically, an ITO layer) to be the lower conductive layer 12, it can be performed by a known manufacturing method. This conductive layer is patterned into a predetermined shape in a conventional process of a liquid crystal display device to form a pixel electrode. In the patterning step of the picture element electrode in the manufacturing process of the conventional liquid crystal display device, the lower conductive layer 12 of the liquid crystal display device of the present embodiment can be patterned. The pattern of the lower conductive layer may be the same as that of the pixel electrode, or may be a divided pattern corresponding to the opening 14a formed in the upper conductive layer 14. The lower conductive layer 12 is electrically connected to a drain electrode or the like (an electrode having substantially the same potential as the drain) of the TFT, like the conventional picture element electrode.
[0148]
The dielectric layer 13 is formed over substantially the entire surface of the substrate 100a on which the lower conductive layer 12 has been patterned. The dielectric layer 13 can be formed using, for example, a transparent photosensitive resin. A conductive layer is deposited on the dielectric layer 13 again. By patterning the obtained conductive layer, an upper conductive layer 14 having an opening 14a is formed.
[0149]
Note that a contact hole for connecting the upper conductive layer 14 to the drain electrode of the TFT is formed in the dielectric layer 13 in advance. This step can also be performed by a known process. When the configuration in which the upper conductive layer 14 and the lower conductive layer 12 are driven at the same potential is adopted, the upper conductive layer 14 and the lower conductive layer 12 may be connected to the same TFT as illustrated. Further, when this configuration is employed, there is an advantage that a conventional driving circuit can be used as it is.
[0150]
Note that a vertical alignment layer (not shown) is typically formed on the surface of the pixel electrode 15 and the counter electrode 22 on the liquid crystal layer 30 side in order to vertically align liquid crystal molecules having negative dielectric anisotropy. ing. The vertical alignment layer is formed by printing in the display region of the substrate 100a after the upper conductive layer 14 having the opening 14a is formed.
[0151]
As the liquid crystal material, a nematic liquid crystal material having negative dielectric anisotropy is used. In addition, a guest-host mode liquid crystal display device can be obtained by adding a dichroic dye to a nematic liquid crystal material having negative dielectric anisotropy. The guest-host mode liquid crystal display device does not require a polarizing plate.
[0152]
(Embodiment 2)
The structure of one picture element region of the liquid crystal display device 400B according to the second embodiment of the present invention will be described with reference to FIGS. In the following drawings, components having substantially the same functions as those of the liquid crystal display device 400 shown in FIG. 11 are denoted by the same reference numerals, and the description thereof will be omitted. FIG. 23A is a top view as seen from the normal direction of the substrate, and FIG. 23B is a cross-sectional view taken along the line 23B-23B ′ in FIG. FIG. 23B schematically illustrates a state where no voltage is applied to the liquid crystal layer.
[0153]
As shown in FIGS. 23A and 23B, the liquid crystal display device 400B is different from the liquid crystal display device 400B in that the TFT substrate 400b has the projection 40 inside the opening 14a of the upper conductive layer 14 as shown in FIG. This is different from the liquid crystal display device 400A of the first embodiment shown in FIGS. A vertical alignment film (not shown) is provided on the surface of the protrusion 40. Hereinafter, the TFT substrate having the protrusion 40 inside the opening 14a is denoted by reference numeral 400b regardless of the structure of the protrusion 40.
[0154]
Here, a liquid crystal display device 400B in which the convex portions 40 are provided in the openings 14a of the upper conductive layer 14 of the liquid crystal display device 400 shown in FIG. 11 is illustrated, but the present invention is applied to another liquid crystal display device of the first embodiment. it can.
[0155]
The cross-sectional shape of the convex portion 40 in the in-plane direction of the substrate 11 is the same as the shape of the opening portion 14a as shown in FIG. However, the adjacent convex portions 40 are connected to each other, and are formed so as to completely surround the unit solid portion 14b 'in a substantially circular shape. The cross-sectional shape of the protrusion 40 in the in-plane direction perpendicular to the substrate 11 is a trapezoid as shown in FIG. That is, it has a top surface 40t parallel to the substrate surface and a side surface 40s inclined at a taper angle θ (<90 °) with respect to the substrate surface. Since the vertical alignment film (not shown) is formed so as to cover the convex portion 40, the side surface 40s of the convex portion 40 has the same direction as the alignment control direction due to the oblique electric field with respect to the liquid crystal molecules 30a of the liquid crystal layer 30. It has an alignment regulating force and acts to stabilize the radially inclined alignment.
[0156]
The operation of the protrusion 40 will be described with reference to FIGS. 24 (a) to 24 (d) and FIGS. 25 (a) and 25 (b).
[0157]
First, the relationship between the alignment of the liquid crystal molecules 30a and the shape of the surface having vertical alignment will be described with reference to FIGS.
[0158]
As shown in FIG. 24A, the liquid crystal molecules 30a on the horizontal surface are perpendicular to the surface due to the alignment regulating force of the surface having vertical alignment (typically, the surface of the vertical alignment film). Orientation. When an electric field represented by an equipotential line EQ perpendicular to the axis direction of the liquid crystal molecules 30a is applied to the liquid crystal molecules 30a in the vertical alignment state, a clockwise or counterclockwise direction is applied to the liquid crystal molecules 30a. Act with equal probability. Therefore, the liquid crystal molecules 30a receiving the clockwise torque and the liquid crystal molecules 30a receiving the counterclockwise torque are mixed in the liquid crystal layer 30 between the electrodes of the parallel plate type opposed to each other. As a result, the change to the alignment state according to the voltage applied to the liquid crystal layer 30 may not occur smoothly.
[0159]
As shown in FIG. 24 (b), when an electric field represented by horizontal equipotential lines EQ is applied to the liquid crystal molecules 30a oriented vertically to the inclined surface, the liquid crystal molecules 30a Is inclined in a direction in which the amount of inclination for becoming parallel to the equipotential line EQ is small (clockwise in the illustrated example). Further, as shown in FIG. 24 (c), the liquid crystal molecules 30a oriented vertically with respect to the horizontal surface are continuous with the liquid crystal molecules 30a oriented vertically with respect to the inclined surface. The liquid crystal molecules 30a are tilted in the same direction (clockwise) as the liquid crystal molecules 30a located on the tilted surface so as to be aligned (matched).
[0160]
As shown in FIG. 24 (d), the top surface of the continuous uneven surface having a trapezoidal cross section is aligned with the alignment direction regulated by the liquid crystal molecules 30a on each inclined surface. And the liquid crystal molecules 30a on the bottom face are aligned.
[0161]
The liquid crystal display device of the present embodiment stabilizes the radially inclined alignment by matching the direction of the alignment control force by such a surface shape (convex portion) with the alignment control direction by the oblique electric field.
[0162]
FIGS. 25A and 25B show states in which a voltage is applied to the liquid crystal layer 30 shown in FIG. 23B, respectively. FIG. FIG. 25B schematically shows a state in which the orientation of the liquid crystal molecules 30a has begun to change (an initial ON state). FIG. 25B shows that the orientation of the liquid crystal molecules 30a changed in accordance with the applied voltage is steady. The state where the state has been reached is schematically shown. Curves EQ in FIGS. 25A and 25B show equipotential lines EQ.
[0163]
When the upper conductive layer 14, the lower conductive layer 12, and the counter electrode 22 are at the same potential (in a state where no voltage is applied to the liquid crystal layer 30), as shown in FIG. Of liquid crystal molecules 30a are aligned perpendicular to the surfaces of both substrates 11 and 21. At this time, the liquid crystal molecules 30a in contact with the vertical alignment film (not shown) on the side surface 40s of the protrusion 40 are aligned perpendicularly to the side surface 40s, and the liquid crystal molecules 30a near the side surface 40s are in contact with the peripheral liquid crystal molecules 30a. (Property as an elastic continuum) as shown in FIG.
[0164]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by an equipotential line EQ shown in FIG. 25A is formed. This equipotential line EQ is parallel to the solid portion 14 b and the surface of the counter electrode 22 in the liquid crystal layer 30 located between the solid portion 14 b of the upper conductive layer 14 and the counter electrode 22. The liquid crystal layer 30 falls on a region corresponding to the opening 14a of the conductive layer 14 and is inclined in the liquid crystal layer 30 on the edge portion of the opening 14a (around the inside of the opening 14a including the boundary (extension) of the opening 14a). An oblique electric field represented by the equipotential line EQ is formed. The liquid crystal layer 30 in a region that is not affected by the potential of the upper conductive layer 14 in a region corresponding to the opening 14a of the upper conductive layer 14 includes a portion parallel to the surface of the lower conductive layer 12 and the counter electrode 22. An electric field represented by the potential line EQ is generated.
[0165]
Due to the oblique electric field, as described above, the liquid crystal molecules 30a on the edge portion EG move clockwise at the right edge portion EG in the drawing as shown by the arrow in FIG. At the left edge portion EG, each of them inclines (rotates) in the counterclockwise direction and is oriented parallel to the equipotential line EQ. The alignment control direction by the oblique electric field is the same as the alignment control direction by the side surface 40s located at each edge portion EG.
[0166]
As described above, the alignment changes starting from the liquid crystal molecules 30a located on the inclined equipotential lines EQ advance, and when the liquid crystal molecules 30a reach a steady state, the alignment state is schematically shown in FIG. 25B. The liquid crystal molecules 30a located near the center of the opening 14a, that is, near the center of the top surface 40t of the projection 40 have substantially the same influence of the alignment of the liquid crystal molecules 30a on the opposite edge portions EG of the opening 14a. Therefore, the liquid crystal molecules 30a in a region away from the center of the opening 14a (the top surface 40t of the convex portion 40) maintain the alignment state perpendicular to the equipotential line EQ, It tilts under the influence of the orientation of the liquid crystal molecules 30a, and forms a tilted orientation that is symmetric with respect to the center SA of the opening 14a (the top surface 40t of the projection 40). In addition, also in a region corresponding to the unit solid portion 14b 'substantially surrounded by the opening 14a and the convex portion 40, an inclined orientation symmetric with respect to the center SA of the unit solid portion 14b' is formed.
[0167]
Thus, in the liquid crystal display device 400B of the second embodiment, similarly to the liquid crystal display device 400A of the first embodiment, the liquid crystal domains having the radially inclined alignment are formed corresponding to the openings 14a and the unit solid portions 14b '. (See FIG. 16C). Since the convex portion 40 is formed so as to completely surround the unit solid portion 14b 'in a substantially circular shape, the liquid crystal domain is formed corresponding to the substantially circular region surrounded by the convex portion 40. Further, the side surface of the convex portion 40 provided inside the opening 14a acts so as to tilt the liquid crystal molecules 30a near the edge EG of the opening 14a in the same direction as the alignment direction by the oblique electric field. Stabilizes the tilt orientation.
[0168]
Naturally, the orientation control force acts on the oblique electric field only when a voltage is applied, and its strength depends on the strength of the electric field (the magnitude of the applied voltage). Therefore, when the electric field strength is weak (that is, when the applied voltage is low), the alignment regulating force by the oblique electric field is weak, and when an external force is applied to the liquid crystal panel, the radially inclined alignment may be broken by the flow of the liquid crystal material. Once the radial tilt orientation is broken, the radial tilt orientation is not restored unless a voltage that generates an oblique electric field that exerts a sufficiently strong alignment regulating force is applied. On the other hand, the alignment regulating force by the side surface 40s of the convex portion 40 acts regardless of the applied voltage, and is very strong as known as the anchoring effect of the alignment film. Therefore, even if the liquid crystal material flows and the radially inclined alignment is once broken, the liquid crystal molecules 30a in the vicinity of the side surface 40s of the projection 40 maintain the same alignment direction as in the radially inclined alignment. Therefore, as long as the flow of the liquid crystal material stops, the radial tilt alignment can be easily restored.
[0169]
As described above, the liquid crystal display device 400B of the second embodiment has a characteristic that it is strong against external force in addition to the characteristics of the liquid crystal display device 400A of the first embodiment. Therefore, the liquid crystal display device 400B is suitably used for a PC or PDA that is likely to be applied with an external force and that is frequently used in a portable manner.
[0170]
When the projection 40 is formed using a highly transparent dielectric, there is an advantage that the contribution of the liquid crystal domain formed corresponding to the opening 14a to the display is improved. On the other hand, when the convex portion 40 is formed using an opaque dielectric, there is an advantage that light leakage due to the retardation of the liquid crystal molecules 30a that are obliquely aligned by the side surface 340s of the convex portion 40 can be prevented. Which one to employ may be determined according to the application of the liquid crystal display device and the like. In any case, the use of the photosensitive resin has an advantage that the patterning process corresponding to the opening 14a can be simplified. In order to obtain a sufficient alignment control force, it is preferable that the height of the projections 40 be in the range of about 0.5 μm to about 2 μm when the thickness of the liquid crystal layer 30 is about 3 μm. In general, it is preferable that the height of the protrusion 40 be in the range of about 1/6 to about 2/3 of the thickness of the liquid crystal layer 30.
[0171]
As described above, the liquid crystal display device 400 </ b> B has the convex portion 40 inside the opening 14 a of the upper conductive layer 14, and the side surface 40 s of the convex portion 40 has an oblique electric field with respect to the liquid crystal molecules 30 a of the liquid crystal layer 30. Has an alignment regulating force in the same direction as the alignment regulating direction. Preferred conditions for the side surface 40s to have the alignment control force in the same direction as the alignment control direction by the oblique electric field will be described with reference to FIGS. 26 (a) to 26 (c).
[0172]
FIGS. 26A to 26C schematically show cross-sectional views of the liquid crystal display devices 400C, 400D, and 400E, respectively, and correspond to FIG. 25A. Each of the liquid crystal display devices 400C, 400D, and 400E has a convex portion at least inside the opening 14a, but the arrangement relationship between the entire convex portion 40 as one structure and the opening 14a is different from that of the liquid crystal display device 400B. ing.
[0173]
In the above-described liquid crystal display device 400B, as shown in FIG. 25A, the entirety of the convex portion 40 as a structure is formed inside the opening portion 14a, and the bottom surface of the convex portion 40 has an opening. It is smaller than the portion 14a. In the liquid crystal display device 400C shown in FIG. 26A, the bottom surface of the projection 40A coincides with the opening 14a, and in the liquid crystal display device 400D shown in FIG. It has a bottom surface larger than the portion 14a and is formed so as to cover a solid portion (conductive film) 14b around the opening 14a. The solid portion 14b is not formed on the side surface 40s of any of these convex portions 40, 40A and 40B. As a result, as shown in each figure, the equipotential line EQ is substantially flat on the solid portion 14b, and drops at the opening 14a as it is. Therefore, the side surfaces 40s of the convex portions 40A and 40B of the liquid crystal display devices 400C and 400D exhibit the same alignment regulating force as that of the oblique electric field, similarly to the convex portion 40 of the liquid crystal display device 400B described above. Stabilizes radial tilt orientation.
[0174]
On the other hand, the bottom surface of the projection 40C of the liquid crystal display device 400E shown in FIG. 26C is larger than the opening 14a, and the solid portion 14b around the opening 14a is formed on the side surface 40s of the projection 40C. Have been. A mountain is formed on the equipotential line EQ under the influence of the solid portion 14b formed on the side surface 40s. The peak of the equipotential line EQ has an inclination opposite to that of the equipotential line EQ falling at the opening 14a, and this generates an oblique electric field that is opposite to the oblique electric field that causes the liquid crystal molecules 30a to radially align. It indicates that. Therefore, in order for the side surface 40s to have the alignment control force in the same direction as the alignment control direction by the oblique electric field, it is preferable that the solid portion (conductive film) 14b is not formed on the side surface 40s.
[0175]
Next, the cross-sectional structure of the protrusion 40 shown in FIG. 23A along the line 27A-27A 'will be described with reference to FIG.
[0176]
As described above, since the convex portion 40 shown in FIG. 23A is formed so as to completely surround the unit solid portion 14b 'in a substantially circular shape, the adjacent unit solid portions 14b' are mutually connected. The portions (branches extending in four directions from the circular portion) that serve to connect to are formed on the convex portions 40 as shown in FIG. Therefore, in the step of depositing the conductive film forming the solid portion 14b of the upper conductive layer 14, there is a high risk that disconnection may occur on the protrusion 40 or separation may occur in a later step of the manufacturing process.
[0177]
Thus, when the independent protrusions 40D are completely included in the openings 14a as in the liquid crystal display device 400F shown in FIGS. 28A and 28B, the solid portions 14b are formed. Since the conductive film is formed on the flat surface of the substrate 11, there is no danger of disconnection or peeling. Although the convex portion 40D is not formed so as to completely surround the unit solid portion 14b ′ in a substantially circular shape, a substantially circular liquid crystal domain corresponding to the unit solid portion 14b ′ is formed. As in the example, the radial tilt orientation is stabilized.
[0178]
By forming the protrusions 40 in the openings 14a, the effect of stabilizing the radially inclined orientation is not limited to the openings 14a of the illustrated patterns, but may be applied to the openings 14a of all the patterns described in the first embodiment. And the same effect can be obtained. In order to sufficiently exhibit the effect of stabilizing the alignment with respect to the external force due to the protrusions 40, the pattern of the protrusions 40 (the pattern when viewed from the normal direction of the substrate) surrounds the liquid crystal layer 30 in an area as large as possible. Preferably, it is shaped. Therefore, for example, a positive type pattern having a circular unit solid portion 14b 'has a larger effect of stabilizing the alignment by the convex portions 40 than a negative type pattern having a circular opening portion 14a.
[0179]
(Embodiment 3)
In the liquid crystal display device of the first embodiment, one of the pixel electrode 15 and the counter electrode 22 that face each other via the liquid crystal layer 30 and define a pixel region (the pixel electrode 15 By forming an opening 14a in the upper conductive layer 14, an oblique electric field was generated when a voltage was applied, and the oblique electric field was used to radially tilt the liquid crystal molecules using the oblique electric field. In the liquid crystal display device according to the second embodiment, the radially inclined alignment is stabilized by providing the convex portion in the opening 14 a of the upper conductive layer 14.
[0180]
In the third embodiment, a liquid crystal display device having a further alignment control structure on a substrate (a counter substrate in the above example) different from a substrate on which a two-layer structure electrode is formed (the TFT substrate in the above example) will be described. In the following description, the above-described electrode structure that realizes the radial tilt alignment by the oblique electric field is referred to as a first alignment control structure, and a further alignment control structure provided on a side different from the first alignment control structure with respect to the liquid crystal layer. It is referred to as a second alignment control structure.
[0181]
Next, the specific structure and operation of the second alignment control structure will be described. A description will be given of a case where the first alignment control structure is provided on the TFT substrate and the second alignment control structure is provided on the opposing substrate, in accordance with the above description.
[0182]
FIGS. 29A to 29E schematically show the counter substrate 200b having the second alignment control structure 28. FIG. Components that are substantially the same as those of the above-described liquid crystal display device are denoted by common reference numerals, and description thereof is omitted here.
[0183]
The second alignment control structure 28 shown in FIGS. 29A to 29E acts to radially tilt the liquid crystal molecules 30 a of the liquid crystal layer 30. However, the direction in which the liquid crystal molecules 30a are inclined is different between the alignment control structure 28 shown in FIGS. 29A to 29D and the alignment control structure 28 shown in FIG. 29E.
[0184]
The tilt direction of the liquid crystal molecules by the second alignment control structure 28 shown in FIGS. 29A to 29D is determined by the first alignment control structure by the unit solid portion 14b ′ of the upper conductive layer 14 (for example, FIG. 11C). (See FIG. 3), and the alignment direction of the radially tilted alignment of the liquid crystal domains formed in the region corresponding to (1). On the other hand, the tilt direction of the liquid crystal molecules by the second alignment control structure 28 shown in FIG. 29E is changed to the opening 14a of the upper conductive layer 14 by the first alignment control structure (for example, see FIG. 11C). It matches the alignment direction of the radial tilt alignment of the liquid crystal domain formed in the corresponding region.
[0185]
The second alignment regulating structure 28 shown in FIG. 29A has an opening of the counter electrode 22 provided at a position facing the upper conductive layer 14 (for example, the unit solid portion 14b ′ in FIG. 15A). 22a. Note that a vertical alignment film (not shown) is provided on the surface of the counter substrate 200b on the liquid crystal layer 30 side.
[0186]
The second alignment control structure 28 expresses an alignment control force only when a voltage is applied, similarly to the first alignment control structure described above. Since the second alignment control structure 28 only needs to act on the liquid crystal molecules in the liquid crystal domains having the radially inclined alignment formed by the first alignment control structure, the size of the opening 22a is limited to the upper layer. It is smaller than the opening 14a provided in the conductive layer 14, and smaller than the unit solid part 14b '(see, for example, FIG. 15A) surrounded by the opening 14a. For example, a sufficient effect can be obtained when the area is not more than half the area of the opening 14a or the unit solid part 14b '. By providing the opening 22a of the counter electrode 22 at a position facing the center of the unit solid portion 14b 'of the upper conductive layer 14, the continuity of the alignment of the liquid crystal molecules is increased, and the central axis of the radially inclined alignment is provided. Can be fixed.
[0187]
As described above, when a structure that exhibits an alignment control force only when a voltage is applied is employed as the second alignment control structure, almost all of the liquid crystal molecules 30a of the liquid crystal layer 30 assume a vertical alignment state when no voltage is applied. When the mari black mode is adopted, light leakage hardly occurs in a black display state, and a display with a good contrast ratio can be realized.
[0188]
However, since no alignment regulating force is generated when no voltage is applied, no radial tilt alignment is formed, and when the applied voltage is low, the alignment regulating force is small, so that if an excessively large stress is applied to the liquid crystal panel, an afterimage may occur. May be viewed.
[0189]
The second alignment control structure 28 shown in FIGS. 29B to 29D exhibits an alignment control force regardless of whether or not a voltage is applied, so that a stable radial tilt alignment can be obtained in all display gradations. And has excellent resistance to stress.
[0190]
First, the second alignment control structure 28 shown in FIG. 29B has a convex portion 22 b protruding toward the liquid crystal layer 30 on the counter electrode 22. There is no particular limitation on the material for forming the protrusion 22b, but the protrusion 22b can be easily formed using a dielectric material such as a resin. Note that a vertical alignment film (not shown) is provided on the surface of the counter substrate 200b on the liquid crystal layer 30 side. The convex portion 22b radially tilt-aligns the liquid crystal molecules 30a by the shape effect of the surface (having vertical alignment). Further, it is preferable to use a resin material that is deformed by heat, because a convex portion 22b having a gentle hill-shaped cross section as shown in FIG. 29B can be easily formed by heat treatment after patterning. As shown in the figure, the convex portion 22b having a gentle cross section having a vertex (for example, a part of a sphere) and the convex having a conical shape are excellent in the effect of fixing the center position of the radially inclined orientation.
[0191]
The second alignment regulating structure 28 shown in FIG. 29C has a liquid crystal layer in an opening 23 a (which may be a recess) provided in the dielectric layer 23 formed below the counter electrode 22 (on the side of the substrate 21). It is constituted by a horizontally oriented surface on the 30 side. Here, the surface in the opening 23a is a horizontal alignment surface by not forming the vertical alignment film 24 formed on the liquid crystal layer 30 side of the counter substrate 200b only in the opening 23a. Alternatively, as shown in FIG. 29D, the horizontal alignment film 25 may be formed only in the opening 23a.
[0192]
In the horizontal alignment film shown in FIG. 29D, for example, a vertical alignment film 24 is once formed on the entire surface of the counter substrate 200b, and the vertical alignment film 24 existing in the opening 23a is selectively irradiated with ultraviolet rays. Then, it may be formed by lowering the vertical orientation. The horizontal alignment required to form the second alignment control structure 28 does not need to have a small pretilt angle unlike an alignment film used in a TN type liquid crystal display device. For example, the pretilt angle is 45 ° or less. I just need.
[0193]
As shown in FIGS. 29 (c) and (d), on the horizontal alignment surface in the opening 23a, the liquid crystal molecules 30a try to align horizontally with respect to the substrate surface. An alignment is formed so as to maintain continuity with the alignment of the vertically aligned liquid crystal molecules 30a, and a radially inclined alignment as shown is obtained.
[0194]
Without providing a concave portion (formed by the opening of the dielectric layer 23) on the surface of the counter electrode 22, a horizontal alignment surface (such as the surface of the electrode or a horizontal alignment film) is formed on the flat surface of the counter electrode 22. The radially inclined orientation can be obtained only by selectively providing, but the radially inclined orientation can be further stabilized by the shape effect of the concave portion.
[0195]
It is preferable to use, for example, a color filter layer or an overcoat layer of a color filter layer as the dielectric layer 23 in order to form a concave portion on the surface of the counter substrate 200b on the liquid crystal layer 30 side, since the process does not increase and thus is preferable. . Further, the structure shown in FIGS. 29C and 29D does not have a region where a voltage is applied to the liquid crystal layer 30 via the protrusion 22b, unlike the structure shown in FIG. 29A. In addition, there is little decrease in light use efficiency.
[0196]
The second alignment control structure 28 shown in FIG. 29E uses the opening 23a of the dielectric layer 23 to form the opposite substrate 200b, similarly to the second alignment control structure 28 shown in FIG. A concave portion is formed on the liquid crystal layer 30 side, and the horizontal alignment film 26 is formed only on the bottom of the concave portion. Instead of forming the horizontal alignment film 26, the surface of the counter electrode 22 may be exposed as shown in FIG.
[0197]
FIGS. 30A and 30B show a liquid crystal display device 400G including the above-described first alignment control structure and second alignment control structure. FIG. 30A is a top view, and FIG. 30B corresponds to a cross-sectional view taken along line 22B-22B ′ in FIG.
[0198]
The liquid crystal display device 400G includes a TFT substrate 400a having an upper conductive layer 14 having an opening 14a constituting a first alignment control structure, and a counter substrate 200b having a second alignment control structure 28. Note that the first alignment regulating structure is not limited to the configuration exemplified here, and the various configurations described above can be used as appropriate. Also, as the second alignment control structure 28, one that exhibits an alignment control force even when no voltage is applied (FIGS. 29B to 29D and 29E) is exemplified. Instead of the first alignment regulating structure shown in (d), the structure shown in FIG. 29A can be used.
[0199]
Among the second alignment control structures 28 provided on the opposite substrate 200b of the liquid crystal display device 400G, the second alignment control structure 28 provided near the center of the region facing the solid portion 14b of the upper conductive layer 14 is 29 (b) to (d), and the second alignment regulating structure 28 provided near the center of the region facing the opening 14a of the upper conductive layer 14 is shown in FIG. This is shown in e).
[0200]
By arranging in this manner, in a state where a voltage is applied to the liquid crystal layer 30, that is, in a state where a voltage is applied between the upper conductive layer 14 and the counter electrode 22, the radial inclination formed by the first alignment regulating structure is formed. The direction of the alignment and the direction of the radial tilt alignment formed by the second alignment control structure 28 match, and the radial tilt alignment is stabilized. This situation is schematically shown in FIGS. FIG. 30A shows a state when no voltage is applied, FIG. 30B shows a state in which the orientation starts to change after voltage application (ON initial state), and FIG. 30C shows a steady state during voltage application. It is shown schematically.
[0201]
As shown in FIG. 31A, the alignment control force by the second alignment control structure (FIGS. 29B to 29D) acts on the nearby liquid crystal molecules 30a even in a state where no voltage is applied, so that the liquid crystal molecules 30a have a radial shape. Form a tilted orientation.
[0202]
When the voltage starts to be applied, an electric field indicated by the equipotential line EQ as shown in FIG. 31B is generated (due to the first alignment control structure), and the electric field is generated in a region corresponding to the opening 14a and the solid portion 14b. Liquid crystal domains in which the liquid crystal molecules 30a are radially inclined are formed, and reach a steady state as shown in FIG. At this time, the tilt direction of the liquid crystal molecules 30a in each liquid crystal domain matches the tilt direction of the liquid crystal molecules 30a due to the alignment control force of the second alignment control structure 28 provided in the corresponding region.
[0203]
When a stress is applied to the liquid crystal display device 400G in a steady state, the radially inclined alignment of the liquid crystal layer 30 once collapses, but when the stress is removed, the alignment control force by the first alignment control structure and the second alignment control structure is reduced. Since it acts on the liquid crystal molecules 30a, it returns to the radially inclined alignment state. Therefore, occurrence of an afterimage due to stress is suppressed. If the alignment control force by the second alignment control structure 28 is too strong, retardation due to radial tilt alignment may occur even when no voltage is applied, and the contrast ratio of display may be reduced. Since the force only needs to have the effect of stabilizing the radially inclined alignment formed by the first alignment control structure and fixing the center axis position, a strong alignment control force is not required, and retardation enough to lower display quality is obtained. An alignment regulating force that does not cause generation is sufficient.
[0204]
For example, when the convex portion 22b shown in FIG. 29B is adopted, the unit solid portion 14b ′ having a diameter of about 30 μm to about 35 μm has a diameter of about 15 μm and a height (thickness) of about 15 μm. By forming the convex portion 22b of 1 μm, a sufficient alignment regulating force can be obtained, and a decrease in contrast ratio due to retardation can be suppressed to a level that does not cause any practical problem.
[0205]
FIGS. 32A and 32B show another liquid crystal display device 400H including the first alignment control structure and the second alignment control structure. FIG. 32A is a top view, and FIG. 32B is a cross-sectional view taken along line 32B-32B ′ of FIG.
[0206]
The liquid crystal display device 400H does not have the second alignment control structure in a region facing the opening 14a of the upper conductive layer 14 of the TFT substrate 400a. Since it is difficult to form the second alignment regulating structure 28 shown in FIG. 29E to be formed in the region facing the opening 14a in FIG. 29 (e), from the viewpoint of productivity, FIG. It is preferable to use only one of the second alignment control structures 28 shown in a) to (d). In particular, the second alignment control structure 28 shown in FIG. 29B is preferable because it can be manufactured by a simple process.
[0207]
Even if the second alignment regulating structure is not provided in the region corresponding to the opening 14a as in the liquid crystal display device 400H, the liquid crystal display device 400G is similar to the liquid crystal display device 400G as schematically shown in FIGS. Is obtained, and its stress resistance has no practical problem.
(Embodiment 4)
In the liquid crystal display device of the present embodiment, the dielectric layer provided between the upper conductive layer and the lower conductive layer of the pixel electrode has a hole (hole) or a concave portion in the opening of the upper conductive layer. That is, the picture element electrode of the two-layer structure of the liquid crystal display device of the present embodiment has a structure in which the entire dielectric layer located in the opening of the upper conductive layer is removed (a hole is formed) or a part thereof is removed. (A concave portion is formed).
[0208]
First, the structure and operation of a liquid crystal display device 500 including a picture element electrode having a hole formed in a dielectric layer will be described with reference to FIG.
[0209]
In the liquid crystal display device 500, the upper conductive layer 14 of the pixel electrode 15 has an opening 14a, and the dielectric layer 13 provided between the lower conductive layer 12 and the upper conductive layer 14 is Has an opening 13a formed corresponding to the opening 14a of the semiconductor device, and the lower conductive layer 12 is exposed in the opening 13a. The side wall of the opening 13a of the dielectric layer 13 is generally formed in a tapered shape (taper angle: θ). The liquid crystal display device 500 has substantially the same structure as the liquid crystal display device 100 of Embodiment 1 except that the dielectric layer 13 has an opening 13a. The electrode 15 operates substantially in the same manner as the picture element electrode 15 of the liquid crystal display device 100, and brings the liquid crystal layer 30 into a radially inclined alignment state when a voltage is applied.
[0210]
The operation of the liquid crystal display device 500 will be described with reference to FIGS. FIGS. 34A to 34C correspond to FIGS. 1A to 1C of the liquid crystal display device 100 of the first embodiment, respectively.
[0211]
As shown in FIG. 34A, when no voltage is applied (OFF state), the liquid crystal molecules 30a in the picture element region are oriented perpendicular to the surfaces of the substrates 11 and 21. Here, for the sake of simplicity, description will be made while ignoring the alignment regulating force by the side wall of the opening 13a.
[0212]
When a voltage is applied to the liquid crystal layer 30, a potential gradient represented by an equipotential line EQ shown in FIG. 34B is formed. As can be seen from the fact that the equipotential lines EQ fall in the region corresponding to the openings 14a of the upper conductive layer 14 ("valleys" are formed), the liquid crystal layer 30 of the liquid crystal display device 500 also has FIG. As in the case of the potential gradient shown in FIG. However, since the dielectric layer 13 of the picture element electrode 15 has the opening 13a in the region corresponding to the opening 14a of the upper conductive layer 14, the liquid crystal layer in the region corresponding to the inside of the opening 14a (the inside of the opening 13a) is provided. The voltage applied to 30 is the potential difference between the lower conductive layer 12 and the counter electrode 22 itself, and no voltage drop (capacity division) by the dielectric layer 13 occurs. In other words, the seven equipotential lines shown between the upper conductive layer 14 and the counter electrode 22 are seven throughout the liquid crystal layer 30 (in FIG. 1B, five equipotential lines EQ (In contrast to one of them penetrating into the dielectric layer 13), a constant voltage is applied over the entire picture element region.
[0213]
By forming the opening 13a in the dielectric layer 13 as described above, the same voltage as that of the liquid crystal layer 30 corresponding to the other region can be applied to the liquid crystal layer 30 corresponding to the opening 13a. However, since the thickness of the liquid crystal layer 30 to which a voltage is applied varies depending on the location in the picture element region, the change in retardation at the time of applying the voltage varies depending on the location. Occurs.
[0214]
In the configuration shown in FIG. 34, the thickness d1 of the liquid crystal layer 30 on the upper conductive layer (other than the opening 14a) 14 and the liquid crystal on the lower conductive layer 12 located in the opening 14a (and the opening 13a). The thickness d2 of the layer 30 differs by the thickness of the dielectric layer 13. When the liquid crystal layer 30 having a thickness of d1 and the liquid crystal layer 30 having a thickness of d2 are driven in the same voltage range, the amount of change in retardation due to the change in alignment of the liquid crystal layer 30 is affected by the thickness of each liquid crystal layer 30. Different from each other. If the relationship between the applied voltage and the amount of retardation of the liquid crystal layer 30 is significantly different depending on the location, the transmittance is sacrificed in a design that emphasizes display quality, and when the transmittance is emphasized, the color temperature of white display shifts and the display quality decreases. The problem of sacrifices arises. Therefore, when the liquid crystal display device 500 is used as a transmission type liquid crystal display device, the thickness of the dielectric layer 13 is preferably thin.
[0215]
Next, FIG. 35 shows a cross-sectional structure of one picture element region of the liquid crystal display device 600 in which the dielectric layer of the picture element electrode has a concave portion.
[0216]
The dielectric layer 13 constituting the picture element electrode 15 of the liquid crystal display device 600 has a concave portion 13b corresponding to the opening 14a of the upper conductive layer 14. Other structures have substantially the same structure as the liquid crystal display device 500 shown in FIG.
[0217]
In the liquid crystal display device 600, since the dielectric layer 13 located in the opening 14a of the upper conductive layer 14 of the picture element electrode 15 is not completely removed, the thickness of the liquid crystal layer 30 located in the opening 14a is reduced. The thickness d3 is smaller than the thickness d2 of the liquid crystal layer 30 located in the opening 14a of the liquid crystal display device 500 by the thickness of the dielectric layer 13 in the recess 13b. Further, since the voltage applied to the liquid crystal layer 30 located in the opening 14a receives a voltage drop (capacity division) by the dielectric layer 13 in the recess 13b, the upper conductive layer (the area excluding the opening 14a) 14 The voltage is lower than the voltage applied to the upper liquid crystal layer 30. Therefore, by adjusting the thickness of the dielectric layer 13 in the recess 13b, the difference in the retardation amount caused by the difference in the thickness of the liquid crystal layer 30 and the difference due to the location of the voltage applied to the liquid crystal layer 30 (opening (A decrease in the voltage applied to the liquid crystal layer in the portion 14a) so that the relationship between the applied voltage and the retardation does not depend on the location in the picture element region. More strictly, the birefringence of the liquid crystal layer, the thickness of the liquid crystal layer, the dielectric constant of the dielectric layer, the thickness of the dielectric layer, and the thickness of the concave portion of the dielectric layer (the depth of the concave portion) are adjusted. Thereby, the relationship between the applied voltage and the retardation can be made uniform at a position in the picture element region, and high-quality display can be performed. In particular, as compared with a transmissive display device having a dielectric layer with a flat surface, the transmittance is reduced (the light is reduced) due to the decrease in the voltage applied to the liquid crystal layer 30 in the region corresponding to the opening 14a of the upper conductive layer 14. There is an advantage that the reduction in utilization efficiency is suppressed.
[0218]
In the above description, the case where the same voltage is supplied to the upper conductive layer 14 and the lower conductive layer 12 constituting the pixel electrode 15 is described. However, different voltages are applied to the lower conductive layer 12 and the upper conductive layer 14. With this configuration, it is possible to increase the variations of the configuration of the liquid crystal display device capable of performing display without display unevenness. For example, in a configuration in which the dielectric layer 13 is provided in the opening 14a of the upper conductive layer 14, a voltage higher than the voltage applied to the upper conductive layer 14 by a voltage drop due to the dielectric layer 13 is applied to the lower conductive layer 12. By applying the voltage, it is possible to prevent the voltage applied to the liquid crystal layer 30 from being different depending on the location in the picture element region.
[0219]
Also in the liquid crystal display devices 500 and 600 according to the fourth embodiment, similarly to the liquid crystal display device 100 according to the first embodiment, the oblique electric field generated by the pixel electrode 15 having the two-layer electrode structure including the upper conductive layer 14 having the opening 14a. As a result, the liquid crystal molecules 30a at the edge of the opening 14a are tilted and aligned, and the liquid crystal layer 30 in the picture element region is in a radially tilted state around the opening 14a. The description of the phenomenon of forming the radially inclined orientation is omitted here.
[0220]
The structure of the pixel electrode of the liquid crystal display device of the present embodiment will be described in more detail with reference to FIG. FIGS. 36A and 36B are schematic cross-sectional views in which the vicinity of the picture element electrode is enlarged. FIG. 36A shows a pixel electrode structure in which the upper conductive layer 14 is not formed on the side wall of the opening 13 a of the dielectric layer 13, and FIG. 36B shows the pixel electrode structure of the opening 13 a of the dielectric layer 13. The picture element electrode structure in which the upper conductive layer 14 is also formed on the side wall is shown.
[0221]
The structure shown in FIG. 36A included in the liquid crystal display devices 500 and 600 shown in FIGS. 34 and 35 described above is more preferable than the pixel electrode structure shown in FIG. 36B. This is because the inclination of the oblique electric field generated at the edge portion of the opening 14a of the upper conductive layer 14 is greater (the inclination angle is larger) in the pixel electrode structure shown in FIG. This is because the liquid crystal molecules 30a in the vicinity of the portion can be more stably aligned (in a unique direction). As can be seen from the equipotential line EQ in FIG. 36A, the equipotential line EQ in the opening 14a partially penetrates the side wall of the opening 13a of the dielectric layer 13, so that the equipotential line EQ Of the opening 14a is stronger than the inclination of the side wall. Accordingly, the liquid crystal molecules 30a whose alignment is vertically regulated on the surface of the side wall of the opening 13a (on the vertical alignment film (not shown) formed on the side surface) are univocally (counterclockwise in the illustrated example). ) Can be tilted. As can be seen from FIG. 36 (a), in order for the liquid crystal molecules 30a on the side wall of the opening 13a to tilt (rotate) in a unique direction due to an oblique electric field, it is preferable that the side wall tilt angle θ is small. .
[0222]
On the other hand, when the upper conductive layer 14 is formed on the side wall of the opening 13a of the dielectric layer 13, as shown by the equipotential line EQ in FIG. Since it is parallel to the surface of the layer 14, the slope of the equipotential line EQ at the edge of the opening 14a is gentler than the slope of the side wall. Therefore, the liquid crystal molecules 30a whose alignment is regulated vertically on the surface of the side wall of the opening 13a of the dielectric layer 13 (on the vertical alignment film (not shown) formed on the upper conductive layer) are equipotential lines. Since the EQs are orthogonal, a problem may occur that the direction in which the liquid crystal molecules 30a incline is not uniquely determined. In order to electrically connect the upper conductive layer 14 and the lower conductive layer 12, a part of the upper conductive layer 14 may be overlapped with a part of the lower conductive layer 12. In this case, there is no need to separately provide a contact hole for electrically connecting the upper conductive layer 14 and the lower conductive layer 12. In particular, in a reflection type liquid crystal display device using the upper conductive layer 14 formed on the flat surface (upper surface) of the dielectric layer 13 as a reflection electrode (reflection layer), the aperture ratio can be improved.
[0223]
The above description of the structure in which the dielectric layer 13 has the opening 13a also applies to the configuration in which the dielectric layer 13 has the recess 13b.
[0224]
As the liquid crystal display device of the present embodiment, a liquid crystal display device in which the upper conductive layer 14 includes a picture element electrode having one opening 14a in a picture element region is illustrated, but the present embodiment is not limited to the above example. The present invention can be applied to a liquid crystal display device having a plurality of openings 14a for each picture element region. The above-described configuration in which the opening 13a or the recess 13b is formed in the dielectric layer 13 corresponding to the opening 14a of the upper conductive layer 14 can be applied to all the liquid crystal display devices described as the first embodiment.
[0225]
(Embodiment 5)
FIG. 37 schematically shows one picture element region of the liquid crystal display device 700 according to the fifth embodiment. FIG. 37A is a cross-sectional view of the liquid crystal display device 700, and FIG. 37B is a plan view of the liquid crystal display device 700. FIG. 37A corresponds to a cross-sectional view taken along a line 37A-37A ′ in FIG. The liquid crystal display device 700 has substantially the same structure as the liquid crystal display device 500 of the fourth embodiment except that the lower conductive layer 12 further has an opening 12a, and a description of the common structure is omitted here. .
[0226]
The lower conductive layer of the picture element electrode 15 of the liquid crystal display device 700 has an opening 12a in a region of the dielectric layer 13 exposed in the opening 13a. As shown in FIG. 37B, the circular opening 13a of the dielectric layer 13 corresponds to the center of the picture element region, that is, the circular opening 14a provided at the center of the upper conductive layer 14. Is provided. The opening 12a formed in the lower conductive layer 12 exposed in the opening 13a of the dielectric layer 13 is located at the center of the opening 14a and the opening 13a.
[0227]
When a voltage is applied to the liquid crystal layer 30 of the liquid crystal display device 700, an electric field represented by an equipotential line EQ shown in FIG. The equipotential line EQ that has fallen at the edge EG of the opening 14 a of the upper conductive layer 14 further falls within the opening 12 a of the lower conductive layer 12.
[0228]
Since an oblique electric field is also formed at the edge of the opening 12a of the lower conductive layer 12, the orientation change of the liquid crystal molecules 30a in the liquid crystal layer 30 to which the voltage is applied is changed by the edge of the opening 14a and the edge of the opening 12a. The tilt of the liquid crystal molecules 30a with respect to the edge portion is triggered, and a radial tilt alignment is formed around the liquid crystal molecules 30a that are vertically aligned at the center of the opening 12a. As described above, in addition to the opening 14a of the upper conductive layer 14, the opening 12a is provided at the center of the lower conductive layer 12 at a position opposite to the opening 14a, so that the radial inclination of the liquid crystal molecules 30a in the opening 14a is increased. Since the position of the orientation can be controlled accurately and stably, the radial tilt orientation can be further stabilized and the response speed can be improved.
[0229]
Since no voltage is applied to the liquid crystal layer 30 corresponding to the opening 12a, the opening 12a is preferably not large. Typically, the thickness is preferably 8 μm or less. Since the opening 12a may be formed only at the center of the radially inclined orientation, one opening 12a may be formed at the center of each opening 14a. The shape of the opening 12a is not limited to a circle, but may be an ellipse or a polygon, as described above for the opening 14a.
[0230]
The operation of the opening 12a has been described for the configuration in which the opening 13a is formed in the dielectric layer 13, but the case where the recess 13b is formed in the dielectric layer 13 (FIG. 35) or the case where the flat dielectric layer 13 is used (FIG. 35). For example, it can be used in FIG. 1). That is, the configuration in which the lower conductive layer 12 of the picture element electrode 15 has the opening 12a in a region opposed to the opening 14a of the upper conductive layer 14 described in the example of the liquid crystal display device 700 is the same as that of the first embodiment described above. 2 can be appropriately combined with the liquid crystal display device. However, since the opening 12a is small (typically 8 μm or less in diameter), if the dielectric layer 13 on the opening 12a is thick, a sufficient effect may not be obtained.
[0231]
(Application to transflective liquid crystal display device)
A transflective liquid crystal display device (hereinafter abbreviated as a “dual liquid crystal display device”) is a liquid crystal having, within a picture element region, a transmissive region for performing display in a transmissive mode and a reflective region for performing display in a reflective mode. Refers to a display device. The transmissive area and the reflective area are typically defined by a transparent electrode and a reflective electrode. Instead of the reflective electrode, the reflective area can be defined by a structure in which a reflective layer and a transparent electrode are combined.
[0232]
This dual-purpose liquid crystal display device can switch and display between the reflection mode and the transmission mode, or can display in both display modes at the same time. Therefore, for example, display in the reflection mode can be realized in an environment with bright ambient light, and display in the transmission mode can be realized in a dark environment. In addition, when the display in both modes is performed at the same time, the liquid crystal display device in the transmission mode is used in an environment where the ambient light is bright (in a state where the light of a fluorescent lamp or sunlight is directly incident on the display surface at a specific angle). Can be suppressed. Thus, the disadvantage of the transmission type liquid crystal display device can be compensated. Note that the ratio of the area of the transmission region to the area of the reflection region can be set as appropriate according to the application of the liquid crystal display device. Further, in a liquid crystal display device exclusively used as a transmissive liquid crystal display device, the above-described drawbacks of the transmissive liquid crystal display device can be compensated for even if the area ratio of the reflection region is reduced to such an extent that display in the reflection mode cannot be performed.
[0233]
The structure and operation of the dual-purpose liquid crystal display device will be described with reference to FIGS. 38A, 38B, and 38C. The dual-purpose liquid crystal display device 150 shown in FIG. 38A is the liquid crystal display device 100 of the first embodiment, the dual-purpose liquid crystal display device 550 shown in FIG. 38B is the liquid crystal display device 500 of the fourth embodiment, and the dual-purpose liquid crystal display device 500 shown in FIG. The liquid crystal display device 650 has basically the same structure as the liquid crystal display device 600 of the fourth embodiment. The dual-purpose liquid crystal display device is not limited to the illustrated examples, and in all of the liquid crystal display devices described in Embodiments 1, 2, and 3, one of the upper electrode layer and the lower electrode layer may be formed of a transparent conductive layer. And the other is a reflective conductive layer.
[0234]
In the liquid crystal display device 150 shown in FIG. 38A, the upper conductive layer 14T of the picture element electrode 15 is formed of a transparent conductive layer, and the lower conductive layer 12R is formed of a conductive layer having light reflection characteristics, typically a metal layer. Is formed. The picture element area defined by the picture element electrode 15 has a reflection area R defined by the reflective lower conductive layer 12R and a transmission area T defined by the transparent upper conductive layer 14T. In consideration of the overlap between the transparent upper conductive layer 14T and the reflective lower conductive layer 12R and the contribution of light obliquely incident to the substrate normal (display surface normal) to the display, the reflective region R and the transmissive region are considered. T overlaps with each other near its boundary, but for simplicity, the two regions are illustrated separately by a display mode using light incident from the normal direction of the substrate.
[0235]
Since the basic structure of the liquid crystal display device 150 is the same as that of the liquid crystal display device 100, the liquid crystal layer is driven in substantially the same manner. That is, the liquid crystal layer 30 has a stable radially tilted orientation by the action of the pixel electrode 15 having a two-layer structure when a voltage is applied, and a liquid crystal display device having excellent viewing angle characteristics is realized.
[0236]
Hereinafter, the display operation of the liquid crystal display device 150 will be described.
[0237]
When the liquid crystal display device 150 is in a white display state, light incident on the transmission region T from a backlight (not shown) provided outside (the lower side in the figure) of the TFT substrate 100 a is transmitted to the substrate 11 and the dielectric layer 13. , Sequentially pass through the transparent upper conductive layer 14 </ b> T, pass through the liquid crystal layer 30, and exit to the counter substrate 100 b side. Light (typically ambient light) incident from the counter substrate 100b side sequentially passes through the substrate 21 and the counter electrode 22, passes through the liquid crystal layer 30 and the dielectric layer 13, enters the reflective lower conductive layer 12R, and is reflected. Then, the light is emitted toward the opposing substrate 100b along the reverse path.
[0238]
As described above, light for displaying in the transmission mode passes through the liquid crystal layer 30 only once, whereas light for displaying in the reflection mode passes through the liquid crystal layer 30 twice. Therefore, when the same voltage is applied to the liquid crystal layer 30 having a uniform thickness (d5) over the entire picture element region (the transmission region T and the reflection region R), the amount of change in the retardation that the transmitted light receives by the liquid crystal layer 30 And the amount of change in the retardation that the reflected light receives from the liquid crystal layer 30 does not match, and when a voltage is applied to the liquid crystal layer 30, the same gradation cannot be displayed simultaneously with the transmitted light and the reflected light, resulting in poor display quality. Problem arises.
[0239]
However, as described below, the liquid crystal display device 150 according to the present invention can avoid the above problems.
[0240]
Since the liquid crystal display device 150 includes the pixel electrode 15 having a two-layer structure, as described in the liquid crystal display device of the first embodiment, the voltage applied to the liquid crystal layer 30 in the reflection region R (opposing the lower conductive layer 12R) Since the voltage between the electrode 22 and the electrode 22 receives a voltage drop due to the dielectric layer 13, the voltage applied to the liquid crystal layer 30 in the transmission region T (the voltage between the upper conductive layer 14 </ b> T and the counter electrode 22). Will also be lower. As a result, the change in retardation of the liquid crystal layer 30 in the reflection area R is smaller than the change in retardation of the liquid crystal layer 30 in the transmission area T. Therefore, by adjusting the birefringence and the thickness of the liquid crystal layer 30 and the dielectric constant and the thickness of the dielectric layer 13, the change in retardation by the liquid crystal layer 30 in the transmission region T and the change in the liquid crystal layer 30 in the reflection region R are caused. The change in retardation can be brought closer. That is, the influence of the optical path length on the retardation of the reflected light can be compensated by adjusting the applied voltage.
[0241]
As described above, when the liquid crystal display device 150 of the present invention is used, the voltage-transmittance characteristics in the transmission mode and the voltage-reflectance characteristics in the reflection mode can be made closer to each other, and the viewing angle characteristics are excellent in all directions. In addition, a transflective liquid crystal display device having high visibility in all environments can be obtained.
[0242]
Next, the structure and operation of another dual-purpose liquid crystal display device 550 will be described with reference to FIG. 38B. The upper conductive layer 14R of the picture element electrode 15 of the dual-use liquid crystal display device 550 is formed of a conductive layer having light reflection characteristics, and the lower conductive layer 12T is formed of a transparent conductive layer. The picture element area defined by the picture element electrode 15 has a reflection area R defined by the reflective upper conductive layer 14R and a transmission area T defined by the transparent lower conductive layer 12T. The other basic configuration of the dual-purpose liquid crystal display device 550 is the same as that of the liquid crystal display device 500 shown in FIG. 34, and a description thereof will not be repeated.
[0243]
The thickness of the liquid crystal layer 30 in a region other than the opening 14a of the reflective upper conductive layer 14R of the liquid crystal display device 550 (that is, in the reflective region R) is d1, the inside of the opening 14a of the reflective upper conductive layer 14R, and the dielectric layer. The thickness of the liquid crystal layer 30 in the thirteen openings 13a (that is, in the transmission region T) is d2. The light (reflected light) contributing to the display in the reflection mode passes twice through the liquid crystal layer 30 having the thickness d1 in the reflection region R, and the light (transmitted light) contributing to the display in the transmission mode is transmitted in the transmission region T. Pass once through the liquid crystal layer 30 having a thickness d2. Therefore, by making the thickness of the dielectric layer 13 equal to d1, if d1 = d2 / 2, the distances of the reflected light and the transmitted light passing through the liquid crystal layer 30 can be made equal to each other. The pixel electrode 15 of the liquid crystal display device 550 has a configuration in which the transparent lower conductive layer 12T is exposed in the opening 13a of the dielectric layer 13 (a configuration in which the dielectric layer 13 does not exist on the transparent lower conductive layer 12T). ), The voltage applied to the liquid crystal layer 30 in the transmission region T is equal to the voltage applied to the liquid crystal layer 30 in the reflection region R.
[0244]
Therefore, if the thickness d1 of the liquid crystal layer 30 in the reflection region R and the thickness d2 of the liquid crystal layer 30 in the transmission region T are set so as to satisfy the relationship of 2 · d1 = d2, the lower conductive layer 12R and the lower conductive layer 12R When the same voltage is applied to upper conductive layer 14T, the amount of change in retardation of transmitted light received by liquid crystal layer 30 and the amount of change of retardation of reflected light received from liquid crystal layer 30 match. However, if the thickness of the liquid crystal layer 30 in the reflection region R and the thickness of the liquid crystal layer 30 in the transmission region T are different from each other, the electric field intensity is different even if the applied voltage is equal. It is more preferable to deviate from the relationship of d1 = d2.
[0245]
As described above, when the liquid crystal display device 550 of the present invention is used, the voltage-transmittance characteristics in the transmission mode and the voltage-reflectance characteristics in the reflection mode can be made close to each other, and the viewing angle characteristics are excellent in all directions. In addition, a transflective liquid crystal display device having high visibility in all environments can be obtained.
[0246]
Next, the structure and operation of another dual-purpose liquid crystal display device 650 will be described with reference to FIG. 38C. The upper conductive layer 14R of the picture element electrode 15 of the dual-purpose liquid crystal display device 650 is formed of a conductive layer having light reflection characteristics, and the lower conductive layer 12T is formed of a transparent conductive layer. The picture element area defined by the picture element electrode 15 has a reflection area R defined by the reflective upper conductive layer 14R and a transmission area T defined by the transparent lower conductive layer 12T. The other basic configuration of the dual-purpose liquid crystal display device 650 is the same as that of the liquid crystal display device 600 shown in FIG. 35, and a description thereof will not be repeated.
[0247]
The thickness of the liquid crystal layer 30 in a region other than the opening 14a of the reflective upper conductive layer 14R of the liquid crystal display device 650 (that is, in the reflective region R) is d1, the inside of the opening 14a of the reflective upper conductive layer 14R, and the dielectric layer. The thickness of the liquid crystal layer 30 in the recess 13b of the thirteen (ie, in the transmission region T) is d3. The thickness d3 of the liquid crystal layer 30 in the transmission region T is greater than the thickness d1 of the liquid crystal layer 30 in the reflection region R by the depth of the concave portion 13b of the dielectric layer 13. The light (reflected light) contributing to the display in the reflection mode passes twice through the liquid crystal layer 30 having the thickness d1 in the reflection region R, and the light (transmitted light) contributing to the display in the transmission mode is transmitted in the transmission region T. Once through the liquid crystal layer 30 having a thickness d3. That is, the distance that the transmitted light passes through the liquid crystal layer 30 is d3, and the distance that the reflected light passes through the liquid crystal layer 30 is 2 · d1.
[0248]
On the other hand, the voltage applied to the liquid crystal layer 30 in the transmission region T is subjected to a voltage drop (capacity division) by the dielectric layer 13 in the concave portion 13b, and thus is lower than the voltage applied to the liquid crystal layer 30 in the reflection region R. Lower. Therefore, by adjusting the thickness of the dielectric layer 13 in the concave portion 13b, the difference in the amount of retardation caused by the difference in the distance passing through the liquid crystal layer 30 and the difference in the location of the voltage applied to the liquid crystal layer 30 By controlling the relationship between the applied voltage and the retardation in the transmission region T and the reflection region R, the relationship between the applied voltage and the retardation can be controlled. More strictly, the birefringence of the liquid crystal layer, the thickness of the liquid crystal layer, the dielectric constant of the dielectric layer, the thickness of the dielectric layer, and the thickness of the concave portion of the dielectric layer (the depth of the concave portion) are adjusted. Thereby, the relationship between the applied voltage and the retardation can be made uniform over the transmission region and the reflection region.
[0249]
As described above, when the liquid crystal display device 650 of the present invention is used, the voltage-transmittance characteristics in the transmission mode and the voltage-reflectance characteristics in the reflection mode can be made close to each other, and the viewing angle characteristics are excellent in all directions. In addition, a transflective liquid crystal display device having high visibility in all environments can be obtained.
[0250]
In FIGS. 38A, 38B and 38C, the surface of the reflective conductive layer (upper or lower conductive layer) is drawn flat in the transmissive / reflective liquid crystal display devices 150, 550 and 650, but the surface of the reflective conductive layer is processed into an uneven shape. By doing so, a function of diffusing and reflecting (or scattering) light can be provided. By providing a light diffusing function to the reflective conductive layer, it is possible to realize a reflection mode display with no display parallax and high display quality.
[0251]
As a method of forming irregularities on the surface of the reflective conductive layer, for example, a method disclosed in Japanese Patent Application Laid-Open No. 6-75238 is mentioned.
[0252]
For example, the dielectric layer 13 is formed using a photoresist (which may be either a negative type or a positive type), and a photolithography process using a photomask having a light-transmitting portion (or a light-shielding portion) of a predetermined pattern is performed. Unevenness is processed on the surface of the resist layer. If necessary, the resist layer on which the unevenness is formed may be heated to make the unevenness smooth (continuous wavy shape) by using a phenomenon (heat dripping) in which the surface of the resist layer is deformed by heat. By forming the reflective upper conductive layer on the uneven surface of the dielectric layer 13 formed as described above, the unevenness can be formed on the surface of the reflective upper conductive layer.
[0253]
However, in a configuration using the reflective upper conductive layer 14R as in the dual-purpose liquid crystal display devices 550 and 650 shown in FIGS. 38B and 38C, the opening 14a is formed as shown in FIGS. 40 (a) and (b). It is preferable that the height of the dielectric layer 13 at the edge portion is uniform.
[0254]
In the liquid crystal display device of the present invention, the liquid crystal molecules are formed by using the oblique electric field generated at the edge of the opening 14a by the two-layered picture element electrode 15 including the reflective upper conductive layer 14R having the opening 14a. Radially inclined orientation.
[0255]
However, as shown in FIG. 39A, the irregularities formed on the surface of the dielectric layer 13 (circles in the figure schematically show concave parts or convex parts) are the openings of the dielectric layer 13. When the dielectric layer 13 is arranged so as to overlap the portion 13a and the concave portion 13b, the thickness of the dielectric layer 13 at the edge of the opening 14a differs depending on the location as shown in FIG. As described above, if the surface of the dielectric layer 13 at the edge portion has irregularities, the direction of the oblique electric field generated at the edge portion (inclination direction of the equipotential line) changes depending on the location, and the opening portion 14a is removed. The stability of the radially inclined orientation at the center decreases, or the state of the radially inclined orientation varies depending on the position of the opening 14a.
[0256]
Therefore, as shown in FIG. 40A, it is assumed that the surface of the dielectric layer 13 around the opening 14a (the opening 13a or the recess 13b of the dielectric layer 13) has no unevenness and has a flat surface. As shown in FIG. 40B, a structure is obtained in which the dielectric layer 13 near the edge has a uniform thickness over the entire circumference of the opening 14a.
[0257]
Note that instead of imparting a light diffusion function to the reflective conductive layer by processing the surface of the reflective conductive layer into an uneven shape, a diffusion layer having a light diffusion function may be provided on the light incident side of the reflective conductive layer. The diffusion layer may be provided inside the liquid crystal panel (the liquid crystal layer side of the substrate) or outside (the observer side). It is preferable that the diffusion layer is selectively provided in a reflection region of the liquid crystal display device.
[0258]
(Arrangement of polarizer and retarder)
A so-called vertical alignment type liquid crystal display device includes a liquid crystal layer in which liquid crystal molecules having negative dielectric anisotropy are vertically aligned when no voltage is applied, and can perform display in various display modes. A birefringence mode in which display is performed by controlling the birefringence of the liquid crystal layer by an electric field is preferable from the viewpoint of display quality. The positional relationship between a polarizing plate and a retardation plate (wave plate) for improving the display quality of a birefringence mode vertical alignment type liquid crystal display device will be described below. By providing a pair of polarizing plates outside (a side opposite to the liquid crystal layer 30) of a pair of substrates (for example, a TFT substrate and a counter substrate) of all the liquid crystal display devices described in the first to fifth embodiments, birefringence is provided. A mode liquid crystal display device can be obtained.
[0259]
First, the arrangement of the polarizing plates will be described with reference to FIGS. FIG. 41 shows a voltage non-applied state (OFF state), and FIG. 42 shows a voltage applied state (ON state).
[0260]
FIG. 41A is a schematic cross-sectional view of a liquid crystal display device 100A having polarizing plates 50a and 50b outside the TFT substrate 100a and the counter substrate 100b, respectively. The liquid crystal display device 100A may be any of the liquid crystal display devices according to the first to fifth embodiments. As shown in FIG. 41A, the liquid crystal molecules 30a in the liquid crystal layer 30 are in a vertical alignment state when no voltage is applied.
[0261]
FIG. 41 (b) shows the transmission axes of the polarizing plates 50a and 50b when the liquid crystal display device 100A is viewed along the display surface normal direction (substrate normal direction) from the counter substrate 100b side (observer side). 2 schematically shows the arrangement relationship of (polarization axis) PA. The solid arrow PA1 in the figure indicates the transmission axis of the polarizing plate (upper) 50b, and the broken arrow indicates the transmission axis PA2 of the polarizing plate (lower) 50a. As shown in FIG. 41B, the transmission axes PA2 and PA1 of the polarizing plates 50a and 50b are arranged to be orthogonal to each other. That is, the polarizing plates 50a and 50b are arranged in a crossed Nicols state.
[0262]
Since the axis direction of the liquid crystal molecules 30a of the liquid crystal layer 30 when no voltage is applied is perpendicular to the substrate surface, no phase difference is given to polarized light that is perpendicularly incident on the liquid crystal layer 30. Note that "perpendicular to the liquid crystal layer 30" means perpendicular to the plane of the liquid crystal layer 30 parallel to the substrates 100a and 100b.
[0263]
Since the liquid crystal layer 30 in the vertical alignment state does not give a phase difference to the vertically polarized light, for example, the light vertically incident on the liquid crystal layer 30 from the TFT substrate 100a side passes through the polarizing plate 50a, and thereby the transmission axis PA2. And enters the liquid crystal layer 30 perpendicularly, and enters the polarizing plate 50b through the liquid crystal layer 30 while maintaining the polarization direction. Since the transmission axes PA2 and PA1 of the polarizing plates 50a and 50b are orthogonal to each other, the linearly polarized light that has passed through the counter substrate 100b is absorbed by the polarizing plate 50b. As a result, the liquid crystal display device 100A with no voltage applied displays black.
[0264]
In the voltage applied state, as shown in FIGS. 42A and 42B, the liquid crystal molecules 30a are in a radially inclined alignment. In FIGS. 42A and 42B, one radially inclined alignment region is shown for simplicity, but as described in the first to fifth embodiments, a plurality of pixels are included in one pixel region. May be formed. In the following drawings, one radial inclined orientation may be illustrated, but a plurality of radial inclined orientation regions may be formed in one pixel region.
[0265]
The liquid crystal layer 30 including the liquid crystal molecules 30a that are radially tilt-aligned has, for example, light that vertically enters the liquid crystal layer 30 from the TFT substrate 100a side has a polarization direction along the transmission axis PA2 by passing through the polarizing plate 50a. The light becomes linearly polarized light and vertically enters the liquid crystal layer 30. The liquid crystal molecules 30a whose liquid crystal molecules 30a are oriented so that their axis directions viewed from the substrate normal direction are parallel or orthogonal to the polarization direction of this linearly polarized light, and the liquid crystal molecules that are in a vertical alignment state (located at the center of the radially inclined alignment) The liquid crystal molecules 30a do not give a phase difference to linearly polarized light that is perpendicularly incident on the liquid crystal layer 30. Therefore, the linearly polarized light having the liquid crystal molecules 30a incident on the region in the above-described alignment direction passes through the liquid crystal layer 30 while maintaining the polarization state, and is incident on the polarizing plate 50b through the counter substrate 100b. Since the transmission axes PA2 and PA1 of the polarizing plates 50a and 50b are orthogonal to each other, the linearly polarized light is absorbed by the polarizing plate 50b. That is, a partial region of the liquid crystal layer 30 in the radially inclined alignment state is in a black display state even when a voltage is applied.
[0266]
On the other hand, of the linearly polarized light having a polarization direction parallel to the transmission axis PA2 of the polarizing plate 50a, the axis direction viewed from the normal direction of the substrate is oriented so as to be parallel or orthogonal to the polarization direction of the linearly polarized light. The liquid crystal layer 30 gives the liquid crystal layer 30 a phase difference between the liquid crystal molecules 30a and the linearly polarized light incident on the region including the liquid crystal molecules 30a other than the liquid crystal molecules 30a in the vertical alignment state. That is, the linearly polarized light loses its polarization state and becomes elliptically polarized light. Also, this phase difference is maximum in a region where the polarization direction of the incident linearly polarized light and the axis direction of the liquid crystal molecules 30a when viewed from the normal direction of the substrate are 45 degrees, and with respect to the polarization direction of the incident linearly polarized light, As the axis orientation of the liquid crystal molecules 30a as viewed from the normal direction of the substrate approaches parallel or orthogonal, the orientation becomes smaller. Therefore, the axis direction of the liquid crystal molecules 30a when viewed from the substrate normal direction is other than parallel or orthogonal to the polarization direction of the incident linearly polarized light, or the molecular axis of the liquid crystal molecules 30a is not parallel to the substrate normal direction. In a region where the axis direction of the liquid crystal molecules 30a when viewed from the normal direction of the substrate is other than parallel or orthogonal, a phase difference is given to the linearly polarized light incident on the liquid crystal layer 30, and the linearly polarized light is broken (in general). It becomes elliptically polarized light.) Therefore, when the polarized light whose polarization state is changed by passing through the liquid crystal layer 30 enters the polarizing plate 50b, a part of the polarized light passes through the polarizing plate 50b. Since the amount of transmitted polarized light depends on the magnitude of the phase difference provided by the liquid crystal layer 30, it can be adjusted by controlling the voltage applied to the liquid crystal layer 30. Therefore, by controlling the voltage applied to the liquid crystal layer 30, gradation display is possible.
[0267]
(Λ / 4 plate)
By providing a quarter-wave plate (λ / 4 plate) between the liquid crystal layer and a pair of polarizing plates disposed on both sides of the liquid crystal layer, the display quality can be further improved. That is, by making the circularly polarized light incident on the liquid crystal layer 30 exhibiting the radially inclined alignment, the light use efficiency can be increased. For example, in a liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 10-301114, in which linearly polarized light is made incident on a vertically-aligned liquid crystal layer of four-divided multi-domain alignment, a boundary region between domains of the multi-domain is caused to contribute to display. However, if a configuration is adopted in which circularly polarized light is incident on a liquid crystal layer exhibiting a radially inclined alignment in which the alignment direction changes continuously, a brighter (high light use efficiency) liquid crystal display device can be realized. it can.
[0268]
The operation of the λ / 4 plate will be described with reference to FIGS. 43 and 44. FIG. 43 schematically shows a state where no voltage is applied, and FIG. 44 schematically shows a state where a voltage is applied. In the specification of the present application, unless otherwise specified, “λ / 4 plate” refers to a single-layer plate, and a plurality of retardation plates laminated to form a retardation plate satisfying the λ / 4 condition as a whole. In particular, it will be referred to as “broadband λ / 4 plate”. Here, a configuration using a single-layer λ / 4 plate will be described.
[0269]
The liquid crystal display device 100B shown in FIGS. 43 and 44 has polarizing plates 50a and 50b and λ / 4 plates 60a and 60b on both sides of the liquid crystal display device 100. The λ / 4 plates 60a and 60b convert linearly polarized light having a polarization direction of 45 ° to its slow axis into circularly polarized light or conversely have circularly polarized light of 45 ° to its slow axis. This is a retardation plate that converts the light into linearly polarized light. The liquid crystal display device is not limited to the liquid crystal display device 100, and any of the liquid crystal display devices according to the first to fifth embodiments can be used.
[0270]
The liquid crystal display device 100B has a λ / 4 plate 60a between the TFT substrate 100a and the polarizing plate 50a provided on the outside thereof (the side opposite to the liquid crystal layer 30), and is provided on the opposite substrate 100b and the outside thereof. And a polarizing plate 50b. The transmission axes PA2 and PA1 of the polarizing plates 50a and 50b and the slow axes SL2 and SL1 of the λ / 4 plates 60a and 60b are arranged as shown in FIG. 43 (b).
[0271]
The slow axis SL2 of the λ / 4 plate 60a forms an angle of 45 ° with the transmission axis PA2 of the polarizing plate 50a, and the slow axis SL1 of the λ / 4 plate 60b forms an angle of 45 ° with the transmission axis PA1 of the polarizing plate 50b. It is arranged to make it. The angles formed by the transmission axes PA1 and PA2 and the slow axes SL2 and SL1 are in the same direction (for example, when viewed from the counter substrate 100b side along the substrate normal direction, as shown in FIG. If both are clockwise, they are clockwise, and if they are counterclockwise, they are both counterclockwise.
[0272]
As shown in FIG. 43 (a), when no voltage is applied, the liquid crystal layer 30 is in the vertical alignment state, so that no phase difference is given to light that is vertically incident on the liquid crystal layer 30. Therefore, for example, light that is vertically incident on the liquid crystal layer 30 from the TFT substrate 100a side passes through the polarizing plate 50a, and becomes linearly polarized light having a polarization direction of 45 ° with respect to the slow axis SL2 of the λ / 4 plate 60a. The light enters the / 4 plate 60a. This linearly polarized light is converted into circularly polarized light by passing through the λ / 4 plate 60a. The circularly polarized light passes through the liquid crystal layer 30 while maintaining the polarization state, and enters the λ / 4 plate 60b. By passing through the λ / 4 plate 60b, the circularly polarized light becomes linearly polarized light having a polarization direction of 45 degrees with respect to the slow axis SL1, and enters the polarizing plate 50b. Since the polarization direction of the linearly polarized light that has passed through the λ / 4 plate 60b is orthogonal to the transmission axis PA1 of the polarizing plate 50b, this linearly polarized light is absorbed by the polarizing plate 50b. Therefore, the liquid crystal display device 100B enters a black display state when no voltage is applied.
[0273]
In a state where a voltage is applied, as shown in FIGS. 44A and 44B, the liquid crystal molecules 30a are radially aligned.
[0274]
The liquid crystal layer 30 including the liquid crystal molecules 30a that are radially tilt-aligned gives a phase difference according to the polarization direction to light incident on the liquid crystal layer 30. For example, light that is vertically incident on the liquid crystal layer 30 from the TFT substrate 100a side passes through the polarizing plate 50a, so that the polarization direction becomes linearly polarized light of 45 ° with respect to the slow axis SL2 of the λ / 4 plate 60a. The light enters the λ / 4 plate 60a. This linearly polarized light is converted into circularly polarized light by passing through the λ / 4 plate 60a. At this time, the liquid crystal molecules 30a in the vertical alignment state (the liquid crystal molecules located at the center of the radially inclined alignment) 30a do not give a phase difference to the polarized light that is vertically incident on the liquid crystal layer 30. Therefore, the circularly polarized light that has entered the region where the liquid crystal molecules 30a are vertically aligned passes through the liquid crystal layer 30 while maintaining the polarization state, and enters the λ / 4 plate 60b. By passing through the λ / 4 plate 60b, the circularly polarized light becomes linearly polarized light having a polarization direction of 45 degrees with respect to the slow axis SL1, and enters the polarizing plate 50b. Since the polarization direction of the linearly polarized light that has passed through the λ / 4 plate 60b is orthogonal to the transmission axis PA1 of the polarizing plate 50b, this linearly polarized light is absorbed by the polarizing plate 50b. That is, a part of the liquid crystal layer 30 in the radially inclined alignment state (only the vertical alignment area) is in a black display state even when a voltage is applied.
[0275]
On the other hand, of the circularly polarized light converted from the linearly polarized light by the λ / 4 plate 60b, the circularly polarized light incident on the region including the liquid crystal molecules 30a other than the liquid crystal molecules 30a in the vertical alignment state is given a phase difference by the liquid crystal layer 30. Can be That is, the polarization state of the circularly polarized light changes (generally becomes elliptically polarized light). Therefore, part of the polarized light that has passed through the λ / 4 plate 60b passes through the polarizing plate 50b. Since the amount of transmitted polarized light depends on the magnitude of the phase difference provided by the liquid crystal layer 30, it can be adjusted by controlling the voltage applied to the liquid crystal layer 30. Therefore, by controlling the voltage applied to the liquid crystal layer 30, gradation display is possible.
[0276]
As described above, in the liquid crystal display device 100B further including the λ / 4 plates 60a and 60b, the region where the black display state is obtained when the voltage is applied is only the vertical alignment region (the center of the radially inclined alignment). In addition, as compared with the liquid crystal display device 100A in which a region oriented in a direction parallel or perpendicular to the transmission axis of the polarizing plate is in a black display state, there are fewer regions in which a black display is performed when a voltage is applied. That is, the liquid crystal display device 100B has higher light use efficiency (effective aperture ratio) and higher luminance than the liquid crystal display device 100A.
[0277]
Generally, it is not easy to completely eliminate the wavelength dispersion of the single-layer λ / 4 plates 60a and 60b. For example, when the λ / 4 plates 60a and 60b are λ / 4 plates manufactured so as to satisfy the λ / 4 condition with respect to the light having the highest visibility at the wavelength of 550 nm, the wavelength of the light increases from 550 nm. As the position shifts, the condition deviates from the λ / 4 condition. As a result, in the liquid crystal display device 100B, in the black display state, visible light having a wavelength shifted from 550 nm passes through the polarizing plate 50b, and as a result, a coloring phenomenon occurs.
[0278]
In order to suppress the occurrence of the coloring phenomenon in the black display state, as in the liquid crystal display device 100C shown in FIG. 45, the transmission axes PA2 and PA1 of the polarizing plates 50a and 50b are orthogonal to each other and the λ / 4 plate 60a And the slow axes SL2 and SL1 of 60b are orthogonal to each other. The transmission axis PA2 of the polarizing plate 50a and the slow axis SL2 of the λ / 4 plate 60a, and the transmission axis PA1 of the polarizing plate 50b and the slow axis SL1 of the λ / 4 plate 60b are the same as in the liquid crystal display device 100B. Each forms an angle of 45 ° in the same direction. Thus, by arranging the slow axis SL2 of the λ / 4 plate 60a and the slow axis SL1 of the λ / 4 plate 60b so as to be orthogonal to each other, each of the λ / 4 plate 60a and the λ / 4 plate 60b is provided. In the black display state, visible light in a wide wavelength range is absorbed by the polarizing plate 50b, and excellent black display is realized. In particular, it is preferable to use the same λ / 4 plate (at least a λ / 4 plate formed of the same material) as the λ / 4 plate 60a and the λ / 4 plate 60b. When such a configuration is adopted, a liquid crystal display device can be configured at a lower cost than a configuration using a broadband λ / 4 plate described below.
[0279]
As another method for suppressing the occurrence of the coloring phenomenon in the black display state due to the wavelength dispersion of the refractive index anisotropy of the single-layer λ / 4 plates 60a and 60b, as an alternative to the single-layer λ / 4 plate And a method using a broadband λ / 4 plate. The broadband λ / 4 plate cancels out the influence of chromatic dispersion by stacking a plurality of retardation plates, and satisfies the λ / 4 condition over the entire visible light (400 nm to 800 nm). The broadband λ / 4 plate can be formed, for example, by laminating a single-layer λ / 4 plate and a single-layer half-wave plate (hereinafter referred to as “λ / 2 plate”).
[0280]
The liquid crystal display device 100D shown in FIG. 46 has polarizing plates 50a and 50b, λ / 4 plates 60a and 60b, and λ / 2 plates 70a and 70b on both sides of the liquid crystal display device 100. On the outside of the TFT substrate 100a (the side opposite to the liquid crystal layer 30), a λ / 4 plate 60a, a λ / 2 plate 70a, and a polarizing plate 50a are provided in this order from the liquid crystal layer 30 side. Is provided with a λ / 4 plate 60b, a λ / 2 plate 70b, and a polarizing plate 50b in this order from the liquid crystal layer 30 side.
[0281]
The λ / 4 plate 60b, the λ / 2 plate 70b, and the polarizing plate 50b arranged on the counter substrate 100b have their respective optical axes arranged as shown in FIG. 46 (b). When the angle between the transmission axis PA1 of the polarizing plate 50b and the slow axis SL3 of the λ / 2 plate 70b is α (°), the transmission axis PA1 of the polarizing plate 50b and the slow axis SL1 of the λ / 4 plate 60b are set. Are arranged so that the angle between them is 2α ± 45 °.
[0282]
On the other hand, the λ / 4 plate 60a, the λ / 2 plate 70a, and the polarizing plate 50a arranged on the TFT substrate 100a have their respective optical axes arranged as shown in FIG. 46 (c). When the angle between the transmission axis PA2 of the polarizing plate 50a and the slow axis SL4 of the λ / 2 plate 70a is β (°), the transmission axis PA2 of the polarizing plate 50a and the slow axis SL2 of the λ / 4 plate 60a. Are arranged so that the angle between them is 2β ± 45 °. This angle (2β ± 45 °) between the transmission axis PA2 of the polarizing plate 50a and the slow axis SL2 of the λ / 4 plate 60a is determined by the delay of the transmission axis PA1 of the polarizing plate 50b and the slowness of the λ / 4 plate 60b. The sign is set so that the sign matches the angle (2α ± 45 °) with the axis SL1. That is, when the angle between PA1 and the slow axis SL1 is 2α + 45 °, the angle between the transmission axis PA2 and the slow axis SL2 is set to 2β + 45 °.
[0283]
Light perpendicularly incident on the liquid crystal layer 30 in the vertical alignment state from the TFT substrate 100a side passes through the polarizing plate 50a, becomes linearly polarized light, passes through the λ / 2 plate 70a, and is shifted by 2β with respect to the transmission axis PA2 of the polarizing plate 50a. It becomes linearly polarized light having an angle of polarization direction. This linearly polarized light enters the λ / 4 plate 60a and is converted into circularly polarized light. This circularly polarized light passes through the liquid crystal layer 30 while maintaining the polarization state, and enters the λ / 4 plate 60b. The λ / 4 plate 60b converts the light into linearly polarized light having a polarization direction at an angle of 45 degrees with respect to the slow axis SL1 of the λ / 4 plate 60b. This linearly polarized light enters the λ / 2 plate 70b, becomes linearly polarized light having an angle of 2β + 45 degrees with respect to the slow axis SL1 of the λ / 4 plate 60b, and enters the polarizing plate 50b. Here, since the polarization direction of the linearly polarized light that has passed through the λ / 2 plate 70b is orthogonal to the transmission axis PA1 of the polarizing plate 50b, this linearly polarized light is absorbed by the polarizing plate 50b. Therefore, the liquid crystal display device 100D enters a black display state when no voltage is applied.
[0284]
The liquid crystal display device 100D has a λ / 2 plate 70a and a λ / 2 plate 70b between the λ / 4 plate 60a and the polarizing plate 50a and between the λ / 4 plate 60b and the polarizing plate 50b, respectively. Since the λ / 2 plates 70a and 70b reduce the wavelength dispersion of the refractive index anisotropy of the λ / 4 plates 60a and 60b, a good black display without coloring can be achieved.
[0285]
In order to further suppress the occurrence of the coloring phenomenon in the black display state, as in a liquid crystal display device 100E shown in FIG. 47, the transmission axes PA2 and PA1 of the polarizing plates 50a and 50b are orthogonal to each other, and the λ / 4 plate is used. The slow axes SL2 and SL1 of 60a and 60b are orthogonal to each other, and the slow axes SL4 and SL3 of the λ / 2 plates 70a and 70b are orthogonal to each other. When the angle between the transmission axis PA1 of the polarizing plate 50b and the slow axis SL3 of the λ / 2 plate 70b is α (°), the delay between the transmission axis PA1 of the polarizing plate 50b and the λ / 4 plate 60b is considered. The angle between the axis SL1 and the slow axis SL4 of the λ / 2 plate 70a is α, and the angle between the transmission axis PA2 of the polarizing plate 50a and the slow axis SL4 of the λ / 2 plate 70a is α. Are arranged so that the angle between the transmission axis PA2 and the slow axis SL2 of the λ / 4 plate 60a is 2α ± 45 °. This angle (2α ± 45 °) between the transmission axis PA2 of the polarizing plate 50a and the slow axis SL2 of the λ / 4 plate 60a is determined by the phase difference between the transmission axis PA1 of the polarizing plate 50b and the lag of the λ / 4 plate 60b. The sign is set so that the sign matches the angle (2α ± 45 °) with the axis SL1.
[0286]
As described above, the transmission axes of the polarizing plates 50a and 50b, the slow axes of the λ / 4 plates 60a and 60b, and the slow axes of the λ / 2 plates 70a and 70b are orthogonal to each other. The wavelength dispersion of the refractive index anisotropy of each of the / 4 plate 60a and the λ / 4 plate 60b can be offset, and in the black display state, visible light in a wide wavelength range is absorbed by the polarizing plate 50b, and the liquid crystal display The device 100E achieves a better black display than the liquid crystal display device 100D.
[0287]
In the above description, the effect of the liquid crystal layer 30 on light that is perpendicularly incident on the liquid crystal layer 30 has been described. In a liquid crystal display device, particularly in a transmission type, light vertically incident on the liquid crystal layer 30 most contributes to display, but light obliquely incident on the liquid crystal layer 30 also contributes to display. Light obliquely incident on the liquid crystal layer 30 is also given a phase difference by the liquid crystal layer 30 in the vertical alignment state. Therefore, when the display surface of the liquid crystal display device is viewed obliquely (in a direction inclined from the normal to the display surface), light leakage occurs in a vertical alignment state that should be a black display state, and the display contrast ratio is reduced. There is.
[0288]
By further providing a retardation plate (viewing angle compensator) having a refractive index anisotropy that cancels out the phase difference with respect to the oblique incident light, a liquid crystal display device having a good contrast ratio in all viewing angle ranges can be realized. Can be. The viewing angle compensator does not need to be a single retarder, but may be a laminate of a plurality of retarders. The viewing angle compensating plate may be provided only on the outside of the TFT substrate 100a (the side farthest from the liquid crystal layer 30), only on the outside of the counter substrate 100b, or on the outside of both the TFT substrate 100a and the counter substrate 100b. Is also good.
[0289]
In the above description of the λ / 4 wavelength plate, a case of a transmission type liquid crystal display device has been described. It is necessary to reduce the wavelength dispersion of a λ / 4 retardation plate arranged on the viewer side of the display device. Therefore, it is preferable to use a broadband λ / 4 plate. Further, in the dual-purpose liquid crystal display device, as described above for the transmission type liquid crystal display device, the wide band λ / 4 plate is arranged on both sides of the liquid crystal display device, and the wavelength dispersion of the wide band λ / 4 plate cancels each other. May be adopted.
[0290]
【Example】
Hereinafter, the present invention will be described based on examples. The present invention is not limited by the following examples. In particular, the patterns (shape and arrangement) of the openings and the solid portions of the upper conductive layer may be the various patterns described in the first embodiment.
[0291]
(Example 1)
FIG. 48 is a cross-sectional view of the transmission type liquid crystal display device 800 according to the first embodiment, and FIG. 49 is a plan view thereof. FIG. 48 is a sectional view taken along the line 48A-48A 'in FIG.
[0292]
The transmissive liquid crystal display device 800 is, for example, a 3.5-type TFT liquid crystal display device having 180,000 picture elements (dots in width 840 × height 220, dot pitch 86 μm × height 229 μm).
[0293]
The liquid crystal display device 800 includes a TFT substrate 800a, a counter substrate 800b, and a vertically aligned liquid crystal layer 30 disposed therebetween. Each of the pixel regions arranged in a matrix is driven by a voltage applied to the pixel electrode 105 and the counter electrode 122. The picture element electrode 105 is connected to a source wiring 114 to which a signal voltage is applied via a TFT 118, and the switching of the TFT 118 is controlled by a scanning signal given from a gate wiring 108. A signal voltage is applied to the picture element electrode 105 connected to the TFT 118 turned on by the scanning signal.
[0294]
The pixel electrode 105 has a lower conductive layer 102, an upper conductive layer 104, and a dielectric layer (interlayer insulating layer 107 and photosensitive resin layer 103) provided therebetween. Lower conductive layer 102 and upper conductive layer 104 are electrically connected to each other at contact hole 107a. The upper conductive layer 104 has an opening 104a, and generates an oblique electric field at the edge when a voltage is applied. One opening 104 a is formed in a region surrounded by the gate wiring 108, the source wiring 114, and the auxiliary capacitance wiring 119. Two openings 104a are formed for each picture element region.
[0295]
Note that the auxiliary capacitance wiring 119 is formed so as to extend substantially in the vicinity of the center of the picture element region in parallel with the gate wiring 108. The storage capacitor line 119 forms a storage capacitor with the lower conductive layer 102 opposed to the storage capacitor via the gate insulating layer 110. The auxiliary capacitance is provided to improve the retention rate of the pixel capacitance. Of course, the auxiliary capacitance may be omitted, and the structure of the auxiliary capacitance is not limited to the above example.
[0296]
First, a method for manufacturing the TFT substrate 800a of the liquid crystal display device 800 will be described with reference to FIG. 50A.
[0297]
As shown in FIG. 50A (a), if necessary, a Ta coat is formed on the insulating transparent substrate 101 as a base coat film. 2 O 5 , SiO 2 An insulating layer (not shown) made of, for example, is formed. After that, a metal layer made of Al, Mo, Ta, or the like is formed by a sputtering method, and is patterned to form a gate electrode (including a gate wiring) 108. Here, the gate electrode 108 is formed using Ta. At this time, the auxiliary capacitance wiring 119 may be formed using the same material in the same step.
[0298]
Next, a gate insulating layer 110 is formed over substantially the entire surface of the substrate 101 so as to cover the gate electrode 108. Here, a gate insulating layer 110 is formed by depositing a SiNx film having a thickness of about 300 nm by a P-CVD method. Note that the gate electrode 108 can be anodized and this anodic oxide film can be used as a gate insulating layer. Of course, a two-layer structure including an anodic oxide film and an insulating film such as SiNx may be used.
[0299]
On the gate insulating layer 110, a Si layer to be the channel layer 111 and the electrode contact layer 112 is continuously deposited by a CVD method. An amorphous Si layer with a thickness of about 150 nm is used for the channel layer 111, and an amorphous Si or microcrystalline Si layer with a thickness of about 50 nm doped with an impurity such as phosphorus is used for the electrode contact layer 112. HCl + SF 6 The channel layer 111 and the electrode contact layer 112 are formed by patterning by a dry etching method using a mixed gas of
[0300]
Thereafter, as shown in FIG. 50A (b), a transparent conductive layer (ITO) 102 constituting a lower conductive layer is deposited to a thickness of about 150 nm by a sputtering method. Subsequently, metal layers 114 and 115 made of Al, Mo, Ta, or the like are stacked. Here, Ta is used. By patterning these metal layers, source electrodes 113 and 114 and drain electrodes 113 and 115 are formed (hereinafter, referred to as “source electrode 114” and “drain electrode 115”). Each of the source electrode 114 and the drain electrode 115 has a two-layer structure, and the conductive layer made of the ITO layer 102 is denoted by reference numeral 113. The ITO layer 102 functions as a lower conductive layer of the pixel electrode having a two-layer structure.
[0301]
Next, as shown in FIG. 50C, an insulating layer made of SiNx or the like is deposited to a thickness of about 300 nm by a CVD method, and then patterned to form an interlayer insulating layer 107. At the time of patterning, a contact hole 107a for electrically connecting the upper conductive layer 103 to be formed later and the ITO layer 102 is formed in the interlayer insulating layer 107 on the auxiliary capacitance wiring 119.
[0302]
Next, as shown in FIG. 50A (d), a photosensitive resin layer 103 serving as a dielectric layer is formed on the interlayer insulating layer 107, and the photosensitive resin layer 103 is exposed and developed to form an interlayer insulating layer. An opening 103a for exposing the drain electrode 102 is formed in the contact hole 107a of 107. The photosensitive resin layer 103 is formed to a thickness of about 1.5 μm using, for example, a positive photosensitive resin (acrylic resin manufactured by JSR; relative permittivity: 3.7). Note that the photosensitive resin layer 103 may be formed using a non-photosensitive resin, and the opening 103a may be formed in the non-photosensitive resin layer by a separate photolithography process using a photoresist.
[0303]
Next, as shown in FIG. 50E, a transparent conductive layer (ITO) 104 constituting an upper conductive layer is formed on the substrate 101 on which the interlayer insulating layer 107 and the photosensitive resin layer 103 are formed by a sputtering method to a thickness of about 100 nm. Formed to a thickness of
[0304]
Thereafter, an opening 104a is formed in the transparent conductive layer 104, whereby the TFT substrate 800a shown in FIG. 48 is obtained. The formation of the opening 104a can be performed, for example, by the following method.
[0305]
A photoresist material is applied on the transparent conductive layer 104, and a photoresist layer having a predetermined pattern is formed by a photolithography process. An opening 104a is formed by etching using this photoresist layer as a mask. Thereafter, the photoresist layer is stripped. Here, as the openings 104a of the transparent conductive layer 104, two types of rectangular openings, a = 68 μm and b = 59 μm (upper side in the figure) and a = 68 μm and b = 36 μm (lower side in the figure) are used. 14a is formed.
[0306]
Thus, a two-layer picture element composed of the lower conductive layer 102 made of the ITO layer, the upper conductive layer 104 made of the ITO layer, and the interlayer insulating layer 107 and the dielectric layer 103 interposed therebetween. A TFT substrate 800a having electrodes is obtained.
[0307]
Here, the dielectric layer sandwiched between the upper conductive layer 104 and the lower conductive layer 102 is formed of two layers of the interlayer insulating layer 107 and the photosensitive resin 103, but it is not necessary. And may further include another layer. The dielectric layer provided between the upper conductive layer and the lower conductive layer may be formed so as to generate an oblique electric field that inclines liquid crystal molecules at the edge of the opening 104a of the upper conductive layer. There is no limitation on the thickness and the number of layers. It is preferable to use a highly transparent material so that light use efficiency does not decrease.
[0308]
Another manufacturing method of the TFT substrate 800a of the liquid crystal display device 800 will be described with reference to FIG. 50B.
[0309]
As shown in FIG. 50B (a), a Ta coat as a base coat film is formed on the insulating transparent substrate 101 as necessary. 2 O 5 , SiO 2 An insulating layer (not shown) made of, for example, is formed. After that, a metal layer made of A1, Mo, Ta, or the like is formed by a sputtering method and patterned to form a gate electrode (including a gate wiring) 108. Here, the gate electrode 108 is formed using a stacked film of Ti / A1 / Ti. At this time, the auxiliary capacitance wiring 119 may be formed using the same material in the same step.
[0310]
Next, a gate insulating layer 110 is formed over substantially the entire surface of the substrate 101 so as to cover the gate electrode 108. Here, a gate insulating layer 110 is formed by depositing a SiNx film having a thickness of about 300 nm by a P-CVD method.
[0311]
On the gate insulating layer 110, a Si layer to be the channel layer 111 and the electrode contact layer 112 is continuously deposited by a CVD method. An amorphous Si layer with a thickness of about 150 nm is used for the channel layer 111, and an amorphous Si or microcrystalline Si layer with a thickness of about 50 nm doped with an impurity such as phosphorus is used for the electrode contact layer 112. HCl + SF 6 The channel layer 111 and the electrode contact layer 112 are formed by patterning by a dry etching method using a mixed gas of
[0312]
Thereafter, as shown in FIG. 50B (b), metal layers 7114 and 115 made of A1, Mo, Ta, or the like are stacked. Here, a laminated film of A1 / Ti is used. By patterning these metal layers, a source electrode 114 and a drain electrode 115 are formed. Next, using the source electrode 114 and the drain electrode 115 as masks, HCl + SF 6 The gap portion 112g of the electrode contact layer 112 is etched by patterning by a dry etching method using a mixed gas of
[0313]
Next, as shown in FIG. 50C, an insulating layer made of SiNx or the like is deposited to a thickness of about 300 nm by a CVD method, and then patterned to form an interlayer insulating layer 107. At the time of patterning, a contact hole 107a for electrically connecting the lower conductive layer 102 made of an ITO layer to be formed later and the drain electrode 115 is formed in the interlayer insulating layer 107 on the auxiliary capacitance wiring 119.
[0314]
Next, as shown in FIG. 50D, a transparent conductive layer (ITO) 102 constituting a lower conductive layer is formed to a thickness of about 140 nm by a sputtering method.
[0315]
Next, as shown in FIG. 50E, a photosensitive resin layer 103 serving as a dielectric layer is formed on the lower conductive layer 102 made of the ITO layer, and the photosensitive resin layer 103 is exposed and developed. Then, an opening 103a for exposing the lower conductive layer 102 made of an ITO layer is formed. The photosensitive resin layer 103 is formed to a thickness of about 1.5 μm using, for example, a positive photosensitive resin (acrylic resin manufactured by JSR; relative permittivity: 3.7). Note that the photosensitive resin layer 103 may be formed using a non-photosensitive resin, and the opening 103a may be formed in the non-photosensitive resin layer by a separate photolithography process using a photoresist.
[0316]
Next, as shown in FIG. 50B (f), a transparent conductive layer (ITO) 104 constituting an upper conductive layer is formed to a thickness of about 100 nm by a sputtering method on the substrate 101 on which the photosensitive resin layer 103 is formed. I do.
[0317]
Thereafter, an opening 104a is formed in the transparent conductive layer 104, whereby the TFT substrate 800a shown in FIG. 48 is obtained. The formation of the opening 104a can be performed, for example, by the following method.
[0318]
A photoresist material is applied on the transparent conductive layer 104, and a photoresist layer having a predetermined pattern is formed by a photolithography process. The opening 104a is formed by etching using this resist layer as a mask. Thereafter, the photoresist layer is stripped.
[0319]
Thus, a two-layer picture element composed of the lower conductive layer 102 made of the ITO layer, the upper conductive layer 104 made of the ITO layer, and the interlayer insulating layer 107 and the dielectric layer 103 interposed therebetween. A TFT substrate 800a having electrodes is obtained.
[0320]
The dielectric layer provided between the upper conductive layer and the lower conductive layer may be formed so as to generate an oblique electric field that tilts the liquid crystal molecules at the edge of the opening 104a of the upper conductive layer, and a stable radial tilt is provided. There is no limitation on the type, thickness, and number of layers of the material as long as orientation can be obtained. It is preferable to use a highly transparent material so that light use efficiency does not decrease.
[0321]
On the other hand, in the counter substrate 800b, a counter electrode 122 made of ITO is formed on the insulating transparent substrate 121 by using a sputtering method.
[0322]
A vertical alignment process is performed on the inner surfaces of the TFT substrate 800a and the counter substrate 800b obtained as described above. For example, a vertical alignment layer is formed using vertical alignment polyimide manufactured by JSR Corporation. No rubbing treatment is performed on the vertical alignment layer.
[0323]
For example, spherical plastic beads having a diameter of 3 μm are sprayed on the inner surface of the opposing substrate 800b, and the opposing substrate 800b and the TFT substrate 800a are bonded to each other using a known sealant. Thereafter, for example, a material obtained by adding a chiral agent to a nematic liquid crystal material having a negative dielectric anisotropy (Δn = 0.0996) manufactured by Merck is injected. Thus, a liquid crystal panel is obtained. Note that among structural units included in the liquid crystal display device, a structural unit having a pair of substrates (here, a TFT substrate 800a and a counter substrate 800b) and a liquid crystal layer sandwiched therebetween is referred to as a “liquid crystal panel”. Name.
[0324]
The polarizing plate 50a is arranged outside the TFT substrate 800a of the obtained liquid crystal panel, and the polarizing plate 50b is arranged outside the counter substrate 800b. The transmission axes of the polarizing plate 50a and the polarizing plate 50a are arranged to be orthogonal to each other (see FIG. 41B). The polarizing plates 50a and 50b are arranged such that the transmission axes of the polarizing plates 50a and 50b are at 45 degrees to the extending direction of the gate wiring of the liquid crystal panel.
[0325]
The liquid crystal display device thus obtained realizes good black display when no voltage is applied (including when a voltage lower than the threshold voltage is applied).
[0326]
FIG. 51 schematically shows the state of the picture element region when a voltage (a voltage equal to or higher than the threshold voltage) is applied to the liquid crystal layer of the liquid crystal display device 800. FIG. 51 shows two adjacent picture element regions.
[0327]
As shown in FIG. 51, a quenching pattern (dark portion) centering on the center of the opening 104a can be seen for each opening 104a. At the center of the quenching pattern (the intersection of the curves), the liquid crystal molecules are in a vertical alignment state, and the liquid crystal molecules around the center are radially tilted around the liquid crystal molecules in the vertical alignment state. This is because an oblique electric field was generated by the pixel electrode having the two-layer structure having the opening 104a. Note that, as described above, the dark portion is observed in a substantially cross shape in the voltage applied state because the transmission direction of the polarizing plate 50a is parallel or perpendicular to the polarization direction of the linearly polarized light incident on the liquid crystal layer. The linearly polarized light that has passed through the region where the liquid crystal molecules are oriented in a direction parallel or orthogonal to the liquid crystal layer) passes through the liquid crystal layer while maintaining the polarization state without being given a phase difference by the liquid crystal layer. This is because they are absorbed and do not contribute to display. In this example, since the liquid crystal material to which the chiral agent is added is used, the liquid crystal layer is in a spiral radially inclined orientation, and as a result, extinction occurs at a position shifted from the absorption axis of the polarizing plate which is orthogonal to each other. Has been observed.
[0328]
The region observed white (bright) when voltage is applied is a region where linearly polarized light incident on the liquid crystal layer is given a phase difference by the liquid crystal layer, and the degree of whiteness (brightness) is determined by the degree of whiteness (brightness). Depending on the magnitude of the phase difference given by Therefore, by controlling the magnitude of the voltage applied to the liquid crystal layer to change the orientation state of the liquid crystal layer and adjusting the magnitude of the phase difference given by the liquid crystal layer, gradation display can be realized.
[0329]
The arrangement of the pair of polarizing plates 50a and 50b whose transmission axes are orthogonal to each other is not limited to the above example, and may be arranged so as to be parallel or orthogonal to the gate wiring. Since the liquid crystal layer of the liquid crystal display device according to the present invention is a vertical alignment type liquid crystal layer which is in a radially inclined alignment state when a voltage is applied, the direction of the transmission axis of the polarizing plate can be set to any direction. It is appropriately set in consideration of the viewing angle characteristics and the like according to the use of the liquid crystal display device. In particular, by setting the transmission axis of the polarizing plate in a direction parallel or perpendicular to the gate wiring (or the source wiring), the viewing angle characteristics in the vertical and horizontal directions of the display surface can be improved. This is because the polarization selectivity of the polarizing plate is highest in the direction parallel or perpendicular to the transmission axis and lowest at 45 ° from the transmission axis. Further, when the transmission axis of the polarizing plate is set in a direction parallel or perpendicular to the gate wiring, the oblique electric field from the gate wiring causes liquid crystal molecules present near the gate wiring to move in a direction perpendicular to the direction in which the gate wiring extends. There is an advantage that light leakage does not occur even when inclined.
[0330]
Further, when a circularly polarized light is incident on the liquid crystal layer by using a λ / 4 plate, the extinction pattern observed substantially along the transmission axis of the polarizing plate can be eliminated, and the light use efficiency can be improved. Can be. Further, by providing a λ / 2 plate or a viewing angle compensating plate, it is possible to obtain a liquid crystal display device capable of suppressing occurrence of coloring of black display and realizing high-quality display.
[0331]
The liquid crystal display device 800 of this embodiment is a vertical alignment type normally black mode liquid crystal display, can display a high contrast ratio, and uses a liquid crystal layer with a radially tilted alignment. It has wide viewing angle characteristics in azimuth. Furthermore, since the oblique electric field formed by the two-layered electrode having the opening is used for the formation of the radial tilt orientation, good controllability and good radial tilt orientation can be realized.
[0332]
Needless to say, the structure of the pixel electrode is not limited to the illustrated structure, but may adopt a two-layer structure of various structures described in the above embodiments. Further, by changing the material for forming the upper conductive layer and / or the lower conductive layer, a reflective liquid crystal display device and a transflective liquid crystal display device can be obtained.
[0333]
(Example 2)
The picture element electrode of the transmission type liquid crystal display device according to the second embodiment has a relatively large number of relatively small openings as compared with the liquid crystal display device 800 according to the first embodiment, and the opening covers the entire picture element electrode (upper conductive layer). It is formed over. The shapes and arrangements of the openings and the solid portions are merely examples, and various patterns exemplified in the first embodiment can be used. From the viewpoint of display luminance, the pattern shown in FIG. 19B is preferable. Further, the area ratio between the opening and the solid portion is optimized according to the guideline described with reference to FIG.
[0334]
Before describing the structure and operation of the liquid crystal display device of the second embodiment, disadvantages that the liquid crystal display device 800 of the first embodiment may have will be described. Note that this disadvantage may not be a problem depending on the application of the liquid crystal display device.
[0335]
First, the opening 104a (especially the larger opening, upper opening in FIG. 49: a = 68 μm, b = 59 μm) of the upper conductive layer 104 of the liquid crystal display device 800 has a relatively large size. , The time from when a voltage is applied to when the liquid crystal layer 30 located in the opening 104a takes a stable radially inclined alignment is long. Therefore, there is a problem that the response speed is slow depending on the application.
[0336]
Further, as shown in FIG. 49, a region between the lower edge portion of the lower opening portion 104a and the gate wiring 108 (the width in the direction parallel to the source line is about 25 μm) from the edge portion of the opening portion 104a. It takes a relatively long time for the liquid crystal layer 30 in the region where the distance is long to take a stable radial tilt alignment. In addition, the liquid crystal layer 30 located at the edge of the upper conductive layer 104 (for example, near the lower right in FIG. 49) distant from the edge of the opening 104a has an oblique electric field generated by the opening 104a and a source wiring. The tilt direction of the liquid crystal molecules 30a may not be stable for each pixel because it is affected by the electric field generated by the signal voltage applied to 114 (113). As a result, the display may be rough.
[0337]
The structure and operation of the liquid crystal display device 900 according to the second embodiment will be described with reference to FIGS. FIG. 52 shows a cross-sectional view of the liquid crystal display device 900, and FIG. 53 shows a plan view thereof. FIG. 52 is a sectional view taken along the line 52A-52A ′ in FIG. In the following description, among the components of the liquid crystal display device 900, components having substantially the same functions as those of the liquid crystal display device 800 of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The liquid crystal display device 900 can be manufactured by substantially the same process as the liquid crystal display device 800.
[0338]
As shown in FIG. 52, the upper conductive layer 104 of the liquid crystal display device 900 has a relatively large number of relatively small openings 104a. Here, 23 circular openings 104a are formed for each pixel electrode 105 (for each upper conductive layer 104). The diameter of the opening 104a is set to 20 μm, and the interval between the adjacent openings 104a in the row direction or the column direction (the direction parallel to the gate wiring or the source wiring) is constant at 4 μm. The openings 104a are arranged in a square lattice shape over the entire pixel electrode 105, and four (2 × 2) openings 104a located at lattice points are arranged so as to have rotational symmetry. I have. The distance between the outermost edge of the opening 104a (closer to the edge of the upper conductive layer 104) and the edge of the upper conductive layer 104 is about 5 μm.
[0339]
Since the diameter of the opening 104a of the upper conductive layer 104 of the liquid crystal display device 900 is relatively small, that is, 20 μm, the liquid crystal layer 30 located in the opening 104a quickly takes a stable radially inclined alignment by applying a voltage. The openings 104a are arranged in a square lattice, and four (2 × 2) openings 104a located at lattice points are arranged so as to have rotational symmetry. The liquid crystal layer 30 located at the same position also adopts a stable radial tilt alignment. Further, since the distance between the adjacent openings 104a is relatively short, 4 μm, the alignment of the liquid crystal layer 30 located between the openings 104a also changes quickly. Further, by disposing the opening 104a near the edge of the upper conductive layer 104 (about 5 μm), a region where the tilt direction of the liquid crystal molecules is not stable near the edge of the upper conductive layer 104 can be reduced. it can.
[0340]
It was actually confirmed that the liquid crystal display device 900 of this example had a higher response speed than the liquid crystal display device 800 and that no display roughness was observed.
[0341]
As described above, by employing a configuration in which a plurality of openings 104a are provided for each pixel electrode 105, the size and arrangement of the openings 104a can be optimized, and the response speed and the stability (reproduction) of the radially inclined orientation can be improved. Liquid crystal display device with improved properties).
[0342]
In the transmission type liquid crystal display devices 800 and 900 of the first and second embodiments described above, the voltage applied to the liquid crystal layer 30 located on the opening 104 a of the upper conductive layer 104 depends on the voltage drop caused by the photosensitive resin layer 103. Receive. Therefore, the voltage applied to the liquid crystal layer 30 located on the opening 104a is lower than the voltage applied to the liquid crystal layer 30 located on the upper conductive layer 104 (the region excluding the opening 104a). Therefore, when the same voltage (signal voltage) is applied to the upper conductive layer 104 and the lower conductive layer 102, the voltage-transmittance characteristics vary depending on the location in the picture element region, and the voltage-transmittance characteristics of the liquid crystal layer 30 located on the opening 104a are different. The transmittance becomes relatively low. Since the liquid crystal display devices 800 and 900 perform display in the normally black mode, the black level does not float (transmittance when no voltage is applied), but a sufficient white level (one for practical use) is obtained. In order to realize the brightest display state, it is necessary to apply a higher voltage than usual to the liquid crystal layer.
[0343]
As described with reference to FIGS. 34 and 35, in order to suppress a voltage drop of the voltage applied to the liquid crystal layer 30 located in the opening 104a due to the photosensitive resin layer 103, as described with reference to FIGS. A concave portion or a hole may be formed in the photosensitive resin layer 103 located at the position shown in FIG. In the first and second embodiments, since a photosensitive resin is used, a concave portion or a hole can be formed by a known photolithography process.
[0344]
If a concave portion or a hole is formed in the photosensitive resin layer 103 located in the opening 104a, a voltage drop of the voltage applied to the liquid crystal layer 30 located in the opening 104a due to the photosensitive resin layer 103 can be reduced. A decrease in transmittance due to the photosensitive resin layer 103 can be reduced, and the light use efficiency can be improved. When the thickness of the photosensitive resin layer 103 in the opening 103a is reduced, the thickness of the liquid crystal layer 30 on the opening 104a is larger than the thickness of the liquid crystal layer 30 on the upper conductive layer 104 other than the opening 104a. Is thick, that is, the retardation is increased, so that the transmittance (light use efficiency) is improved.
[0345]
(Example 3)
A cross-sectional view and a plan view of a transflective liquid crystal display device 1000 according to the third embodiment are shown in FIGS. FIG. 54 is a sectional view taken along the line 54A-54A 'in FIG. In the following description, among the components of the liquid crystal display device 1000, components having substantially the same functions as those of the liquid crystal display device 800 of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.
[0346]
The liquid crystal display device 1000 includes a TFT substrate 1000a, a counter substrate 800b, and a vertically aligned liquid crystal layer 30 disposed therebetween. Each of the pixel regions arranged in a matrix is driven by a voltage applied to the pixel electrode 105 and the counter electrode 122. The picture element electrode 105 is connected to the source wiring 114 via the TFT 118. The switching of the TFT 118 is controlled by a scanning signal given from the gate wiring 108. A signal voltage is applied to the picture element electrode 105 connected to the TFT 118 turned on by the scanning signal.
[0347]
The pixel electrode 105 includes a transparent lower conductive layer 102T functioning as a transparent electrode, a reflective upper conductive layer 104R functioning as a reflective electrode, and a dielectric layer (interlayer insulating layer 107 and photosensitive resin layer) provided therebetween. 103). The transparent lower conductive layer 102T and the reflective upper conductive layer 104R are electrically connected to each other at a contact hole 107a. The reflective upper conductive layer 104R has an opening 104a, and generates an oblique electric field at the edge when a voltage is applied. The photosensitive resin layer 103 has an opening 103a formed to correspond to the opening 104a. The transparent lower conductive layer 102T is exposed in the opening 103a. Eight openings 104a and 103a are formed for each picture element region.
[0348]
The liquid crystal display device 1000 can be manufactured as follows. A description of the same steps as in the method for manufacturing the liquid crystal display device 800 will be omitted.
[0349]
The TFT substrate 1000a can be formed in the same steps as the TFT substrate 800a up to the step of applying the photosensitive resin layer 103 (see FIGS. 50A (a) to 50 (c)).
[0350]
Next, as shown in FIG. 56A, a photosensitive resin is applied on the interlayer insulating layer 107. For example, a positive photosensitive resin (acrylic resin manufactured by JSR Corporation) is used as the photosensitive resin, and is applied to a thickness of about 3.7 μm. This thickness is set to be about 3 μm after the completion of the post-baking step.
[0351]
In this exposure step, the photosensitive resin 103 is exposed (for example, by using a photomask having a predetermined pattern for forming a plurality of smooth uneven portions on the surface of the photosensitive resin layer 103 (see FIG. 40, for example). Exposure amount is about 50 mJ).
[0352]
By developing the exposed photosensitive resin layer 103, a contact hole 107a, an opening 103a and surface irregularities (not shown) are formed. In addition, by performing a heat treatment as needed, the unevenness formed on the surface of the photosensitive resin layer 103 can be smoothed.
[0353]
Next, as shown in FIG. 56 (b), a Mo layer 104R1 and an Al layer 104R2 to be upper conductive layers are formed in this order to a thickness of about 100 nm by sputtering on almost the entire surface of the substrate 101.
[0354]
Thereafter, the opening 104a is formed by processing the reflective upper conductive layer 104R including the Al layer 104R2 / Mo layer 104R1 into a predetermined pattern using a photolithography process. The opening 104a can be implemented by the method described in the first embodiment.
[0355]
Further, here, the dielectric layer sandwiched between the upper conductive layer 104 and the lower conductive layer 113 is formed of two layers of the interlayer insulating layer 107 and the photosensitive resin 103, but is formed of one of the two layers. It is the same as in the first embodiment that it may be formed by two or more layers.
[0356]
Next, a vertical alignment process is performed on the inner surface of the TFT substrate 800a obtained as described above and the counter substrate 800b manufactured according to a conventional method. For example, a vertical alignment layer is formed using vertical alignment polyimide manufactured by JSR Corporation. No rubbing treatment is performed on the vertical alignment layer.
[0357]
For example, spherical plastic beads having a diameter of 3.0 μm are sprayed on the inner surface of the opposing substrate 800b, and the opposing substrate 800b and the TFT substrate 1000a are bonded together using a known sealing agent. Thereafter, for example, a nematic liquid crystal material having a negative dielectric anisotropy (Δn = 0.0649) manufactured by Merck is injected. Thus, a liquid crystal panel is obtained.
[0358]
The thickness of the liquid crystal layer 30 in the reflective region (on the reflective upper conductive layer 104R) of the obtained liquid crystal panel is 3 μm of the plastic bead diameter, and is 3 μm in the transmissive region (the region corresponding to the opening 104a). And about 3 μm of the thickness of the photosensitive resin layer 103 after the post-baking. As described above, by adjusting the thickness of the photosensitive resin layer 103, the retardation (the liquid crystal thickness d × birefringence Δn) with respect to the light used for display can be made substantially equal between the transmission region and the reflection region. It becomes possible, and the light use efficiency is improved.
[0359]
As shown in FIGS. 43A and 43B, a pair of polarizing plates 50a and 50b and a pair of λ / 4 plates 60a and 60b are arranged on the obtained liquid crystal panel. Since the display operation in the transmission mode has been described above, the display operation in the reflection mode in the reflection area of the liquid crystal display device 1000 will be described here.
[0360]
First, a display operation when no voltage is applied will be described. Light incident on the reflection region perpendicularly to the opposing substrate 800b from the opposing substrate 800b passes through the polarizing plate 50b, becomes linearly polarized light, and is incident on the λ / 4 plate 60b. After being converted into circularly polarized light by the λ / 4 plate 60b, the light enters the liquid crystal layer 30. The circularly polarized light that has passed through the liquid crystal layer 30 and has reached the reflective upper conductive layer 104R is reflected on the surface of the reflective upper conductive layer 104R, becomes reverse circularly polarized light, passes through the liquid crystal layer 30 again, and passes through the λ / 4 plate 60b. Incident on. The circularly polarized light is converted by the λ / 4 plate 60b into linearly polarized light having a polarization direction of 45 degrees with respect to the slow axis SL1 of the λ / 4 plate 60b, and is incident on the polarizing plate 50b. Since the transmission axis PA1 of the polarizing plate 50b is orthogonal to the polarization axis of the linearly polarized light passing through the λ / 4 plate 60b, the linearly polarized light is absorbed by the polarizing plate 50b. Therefore, the reflection area of the liquid crystal display device 1000 is in a black display state when no voltage is applied, similarly to the transmission area.
[0361]
Next, a display operation in a voltage application state will be described.
[0362]
In the liquid crystal layer 30 in the radially inclined alignment state in the voltage applied state, the liquid crystal molecules 30a vertically aligned with respect to the substrate surface do not give a phase difference to the circularly polarized light, so that this region is in a black display state. . The circularly polarized light that has entered other regions (regions other than the vertical alignment region) of the liquid crystal layer 30 is given a phase difference by the liquid crystal layer 30 while passing through the liquid crystal layer 30 twice, and is incident on the λ / 4 plate 60b. . Since the polarization state of the light incident on the λ / 4 plate 60b is deviated from the circular polarization state, a part of the light passing through the λ / 4 plate 60b passes through the polarization plate 50b. Since the amount of transmitted polarized light depends on the magnitude of the phase difference provided by the liquid crystal layer 30, it can be adjusted by controlling the voltage applied to the liquid crystal layer 30. Therefore, by controlling the voltage applied to the liquid crystal layer 30, gradation display can be performed even in the reflection region.
[0363]
The arrangement of the polarizing plate and the phase difference plate is not limited to the above example, and a λ / 2 plate, a viewing angle compensating plate, and the like may be further provided as described with reference to FIGS.
[0364]
When a dual-purpose liquid crystal display device is configured using the liquid crystal display device according to the present invention, the shape, size, number, and arrangement of the openings 104a are not only required to obtain a radially inclined alignment, but also to achieve desired display characteristics (transmission region). And the area ratio between the reflection region and the reflection region).
[0365]
For example, in a dual-purpose liquid crystal display device that emphasizes the use of reflected light, it is necessary to increase the area ratio occupied by the reflective upper conductive layer 104R other than the opening 104a. If a sufficient number of openings 104a having a sufficient size cannot be formed, it becomes difficult to stably radially orient the liquid crystal layer 30 in the reflective region (on the reflective upper conductive layer 104R). That is, the azimuth of the tilt direction of the molecular axis of the liquid crystal molecules 30a when voltage is applied is not stable (the orientation direction of the liquid crystal molecules 30a in the substrate plane as viewed from the normal direction of the substrate does not become radial but varies depending on the location). Therefore, the orientation of the molecular axis of the liquid crystal molecules 30a in the substrate surface often differs depending on the picture element region.
[0366]
Here, a display operation when a voltage is applied to the liquid crystal layer 30 in the reflection region of the liquid crystal display device 1000 will be described with reference to FIG. FIG. 57 schematically shows a region where the tilt direction (azimuth) of the liquid crystal molecules 30a differs by 180 degrees.
[0367]
As shown in FIG. 57, the light incident on the two left and right liquid crystal molecules 30a having different inclination directions is reflected by the reflective upper conductive layer 104R and is given from the liquid crystal molecules 30a before being emitted to the observer side. The phase difference is the same. As can be understood from the above, the variation in the azimuthal direction of the alignment direction in the liquid crystal layer in the reflection region where the display is performed in the reflection mode is hardly visually recognized as the roughness of the display as in the transmission mode.
(Example 4)
FIG. 58 is a cross-sectional view of a transflective liquid crystal display device 1100 according to the fourth embodiment. A plan view of the dual-use liquid crystal display device 1100 is substantially the same as that of FIG. FIG. 58 is a sectional view taken along the line 54A-54A 'in FIG.
[0368]
In the following description, among components of the liquid crystal display device 1100, components having substantially the same functions as those of the liquid crystal display device 1000 according to the third embodiment are denoted by the same reference numerals, and description thereof is omitted. The liquid crystal display device 1100 can be manufactured by substantially the same process as the liquid crystal display device 1000.
[0369]
The liquid crystal display device 1100 differs from the dual-purpose liquid crystal display device 1000 of the third embodiment in that the photosensitive resin layer 103 has a concave portion 103b. The concave portion 103b of the photosensitive resin layer 103 can be formed, for example, as follows.
[0370]
In the manufacturing process of the liquid crystal display device 1000 described with reference to FIG. 56, a positive photosensitive resin (acrylic resin manufactured by JSR) applied to a thickness of about 3.7 μm (thickness after post-baking is about 3 μm) ) May be exposed (for example, an exposure amount of about 100 mJ) so as to leave a part (for example, a thickness of about 1 μm) of the photosensitive resin 103 in the opening 104a (transmission region). The recess 103b having a predetermined depth (here, about 2 μm) is formed through a later development step.
[0371]
Hereinafter, the liquid crystal panel of the liquid crystal display device 1100 is obtained in the same manner as the liquid crystal display device 1000 of the third embodiment. Here, the setting of the cell gap and the liquid crystal material are the same as those in the third embodiment.
[0372]
The thickness of the liquid crystal layer 30 in the reflective region (on the reflective upper conductive layer 104R) of the obtained liquid crystal panel is 3 μm of the plastic bead diameter, and is 3 μm in the transmissive region (the region corresponding to the opening 104a). And about 3 μm of the thickness of the photosensitive resin layer 103 after the post-baking, and subtracting about 1 μm of the remaining amount of the photosensitive resin layer 103 in the opening 104 a from the sum of the thickness and about 5 μm. As described above, by adjusting the thickness of the photosensitive resin layer 103, the retardation (the liquid crystal thickness d × birefringence Δn) with respect to the light used for display can be made substantially equal between the transmission region and the reflection region. It becomes possible, and the light use efficiency is improved.
[0373]
Next, referring to FIGS. 59A and 59B, the opening 103a of the photosensitive resin layer 103 in the liquid crystal display device 1000 according to the third embodiment and the photosensitive resin layer 103 in the liquid crystal display device 1100 according to the fourth embodiment. The structure of the edge of the concave portion 103b will be described.
[0374]
As shown in FIG. 59A, the edge of the opening 103a of the photosensitive resin layer 103 gradually changes while continuously changing the film thickness from a region where the photosensitive resin is present to a region where the photosensitive resin is not present. ing. That is, the side surface of the opening 103a is tapered. The side surface of the opening 103a is tapered due to the photosensitive characteristics and developing characteristics of the photosensitive resin.
[0375]
At the edge of the opening 103a in the third embodiment, as shown in FIG. 59A, a tapered side surface having a taper angle θ of about 45 degrees is formed. When a vertical alignment layer (not shown) is formed on the tapered side surface, the liquid crystal molecules 30a tend to be aligned perpendicular to the tapered side surface. Therefore, the liquid crystal molecules 30a on the tapered side surface are inclined from the direction perpendicular to the surface of the substrate (substrate normal) even when no voltage is applied, as shown in the figure. When the taper angle is large, the liquid crystal molecules 30a on the tapered side surface are tilted in the direction opposite to the tilt direction due to the oblique electric field generated at the time of voltage application, which causes disturbance of the radial tilt alignment.
[0376]
On the other hand, in the recess 103b in the fourth embodiment, as shown in FIG. 59B, by leaving a part of the photosensitive resin layer 103 in the opening 104a, the taper angle θ of the tapered side surface can be reduced. Since the photosensitive resin 103 exists between the liquid crystal layer 30 and the lower conductive layer 102T in the opening 104a, an oblique electric field effectively acts on the liquid crystal layer 30 when a voltage is applied, and a stable radial tilt alignment can be obtained. . As a result, a liquid crystal display device having good display quality without roughness can be obtained.
[0377]
(Example 5)
The picture element electrode of the transmission type liquid crystal display device according to the fifth embodiment is different from the transmission type liquid crystal display device 900 according to the second embodiment in that an opening is also formed at the edge of the picture element electrode (upper conductive layer). The liquid crystal display device of the fifth embodiment has substantially the same configuration as the liquid crystal display device of the second embodiment except that the arrangement of the openings of the upper conductive layer 104 is different. Therefore, the description of the common structure is omitted here. I do.
[0378]
Before describing the structure and operation of the liquid crystal display device of the fifth embodiment, disadvantages that the liquid crystal display device 900 of the second embodiment may have will be described. Note that this disadvantage may not be a problem depending on the application of the liquid crystal display device.
[0379]
FIG. 60 schematically illustrates a part of the upper conductive layer 104 of the liquid crystal display device 900 according to the second embodiment. The upper conductive layer 104 has a relatively large number of relatively small openings 104a, and the openings 104a are arranged in a square lattice shape over the entire pixel electrode 105, and are located at lattice points. The four (2 × 2) openings 104a located are arranged so as to have rotational symmetry.
[0380]
When a voltage is applied to the liquid crystal layer 30, the liquid crystal layer 30 located in the circular opening 104 a (region A) of the upper conductive layer 104 quickly becomes a stable radial tilt centered on the center SA of the opening 104 a. Take the orientation. The liquid crystal layer 30 in a region surrounded by four (2 × 2) openings 104a located at lattice points as shown in a region B in FIG. 60 has a square shape surrounded by lattice points by application of a voltage. A stable radially inclined orientation centered on the diagonal intersection SA is taken.
[0381]
However, as shown in a region C of FIG. 60, the liquid crystal layer 30 located between the outermost opening 104a (closer to the edge of the upper conductive layer 104) of the opening 104a and the edge of the upper conductive layer 104 has: Symmetry of the oblique electric field generated at the edge of the upper conductive layer 104 and the oblique electric field generated at the edge of the opening 104a as compared with the area surrounded by the four lattice points shown in the area B of FIG. Is low (the direction of the electric field and the symmetry of the intensity distribution), so that a stable alignment state cannot be obtained. As a result, display roughness, afterimages, and the like are visually recognized, and display quality may be degraded.
[0382]
The above drawback is that the opening 104a is arranged near the edge of the upper conductive layer 104 (about 5 μm) as in the liquid crystal display device 900 of the second embodiment, and the inclination of the liquid crystal molecules near the edge of the upper conductive layer 104. The problem can be solved to some extent by narrowing the area in which the direction is not stable (area C). However, as long as the area is used as a display area, it has some adverse effect on display quality.
[0383]
When the opening 104a is formed too close to the edge of the upper conductive layer 104, the liquid crystal layer 30 in the opening 104a can have a stable radially inclined orientation due to the oblique electric field at the edge of the upper conductive layer 104. Disappears. Therefore, there is a limit to narrowing a region (region C) where the tilt direction of the liquid crystal molecules is not stable near the edge of the upper conductive layer 104. Here, one solution is to shield the region where the tilt direction of the liquid crystal molecules is not stable, such as the region C in FIG. 60, but it is not preferable because the aperture ratio decreases.
[0384]
On the other hand, as shown schematically in FIGS. 61, 62 and 63, the upper conductive layer 104 of the liquid crystal display device of Example 5 has openings 104a at the edges (sides and corners) of the upper conductive layer 104. Having '. The structure of the upper conductive layer 104 of Example 5 and the operation of liquid crystal molecules when a voltage is applied to the liquid crystal layer 30 will be described below with reference to these drawings. Note that the edge of the upper conductive layer 104 is defined by the extension of the upper conductive layer 104 (a shape obtained by connecting the outermost sides with straight lines), and is indicated by a solid line in FIGS. 61, 62, and 63.
[0385]
As shown in FIGS. 61, 62, and 63, the upper conductive layer 104 of the liquid crystal display device of the fifth embodiment has an opening 104a 'at an edge thereof. Each of the openings 104a provided except for the edge preferably has a shape (here, circular) having rotational symmetry, and the sizes of the respective openings 104a are equal to each other. The centers (positions of rotational symmetry axes) of the plurality of openings 104a are arranged so as to have rotational symmetry (typically in a square lattice as shown). The opening 104a 'formed at the edge corresponds to the opening 104a having the center of the opening 104a at the edge of the upper conductive layer 104. Unlike the opening 104a, the opening 104a' does not have a shape having rotational symmetry. It has a shape in which a part thereof is missing. For example, when the opening 104a is circular, the shape of the opening 104a 'whose center is located on the side of the upper conductive layer 104 is a semicircle as shown in FIG. The shape of the opening 104a 'whose center is located at the corner (angle: 90 °) of the upper conductive layer 104 is a quarter circle as shown in FIG. Further, when the upper conductive layer 104 has a shape in which a part of a rectangle is cut out, the opening 104a ′ located at the corner (angle: 270 °) of the notch is, as shown in FIG. 3 yen.
[0386]
As described above, since the shape of the opening 104a ′ provided at the edge of the upper conductive layer 104 is a shape in which a part of the shape having the rotational symmetry is missing, the shape having the center on the four lattice points of the square lattice is obtained. If at least one of the openings 104a includes an opening 104a 'provided at the edge, these arrangements will not have rotational symmetry. However, focusing on the square lattice (square) formed by the centers of the openings 104a and 104a ', the corners of each square are a quarter circle of each of the four openings 104a and 104a'. And the quarter circles of these four openings 104a and 104a 'are arranged to have rotational symmetry.
[0387]
Here, considering a portion of a quarter circle of the opening 104a and the opening 104a 'located at the corner of each square (this will be referred to as a "sub opening"), All of the area defined by the edge of the upper conductive layer 104 is divided into a number of mutually equivalent square areas defined by the sub-openings. The four sub-openings adjacent to each other form an opening 104a having a shape (here, circular) having one rotational symmetry. Note that the sub-opening defining the square area including the side of the upper conductive layer 104 does not have three adjacent sub-openings, and thus has a shape in which a part (circle) having rotational symmetry is partially omitted. (3/4 circle, half circle or 1/4 circle) 104a 'is formed.
[0388]
That is, when the openings 104a and 104a 'are arranged as described above, in the region (typically, corresponding to the pixel) defined by the edge of the upper conductive layer 104, the opening 104a' located at the edge is formed. The corresponding area has a shape with low symmetry, but the other area is an aggregate of areas having rotational symmetry (a square area and a circular opening 104a).
[0389]
Therefore, when a voltage is applied to the liquid crystal layer 30 of the liquid crystal display device having the upper conductive layer 104 having the openings 104a and 104a 'arranged as described above, the region A in the opening 104a and the region surrounded by the opening 104a are surrounded by the region A. In addition to the region B, the region C (the region including the side of the upper conductive layer 104 (excluding the corner)) and the region D (the corner of the upper conductive layer 104) are surrounded by the opening 104a and the opening 104a '. The liquid crystal layer 30 has a radially inclined alignment. As a result, in the liquid crystal display device of the fifth embodiment, the area of the region that takes a radially inclined orientation when a voltage is applied is larger than that in the liquid crystal display device 900 of the second embodiment, and is high in quality without any roughness or afterimage. Display can be realized.
[0390]
In FIGS. 61, 62, and 63, the shape of the opening 104a 'formed at the edge of the upper conductive layer 104 is set to 分 の, も し く は, or の of the opening 104a. However, depending on the pixel pitch and the size of the upper conductive layer 104, it is not always possible to arrange the openings 104a 'as illustrated. In such a case, if the liquid crystal layer 30 at the edge of the upper conductive layer 104 has a stable radially inclined orientation when a voltage is applied, the shape of the opening 104a 'formed at the edge of the upper conductive layer 104 is The opening 104a 'need not be three-quarters, one-half, or one-fourth of the opening 104a, and the center of the opening 104a' may be displaced from a position having rotational symmetry.
[0391]
Further, the openings 104a 'need not be formed on all sides and corners of the upper conductive layer 104. In particular, the liquid crystal according to the second embodiment can be formed on the sides and corners of the upper conductive layer 104 located on components such as bus wiring (signal wiring and scanning wiring) that do not transmit light without forming the opening 104a '. The display quality of the display device 900 can be significantly improved.
[0392]
As in the transmissive liquid crystal display devices of Examples 1 and 2, in order to suppress a voltage drop of the voltage applied to the liquid crystal layer 30 located in the opening 104a due to the photosensitive resin layer 103, FIG. As described with reference to FIG. 35 and FIG. 35, a concave portion or a hole may be formed in the photosensitive resin layer 103 located in a part of the opening 104a.
[0393]
In this embodiment, a transmissive liquid crystal display device has been described as an example. However, the arrangement of the openings 104a and 104a 'can be applied to a transflective liquid crystal display device. In this case, as in the transflective liquid crystal display devices of Examples 3 and 4, in order to suppress a voltage drop due to the photosensitive resin layer 103, the photosensitive resin layer 103 located in some of the openings 104a is provided. A concave portion or a hole may be formed.
[0394]
(Example 6)
The picture element electrode (upper conductive layer) of the transmission type liquid crystal display device according to the sixth embodiment has openings 104a arranged differently from the fifth embodiment, and the liquid crystal layer 30 at the edge of the upper conductive layer has a radially inclined orientation. Has stabilized. The liquid crystal display device of Example 6 has substantially the same configuration as the liquid crystal display devices of Example 2 and Example 5 except that the arrangement of the openings of the upper conductive layer 104 is different. Is omitted here.
[0395]
FIG. 64 shows a part of the upper conductive layer 104 of the liquid crystal display device of the sixth embodiment. The structure of the upper conductive layer 104 of Example 6 and the operation of the liquid crystal molecules when a voltage is applied to the liquid crystal layer 30 will be described with reference to FIG. As shown in FIG. 64, the openings 104a of the upper conductive layer 104 are arranged in a square lattice, and four (2 × 2) openings 104a located at lattice points have rotational symmetry. Are located in Further, among these openings 104a, the opening 104a closest to the edge of the upper conductive layer 104 is a virtual opening 104a ″ (actually, provided outside the upper conductive layer 104). (Absent) and form a square lattice, and are arranged such that the edge of the virtual opening 104 a ″ overlaps the edge of the upper conductive layer 104.
[0396]
That is, when a region outside the upper conductive layer 104 where the conductive layer is not formed is regarded as an opening, a relative arrangement having rotational symmetry together with the opening 104a formed in the upper conductive layer 104 (here, in this case). The openings 104a are arranged so as to form a square lattice. The difference from the arrangement of the openings (including 104a and 104a ') in the fifth embodiment is that all of the openings formed in the upper conductive layer 104 have the same shape (preferably a shape having rotational symmetry (here, circular)). ).
[0397]
When a voltage is applied to the liquid crystal layer 30 of the liquid crystal display device having the upper conductive layer 104, the liquid crystal layer 30 located in the opening 104a (region A) of the upper conductive layer 104 quickly assumes a stable radially inclined orientation. . The openings 104a are arranged in a square lattice, and four (2 × 2) openings 104a located at lattice points are arranged so as to have rotational symmetry. The liquid crystal layer 30 located in (region B) also has a stable radial tilt alignment. Further, in a region C near the edge of the upper conductive layer 104 (a region including the side of the upper conductive layer 104), three openings 104a located at the lattice points and the corresponding lattice points are located at the lattice points. The liquid crystal layer 30 has a stable radially inclined orientation due to the virtual opening 104a ″ (region without a conductive layer) where the edge of the layer 104 overlaps the edge. In a region D including a corner of the upper conductive layer 104, two openings 104a closest to the corner of the upper conductive layer 104 and a grid point corresponding to the two openings 104a, The liquid crystal layer 30 has a stable radially inclined orientation due to the two virtual openings 104a ″ (regions without a conductive layer) whose edges overlap.
[0398]
In FIG. 64, the opening 104a is formed so that the edge of the virtual opening 104a ″ located at the lattice point overlaps the side of the upper conductive layer 104, but the pixel pitch and the upper conductive layer 104 Depending on the size, the opening 104a may not always be arranged as shown. In such a case, if the liquid crystal layer 30 at the edge of the upper conductive layer 104 has a stable radially inclined orientation at the time of voltage application, the position of the edge of the virtual opening 104a ″ is shifted from the edge of the upper conductive layer 104. The opening 104a may be formed so as to form a square lattice.
[0399]
FIG. 65 shows another arrangement example different from FIG. The upper conductive layer 104 shown in FIG. 65 is formed so that the virtual opening 104a ″ located at the lattice point overlaps the edge of the upper conductive layer 104, similarly to the upper conductive layer 104 in FIG. However, in FIG. 64, the opening 104a closest to the edge of the upper conductive layer 104 has a shape having rotational symmetry like the other openings 104a, whereas in FIG. The opening 104a 'closest to the edge of 104 has a shape in which a part of the other opening 104a is missing. The opening 104a ′ having a shape in which a part of the opening 104a is missing is different from the opening 104a ′ of the upper conductive layer 104 of the fifth embodiment (see, for example, FIG. 61). It is located inside the edge of 104.
[0400]
Even when the openings 104a and 104a 'are arranged as shown in FIG. 65, the edge portions (regions C and D) of the upper conductive layer 104 when voltage is applied in the same manner as described above with reference to FIG. Liquid crystal layer 30 has a stable radially inclined alignment. Further, as described above, if the liquid crystal layer 30 at the edge of the upper conductive layer 104 has a stable radially inclined orientation when a voltage is applied, the edge of the virtual opening 104a ″ becomes the edge of the upper conductive layer 104. The opening 104a may be formed so as to form a square lattice at a position shifted from the position.
[0401]
(Example 7)
The transmissive liquid crystal display device 1200 according to the seventh embodiment is different from the transmissive liquid crystal display device 900 according to the second embodiment in that a plurality of contact holes 117a for electrically connecting the upper conductive layer 103 and the lower conductive layer 102 are provided. The openings 104a are formed at lattice points of a square lattice formed by the arrangement.
[0402]
Before describing the structure and operation of the liquid crystal display device 1200 according to the seventh embodiment, defects that the liquid crystal display device 900 according to the second embodiment may have will be described. Note that this disadvantage may not be a problem depending on the application of the liquid crystal display device.
[0403]
As shown in FIG. 53, the upper conductive layer 104 of the liquid crystal display device 900 according to the second embodiment has a relatively large number of relatively small openings 104a arranged in a square grid pattern over the entire pixel electrode 105. The four (2 × 2) openings 104a located at the lattice points are arranged so as to have rotational symmetry. Therefore, when a voltage is applied to the liquid crystal layer 30, the liquid crystal layer 30 located in the opening 104a of the upper conductive layer 104 quickly and stably assumes a radially inclined orientation. When a voltage is applied to the liquid crystal layer 30 in a region surrounded by four (2 × 2) openings 104a located at the lattice points, a stable center having the center at the intersection of the diagonal lines of the square surrounded by the lattice points is obtained. A radial tilt orientation is obtained.
[0404]
However, if the opening 104a is formed so as to overlap with the contact hole 107a, electrical connection between the lower conductive layer 102 and the upper conductive layer 104 cannot be made at that portion. It is difficult to arrange the openings 104a in the layer 104 in a square lattice. Therefore, in the vicinity of the contact hole 107a, since the oblique electric field has low symmetry (the symmetry of the electric field direction and the intensity distribution), a stable alignment state cannot be obtained. As a result, display roughness or afterimages may be visually recognized, and display quality may be degraded.
[0405]
The disadvantage is that the tilt direction of the liquid crystal molecules around the contact hole 107a is not stable by forming the contact hole 107a on the region where the backlight is shielded, such as the auxiliary capacitance line 119, as in the second embodiment. The problem can be solved to some extent by making the region almost invisible, but as long as the region exists at least partially in the light transmitting portion, it has some adverse effect on display quality. Here, one solution is to completely shield the area around the contact hole 107a in FIG. 53 where the tilt direction of the liquid crystal molecules is not stable, but this is not preferable because the aperture ratio decreases.
[0406]
On the other hand, in the liquid crystal display device 1200 according to the seventh embodiment, as shown in FIGS. 66 and 67, the openings 104a are arranged in a square lattice over the entire pixel electrode 105, and the contact holes are formed. 117a is formed at the position of the lattice point of the square lattice. The structure and operation of the liquid crystal display device 1200 according to the seventh embodiment will be described with reference to these drawings. In the following description, among the components of the liquid crystal display device 1200, components having substantially the same functions as those of the liquid crystal display device 900 of the second embodiment are denoted by the same reference numerals, and description thereof is omitted. . Further, the liquid crystal display device 1200 can be manufactured by substantially the same process as the liquid crystal display device 900.
[0407]
As shown in FIGS. 66 and 67, the openings 104a are arranged in a square lattice shape over the entire pixel electrode 105, and the contact holes 117a are formed at the positions of the lattice points. In the region where the backlight light does not transmit on the auxiliary capacitance line 119, the openings 104a of the upper conductive layer 104 are formed at lattice points. Therefore, when a voltage is applied to the liquid crystal layer 30, the liquid crystal layer 30 located in the opening 104a of the upper conductive layer 104 quickly and stably assumes a radially inclined orientation. The liquid crystal layer 30 located on the contact hole 117a also quickly and stably assumes a radially inclined alignment. This is because the contact hole 117a functions in the same manner as the concave portion 103b formed in the photosensitive resin layer 103 in the transflective liquid crystal display device 1100 of Embodiment 4 shown in FIG.
[0408]
The openings 104a are arranged in a square lattice, and four (2 × 2) openings 104a located at lattice points are arranged so as to have rotational symmetry. The liquid crystal layer 30 located at the same position also adopts a stable radial tilt alignment. Further, the contact holes 117a and the openings 104a are arranged in a square lattice, and the four (2 × 2) openings 104a and the contact holes 117a located at the lattice points are arranged so as to have rotational symmetry. Therefore, the liquid crystal layer 30 located between the contact hole 117a and the opening 104a and near the contact hole 117a also has a stable radially inclined orientation.
[0409]
As described above, in the liquid crystal display device 1200 according to the seventh embodiment, the region in which the tilt direction of the liquid crystal molecules is not stable around the contact hole 107a seen in the liquid crystal display device 900 according to the second embodiment can be eliminated. A liquid crystal display device with good display quality, in which roughness and afterimages are not visually recognized, can be obtained.
[0410]
Here, as shown in FIG. 66, the size of the contact hole 117a is preferably the same as the size of the opening 104a so that the contact hole 117a acts on the liquid crystal molecules in the same manner as the opening 104a. . In particular, when the contact hole 117a has the same size and the same shape as the opening 104a, a liquid crystal display device with particularly excellent alignment stability at the peripheral portion of the contact hole 117a can be obtained. However, even if it is difficult to form the contact hole 117a and the opening 104a in the same size and the same shape due to the pixel pitch and the structural limitation, the contact hole 117a and the opening 104a have rotational symmetry. By arranging them so as to have them (typically the illustrated square lattice), the orientation of the liquid crystal layer around the contact holes 117a can be sufficiently stabilized.
[0411]
Of course, the configuration exemplified in this embodiment can be applied to a transflective liquid crystal display device, and can be appropriately combined with the previous embodiment.
[0412]
Although several examples of the liquid crystal display device according to the present invention have been described, the liquid crystal display devices according to the first to fifth embodiments of the present invention can be similarly implemented.
[0413]
【The invention's effect】
According to the present invention, an oblique electric field is generated at an edge portion of an opening of an upper conductive layer by a two-layer structure electrode including an upper conductive layer having an opening, a dielectric layer, and a lower conductive layer, thereby generating a vertical electric field. Since the liquid crystal molecules of the alignment liquid crystal layer are radially tilt-aligned, the radial tilt alignment can be stably and reproducibly formed. Therefore, according to the present invention, a liquid crystal display device with high display quality is provided.
[0414]
In particular, when a configuration in which the upper conductive layer has a plurality of openings is employed, a stable radial tilt alignment can be obtained over the entire pixel region, and a liquid crystal display device in which a decrease in response speed is suppressed is provided.
[0415]
Further, by adopting a configuration in which a substrate having a two-layer structure electrode (first alignment control structure) and a second alignment control structure provided on a substrate opposed to the substrate with a liquid crystal layer interposed therebetween, a liquid crystal display in which radial tilt alignment is further stabilized. An apparatus is provided. The effect of stabilizing the orientation can also be obtained by employing a configuration having a convex portion in the opening of the upper conductive layer of the two-layer structure electrode.
[0416]
Further, in a configuration having a concave portion or a hole in the dielectric layer corresponding to the opening of the upper conductive layer, adopting a configuration in which the upper conductive layer is a reflective electrode and the lower conductive layer is a transparent electrode, the display characteristics of the transmission mode and Provided is a transmission / reflection type liquid crystal display device in which display characteristics in a reflection mode are respectively optimized.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a cross section of one picture element region of a liquid crystal display device 100 according to an embodiment of the present invention.
FIGS. 2A and 2B are diagrams schematically showing a cross section of one picture element region of another liquid crystal display device 100 ′ and 100 ″ according to an embodiment of the present invention, respectively.
FIGS. 3A, 3B and 3C are cross-sectional views schematically showing one picture element region of a conventional liquid crystal display device 200. FIGS.
FIG. 4 is a sectional view schematically showing one picture element region of a liquid crystal display device 300 for comparison.
FIG. 5 is a diagram schematically showing a relationship between lines of electric force and alignment of liquid crystal molecules.
FIG. 6 is a diagram schematically showing an alignment state of liquid crystal molecules as viewed from a normal direction of a substrate in a liquid crystal display device according to an embodiment of the present invention.
FIGS. 7A and 7B are schematic diagrams showing examples of spiral radially tilted alignment of liquid crystal molecules.
FIG. 8 is a diagram schematically illustrating an example of radially inclined alignment of liquid crystal molecules.
FIG. 9 is a diagram schematically showing an alignment state of liquid crystal molecules as viewed from a normal direction of the substrate in the liquid crystal display device of the embodiment according to the present invention.
FIG. 10 is a diagram schematically illustrating an example of radially inclined alignment of liquid crystal molecules.
FIG. 11 is a diagram schematically showing a cross-sectional structure of one picture element region of a liquid crystal display device 400 according to an embodiment of the present invention.
12A to 12C are diagrams schematically showing a relationship between a relative arrangement of a plurality of square openings and an alignment of liquid crystal molecules.
13A to 13C are diagrams schematically showing a relationship between a relative arrangement of a plurality of circular openings and an alignment of liquid crystal molecules.
FIG. 14 is a diagram schematically showing the relationship between another relative arrangement of a plurality of circular openings and the orientation of liquid crystal molecules.
15A and 15B are diagrams schematically showing a structure of one picture element region of the liquid crystal display device 400A according to the first embodiment of the present invention, wherein FIG. 15A is a top view, and FIG. It is sectional drawing along 15B 'line.
FIGS. 16A to 16C are diagrams schematically illustrating examples of radially inclined alignment of liquid crystal molecules.
FIGS. 17 (a) and (b) are top views schematically showing another picture element electrode used for the liquid crystal display device of Embodiment 1 according to the present invention.
FIGS. 18A and 18B are top views schematically showing still another pixel electrode used in the liquid crystal display device according to the first embodiment of the present invention.
FIGS. 19A and 19B are top views schematically showing still another pixel electrode used in the liquid crystal display device according to the first embodiment of the present invention.
FIG. 20 is a top view schematically showing still another picture element electrode used in the liquid crystal display device according to the first embodiment of the present invention.
FIGS. 21A and 21B are top views schematically showing still another pixel electrode used in the liquid crystal display device according to the first embodiment of the present invention.
22A is a diagram schematically showing a unit lattice of the pattern shown in FIG. 15A, and FIG. 22B is a diagram schematically showing a unit lattice of the pattern shown in FIG. (C) is a graph showing the relationship between the pitch p and the solid part area ratio.
23A and 23B are diagrams schematically showing the structure of one picture element region of a liquid crystal display device 400B according to a second embodiment of the present invention, wherein FIG. 23A is a top view, and FIG. It is sectional drawing which followed the 23B 'line.
FIGS. 24A to 24D are schematic diagrams for explaining the relationship between the alignment of the liquid crystal molecules 30a and the shape of the surface having vertical alignment.
FIGS. 25A and 25B are diagrams showing a state in which a voltage is applied to the liquid crystal layer 30 of the liquid crystal display device 400B, where FIG. Schematically shows a steady state.
FIGS. 26A to 26C are schematic cross-sectional views of liquid crystal display devices 400C, 400D, and 400E of Embodiment 2 in which the arrangement relationship between the opening and the projection is different.
FIG. 27 is a diagram schematically showing a cross-sectional structure of the liquid crystal display device 400B, and is a cross-sectional view taken along line 27A-27A ′ in FIG.
28A and 28B are diagrams schematically showing the structure of one picture element region of a liquid crystal display device 400F according to a second embodiment of the present invention, where FIG. 28A is a top view, and FIG. It is sectional drawing along 28A 'line.
FIGS. 29A to 29E are diagrams schematically showing a counter substrate 200b having a second alignment control structure 28. FIGS.
30A and 30B are diagrams schematically illustrating a liquid crystal display device 400G including a first alignment control structure and a second alignment control structure, wherein FIG. 30A is a top view, and FIG. 30B is a view illustrating 30B- in FIG. It is sectional drawing along 30B 'line.
31A and 31B are diagrams schematically showing a cross-sectional structure of one picture element region of a liquid crystal display device 400G, where FIG. 31A shows a state where no voltage is applied, and FIG. (C), and (c) shows a steady state.
FIGS. 32A and 32B are diagrams schematically showing another liquid crystal display device 400H including a first alignment control structure and a second alignment control structure, wherein FIG. 32A is a top view and FIG. It is sectional drawing along the 32B-32B 'line.
FIGS. 33A and 33B are diagrams schematically showing a cross-sectional structure of one picture element region of the liquid crystal display device 400H, wherein FIG. 33A shows a state where no voltage is applied, and FIG. (C), and (c) shows a steady state.
FIG. 34 is a diagram schematically showing a cross-sectional structure of one picture element region of the liquid crystal display device 500 according to the embodiment of the present invention.
FIG. 35 is a diagram schematically showing a cross-sectional structure of one picture element region of the liquid crystal display device 600 of the embodiment according to the present invention.
FIG. 36 is a schematic cross-sectional view in which the vicinity of a picture element electrode of a liquid crystal display device according to an embodiment of the present invention is enlarged.
FIG. 37 is a diagram schematically showing a cross-sectional structure of one picture element region of the liquid crystal display device 700 of the embodiment according to the present invention.
FIG. 38A is a diagram schematically showing a cross-sectional structure of one picture element region of a dual-use liquid crystal display device 150 according to an embodiment of the present invention.
FIG. 38B is a diagram schematically showing a cross-sectional structure of one picture element region of the dual-use liquid crystal display device 550 according to the embodiment of the present invention.
FIG. 38C is a drawing schematically showing a cross-sectional structure of one picture element region of the dual-use liquid crystal display device 650 according to the embodiment of the present invention.
FIG. 39 is a schematic view showing a structure near an opening in a dual-use liquid crystal display device according to an embodiment of the present invention.
FIG. 40 is a schematic diagram showing a structure near an opening in a dual-use liquid crystal display device according to an embodiment of the present invention.
FIG. 41 is a diagram showing an alignment state of liquid crystal molecules and an arrangement of a polarizing plate in a liquid crystal display device according to an embodiment of the present invention (in a state where no voltage is applied).
FIG. 42 is a diagram illustrating an alignment state of liquid crystal molecules and an arrangement of a polarizing plate in a liquid crystal display device according to an embodiment of the present invention (voltage applied state).
FIG. 43 is a diagram showing an alignment state of liquid crystal molecules and an arrangement of a polarizing plate and a λ / 4 plate in the liquid crystal display device of the embodiment according to the present invention (state in which no voltage is applied).
FIG. 44 is a view showing an alignment state of liquid crystal molecules and an arrangement of a polarizing plate and a λ / 4 plate in a liquid crystal display device according to an embodiment of the present invention (voltage applied state).
FIG. 45 is a diagram showing an alignment state of liquid crystal molecules and another arrangement of a polarizing plate and a λ / 4 plate in a liquid crystal display device according to an embodiment of the present invention (in a state where no voltage is applied).
FIG. 46 is a diagram showing an alignment state of liquid crystal molecules and an arrangement of a polarizing plate, a λ / 4 plate, and a λ / 2 plate in a liquid crystal display device according to an embodiment of the present invention (with no voltage applied).
FIG. 47 is a diagram illustrating an alignment state of liquid crystal molecules and another arrangement of a polarizing plate, a λ / 4 plate, and a λ / 2 plate in a liquid crystal display device according to an embodiment of the present invention (state in which no voltage is applied).
FIG. 48 is a schematic sectional view of a transmissive liquid crystal display device 800 according to a first embodiment of the present invention.
FIG. 49 is a schematic plan view of a transmission type liquid crystal display device 800 according to Embodiment 1 of the present invention.
FIG. 50A is a schematic cross-sectional view showing a manufacturing step of the liquid crystal display device 800.
FIG. 50B is a schematic sectional view showing another manufacturing step of the liquid crystal display device 800;
FIG. 51 is a view schematically showing a state of a picture element region when a voltage is applied to a liquid crystal layer of the liquid crystal display device 800.
FIG. 52 is a schematic sectional view of a transmission type liquid crystal display device 900 according to a second embodiment of the present invention.
FIG. 53 is a schematic plan view of a transmission type liquid crystal display device 900 according to Embodiment 2 of the present invention.
FIG. 54 is a schematic sectional view of a dual-use liquid crystal display device 1000 according to a third embodiment of the present invention.
FIG. 55 is a schematic plan view of a dual-use liquid crystal display device 1000 according to a third embodiment of the present invention.
FIG. 56 is a schematic sectional view showing the manufacturing process of the liquid crystal display device 1000.
FIG. 57 is a schematic diagram for explaining a display operation when a voltage is applied to a liquid crystal layer in a reflection region of the liquid crystal display device 1000.
FIG. 58 is a schematic sectional view of a dual-use liquid crystal display device 1100 according to a fourth embodiment of the present invention.
FIG. 59 is a diagram schematically showing a structure of an opening portion 103a of the photosensitive resin layer 103 in the liquid crystal display device 1000 and an edge portion of a concave portion 103b of the photosensitive resin layer 103 in the liquid crystal display device 1100.
FIG. 60 is a plan view schematically showing a part of the upper conductive layer 104 of the liquid crystal display device 900 according to the second embodiment of the present invention.
FIG. 61 is a diagram schematically showing the arrangement of openings provided near the sides of the upper conductive layer 104 of the liquid crystal display device of Example 5 according to the present invention.
FIG. 62 is a diagram schematically showing an arrangement of openings provided near corners of the upper conductive layer 104 of the liquid crystal display device of Example 5 according to the present invention.
FIG. 63 is a diagram schematically showing an arrangement of openings provided in the vicinity of a notch in an upper conductive layer 104 of a liquid crystal display device according to a fifth embodiment of the present invention.
FIG. 64 is a diagram schematically showing an arrangement of openings of an upper conductive layer 104 of a liquid crystal display device according to a sixth embodiment of the present invention.
FIG. 65 is a diagram schematically showing another arrangement of the openings in the upper conductive layer 104 of the liquid crystal display device of Example 6 according to the present invention.
FIG. 66 is a schematic plan view of a liquid crystal display device 1200 according to Embodiment 7 of the present invention.
FIG. 67 is a schematic sectional view of a liquid crystal display device 1200 according to Embodiment 7 of the present invention.
[Explanation of symbols]
11,21 Transparent insulating substrate
12 Lower conductive layer
13 Dielectric layer
1414A, 14B, 14C, 14D, 14E, 14F, 14G, 14H, 14I Upper conductive layer
14a opening
15 Picture element electrode (two-layer structure electrode)
22 Counter electrode
30 liquid crystal layer
30a Liquid crystal molecule
50a, 50b Polarizing plate
60a, 60b λ / 4 plate
70a, 70b λ / 2 plate
100, 100 ', 100''liquid crystal display device
100a, 400a, 400b TFT substrate
100b, 200b Counter substrate
14a opening
14b Solid part (conductive film)
14b 'unit solid part
22 Counter electrode
30 liquid crystal layer
30a Liquid crystal molecule
40, 40A, 40B, 40C, 40D convex part
40s Side of convex part
40t Top of convex part
100, 100 ', 100''liquid crystal display device
100a, 400b TFT substrate
100b Counter substrate

Claims (8)

  1. A first substrate, a second substrate, and a liquid crystal layer provided between the first substrate and the second substrate;
    A plurality of electrodes each defined by a first electrode provided on the liquid crystal layer side of the first substrate and a second electrode provided on the second substrate and facing the first electrode via the liquid crystal layer. Having a pixel area of
    The first electrode includes a lower conductive layer, a dielectric layer covering at least a portion of the lower conductive layer, and said dielectric layer upper conductive layer wherein was found provided on the liquid crystal layer side of,
    In each of the plurality of picture element regions, the upper conductive layer has a plurality of openings and a solid portion, and the liquid crystal layer applies a voltage between the first electrode and the second electrode. It takes a vertical alignment state when not performed, and when a voltage is applied between the first electrode and the second electrode, it is generated at the edges of the plurality of openings in the upper conductive layer. A plurality of liquid crystal domains each having a radially inclined alignment state are formed in the plurality of openings and the solid portion by an oblique electric field, and the orientation of the liquid crystal domains formed in the plurality of openings and the solid A liquid crystal display device, wherein the liquid crystal domains formed in the portion are continuous with each other , and display is performed by changing the alignment state of the plurality of liquid crystal domains in accordance with an applied voltage.
  2. At least a portion of the opening portion of the plurality of openings is substantially of equal size with the same shape, to form at least one unit cell arranged so as to have rotational symmetry, claim 1 3. The liquid crystal display device according to 1.
  3. The liquid crystal display device according to claim 2 , wherein each of the at least some of the plurality of openings has a rotational symmetry.
  4. The liquid crystal display device according to claim 2 or 3, respectively a substantially circular at least part of the opening of the plurality of openings.
  5. Said solid portion, to each of the at least a portion of the opening portion has a substantially a plurality of unit solid portions surrounded, each of the plurality of unit solid portion is substantially circular, according to claim 2 5. The liquid crystal display device according to any one of items 1 to 4 .
  6. In each of the plurality of picture element regions, the sum of the plurality of areas of the openings of the first electrode, the first electrode wherein in an area smaller than the real part of, according to any one of claims 1 to 5 Liquid crystal display device.
  7. A protrusion is further provided inside each of the plurality of openings, and a cross-sectional shape of the protrusion in an in-plane direction of the first substrate is the same as the shape of the plurality of openings, and a side surface of the protrusion is provided. is the liquid crystal molecules of the liquid crystal layer has an alignment regulating force of the same direction as the alignment regulation direction of the oblique electric field, the liquid crystal display device according to any one of claims 1 to 6.
  8. The first substrate further includes an active element provided corresponding to each of the plurality of picture element regions,
    The first electrode is a pixel electrode provided for each of the plurality of pixel regions and is switched by the active element, and the second electrode is at least one counter electrode facing the plurality of pixel electrodes. The liquid crystal display device according to any one of claims 1 to 7 , wherein
JP2001038556A 2000-02-25 2001-02-15 Liquid crystal display Expired - Fee Related JP3600531B2 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
JP2000049495 2000-02-25
JP2000161588 2000-05-31
JP2000-161588 2000-05-31
JP2000-49495 2000-05-31
JP2001038556A JP3600531B2 (en) 2000-02-25 2001-02-15 Liquid crystal display

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
JP2001038556A JP3600531B2 (en) 2000-02-25 2001-02-15 Liquid crystal display
US09/790,802 US6924876B2 (en) 2000-02-25 2001-02-23 Liquid crystal display device
TW90104208A TWI290252B (en) 2000-02-25 2001-02-23 Liquid crystal display device
KR20010009631A KR100457365B1 (en) 2000-02-25 2001-02-26 Liquid crystal display device
US11/104,523 US7084943B2 (en) 2000-02-25 2005-04-13 Liquid crystal display device

Publications (2)

Publication Number Publication Date
JP2002055343A JP2002055343A (en) 2002-02-20
JP3600531B2 true JP3600531B2 (en) 2004-12-15

Family

ID=27342482

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2001038556A Expired - Fee Related JP3600531B2 (en) 2000-02-25 2001-02-15 Liquid crystal display

Country Status (1)

Country Link
JP (1) JP3600531B2 (en)

Families Citing this family (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6965422B2 (en) 1998-07-24 2005-11-15 Sharp Kabushiki Kaisha Liquid crystal display device
JP3601788B2 (en) 2000-10-31 2004-12-15 シャープ株式会社 Liquid crystal display
JP4248835B2 (en) 2002-04-15 2009-04-02 シャープ株式会社 Substrate for liquid crystal display device and liquid crystal display device including the same
JP4342200B2 (en) * 2002-06-06 2009-10-14 シャープ株式会社 Liquid crystal display
JP3778185B2 (en) 2002-11-08 2006-05-24 セイコーエプソン株式会社 Liquid crystal display device and electronic device
JP3900141B2 (en) 2003-03-13 2007-04-04 セイコーエプソン株式会社 Liquid crystal display device and electronic device
JP4520099B2 (en) * 2003-03-20 2010-08-04 株式会社リコー Optical element, light deflection element, and image display device
TW594310B (en) * 2003-05-12 2004-06-21 Hannstar Display Corp Transflective LCD with single cell gap and the fabrication method thereof
JP2005055880A (en) * 2003-07-24 2005-03-03 Sharp Corp Liquid crystal display device and driving method for the same
JP4265788B2 (en) 2003-12-05 2009-05-20 シャープ株式会社 Liquid crystal display
US7573551B2 (en) 2004-05-21 2009-08-11 Sanyo Electric Co., Ltd. Transflective liquid crystal display device and color liquid crystal display device
JP2006011362A (en) * 2004-05-21 2006-01-12 Sanyo Electric Co Ltd Transflective liquid crystal display device
JP2006091229A (en) * 2004-09-22 2006-04-06 Sharp Corp Liquid crystal display
JP4104639B2 (en) 2004-12-28 2008-06-18 シャープ株式会社 Liquid crystal display device and driving method thereof
US7884890B2 (en) 2005-03-18 2011-02-08 Sharp Kabushiki Kaisha Liquid crystal display device
US7948463B2 (en) 2005-03-18 2011-05-24 Sharp Kabushiki Kaisha Liquid crystal display device
JP5168760B2 (en) * 2005-05-16 2013-03-27 セイコーエプソン株式会社 Liquid crystal device and electronic device
JP4813842B2 (en) * 2005-07-29 2011-11-09 パナソニック液晶ディスプレイ株式会社 Liquid crystal display
CN101233447A (en) * 2005-08-01 2008-07-30 夏普株式会社 Liquid crystal display device
CN101950104B (en) * 2005-09-30 2012-10-10 夏普株式会社 Liquid crystal display and method for manufacturing same
EP2261729B1 (en) * 2005-10-18 2014-05-07 Semiconductor Energy Laboratory Co, Ltd. Liquid crystal display device and electronic apparatus
US7907241B2 (en) 2005-12-02 2011-03-15 Sharp Kabushiki Kaisha Liquid crystal display device
JP4600265B2 (en) 2005-12-12 2010-12-15 ソニー株式会社 Liquid crystal device and electronic device
JP2007212872A (en) * 2006-02-10 2007-08-23 Hitachi Displays Ltd Liquid crystal display device
US8111356B2 (en) 2006-09-12 2012-02-07 Sharp Kabushiki Kaisha Liquid crystal display panel provided with microlens array, method for manufacturing the liquid crystal display panel, and liquid crystal display device
US8174641B2 (en) 2006-09-28 2012-05-08 Sharp Kabushiki Kaisha Liquid crystal display panel with microlens array, its manufacturing method, and liquid crystal display device
WO2008062597A1 (en) * 2006-11-20 2008-05-29 Sharp Kabushiki Kaisha Field angle control panel, and liquid crystal display device
CN101568877B (en) 2006-12-18 2011-05-11 夏普株式会社 Liquid crystal display
US8300188B2 (en) 2007-01-11 2012-10-30 Sharp Kabushiki Kaisha Liquid crystal display panel with micro-lens array and liquid crystal display device
KR20090027920A (en) * 2007-09-13 2009-03-18 삼성전자주식회사 Display substrate and display panel having the same
WO2012090775A1 (en) * 2010-12-28 2012-07-05 シャープ株式会社 Circuit substrate, liquid crystal display panel and liquid crystal display device
WO2012090776A1 (en) * 2010-12-28 2012-07-05 シャープ株式会社 Liquid crystal display panel and liquid crystal display device
WO2012090773A1 (en) * 2010-12-28 2012-07-05 シャープ株式会社 Liquid crystal display panel and liquid crystal display device
TWI640823B (en) * 2017-10-24 2018-11-11 友達光電股份有限公司 Pixel structure and display panel

Also Published As

Publication number Publication date
JP2002055343A (en) 2002-02-20

Similar Documents

Publication Publication Date Title
US8804079B2 (en) Liquid crystal display device
US8638403B2 (en) Liquid crystal display device
US8537316B2 (en) Transflective liquid crystal display device and color liquid crystal display device
US8049848B2 (en) Liquid crystal display and method of manufacturing the same and method of driving the same
US20130293797A1 (en) Substrate for liquid crystal display, liquid crystal display having the same and method of manufacturing the same
US7570332B2 (en) Liquid crystal displays having multi-domains and a manufacturing method thereof
US6853425B2 (en) Liquid crystal display device and a method of manufacturing a viewing angle compensation film for the same
EP1484633B1 (en) Liquid crystal display device, method of manufacturing the same, and electronic apparatus
US7525614B2 (en) Fringe field switching mode transflective LCD having slits in the reflective area of a pixel electrode that have an inclination angle greater than slits in the transmissive area by about 10 to 40 degrees
US5689322A (en) Liquid crystal display device having regions with different twist angles
US7538839B2 (en) Liquid crystal display and electronic appliance
JP4080245B2 (en) Liquid crystal display
KR100568197B1 (en) Liquid crystal display device and method of manufacturing the same
EP1870767B1 (en) Verically-aligned (VA) liquid crystal display device
TWI255379B (en) Liquid crystal display device and fabrication method therefor
US6522375B1 (en) Reflection type liquid crystal display and a method for fabricating the same
US7656478B2 (en) Diffusing reflector and manufacture of the same and reflection type display apparatus
JP3917417B2 (en) Reflective liquid crystal display
JP3251519B2 (en) Closed cavity type liquid crystal display and manufacturing method thereof
US9069212B2 (en) Exposure apparatus, liquid crystal display device, and method for manufacturing liquid crystal display device
CN100407013C (en) Liquid crystal display device
US6339462B1 (en) LCD having polymer wall and column-like projection defining cell gap
US7250996B2 (en) Liquid crystal display and method of manufacturing the same
TWI480651B (en) Liquid crystal display device and method for preparing the same
US8259269B2 (en) Liquid crystal display device with pixel electrode or common electrode having slit like aperture with increasing width

Legal Events

Date Code Title Description
A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20040607

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20040630

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20040827

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20040914

R150 Certificate of patent or registration of utility model

Free format text: JAPANESE INTERMEDIATE CODE: R150

Ref document number: 3600531

Country of ref document: JP

Free format text: JAPANESE INTERMEDIATE CODE: R150

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20040916

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20080924

Year of fee payment: 4

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20080924

Year of fee payment: 4

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20090924

Year of fee payment: 5

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20090924

Year of fee payment: 5

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20100924

Year of fee payment: 6

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20110924

Year of fee payment: 7

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120924

Year of fee payment: 8

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130924

Year of fee payment: 9

LAPS Cancellation because of no payment of annual fees