JP2004205755A - Liquid crystal display and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display with which a bright, high contrast and further wide viewing angle display is obtainable in a transflective liquid crystal display. <P>SOLUTION: A vertical alignment mode using a liquid crystal layer with a vertically aligned initial alignment state is adopted in the liquid crystal display. A reflective display region R is arranged in a dot so as to surround a circumference of a transmission display region T. An insulating film 21 to adjust liquid crystal layer thickness is disposed on a region corresponding to the reflective display region R on the peripheral part of the dot. Furthermore, on at least one electrode, a slit-shaped opening part 31s is arranged on the boundary region between the reflective display region R and the transmission display region T. A planar shape of the opening part 31s is formed in a nearly elliptical shape. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００６２】
［表１］の結果から明らかなように、スリットの曲率半径Ｒを１μｍ以上とすれば、液晶の配向乱れを概ね抑えることができ、良好な画質を持つ液晶表示装置を実現することができる。また、好ましくは３μｍ以上とすれば、配向乱れが全く観察されない極めて良好な画質を持つ液晶表示装置を実現することができる、ということがわかった。
【図面の簡単な説明】
【図１】本発明の第１実施形態の液晶表示装置の等価回路図である。
【図２】同、液晶表示装置の１ドットの構成を示す平面図である。
【図３】同、液晶表示装置の図２のＡ−Ａ’線に沿う断面図である。
【図４】同、液晶表示装置の液晶分子の倒れる様子を示す模式図である。
【図５】本発明の第２実施形態の液晶表示装置の断面図である。
【図６】本発明の第３実施形態の液晶表示装置の断面図である。
【図７】本発明の第４実施形態の液晶表示装置の１ドットの平面図である。
【図８】本発明の第５実施形態の液晶表示装置の１ドットの平面図である。
【図９】本発明の第６実施形態の液晶表示装置の１ドットの平面図である。
【図１０】本発明の電子機器の一例を示す斜視図である。
【符号の説明】
９…画素電極、１０…ＴＦＴアレイ基板、２０…反射膜、２１…絶縁膜（液晶層厚調整層）、２１ａ…傾斜面、２５…対向基板、３１…共通電極、３１ｓ…開口部、５０…液晶層、Ｒ…反射表示領域、Ｔ…透過表示領域[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device and an electronic apparatus, and more particularly to a technique capable of obtaining a display with a high contrast and a wide viewing angle in a transflective liquid crystal display device that performs display in both a reflection mode and a transmission mode. .
[0002]
[Prior art]
There has been proposed a liquid crystal display device in which external light is used in a bright place similarly to a reflective liquid crystal display device, and in a dark place, the display can be visually recognized by an internal light source such as a backlight. In other words, this liquid crystal display device employs a display system that has both a reflective type and a transmissive type, and reduces power consumption by switching between the reflective mode and the transmissive mode according to the surrounding brightness. In addition, even when the surroundings are dark, clear display can be performed, which is suitable for a display unit of a portable device. Hereinafter, in this specification, this type of liquid crystal display device is referred to as a “semi-transmissive reflective liquid crystal display device”.
[0003]
As such a transflective liquid crystal display device, a liquid crystal layer is sandwiched between an upper substrate and a lower substrate, and a reflection film in which an opening for light transmission is formed in a metal film such as aluminum is disposed below. There has been proposed a liquid crystal display device provided on the inner surface of a substrate and using this reflection film as a transflective plate. In this case, in the reflection mode, external light incident from the upper substrate side passes through the liquid crystal layer, is reflected by the reflection film on the inner surface of the lower substrate, passes through the liquid crystal layer again, and is emitted from the upper substrate side, contributing to display. I do. On the other hand, in the transmission mode, light from the backlight incident from the lower substrate side passes through the liquid crystal layer from the opening of the reflection film, and then exits from the upper substrate side to contribute to display. Therefore, of the reflective film forming region, the region where the opening is formed is the transmissive display region, and the other region is the reflective display region.
[0004]
However, the conventional transflective liquid crystal device has a problem that the viewing angle in transmissive display is narrow. This is because a transflective plate is provided on the inner surface of the liquid crystal cell so that parallax does not occur, and there is a restriction that reflective display must be performed with only one polarizing plate provided on the viewer side. This is because the degree of freedom in design is small. In order to solve this problem, Jisaki et al. Proposed a new transflective liquid crystal display device using a vertically aligned liquid crystal in Non-Patent Document 1 below. The features are the following three points.
(1) A "VA (Vertical Alignment) mode" in which a liquid crystal having a negative dielectric anisotropy is vertically aligned with a substrate and is tilted by applying a voltage.
(2) A multi-gap structure in which the liquid crystal layer thickness (cell gap) of the transmissive display region and the reflective display region is different (for this point, see, for example, Patent Document 1).
(3) The transmissive display area is a regular octagon, and a projection is provided at the center of the transmissive display area on the opposing substrate so that the liquid crystal falls in eight directions in this area. That is, an "alignment division structure" is adopted.
[0005]
[Patent Document 1]
JP-A-11-242226
[Non-patent document 1]
"Development of transflective LCD for high contrast and wide viewing angle by using homeotropic alignment", M. Jisaki et al., Asia Display / IDW'01, p.133-136 (2001)
[0006]
[Problems to be solved by the invention]
However, in the paper by Jisaki et al., The direction in which the liquid crystal falls in the transmissive display area is controlled using protrusions, but there is no configuration for controlling the direction in which the liquid crystal falls in the reflective display area. Therefore, in the reflective display area, the liquid crystal falls in a random direction. In this case, a discontinuous line called disclination appears at the boundary between different liquid crystal alignment areas, which causes afterimages and the like. In addition, since the respective alignment regions of the liquid crystal have different viewing angle characteristics, there is also a problem that when the liquid crystal device is viewed from an oblique direction, the liquid crystal device appears as a rough spot-like unevenness. Furthermore, even if the liquid crystal molecules in the transmissive display area fall in eight directions, the improvement of the viewing angle characteristics is still insufficient, and the alignment of the liquid crystal is disturbed at the boundary between different alignment areas, and disclination also occurs.
[0007]
The present invention has been made to solve the above problems, and in a transflective liquid crystal display device, display defects such as afterimages and spot-like unevenness are suppressed, and further, a high contrast and a wide viewing angle are provided. It is an object of the present invention to provide a liquid crystal display device that can be used.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a liquid crystal display device of the present invention has a liquid crystal layer sandwiched between a pair of substrates, and has a transmissive display area for performing transmissive display in one dot area and a reflective display for performing reflective display. A liquid crystal display device provided with a region, wherein the liquid crystal layer is made of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and at least one of the pair of substrates and the liquid crystal layer. Between the liquid crystal layer, a liquid crystal layer thickness adjustment layer that varies the thickness of the liquid crystal layer between the reflective display region and the transmissive display region is provided at least in the reflective display region, and on the inner surfaces of the pair of substrates. An electrode for driving the liquid crystal is provided, and at least one of the electrodes of the pair of substrates is provided with a slit-shaped opening in a boundary region between the reflective display region and the transmissive display region. The opening The planar shape of the parts is characterized in that it consists of all curves.
[0009]
The liquid crystal display device of the present invention is obtained by combining a transflective liquid crystal display device with a liquid crystal in a vertical alignment mode. In recent years, in a transflective liquid crystal display device, in order to solve the problem of a decrease in contrast due to a retardation difference in both the reflective and transmissive display modes, for example, an insulating film having a predetermined thickness in a reflective display region on a lower substrate Is formed so as to protrude toward the liquid crystal layer side, so that the thickness of the liquid crystal layer is changed between the reflective display area and the transmissive display area (Japanese Patent Application Laid-Open No. H11-163,019). The present applicant has already applied for many inventions of this type of liquid crystal display device. According to this configuration, the thickness of the liquid crystal layer in the reflective display area is reduced by the presence of the insulating film (in the present specification, the insulating film performing such a function is referred to as a “liquid crystal layer thickness adjustment layer”). Since the thickness of the liquid crystal layer can be made smaller than the thickness of the liquid crystal layer, the retardation in the reflective display area and the retardation in the transmissive display area can be made sufficiently close to or substantially equal to each other, whereby the contrast can be improved.
[0010]
Therefore, the present inventor has found that by combining a liquid crystal display device having the above-described insulating film with a liquid crystal layer in a vertical alignment mode, the alignment direction of a liquid crystal in a vertical alignment mode when an electric field is applied can be controlled. In other words, when the vertical alignment mode is adopted, a liquid crystal having a negative dielectric anisotropy (negative liquid crystal) is generally used. Since the liquid crystal molecules are tilted by applying voltage, the direction in which the liquid crystal molecules are tilted cannot be controlled without any contrivance (unless a pretilt is provided), and misalignment (disclination) occurs, causing display defects such as light leakage. And the display quality is degraded. Therefore, in adopting the vertical alignment mode, control of the alignment direction of liquid crystal molecules when an electric field is applied is an important factor. Therefore, in a liquid crystal display device having the above-mentioned liquid crystal layer thickness adjusting layer, the liquid crystal layer exhibits vertical alignment in an initial state because the liquid crystal layer thickness adjusting layer protrudes toward the liquid crystal layer and becomes a projection, so to speak. And has a pretilt according to the shape of the projection. Furthermore, since only the shape of the liquid crystal layer thickness adjustment layer has a weak pretilt imparting force, the inventors have conceived a configuration in which an opening in which a liquid crystal driving electrode does not exist is provided in the boundary region between the reflective display region and the transmissive display region. According to this configuration, the electric field (potential line) generated between the electrodes on both substrates is obliquely distorted in the vicinity of the opening, and the control of the alignment direction of the liquid crystal molecules is more easily realized by the action of the distorted electric field. can do.
[0011]
Thus, it was found that by providing an opening in at least one of the pair of electrodes, the orientation direction of the liquid crystal molecules could be controlled. For example, in a configuration in which a rectangular transmissive display area is provided in the center of a pixel, if a rectangular slit-shaped opening is provided in a boundary area between the reflective display area and the transmissive display area, the orientation direction of liquid crystal molecules is set to each side of the rectangle. As a result of being defined in the four perpendicular directions, regions having four different orientation directions are formed in one dot region, and an orientation division structure can be realized, so that a wider viewing angle can be achieved. However, it has been found that, with this configuration alone, disclination occurs at the boundary between four different alignment regions, as in Non-Patent Document 1, and display defects are induced. Therefore, in the present invention, the planar shapes of the slit-shaped openings are all configured by curves. Accordingly, a clear boundary between the alignment regions as in the case of a rectangular (polygonal) shape does not occur, and disclination can be suppressed. By such an operation, display with high contrast and a wide viewing angle can be realized without display defects such as light leakage and spot-like unevenness.
[0012]
The above-mentioned effect can be obtained as long as the planar shape of the slit-shaped opening is all curved, but it is particularly desirable that the slit-shaped opening be a perfect circle or an ellipse.
With this configuration, the liquid crystal molecules can be made to fall isotropically and continuously in almost all directions in one pixel, so that the viewing angle characteristics can be made substantially isotropic.
[0013]
In addition to the above configuration, it is desirable that all the planar shapes of the steps of the liquid crystal layer thickness adjustment layer, which is the boundary region between the reflective display region and the transmissive display region, be configured by curves.
With this configuration, in addition to the effect of the oblique electric field due to the opening of the electrode, the shape effect of the step portion of the liquid crystal layer thickness adjustment layer can further more isotropically affect the orientation direction of the liquid crystal molecules. Thus, a configuration in which disclination is less likely to occur can be realized.
[0014]
It is preferable that the opening of the electrode and the step of the liquid crystal layer thickness adjusting layer at least partially overlap in plan view.
With this configuration, for example, the effect of the oblique electric field due to the opening of the electrode and the stepped portion of the liquid crystal layer thickness adjustment layer are smaller than the case where the opening of the electrode and the step portion of the liquid crystal layer thickness adjustment layer are far apart. Can further enhance the synergistic effect with the shape action.
[0015]
As described above, the example in which the planar shape of the opening of the electrode is entirely configured by a curve has been described, but a linear portion may be included. However, it is necessary to increase the radius of curvature of the curved portion connecting the straight portions to each other to some extent. The following configuration of the present invention defines the radius of curvature.
That is, in another liquid crystal display device of the present invention, a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display region for performing transmissive display and a reflective display region for performing reflective display are provided in one dot region. Liquid crystal display device, wherein the liquid crystal layer is composed of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and a liquid crystal layer between at least one of the pair of substrates and the liquid crystal layer. A liquid crystal layer thickness adjustment layer that makes the thickness of the liquid crystal layer different between the reflective display region and the transmissive display region is provided at least in the reflective display region, and the liquid crystal is driven on inner surfaces of the pair of substrates. Electrodes are provided, and at least one of the electrodes of the pair of substrates is provided with a slit-shaped opening in a boundary region between the reflective display region and the transmissive display region. Plane shape Together it is constituted by a curve having a linear and constant radius of curvature, wherein the radius of curvature is 1μm or more. More preferably, the radius of curvature is 3 μm or more.
[0016]
The liquid crystal display device of the present invention is intended to prevent a distinct boundary between alignment regions, such as when the opening of an electrode is rectangular (polygonal), and to suppress disclination. Therefore, even if a straight line portion is included in the planar shape of the opening, if the curved portion is slightly gently bent, a clear boundary of the alignment region does not occur. Specific grounds for the numerical value of the radius of curvature will be described in detail in the section of Examples.
[0017]
As in the case where the planar shapes of the electrode openings are all curved, the planar shape of the step portion of the liquid crystal layer thickness adjustment layer corresponding to the boundary region between the reflective display region and the transmissive display region also has a straight line and a constant radius of curvature. It is desirable to configure with a curve. Further, it is desirable that the opening and the step portion overlap at least partially in plan view. These reasons are as described above.
[0018]
The example in which the opening is provided in the electrode and the alignment direction of the liquid crystal molecules is controlled by the oblique electric field has been described above. On the other hand, when the ridges (projections) are provided on the electrodes, the orientation direction of the liquid crystal molecules can be controlled by the action of the projections protruding into the liquid crystal layer, similarly to the action of the liquid crystal layer thickness adjustment layer. it can. As described above, although the mechanism is different, as the means for controlling the alignment direction of the liquid crystal molecules, both the opening of the electrode and the ridge can be used. Therefore, in the above-described configuration of the liquid crystal display device of the present invention, the opening of the electrode can be replaced with a ridge made of a dielectric formed on the electrode.
[0019]
Another liquid crystal display device according to the present invention is a liquid crystal display in which a liquid crystal layer is sandwiched between a pair of substrates, and in which a transmissive display region for performing transmissive display and a reflective display region for performing reflective display are provided in one dot region. In a display device, the liquid crystal layer is composed of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and between at least one of the pair of substrates and the liquid crystal layer, A liquid crystal layer thickness adjustment layer that varies the thickness of the liquid crystal layer between the reflective display region and the transmissive display region is provided at least in the reflective display region, and an inner surface of the pair of substrates is provided for driving the liquid crystal. An electrode is provided, and a ridge made of a dielectric is provided on a boundary region between the reflective display region and the transmissive display region on at least one of the electrodes of the pair of substrates. Are all curved Characterized in that it is configured.
[0020]
Further, the planar shape of the ridge is desirably a perfect circle or an ellipse.
In addition, it is preferable that all the planar shapes of the step portions of the liquid crystal layer thickness adjustment layer corresponding to a boundary region between the reflective display region and the transmissive display region are configured by curves.
In addition, it is preferable that the convex portion and the step portion overlap at least partially in plan view.
[0021]
Another liquid crystal display device according to the present invention is a liquid crystal display in which a liquid crystal layer is sandwiched between a pair of substrates, and in which a transmissive display region for performing transmissive display and a reflective display region for performing reflective display are provided in one dot region. In a display device, the liquid crystal layer is composed of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and between at least one of the pair of substrates and the liquid crystal layer, A liquid crystal layer thickness adjustment layer that varies the thickness of the liquid crystal layer between the reflective display region and the transmissive display region is provided at least in the reflective display region, and an inner surface of the pair of substrates is provided for driving the liquid crystal. An electrode is provided, and a ridge made of a dielectric is provided on a boundary region between the reflective display region and the transmissive display region on at least one of the electrodes of the pair of substrates. The plane shape of Together it is constituted by a curve having a radius of curvature, wherein the radius of curvature is 1μm or more.
[0022]
Further, the radius of curvature is desirably 3 μm or more.
Further, it is preferable that the planar shape of the step portion of the liquid crystal layer thickness adjustment layer, which corresponds to a boundary region between the reflective display region and the transmissive display region, is composed of a straight line and a curve having a constant radius of curvature.
In addition, it is preferable that the convex portion and the step portion overlap at least partially in plan view.
[0023]
It is preferable that a boundary region between the reflective display region and the transmissive display region includes an inclined region having an inclined surface so that the thickness of the liquid crystal layer thickness adjustment layer changes continuously.
The edge of the liquid crystal layer thickness adjustment layer corresponding to the boundary region between the reflective display region and the transmissive display region may have a step-like step, but in that case, near the boundary between the reflective display region and the transmissive display region. Since the thickness of the liquid crystal layer changes abruptly due to the above-described steps, the alignment of the liquid crystal is disturbed, which may adversely affect the display. On the other hand, if an inclined surface whose thickness changes continuously is formed in the liquid crystal layer thickness adjusting layer, the alignment state of the liquid crystal also changes continuously according to the position of the inclined surface. Disorder of the alignment does not occur, and display defects can be avoided.
[0024]
The color filter may be provided on the inner surface of one of the pair of substrates.
According to this configuration, it is possible to realize color display with high contrast and a wide viewing angle without display defects such as light leakage and spot-like unevenness.
Furthermore, by providing circularly polarized light incidence means for injecting circularly polarized light into each of the pair of substrates, it is possible to perform favorable display in both reflective display and transmissive display regardless of the direction in which the liquid crystal molecules fall. .
[0025]
An electronic apparatus according to the present invention includes the liquid crystal display device according to the present invention.
According to this configuration, it is possible to provide an electronic apparatus having a bright, high-contrast, wide-viewing-angle liquid crystal display unit regardless of the use environment.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The liquid crystal display device of this embodiment is an example of an active matrix liquid crystal display device using thin film transistors (hereinafter, abbreviated as TFTs) as switching elements.
[0027]
FIG. 1 is an equivalent circuit diagram of a plurality of dots arranged in a matrix forming an image display area of the liquid crystal display device of the present embodiment. FIG. 2 is a plan view showing the structure of one dot on a TFT array substrate. FIG. 3 is a cross-sectional view showing the structure of the liquid crystal device, and is a cross-sectional view taken along line AA ′ of FIG. 2, and FIG. 4 is a schematic view showing the state of the liquid crystal molecules falling. In the following drawings, the scale of each layer and each member is different in order to make each layer and each member have a size recognizable in the drawings.
[0028]
In the liquid crystal display device of the present embodiment, as shown in FIG. 1, a plurality of dots arranged in a matrix forming an image display area include a pixel electrode 9 and a switching element for controlling the pixel electrode 9. Are formed, and the data line 6a to which an image signal is supplied is electrically connected to the source of the TFT 30. The image signals S1, S2,..., Sn to be written to the data lines 6a are supplied line-sequentially in this order or supplied to a plurality of adjacent data lines 6a for each group. The scanning lines 3a are electrically connected to the gates of the TFTs 30, and the scanning signals G1, G2,..., Gm are applied to the plurality of scanning lines 3a in a pulsed line-sequential manner at a predetermined timing. The pixel electrode 9 is electrically connected to the drain of the TFT 30. When the TFT 30 serving as a switching element is turned on for a predetermined period, the image signals S1, S2,... Write at the timing of
[0029]
The image signals S1, S2,..., Sn of a predetermined level written in the liquid crystal through the pixel electrodes 9 are held for a certain period between the common electrodes described later. The liquid crystal modulates light by changing the orientation and order of the molecular assembly depending on the applied voltage level, thereby enabling gray scale display. Here, in order to prevent the held image signal from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the common electrode. Note that reference numeral 3b is a capacitance line.
[0030]
Next, a planar structure of the TFT array substrate 10 constituting the liquid crystal display device of the present embodiment will be described with reference to FIG.
As shown in FIG. 2, on the TFT array substrate 10, a plurality of rectangular pixel electrodes 9 (outlined by dotted lines 9A) are provided in a matrix, and each pixel electrode 9 extends along the vertical and horizontal boundaries of the pixel electrode 9. A data line 6a, a scanning line 3a and a capacitance line 3b are provided. In the present embodiment, one dot region is inside a region where each pixel electrode 9 and the data line 6a, the scanning line 3a, the capacitor line 3b, and the like provided so as to surround each pixel electrode 9 are formed. The structure is such that display is possible for each dot region arranged in a matrix.
[0031]
The data line 6a is electrically connected to a source region, which will be described later, of the semiconductor layer 1a constituting the TFT 30, for example, a polysilicon film via the contact hole 5, and the pixel electrode 9 is connected to the semiconductor layer 1a. Among them, it is electrically connected to a drain region described later via a contact hole 8. In addition, the scanning line 3a is arranged to face the channel region (the diagonally shaded region ascending in the figure) of the semiconductor layer 1a, and the scanning line 3a functions as a gate electrode in a portion facing the channel region. .
[0032]
The capacitance line 3b is formed from a main line portion extending substantially linearly along the scanning line 3a (that is, a first region formed along the scanning line 3a when viewed in plan) and a portion intersecting the data line 6a. And a projection (ie, a second region extending along the data line 6a when viewed in a plan view) protruding forward (upward in the figure) along the data line 6a. In FIG. 2, a plurality of first light-shielding films 11a are provided in a region indicated by oblique lines rising to the right.
[0033]
More specifically, the first light-shielding film 11a is provided at a position covering the TFT 30 including the channel region of the semiconductor layer 1a as viewed from the TFT array substrate side, and further, is opposed to the main line of the capacitor line 3b. A main line portion extending linearly along the scanning line 3a, and a protruding portion protruding from a location intersecting the data line 6a toward a subsequent stage (that is, downward in the drawing) adjacent to the data line 6a. The tip of the downward projection in each stage (pixel row) of the first light-shielding film 11a overlaps the tip of the upward projection of the capacitor line 3b in the next stage below the data line 6a. A contact hole 13 for electrically connecting the first light-shielding film 11a and the capacitance line 3b to each other is provided in the overlapping portion. That is, in the present embodiment, the first light-shielding film 11 a is electrically connected to the preceding or subsequent capacitive line 3 b by the contact hole 13.
[0034]
As shown in FIG. 2, a rectangular frame-shaped reflection film 20 is formed on the periphery of one dot region, and the region where the reflection film 20 is formed becomes a reflection display region R, and the reflection film inside the reflection display region R is formed. The area where 20 is not formed is the transmissive display area T. In addition, a rectangular frame-shaped insulating film 21 (liquid crystal layer thickness adjusting layer) is formed so as to include the formation region of the reflective film 20 when viewed in a plan view. In the case of the present embodiment, the insulating film 21 has the inclined surface 21a, and in this specification, this portion is defined as a boundary region between the reflective display region R and the transmissive display region T. The common electrode 31 on the counter substrate 25 described later has a slit-shaped opening 31s for each dot region, and the opening 31s has a substantially elliptical planar shape. However, if the ellipse is completely closed, the common electrode 31 is divided between the inside and the outside of the ellipse, so that it becomes difficult to apply a voltage. Therefore, in the case of the present embodiment, the connection portions 31c of the common electrode are provided at two locations on the ellipse. The connecting portion 31c may be provided in at least one place. In addition, a part of the opening 31s overlaps a part of the boundary region (the inclined surface 21a) in a planar manner.
[0035]
Next, a sectional structure of the liquid crystal display device of the present embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. 2. However, the present invention is characterized by the configuration of the insulating film and the electrodes, and the cross-sectional structure of the TFT and other wirings is not different from the conventional one. Illustration and description of the TFT and the wiring portion are omitted.
[0036]
As shown in FIG. 3, a liquid crystal layer 50 made of a liquid crystal having a negative dielectric anisotropy and exhibiting a vertical initial alignment state is sandwiched between a TFT array substrate 10 and an opposing substrate 25 disposed opposite thereto. I have. In the TFT array substrate 10, a reflective film 20 made of a metal film having a high reflectivity such as aluminum or silver is formed on the surface of a substrate main body 10A made of a translucent material such as quartz or glass. As described above, the area where the reflective film 20 is formed becomes the reflective display area R, and the area where the reflective film 20 is not formed becomes the transmissive display area T. On the reflective film 20 located in the reflective display region R and on the substrate body 10A located in the transmissive display region T, a dye layer 22 constituting a color filter is provided. In the pigment layer 22, pigment layers of different colors of red (R), green (G), and blue (B) are arranged for each adjacent dot region, and one pixel is constituted by three adjacent dot regions. I do. Alternatively, in order to compensate for the difference in the saturation of the display color between the reflective display and the transmissive display, a dye layer having a different color purity between the reflective display region R and the transmissive display region T may be separately provided.
[0037]
On the dye layer 22 of the color filter, an insulating film 21 is formed at a position corresponding to the reflective display region R (peripheral portion of the dot region). The insulating film 21 is made of, for example, an organic film such as an acrylic resin having a thickness of about 2 μm ± 1 μm, and has an inclined surface near the boundary between the reflective display region R and the transmissive display region T so that its own layer thickness changes continuously. It has an inclined area with 21a. Since the thickness of the liquid crystal layer 50 in the portion where the insulating film 21 does not exist is about 2 to 6 μm, the thickness of the liquid crystal layer 50 in the reflective display region R is about half the thickness of the liquid crystal layer 50 in the transmissive display region T. That is, the insulating film 21 functions as a liquid crystal layer thickness adjustment layer that varies the thickness of the liquid crystal layer 50 between the reflective display region R and the transmissive display region T according to its own film thickness. In the case of the present embodiment, the edge of the flat surface above the insulating film 21 and the edge of the reflective film 20 (reflective display area) substantially match, and the inclined area is included in the transmissive display area T.
[0038]
On the surface of the TFT array substrate 10 including the surface of the insulating film 21, a pixel electrode 9 made of a transparent conductive film such as indium tin oxide (hereinafter abbreviated as ITO) is formed. The pixel electrode 9 has a slit-shaped opening 9s at the center of the transmissive display area (not shown in the plan view of FIG. 2). An alignment film 23 made of polyimide or the like is formed on the pixel electrode 9.
[0039]
On the other hand, on the counter substrate 25 side, a common electrode 31 made of a transparent conductive film such as ITO and an alignment film 33 made of polyimide or the like are sequentially formed on a substrate body 25A made of a light-transmitting material such as glass or quartz. . As described above, the common electrode 31 has the slit-shaped opening 31 s having a substantially elliptical planar shape, and the opening 31 s is located above the inclined surface 21 a of the insulating film 21. Both the alignment films 23 and 33 of the TFT array substrate 10 and the counter substrate 25 are subjected to vertical alignment processing, but are not provided with a means for imparting pretilt such as rubbing.
[0040]
Further, on the outer surface side of the TFT array substrate 10 and the outer surface side of the counter substrate 25, retardation plates 43, 41 and polarizing plates 44, 42 are sequentially provided from the substrate bodies 10A, 25A side, respectively. The phase difference plates 43 and 41 have a phase difference of about 1/4 wavelength with respect to the wavelength of visible light, and the combination of the phase difference plates 43 and 41 and the polarizing plates 44 and 42 makes the TFT array substrate 10 Circularly polarized light enters the liquid crystal layer 50 from both the side and the counter substrate 25 side. A backlight 64 having a light source 61, a reflector 62, a light guide plate 63, and the like is provided outside the liquid crystal cell on the outer surface side of the TFT array substrate 10.
[0041]
According to the liquid crystal display device of the present embodiment, the thickness of the liquid crystal layer 50 in the reflective display region R is reduced to approximately half the thickness of the liquid crystal layer 50 in the transmissive display region T by providing the insulating film 21 in the reflective display region R. Since the size can be reduced, the retardation in the reflective display region R and the retardation in the transmissive display region T can be made substantially equal, thereby improving the contrast. Further, the insulating film 21 is a protrusion protruding toward the liquid crystal layer 50, and slit-shaped openings 9s, 31s are provided at positions corresponding to the center of the pixel electrode 9 and the boundary region of the common electrode 31, respectively. Accordingly, the electric field applied between the upper and lower electrodes is obliquely distorted, and the orientation of the liquid crystal molecules 50b can be controlled by the shape action of the insulating film 21 and the action of the oblique electric field.
[0042]
Further, in the case of the present embodiment, since the planar shape of the slit-shaped opening 31s of the common electrode 31 does not have a corner and is entirely constituted by a curve, when the slit is formed in a rectangular shape (polygonal shape). Such a clear boundary between alignment regions does not occur, and disclination can be suppressed. More specifically, as shown in FIG. 4, since the planar shape of the slit-shaped opening 31 s is substantially elliptical, the liquid crystal molecules 50 b can be continuously and isotropically inclined in all directions. And the viewing angle characteristics can be made substantially isotropic. In the liquid crystal display device of the present embodiment, by such an operation, display with high contrast and a wide viewing angle can be realized without display defects such as light leakage and spot-like unevenness.
[0043]
[Second embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
The basic configuration of the liquid crystal display device of the present embodiment is exactly the same as that of the first embodiment, and is different from the first embodiment only in that a ridge is provided instead of providing an opening in the common electrode. FIG. 5 is a sectional view of the liquid crystal display device of the present embodiment. 5, the same reference numerals are given to the same components as those in FIG. 3, and the detailed description will be omitted.
[0044]
In the case of this embodiment, as shown in FIG. 5, the configuration on the TFT array substrate 10 side is not different from that of the first embodiment. An article 71 is provided. The ridge 71 is formed of a dielectric material such as an acrylic resin, for example. The planar shape of the ridge 71 is also elliptical, like the shape of the opening 31s shown in FIG. However, in the case of the convex streak 71 of the present embodiment, since it is not related to the application of the voltage to the common electrode 31, it may be a closed elliptical shape. Further, as in the case of the opening 31, the formation position of the ridge 71 may be a position substantially overlapping the boundary region (the inclined surface 21 a of the insulating film 21) between the transmissive display region T and the reflective display region R.
[0045]
In the case of the ridge 71, an oblique electric field is generated in the liquid crystal layer 50 by the dielectric material of the ridge 71 as in the case where the opening 31s is provided in the common electrode 31, so that the alignment direction can be controlled. The liquid crystal molecules 50b in the liquid crystal layer 50 are tilted in the same direction as in the case of FIG. 3 by the shape action of the ridge 71 projecting into the layer 50, and the alignment direction can be controlled. Also in the present embodiment, the same effects as in the first embodiment, such as a liquid crystal display device capable of displaying with high contrast and a wide viewing angle without display defects such as light leakage and spot-like unevenness, can be obtained. Obtainable.
[0046]
[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.
The liquid crystal display device of the present embodiment is different from the first and second embodiments in that each component is arranged on a TFT array substrate or on a counter substrate. FIG. 6 is a sectional view of the liquid crystal display device of the present embodiment. 6, the same components as those in FIGS. 3 and 5 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0047]
In the liquid crystal display device of the present embodiment, as shown in FIG. 6, the configuration on the TFT array substrate 10 side is such that an insulating film 21 functioning as a liquid crystal layer thickness adjustment layer is directly formed on the inner surface of the substrate main body 10A. I have. The pixel electrode 9 is formed over the insulating film 21 and the substrate body 10A. In the present embodiment, the pixel electrode 9 has a portion corresponding to the transmissive display region T formed of a transparent conductive film such as ITO, and a portion corresponding to the reflective display region R formed of a metal material having high reflectivity such as Al. The pixel electrode 9 in the reflective display region R also serves as a reflective film. In addition, irregularities for scattering reflected light are formed on the surface of the metal film such as Al in the reflective display region R. An alignment film 23 for vertical alignment is formed on the pixel electrode 9. On the other hand, in the configuration on the counter substrate 25 side, the dye layer 22 of the color filter is formed on the inner surface of the substrate body 25A, and the common electrode 31 and the alignment film 33 are formed on the dye layer 22. The shapes, formation positions, and the like of the openings 9s and 31s provided in the pixel electrode 9 and the common electrode 31 are exactly the same as those in the first embodiment.
[0048]
Also in this embodiment, similar to the first and second embodiments, a liquid crystal display device capable of displaying with high contrast and a wide viewing angle without display defects such as light leakage and spot-like unevenness is obtained. The effect of can be obtained.
[0049]
[Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.
The basic configuration of the liquid crystal display device of the present embodiment is exactly the same as that of the first embodiment, except that the planar shape of the opening provided in the common electrode is different.
FIG. 7 is a plan view showing only a central portion of one dot region of the liquid crystal display device of the present embodiment. 7, the same reference numerals are given to the same components as those in FIG. 2, and the detailed description will be omitted.
[0050]
In the first embodiment shown in FIG. 2, the opening 31s has a substantially elliptical planar shape, whereas in the liquid crystal display device of the present embodiment, the slit-like opening of the common electrode 31 is provided. The planar shape of the portion 31s has a part of a straight line portion and is substantially rectangular. However, the portion connecting the straight portions is not bent at a right angle but is rounded with a constant radius of curvature, for example, a radius of curvature R of 5 μm. The radius of curvature R needs to be 1 μm or more, and desirably 3 μm or more. The opening 31s overlaps the inclined region (the inclined surface 21a) of the insulating film 21 in a planar manner.
[0051]
The liquid crystal display device of the present embodiment differs from the first embodiment in that the planar shape of the opening 31s includes a linear portion, but the curved portion connecting the straight lines is slightly curved to some extent. Is continuously changed in this portion, and no clear boundary of the alignment region is generated. Therefore, in the present embodiment, although it is slightly inferior in that the liquid crystal molecules continuously fall in all directions in comparison with the first embodiment, it is sufficiently discriminated as compared with the case where the liquid crystal molecules have a polygonal shape having corners. Nation can be suppressed. As a result, it is possible to provide a liquid crystal display device capable of displaying with high contrast and a wide viewing angle without display defects such as light leakage and spot-like unevenness.
[0052]
[Fifth Embodiment]
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG.
The basic configuration of the liquid crystal display device of this embodiment is exactly the same as that of the first and fourth embodiments, except that the planar shape of the opening provided in the common electrode is different.
FIG. 8 is a plan view showing only the central portion of one dot region of the liquid crystal display device of the present embodiment. 8, the same components as those in FIGS. 2 and 7 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0053]
In the first embodiment shown in FIG. 2, the opening 31s has a substantially elliptical planar shape, whereas in the liquid crystal display device of the present embodiment, the slit-like opening of the common electrode 31 is provided. The planar shape of the portion 31s has a straight line portion. In the fourth embodiment, the shape of the opening 31s corresponds to the boundary area between the reflective display area R and the transmissive display area T, and is substantially rectangular. In the example, the shape of the opening 31s does not correspond to the boundary region between the reflective display region R and the transmissive display region T, and is zigzag. However, as in the fourth embodiment, the portion connecting the linear portions is not bent at an acute angle but is rounded with a constant radius of curvature, for example, a radius of curvature R of 5 μm. The radius of curvature needs to be 1 μm or more, and preferably 3 μm or more.
[0054]
Also in the liquid crystal display device of the present embodiment, since the opening 31a of the common electrode 31 has a shape without a corner, disclination can be sufficiently suppressed as compared with a case where the opening 31a has a polygon with a corner. It is possible to provide a liquid crystal display device that can display with high contrast and a wide viewing angle without display defects such as light leakage and spot-like unevenness.
[0055]
[Sixth Embodiment]
Hereinafter, a sixth embodiment of the present invention will be described with reference to FIG.
The basic configuration of the liquid crystal display device of the present embodiment is completely the same as that of the first embodiment, except that the planar shape of the transmissive display area (reflective display area) is different.
FIG. 9 is a plan view showing only a central portion of one dot region of the liquid crystal display device of the present embodiment. In FIG. 9, the same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description will be omitted.
[0056]
In the first embodiment shown in FIG. 2, the plane shape of the transmissive display region T is rectangular and the plane shape of the reflective display region R is rectangular in the outside. In the liquid crystal display device according to the embodiment, the planar shape of the transmissive display region T is formed in an elliptical shape, and the planar shape of the reflective display region R is formed in an elliptical ring outside thereof. That is, the contour of the edge of the insulating film 21 is elliptical, and the planar shape of the inclined surface 21a of the insulating film 21 is also elliptical. The slit-shaped opening 31 s provided in the common electrode 31 has a substantially elliptical shape as in the first embodiment, and the opening 31 s is formed on the inclined surface 21 a of the insulating film 21, that is, the transmission display region T and the reflection surface 21. The plane overlaps with the boundary area with the display area R.
[0057]
In the liquid crystal display device of the present embodiment, the boundary between the transmissive display region T and the reflective display region R, that is, the contour of the edge of the insulating film 21 is formed into an elliptical shape (a continuous closed curve), and the opening of the common electrode 31 is formed. By making the 31s also elliptical, both the shape effect of the insulating film 21 on the alignment direction of the liquid crystal and the effect of the oblique electric field by the opening 31s become more isotropic in all directions. As a result, there is provided a liquid crystal display device which is capable of suppressing disclination most in the above-described embodiments, has no display defects such as light leakage and spot-like unevenness, and is capable of displaying a high contrast and a wide viewing angle. can do.
[0058]
[Electronics]
Next, a specific example of an electronic apparatus including the liquid crystal display device according to the above embodiment of the present invention will be described.
FIG. 10 is a perspective view showing an example of a mobile phone. In FIG. 10, reference numeral 500 denotes a mobile phone main body, and reference numeral 501 denotes a display unit using the liquid crystal display device.
Since the electronic device illustrated in FIG. 10 includes the display portion using the liquid crystal display device in any of the above embodiments, the electronic device includes a liquid crystal display portion with a bright, high contrast, and wide viewing angle regardless of the use environment. Equipment can be realized.
[0059]
The technical scope of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the spirit of the present invention. For example, in the above-described third to sixth embodiments, all the examples have been described with reference to the openings (slits) provided in the electrodes. However, the same effects can be expected even if the openings are replaced with ridges. In addition, a closed curved slit is provided on the common electrode side, and a linear slit is provided on the pixel electrode side. However, these slits may be provided on either the common electrode or the pixel electrode. Further, the slit and the ridge can be appropriately combined. In the above-described embodiment, an example in which the present invention is applied to an active matrix type liquid crystal display device using a TFT as a switching element has been described. However, an active matrix type liquid crystal display using a thin film diode (TFD) as a switching element has been described. The present invention can be applied to a device, a passive matrix type liquid crystal display device, and the like. In addition, specific descriptions regarding materials, dimensions, shapes, and the like of various components can be appropriately changed.
[0060]
【Example】
The inventor has investigated the optimum radius of curvature of the opening of the electrode exemplified in the fourth and fifth embodiments. Report the results.
Specifically, assuming a liquid crystal display device having an electrode opening having the shape illustrated in the fourth embodiment, the radius of curvature R is 0 μm, 0.2 μm, 0.6 μm, 1.0 μm, 2.3 μm, Samples having eight kinds of samples in the range of 0 to 10 μm, such as 3.1 μm, 4.8 μm, and 10.0 μm, were made as prototypes, and the movement of the liquid crystal during voltage application was observed with a microscope. The length of the slit of the rectangular opening was about 20 μm in the short side direction, about 150 μm in the long side direction, and the width of the slit was about 5 μm.
The alignment disorder of the liquid crystal was evaluated by the following three stages by microscopic observation.
：: No alignment disorder of the liquid crystal occurred.
Δ: Liquid crystal alignment disorder was slightly generated.
×: Disorder in the alignment of the liquid crystal was apparently generated.
[0061]
[Table 1]

[0062]
As is clear from the results of Table 1, when the radius of curvature R of the slit is 1 μm or more, it is possible to substantially suppress the alignment disorder of the liquid crystal, and to realize a liquid crystal display device having good image quality. Further, it was found that a liquid crystal display device having extremely good image quality, in which no alignment disturbance is observed, can be realized if the thickness is preferably 3 μm or more.
[Brief description of the drawings]
FIG. 1 is an equivalent circuit diagram of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a plan view showing a configuration of one dot of the liquid crystal display device.
FIG. 3 is a cross-sectional view of the same liquid crystal display device taken along line AA ′ of FIG. 2;
FIG. 4 is a schematic view showing a state in which liquid crystal molecules of the liquid crystal display device are tilted.
FIG. 5 is a sectional view of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 6 is a sectional view of a liquid crystal display device according to a third embodiment of the present invention.
FIG. 7 is a plan view of one dot of a liquid crystal display device according to a fourth embodiment of the present invention.
FIG. 8 is a plan view of one dot of a liquid crystal display device according to a fifth embodiment of the present invention.
FIG. 9 is a plan view of one dot of a liquid crystal display device according to a sixth embodiment of the present invention.
FIG. 10 is a perspective view illustrating an example of an electronic apparatus according to the invention.
[Explanation of symbols]
Reference numeral 9: pixel electrode, 10: TFT array substrate, 20: reflective film, 21: insulating film (liquid crystal layer thickness adjusting layer), 21a: inclined surface, 25: counter substrate, 31: common electrode, 31s: opening, 50: Liquid crystal layer, R: reflective display area, T: transmissive display area

Claims (20)

A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display area for performing transmissive display and a reflective display area for performing reflective display are provided in one dot area,
The liquid crystal layer is composed of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and between the liquid crystal layer and at least one of the pair of substrates, the reflective display region and the liquid crystal layer. A liquid crystal layer thickness adjustment layer that makes the thickness of the liquid crystal layer different from the transmissive display region is provided at least in the reflective display region, and electrodes for driving the liquid crystal are provided on inner surfaces of the pair of substrates, respectively. At least one of the electrodes of the pair of substrates is provided with a slit-shaped opening in a boundary region between the reflective display region and the transmissive display region, and the planar shape of the opening is all curved. A liquid crystal display device characterized in that: 2. The liquid crystal display device according to claim 1, wherein the planar shape of the opening is a perfect circle or an ellipse. 3. The liquid crystal display device according to claim 1, wherein the planar shape of the step portion of the liquid crystal layer thickness adjustment layer, which is a boundary region between the reflective display region and the transmissive display region, is entirely formed of a curve. 4. . 4. The liquid crystal display device according to claim 3, wherein the opening and the step portion overlap at least partially in plan view. 5. A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display area for performing transmissive display and a reflective display area for performing reflective display are provided in one dot area,
The liquid crystal layer is composed of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and between the liquid crystal layer and at least one of the pair of substrates, the reflective display region and the liquid crystal layer. A liquid crystal layer thickness adjustment layer that makes the thickness of the liquid crystal layer different from the transmissive display region is provided at least in the reflective display region, and electrodes for driving the liquid crystal are provided on inner surfaces of the pair of substrates, respectively. At least one of the electrodes of the pair of substrates is provided with a slit-shaped opening in a boundary region between the reflective display region and the transmissive display region, and the planar shape of the opening is linear and constant. A liquid crystal display device comprising a curve having a radius of curvature, wherein the radius of curvature is 1 μm or more. The liquid crystal display device according to claim 5, wherein the radius of curvature is 3 µm or more. 6. The planar shape of a step portion of the liquid crystal layer thickness adjustment layer corresponding to a boundary region between the reflective display region and the transmissive display region is constituted by a straight line and a curve having a constant radius of curvature. Or the liquid crystal display device according to 6. The liquid crystal display device according to claim 7, wherein the opening and the step portion overlap at least partially in plan view. A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display area for performing transmissive display and a reflective display area for performing reflective display are provided in one dot area,
The liquid crystal layer is composed of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and between the liquid crystal layer and at least one of the pair of substrates, the reflective display region and the liquid crystal layer. A liquid crystal layer thickness adjustment layer that makes the thickness of the liquid crystal layer different from the transmissive display region is provided at least in the reflective display region, and electrodes for driving the liquid crystal are provided on inner surfaces of the pair of substrates, respectively. On at least one of the electrodes of the pair of substrates, a convex portion made of a dielectric is provided in a boundary region between the reflective display region and the transmissive display region, and the planar shapes of the convex portions are all curved. A liquid crystal display device comprising: 10. The liquid crystal display device according to claim 9, wherein a planar shape of the ridge is a perfect circle or an ellipse. The liquid crystal display device according to claim 9, wherein the planar shape of the step portion of the liquid crystal layer thickness adjustment layer corresponding to a boundary region between the reflective display region and the transmissive display region is formed by a curve. . 12. The liquid crystal display device according to claim 11, wherein the ridge and the step portion overlap at least partially in plan view. A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and a transmissive display area for performing transmissive display and a reflective display area for performing reflective display are provided in one dot area,
The liquid crystal layer is composed of a liquid crystal having a negative dielectric anisotropy in which an initial alignment state exhibits vertical alignment, and between the liquid crystal layer and at least one of the pair of substrates, the reflective display region and the liquid crystal layer. A liquid crystal layer thickness adjustment layer that makes the thickness of the liquid crystal layer different from the transmissive display region is provided at least in the reflective display region, and electrodes for driving the liquid crystal are provided on inner surfaces of the pair of substrates, respectively. On at least one of the electrodes of the pair of substrates, a convex portion made of a dielectric is provided in a boundary region between the reflective display region and the transmissive display region, and the planar shape of the convex portion is a straight line. A liquid crystal display device comprising a curve having a constant radius of curvature, wherein the radius of curvature is 1 μm or more. 14. The liquid crystal display device according to claim 13, wherein the radius of curvature is 3 μm or more. The planar shape of a step portion of the liquid crystal layer thickness adjustment layer corresponding to a boundary region between the reflective display region and the transmissive display region is constituted by a straight line and a curve having a constant radius of curvature. Or the liquid crystal display device according to 14. 16. The liquid crystal display device according to claim 15, wherein the ridge and the step portion overlap at least partially in plan view. 17. The liquid crystal display device according to claim 1, wherein a boundary region between the reflective display region and the transmissive display region includes an inclined region having an inclined surface so that the thickness of the liquid crystal layer thickness adjusting layer changes continuously. The liquid crystal display device according to claim 1. 18. The liquid crystal display device according to claim 1, wherein a color filter is provided on an inner surface of one of the pair of substrates. 19. The liquid crystal display device according to claim 1, further comprising a circularly polarized light incidence unit for causing circularly polarized light to enter each of the pair of substrates. An electronic apparatus comprising the liquid crystal display device according to claim 1.

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