JP2006337888A - Liquid crystal device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal device employing a lateral electric field system and to provide a liquid crystal device and an electronic apparatus excellent in display characteristics with high contrast. <P>SOLUTION: The liquid crystal device 100 has a first substrate and a second substrate disposed opposing to each other holding a liquid crystal layer and has a first electrode 19 and a second electrode 9 on the liquid crystal layer side of the first substrate to drive the liquid crystal layer by an electric field E generated between the first electrode 19 and the second electrode 9. The liquid crystal layer contains a chiral agent which rotates liquid crystal molecules in an opposite direction to the rotating direction of the liquid crystal molecules when an electric field E is generated between the first electrode 19 and the second electrode 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal device and an electronic apparatus.

  2. Description of the Related Art In recent years, a method for controlling the alignment of liquid crystal molecules by generating an electric field in a substrate surface direction in a liquid crystal layer (hereinafter referred to as a lateral electric field method) is known for liquid crystal devices. In addition, as an electrode for generating an electric field, an IPS (In-Plane Switching) system is known in which an electric field is generated between electrodes that are meshed with each other in a comb-tooth shape (for example, Patent Documents 1 to 3). reference).

Here, in the liquid crystal device of Patent Document 1, a chiral agent in the same direction as the direction in which the liquid crystal molecules rotate when a voltage is applied is added to the liquid crystal layer, and the liquid crystal molecules are easily rotated by the chiral agent.
Further, in the liquid crystal devices of Patent Documents 2 and 3, the alignment processing directions of the opposing substrates are perpendicular to each other, and the initial alignment of liquid crystal molecules when no voltage is applied by adding a chiral agent to the liquid crystal layer. Is twisted.

Further, in a horizontal electric field type liquid crystal device, not only the IPS method but also an FFS (Frige-Field Switching) method is known. The FFS mode is a liquid crystal device that aligns liquid crystal by generating an electric field between an insulating film provided on one electrode and the other comb-like electrode provided on the insulating film.
JP 2001-91962 A JP 2002-344837 A JP-A-10-90704

By the way, in such a horizontal electric field type liquid crystal device, the present inventor has found that it is difficult to obtain a high contrast as compared with the vertical electric field type.
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a liquid crystal device adopting a horizontal electric field method, and a liquid crystal device and an electronic apparatus having excellent high-contrast display characteristics. It is said.

The present inventor has found the following knowledge and arrived at the present invention.
FIG. 9 is a diagram showing VT characteristics (voltage-transmittance characteristics) comparing the IPS mode of the horizontal electric field type and the TN (Twisted Nematic) mode of the vertical electric field type. As shown in FIG. 9, the VT characteristic of the TN mode has a characteristic in which the transmittance sharply increases from the low voltage region to the high voltage region, whereas the VT characteristic of the IPS method has a low voltage characteristic. In the region, the transmittance gradually increases.
As apparent from the difference in the VT characteristics, the present inventor compared with the TN mode because the saturation voltage of the VT characteristics of the horizontal electric field method is relatively high and the threshold voltage is unclear. And found that the contrast is low.
In addition, in the normally black mode in which the transmission axes of the polarizing plates are arranged in a cross arrangement, it is found that the black display floats due to the unclearness of the threshold voltage, resulting in a low contrast display. It was done. In the normally white mode, it has been found that a black color is produced when displaying white.
Accordingly, the present inventor has come up with the present invention having the following means in order to solve the above-mentioned problems.

In other words, the liquid crystal device of the present invention includes a first substrate and a second substrate that are disposed to face each other with a liquid crystal layer interposed therebetween, and the first electrode and the second electrode are provided on the liquid crystal layer side of the first substrate. A liquid crystal device in which the liquid crystal layer is driven by an electric field generated between the first electrode and the second electrode, wherein the liquid crystal layer includes a gap between the first electrode and the second electrode. A chiral agent that rotates in the direction opposite to the rotation direction of the liquid crystal molecules when the electric field is generated is included.
In this way, when an electric field is generated, the liquid crystal molecules rotate in the direction of one direction between the first electrode and the second electrode. On the other hand, the chiral agent has a spiral in the direction opposite to the rotation direction of the liquid crystal molecules, so that the rotation of the liquid crystal molecules is prevented.
When the electric field is low, the rotational force of the liquid crystal molecules is small, and thus the movement (rotation) of the liquid crystal is suppressed by the spiral of the chiral agent. In addition, when the electric field is high, the rotational force of the liquid crystal molecules is larger than the rotational inhibitory force of the chiral agent, so that the inhibitory force due to the spiral of the chiral agent contributes little and the liquid crystal molecules rotate.
Therefore, according to the present invention, when the electric field is low, the threshold value in the VT characteristic can be made relatively clear, and high contrast can be realized and clear display can be performed.

In the liquid crystal device of the present invention, the first electrode and / or the second electrode are formed in a linear shape.
Here, it is preferable that the first electrode and / or the second electrode is formed in a comb-like shape, and the comb-like electrode is formed in a straight line shape from the base end portion toward the tip end portion. In addition, it is preferable that the first electrode and / or the second electrode have no "<"-shaped bent portion, and it is preferable that no uneven portion is formed on the side surface of the electrode. Thus, by forming the first electrode and / or the second electrode in a straight line, an electric field generated between the first electrode and the second electrode can be generated only in one direction. As a result, the liquid crystal molecules can be rotated in only one direction. Therefore, the chiral agent can prevent the rotation of the liquid crystal molecules rotating only in the one direction.
On the other hand, in the case where the first electrode and / or the second electrode is formed with a bent portion or a side uneven portion, an electric field is generated in at least two directions. Can not be caused. Along with this, the liquid crystal molecules rotate in one direction (for example, clockwise) and in the opposite direction to the one direction (for example, counterclockwise). In this case, the chiral agent tries to prevent the movement of the liquid crystal molecules rotating in one direction, but works to assist the movement of the liquid crystal molecules rotating in the opposite direction. Therefore, since the first electrode and / or the second electrode are formed in a straight line, the rotation of the liquid crystal molecules when an electric field is generated can be suppressed by the chiral agent, and the above effect can be obtained.

The liquid crystal device of the present invention is characterized by a normally black mode in which black display is performed when the electric field is not generated.
Here, the normally black mode liquid crystal device is configured by disposing two polarizing plates disposed outside the first substrate and the second substrate so that their transmission axes intersect each other. In the normally black mode, black display is performed when no electric field is generated, and white display is performed as the electric field gradually increases. As described above, the lateral electric field type liquid crystal device has a problem in that the threshold voltage in a state where the electric field is low (low voltage) becomes unclear, black display becomes floating, and high contrast cannot be obtained. Therefore, as in the present invention, since the liquid crystal layer contains a chiral agent, the threshold voltage in a state where the electric field in the normally black mode is low can be clarified, so that clear black display can be performed and high Contrast can be obtained.

In the liquid crystal device of the present invention, the alignment film provided on the first substrate side of the liquid crystal layer and the alignment film provided on the second substrate side have the same alignment of liquid crystal molecules and are the same. It is characterized by being an alignment film that imparts a pretilt in the direction.
By adopting such a configuration, the alignment film can impart so-called parallel alignment to the liquid crystal layer.
In the liquid crystal device of the present invention, the alignment film provided on the first substrate side and the alignment film provided on the second substrate side of the liquid crystal layer have liquid crystal molecules aligned in parallel with each other and reciprocal. The film is characterized in that it is an alignment film that imparts a pretilt in the direction to be applied.
By adopting such a configuration, the alignment film can impart so-called antiparallel alignment to the liquid crystal layer.

  Here, in order to give parallel alignment or anti-parallel alignment to the alignment film, the resin film such as polyimide is subjected to rubbing treatment or oblique vapor deposition. In this way, liquid crystal molecules can be aligned between the first substrate and the second substrate by parallel alignment or antiparallel alignment.

  In the liquid crystal device of the present invention, each of the first electrode and the second electrode includes one or a plurality of strip electrodes, and the strip electrode of the first electrode and the strip electrode of the second electrode are It is preferable that it is the structure arrange | positioned substantially parallel. That is, the liquid crystal device of the present invention can employ an IPS (In-Plane Switching) type electrode configuration.

  In the liquid crystal device of the present invention, the first electrode includes a plurality of strip-shaped electrodes, and is formed on the planar second solid electrode with an insulating film interposed therebetween. It is preferable that it is the structure arrange | positioned substantially parallel. That is, the liquid crystal device of the present invention can employ an FFS (Fringe Field Switching) type electrode configuration.

According to another aspect of the invention, an electronic apparatus includes the liquid crystal device described above.
In this way, an electronic apparatus including a display unit that realizes high contrast is provided.

Hereinafter, a liquid crystal device according to a first embodiment of the present invention will be described with reference to the drawings.
In each drawing, each layer and each member are displayed in different scales so that each layer and each member can be recognized on the drawing.

(First embodiment)
The liquid crystal device of this embodiment is a liquid crystal device that employs a method called an IPS method among horizontal electric field methods in which an image is displayed by generating an electric field in the substrate plane direction with respect to the liquid crystal and controlling the alignment.
In addition, the liquid crystal device of the present embodiment is a color liquid crystal device having a color filter on a substrate, and three dots that output light of each color of R (red), G (green), and B (blue) are 1 Each pixel is configured. Therefore, a display area that is a minimum unit that constitutes a display is referred to as a “dot area”, and a display area that is composed of a set of (R, G, B) dots is referred to as a “pixel area”.

  FIG. 1 is a circuit configuration diagram of a plurality of dot regions formed in a matrix that constitutes the liquid crystal device of the present embodiment. FIG. 2 is a plan configuration diagram in an arbitrary one-dot region of the liquid crystal device 100. FIG. 3 is a partial cross-sectional configuration diagram taken along the line AA ′ of FIG. FIG. 4 is a schematic cross-sectional view of the liquid crystal device 100, and is a diagram for explaining the alignment direction of the alignment film in parallel alignment and liquid crystal molecules to which a pretilt is given by the alignment film.

  As shown in FIG. 1, each of a plurality of dot regions formed in a matrix that forms an image display region of the liquid crystal device 100 includes a pixel electrode 9 and a TFT (thin film transistor) for switching control of the pixel electrode 9. ) 30, and the data line 6 a extending from the data line driving circuit 101 is electrically connected to the source of the TFT 30. The data line driving circuit 101 supplies image signals S1, S2,..., Sn to each dot region via the data line 6a. The image signals S1 to Sn may be supplied line-sequentially in this order, or may be supplied for each group to a plurality of adjacent data lines 6a, or to all the data lines 6a. May be supplied simultaneously.

  Further, the scanning line 3a extending from the scanning line driving circuit 102 is electrically connected to the gate of the TFT 30, and the scanning signal G1 is supplied from the scanning line driving circuit 102 to the scanning line 3a in a pulse manner at a predetermined timing. , G2,..., Gm are applied to the gate of the TFT 30 in the order of lines in this order. The pixel electrode 9 is electrically connected to the drain of the TFT 30. The TFT 30 serving as a switching element is turned on for a certain period by the input of scanning signals G1, G2,..., Gm, so that the image signals S1, S2,. Writing is performed on the pixel electrode 9.

  Image signals S1, S2,..., Sn written to the liquid crystal via the pixel electrode 9 are held for a certain period between the pixel electrode 9 and the common electrode opposed via the liquid crystal. Here, in order to prevent the held image signal from leaking, a storage capacitor 70 is provided in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the common electrode. The storage capacitor 70 is provided between the drain of the TFT 30 and the capacitor line 3b.

  Next, a detailed configuration of the liquid crystal device 100 will be described with reference to FIGS. The liquid crystal device 100 has a configuration in which a liquid crystal layer 50 is sandwiched between a TFT array substrate (first substrate) 10 and a counter substrate (second substrate) 20 as shown in FIG. The TFT array substrate 10 and the counter substrate 20 are sealed between the substrates 10 and 20 by a seal material (not shown) provided along an edge of a region where the TFT array substrate 10 and the counter substrate 20 face each other. A backlight 90 including a light guide plate 91 and a reflection plate 92 is provided on the back side (the lower side in the figure) of the TFT array substrate 10.

  As shown in FIG. 2, the dot region of the liquid crystal device 100 includes a pixel electrode (second electrode) 9 that is substantially rake-like (comb-like) in plan view and that is long in the Y-axis direction. And a common electrode (first electrode) 19 extending in the X-axis direction. In the dot region, columnar spacers (not shown) are erected to hold the TFT array substrate 10 and the counter substrate 20 at a predetermined interval.

  The pixel electrode 9 is connected to a plurality (two in the figure) of strip-shaped electrodes 9c extending in the Y-axis direction, and to the respective lower ends (−Y side) of the plurality of strip-shaped electrodes 9c in the X-axis direction. And a contact portion 9b extending to the −Y side from the central portion in the X-axis direction of the base end portion 9a.

  The common electrode 19 is arranged alternately with the strip electrodes 9c of the pixel electrode 9 and extends in parallel (in the Y-axis direction) with the strip electrodes 9c (two in the drawing), and + Y of the strip electrodes 19c. And a main line portion 19a connected to the end portion on the side and extending in the X-axis direction. The common electrode 19 is a substantially comb-like electrode member in plan view that extends across a plurality of dot regions arranged in the X-axis direction.

  Further, the strip electrodes 9c and 19c are formed in a straight line shape in the vertical direction on the paper surface in FIG. That is, the band-shaped electrodes 9c and 19c are not formed with a "<"-shaped bent portion, and the side surfaces of the band-shaped electrodes 9c and 19c are not formed with uneven portions. Since the strip electrodes 9c and 19c are thus formed in a straight line, the electric field E generated between the strip electrodes 9c and 19c is generated only in one direction.

Therefore, in the dot region shown in FIG. 2, a voltage is applied between the two strip electrodes 9c extending in the Y-axis direction and the two strip electrodes 19c arranged between the strip electrodes 9c. An electric field E in the XY plane direction (substrate plane direction) is generated in the liquid crystal in the dot region, and the liquid crystal molecules are rotated so as to follow the direction of the electric field E.
Further, the band-like parts 9c and 19c are arranged so as to mesh with each other in a comb-tooth shape, and the band-like part 9c is arranged so as to be surrounded by the band-like part 19c. The pixel electrode 9 has a characteristic that when the TFT 30 is off, the pixel electrode 9 has high impedance and is easily affected by adjacent data lines. Therefore, the pixel electrode 9 can be stabilized by surrounding the strip 9c of the pixel electrode 9 with the strip 19c of the common electrode as in the present embodiment.

  In the dot area shown in FIG. 2, the data line 6a extending in the Y-axis direction, the scanning line 3a extending in the X-axis direction, and the edge of the dot area opposite to the scanning line 3a are parallel to the scanning line 3a. And a capacitance line 3b extending in the direction. A TFT 30 is provided in the vicinity of the intersection of the data line 6a and the scanning line 3a. The TFT 30 includes a semiconductor layer 35 made of amorphous silicon partially formed in a plane region of the scanning line 3a, and a source electrode 6b and a drain electrode 32 formed to partially overlap the semiconductor layer 35 in a plane. I have. The scanning line 3 a functions as a gate electrode of the TFT 30 at a position overlapping the semiconductor layer 35 in plan view.

  Further, the source electrode 6 b of the TFT 30 is formed in a substantially L shape in plan view that extends from the data line 6 a and extends to the semiconductor layer 35. The drain electrode 32 is electrically connected to the capacitor electrode 31 having a larger area than the drain electrode 32 and extending toward the + Y side. The capacitor electrode 31 is provided so as to overlap the capacitor line 3b with the insulating film 11 interposed therebetween. As a result, a storage capacitor 70 having the capacitor electrode 31 and the capacitor line 3b facing each other in the thickness direction is formed in a region where the capacitor electrode 31 and the capacitor line 3b overlap in a plane. Further, the contact portion 9b of the pixel electrode 9 is disposed on the capacitor electrode 31 so as to overlap in a plane, and the pixel that electrically connects the capacitor electrode 31 and the pixel electrode 9 to the position where both are overlapped. A contact hole 45 is provided.

Next, referring to the cross-sectional structure shown in FIG. 3, the liquid crystal layer 50 is sandwiched between the TFT array substrate 10 and the counter substrate 20 that are arranged to face each other.
The TFT array substrate 10 has a translucent substrate body 10A made of glass, quartz, plastic, or the like as a base, and scanning lines 3a and capacitance lines 3b are formed on the inner surface side (the liquid crystal layer 50 side) of the substrate body 10A. A gate insulating film 11 made of a transparent insulating film such as silicon oxide is formed so as to cover the scanning line 3a and the capacitor line 3b.

  An amorphous silicon semiconductor layer 35 is formed on the gate insulating film 11, and a source electrode 6 b and a drain electrode 32 are provided so as to partially run over the semiconductor layer 35. The drain electrode 32 is formed integrally with the capacitor electrode 31. The semiconductor layer 35 is disposed to face the scanning line 3 a via the gate insulating film 11, and the scanning line 3 a constitutes the gate electrode of the TFT 30 in the facing region. The capacitor electrode 31 is formed at a position facing the capacitor line 3b with the gate insulating film 11 interposed therebetween. The capacitor electrode 31 and the capacitor line 3b are used as electrodes, and the gate insulating film 11 sandwiched between both is used as a dielectric film. Is formed.

  The first interlayer insulating film 12 made of silicon oxide or the like and the second interlayer insulating film made of silicon nitride or the like cover the semiconductor layer 35, the source electrode 6b (data line 6a), the drain electrode 32, and the capacitor electrode 31. The pixel electrode 9 and the common electrode 19 made of a transparent conductive material such as ITO are formed on the second interlayer insulating film 13. The pixel electrode 9 and the common electrode 19 are made of a transparent conductive material such as ITO. Furthermore, a pixel contact hole 45 that reaches the capacitor electrode 31 through the interlayer insulating films 12 and 13 is formed, and the contact portion 9b of the pixel electrode 9 is partially embedded in the pixel contact hole 45, The pixel electrode 9 and the capacitor electrode 31 are electrically connected. Further, an alignment film 18 made of polyimide or the like is formed so as to cover the pixel electrode 9 and the common electrode 19.

  The counter substrate 20 has a translucent substrate body 20A such as glass, quartz, or plastic as a base, and the inner surface side (the liquid crystal layer 50 side) of the substrate body 20A has substantially the same planar shape as the dot region. A color filter 22 is provided. In addition, a black matrix BM that separates the color filters 22 having different colors is provided between adjacent dot regions. Further, an alignment film 28 made of polyimide or the like is formed so as to cover the color filter 22 and the black matrix BM.

  Further, a positive liquid crystal is employed as the liquid crystal layer 50 of the present embodiment, and the liquid crystal molecules LC constituting the positive liquid crystal are given initial alignment by the alignment films 18 and 28. Here, when the electric field E in the substrate plane direction is generated between the band-like electrode 9c of the pixel electrode 9 and the band-like electrode 19c of the common electrode 19, the liquid crystal molecule LC has an electric field in the major axis direction of the liquid crystal molecule LC. Oriented to follow the direction.

Furthermore, as described as a feature of the present invention, the liquid crystal layer 50 includes a chiral agent having a spiral in a direction opposite to the rotation direction of the liquid crystal molecules LC when an electric field is generated.
Further, the concentration of the chiral agent added to the liquid crystal layer 50 is adjusted so that d / p becomes a suitable value when the cell gap is d and the spontaneous pitch of the liquid crystal molecules is p.

  Further, the alignment films 18 and 28 are rubbed in the direction indicated by symbol H in FIG. 2 to give the liquid crystal molecules LC when the electric field is not generated an initial alignment so as to follow the rubbing direction H. . In addition, the alignment directions of the alignment films 18 and 28 are defined so as to be parallel alignment. That is, the rubbing process of the alignment films 18 and 28 is rubbed in the same plane direction in a plan view.

Specifically, referring to FIG. 4, the alignment direction of the alignment film 18 of the TFT array substrate 10 is the same as the alignment direction of the alignment film 28 of the counter substrate 20. The alignment films 18 and 28 are each subjected to an alignment process in the direction of reference numerals 18a and 28a from the left side to the right side of the drawing.
The liquid crystal layer 50 held between the TFT array substrate 10 and the counter substrate 20 in contact with the alignment films 18 and 28 is given a pretilt in the same direction by the alignment films 18 and 28. Specifically, in the liquid crystal molecule LC in contact with the alignment film 18, a pretilt is given in the direction of reference numeral 18b with the major axis direction of the liquid crystal molecule LC from the alignment film 18 toward the alignment film 28. ing. Further, in the liquid crystal molecules LC in contact with the alignment film 28, a pretilt is given in the direction of reference numeral 28b with the major axis direction of the liquid crystal molecules LC from the alignment film 28 toward the alignment film 18 side. Further, the liquid crystal molecules LC between the alignment films 18 and 28 are aligned in the horizontal direction indicated by the symbol M as they move away from the alignment films 18 and 28.
That is, in the liquid crystal device 100 of the present embodiment, homogeneous alignment (parallel alignment) is given to the liquid crystal molecules LC of the liquid crystal layer 50.

  In the liquid crystal device according to the present embodiment, the alignment films 18 and 28 are formed by rubbing a resin film such as polyimide. You may form the orientation film which consists of the columnar structure arranged diagonally.

Here, returning to FIGS. 2 and 3, the configuration of the liquid crystal device 100 will be described.
As shown in FIG. 3, polarizing plates 24 and 14 are disposed on the outer surface side (the side opposite to the liquid crystal layer 50) of the TFT array substrate 10 and the counter substrate 20, respectively. Further, the transmission axes 24a and 14a of the polarizing plates 24 and 14 intersect at right angles (cross arrangement) as shown in FIG. Further, the transmission axis 14 a of the polarizing plate 14 is disposed so as to be parallel to the rubbing direction H.

  In all the dot regions in the liquid crystal device 100, the illumination light of the backlight 90 is transmitted, and thus the transmissive liquid crystal device 100 is configured. Further, the liquid crystal device 100 is in a normally black mode in which black display is performed in a state where no voltage is applied between the pixel electrode 9 and the common electrode 19 (a state where no electric field is generated).

In such a liquid crystal device 100, when a voltage is applied between the pixel electrode 9 and the common electrode 19, an electric field E is generated between the strip electrodes 9c and 19c as shown in FIG. At the same time, all the liquid crystal molecules LC rotate in the same direction. The liquid crystal layer 50 includes a chiral agent having a spiral opposite to the rotation direction of the liquid crystal molecules LC, that is, a counterclockwise spiral, so that the chiral agent prevents rotation of the liquid crystal molecules LC. To do. That is, the counterclockwise rotation suppression force indicated by the symbol K is generated for the liquid crystal molecules LC.
When the electric field E is low, the rotational force of the liquid crystal molecules LC is small, so that the movement (rotation) of the liquid crystal molecules LC is suppressed by the spiral of the chiral agent. In addition, when the electric field E is high, the rotational force of the liquid crystal molecules LC is larger than the rotational inhibitory force of the chiral agent. Therefore, the inhibitory force due to the spiral of the chiral agent hardly contributes, and the liquid crystal molecules LC rotate in the clockwise direction. .

As described above, in the liquid crystal device 100 of the present embodiment, the chiral agent works to prevent the rotation of the liquid crystal molecules LC in a low electric field, so that the threshold value of the VT characteristic when the electric field E is low is relatively clear. Thus, clear black display can be realized in a low electric field, and contrast can be improved.
In addition, since the liquid crystal device 100 employs a normally black mode, a black display is not lifted, a clear black display can be performed, and a high contrast can be obtained.

  In the liquid crystal device 100 of the present embodiment, since the strip electrodes 9c and 19c are formed in a straight line, the electric field E generated between the strip electrodes 9c and 19c can be generated only in one direction. As a result, the liquid crystal molecules LC can be rotated in only one direction. Therefore, the chiral agent can prevent the rotation of the liquid crystal molecules rotating only in the one direction. On the other hand, when the belt-like electrodes 9c and 19c are formed with bent portions or side surface uneven portions, the electric field E is generated in at least two directions, so the direction of the electric field E is generated only in one direction. I can't let you. Along with this, the liquid crystal molecules LC rotate in one direction (for example, clockwise) and in the opposite direction to the one direction (for example, counterclockwise). In this case, the chiral agent tries to prevent the movement of the liquid crystal molecules LC rotating in one direction, but works to assist the movement of the liquid crystal molecules LC rotating in the opposite direction. Accordingly, since the strip electrodes 9c and 19c are formed in a straight line, the rotation of the liquid crystal molecules LC when the electric field E is generated can be suppressed by the chiral agent, and the above effect can be obtained.

(Modification of the first embodiment)
Next, a liquid crystal device according to a modification of the first embodiment of the present invention will be described with reference to FIG.
In the present embodiment, only parts different from the first embodiment described above will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted.

FIG. 5 is a schematic cross-sectional view of the liquid crystal device of the present embodiment, and is a diagram for explaining the alignment direction of the alignment film having antiparallel alignment and liquid crystal molecules to which a pretilt is given by the alignment film. .
As shown in FIG. 5, the alignment direction of the alignment film 18 of the TFT array substrate 10 is opposite to the alignment direction of the alignment film 28 of the counter substrate 20. The alignment film 18 is subjected to an alignment process in the direction of reference numeral 18a from the left side to the right side of the drawing. The alignment film 28 is subjected to an alignment process in the direction of reference numeral 28a from the right side to the left side of the drawing.
The liquid crystal layer 50 held between the TFT array substrate 10 and the counter substrate 20 in contact with the alignment films 18 and 28 is given a pretilt in the opposite direction by the alignment films 18 and 28. Specifically, in the liquid crystal molecule LC in contact with the alignment film 18, a pretilt is given in the direction of reference numeral 18b with the major axis direction of the liquid crystal molecule LC from the alignment film 18 toward the alignment film 28. ing. Further, in the liquid crystal molecules LC in contact with the alignment film 28, a pretilt is given in the direction of reference numeral 28b with the major axis direction of the liquid crystal molecules LC from the alignment film 28 toward the alignment film 18 side. Further, the liquid crystal molecules LC between the alignment films 18 and 28 are aligned in the horizontal direction indicated by the symbol M as they move away from the alignment films 18 and 28.
That is, in the liquid crystal device 100 of the present embodiment, homogeneous alignment is imparted to the liquid crystal molecules LC of the liquid crystal layer 50.
Also in the alignment films 18 and 28 in which the alignment process is performed in such an anti-parallel alignment, the same effect as the first embodiment described above can be obtained.

  In the liquid crystal device according to the present embodiment, the alignment films 18 and 28 are formed by rubbing a resin film such as polyimide. You may form the orientation film which consists of the columnar structure arranged diagonally.

(Second Embodiment)
Next, a liquid crystal device according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a plan configuration diagram showing an arbitrary one-dot region in the liquid crystal device 200 of the present embodiment. FIG. 7 is a cross-sectional configuration diagram taken along the line DD ′ of FIG.

The liquid crystal device of this embodiment is a liquid crystal device that employs a method called an FFS method among horizontal electric field methods in which an image is displayed by generating an electric field in the substrate plane direction with respect to the liquid crystal and controlling the alignment. .
Note that the circuit configuration and overall configuration of the liquid crystal device 200 of the present embodiment are the same as those of the liquid crystal device 100 of the first embodiment, and are shown in FIGS. 1 to 4 in each drawing referred to in the present embodiment. Constituent elements common to the liquid crystal device 100 of the first embodiment are denoted by the same reference numerals, and description of these common constituent elements is omitted below.

  As shown in FIG. 6, the dot region of the liquid crystal device 200 includes a pixel electrode (second electrode) 9 that is substantially rake-like (comb-like) in plan view and that is long in the Y-axis direction. And a common electrode (first electrode) 119 having a substantially flat surface disposed in a plane. A columnar spacer 40 is erected on the upper left corner of the dot area to hold the TFT array substrate 10 and the counter substrate 20 at a predetermined interval.

The common electrodes 119 are arranged extending in the X-axis direction over the entire image display area.
In the present embodiment, the common electrode 119 is a conductive film made of a transparent conductive material such as ITO (indium tin oxide).

  In the dot region, a data line 6a extending in the X-axis direction, a scanning line 3a extending in the Y-axis direction, and a capacitance line 3b extending adjacent to the scanning line 3a and parallel to the scanning line 3a are formed. A TFT 30 is provided in the vicinity of the intersection of the data line 6a and the scanning line 3a. The TFT 30 includes a semiconductor layer 35 made of amorphous silicon partially formed in a planar region of the scanning line 3a, a source electrode 6b formed partially overlapping the semiconductor layer 35, and a drain electrode 132. ing. The scanning line 3 a functions as a gate electrode of the TFT 30 at a position overlapping the semiconductor layer 35 in plan view.

  The source electrode 6b of the TFT 30 is formed in a substantially L shape in plan view that branches from the data line 6a and extends to the semiconductor layer 35, and the drain electrode 132 extends to the −Y side and has a substantially rectangular capacity electrode 131 in plan view. And are electrically connected. On the capacitor electrode 131, a contact portion 9b of the pixel electrode 9 is disposed so as to advance from the −Y side, and the capacitor electrode 131 and the pixel are connected via a pixel contact hole 45 provided at a position where they are two-dimensionally overlapped. The electrode 9 is electrically connected. The capacitor electrode 131 is disposed in the plane region of the capacitor line 3b, and a storage capacitor 70 having the capacitor electrode 131 and the capacitor line 3b facing each other in the thickness direction is formed at the position.

  The pixel electrode 9 includes a base end portion 9a connected to the contact portion 9b and extending in the X-axis direction, and three strip electrodes 9c extending from the base end portion 9a to the −Y side. ing. The strip-shaped electrode 9c is formed in a straight line shape in the vertical direction of the paper in FIG. That is, the band-shaped electrode 9c is not formed with a "<"-shaped bent portion, and the side surface of the band-shaped electrode 9c is not formed with an uneven portion. Since the strip electrode 9c is formed in a straight line in this way, the electric field E generated between the adjacent strip electrodes 9c is generated only in one direction.

Next, referring to the cross-sectional structure shown in FIG. 7, the liquid crystal layer 50 is sandwiched between the TFT array substrate 10 and the counter substrate 20 that are arranged to face each other.
The TFT array substrate 10 has a substrate body 10A as a base body, and scanning lines 3a and capacitor lines 3b are formed on the inner surface side (liquid crystal layer 50 side) of the substrate body 10A. A gate insulating film 11 is formed so as to cover it.

An amorphous silicon semiconductor layer 35 is formed on the gate insulating film 11, and a source electrode 6 b and a drain electrode 132 are provided so as to partially run over the semiconductor layer 35. A capacitor electrode 131 is integrally formed on the right side of the drain electrode 132 in the figure. The semiconductor layer 35 is disposed to face the scanning line 3 a via the gate insulating film 11, and the scanning line 3 a constitutes the gate electrode of the TFT 30 in the facing region.
The capacitor electrode 131 is disposed opposite to the capacitor line 3b via the gate insulating film 11, and a storage capacitor 70 having the gate insulating film 11 as a dielectric film is formed in a region where the capacitor electrode 131 and the capacitor line 3b are opposed to each other. Is formed.

  A first interlayer insulating film 12 is formed so as to cover the semiconductor layer 35, the source electrode 6b, the drain electrode 132, and the capacitor electrode 131, and a common conductive material such as ITO is formed on the first interlayer insulating film 12. An electrode 119 is formed. Therefore, in the liquid crystal device 200 of the present embodiment, a region where the planar region of the common electrode 119 overlaps with the planar region including the pixel electrode 9 in the one-dot region shown in FIG. Thus, the light transmitted through the liquid crystal layer 50 is modulated to perform display.

A second interlayer insulating film 13 made of silicon oxide, silicon nitride, or the like is formed on the common electrode 119 so as to cover the common electrode 119.
In the present embodiment, after the common electrode is formed, silicon nitride is deposited by about 400 nm by plasma CVD or the like to form the second interlayer insulating film 13. A pixel electrode 9 made of a transparent conductive material such as ITO is formed on the second interlayer insulating film 13. Further, a pixel contact hole 45 that penetrates the first interlayer insulating film 12 and the second interlayer insulating film 13 and reaches the capacitor electrode 31 is formed, and the contact portion 9 b of the pixel electrode 9 is one in the pixel contact hole 45. By being embedded, the pixel electrode 9 and the capacitor electrode 31 are electrically connected. Note that an opening is also provided in the common electrode 119 corresponding to the formation region of the pixel contact hole 45 so that the common electrode 119 and the pixel electrode 9 do not contact each other. An alignment film 18 is formed on the pixel electrode 9 in a region on the second interlayer insulating film 13 covering the pixel electrode 9.

  The counter substrate 20 has a translucent substrate body 20A such as glass, quartz, or plastic as a base, and the inner surface side (the liquid crystal layer 50 side) of the substrate body 20A has substantially the same planar shape as the dot region. A color filter 22 is provided. Further, a black matrix (not shown) that separates the color filters 22 having different colors is provided between adjacent dot regions. Further, an alignment film 28 made of polyimide or the like is formed so as to cover the color filter 22 and the black matrix.

  Further, a positive liquid crystal is employed as the liquid crystal layer 50 of the present embodiment, and the liquid crystal molecules LC constituting the positive liquid crystal are given initial alignment by the alignment films 18 and 28. Here, when an electric field in the substrate plane direction is generated between the strip electrode 9 c of the pixel electrode 9 and the strip electrode 19 c of the common electrode 19, the liquid crystal molecule LC has an electric field E in the major axis direction of the liquid crystal molecule LC. Oriented to follow the direction.

Furthermore, as described as a feature of the present invention, the liquid crystal layer 50 includes a chiral agent having a spiral in a direction opposite to the rotation direction of the liquid crystal molecules LC when an electric field is generated.
Further, the concentration of the chiral agent added to the liquid crystal layer 50 is adjusted so that d / p becomes a suitable value when the cell gap is d and the spontaneous pitch of the liquid crystal molecules is p.

In addition, the alignment films 18 and 28 are rubbed in the direction indicated by the symbol H in FIG. 7, and give initial alignment to the liquid crystal molecules LC when no voltage is applied so as to follow the rubbing direction H. In addition, the alignment directions of the alignment films 18 and 28 are defined so as to be parallel alignment or antiparallel alignment. That is, in the liquid crystal device 200 of the present embodiment, homogeneous alignment is imparted to the liquid crystal molecules LC of the liquid crystal layer 50.
Further, polarizing plates 24 and 14 are disposed on the outer surface side (the side opposite to the liquid crystal layer 50) of the TFT array substrate 10 and the counter substrate 20, respectively. Further, the transmission axes 24a and 14a of the polarizing plates 24 and 14 intersect at right angles (cross arrangement) as shown in FIG. Further, the transmission axis 14 a of the polarizing plate 14 is disposed so as to be parallel to the rubbing direction H.

  In all the dot regions in the liquid crystal device 200, the illumination light of the backlight 90 is transmitted, and thus the transmissive liquid crystal device 100 is configured. Further, the liquid crystal device 200 is in a normally black mode in which black display is performed in a state where no voltage is applied between the pixel electrode 9 and the common electrode 19.

In the FFS mode liquid crystal device 200 of the present embodiment, the direction in which the electric field is generated is slightly different compared to the IPS mode of the first embodiment. In the IPS method, the pixel electrodes 9 and the strip-like electrodes 9c, 19c of the common electrode 19 are arranged to face each other in the substrate plane direction to generate an electric field in a substantially substrate plane direction. On the other hand, in the FFS method, since the strip electrode 9c of the pixel electrode 9 and the common electrode 119 are opposed to each other in the vertical direction of the substrate, an electric field E is generated from the strip electrode 9c in a substantially substrate plane direction and the strip electrode 9c. The electric lines of force generated from the side of the electrode are generated toward the common electrode 119 as the distance from the strip electrode 9c increases.
In addition, since the strip electrode 9c and a part of the common electrode 119 are opposed to each other, a storage capacitor using the second interlayer insulating film 13 as a dielectric is formed. Therefore, in the present embodiment, a configuration using the storage capacitor 70 and the storage capacitor formed by the strip electrode 9c and the common electrode 119 are used.

In the liquid crystal device 200 configured as described above, when a voltage is applied between the pixel electrode 9 and the common electrode 119, an electric field E is generated between the strip electrodes 9c as shown in FIG. In sequence, all the liquid crystal molecules LC rotate in the same direction. The liquid crystal layer 50 includes a chiral agent having a spiral opposite to the rotation direction of the liquid crystal molecules LC, that is, a counterclockwise spiral, so that the chiral agent prevents rotation of the liquid crystal molecules LC. To do. That is, the counterclockwise rotation suppression force indicated by the symbol K is generated for the liquid crystal molecules LC.
When the electric field E is low, the rotational force of the liquid crystal molecules LC is small, so that the movement (rotation) of the liquid crystal molecules LC is suppressed by the spiral of the chiral agent. In addition, when the electric field E is high, the rotational force of the liquid crystal molecules LC is larger than the rotational inhibitory force of the chiral agent. Therefore, the inhibitory force due to the spiral of the chiral agent hardly contributes, and the liquid crystal molecules LC rotate in the clockwise direction. .

As described above, in the liquid crystal device 200 of the present embodiment, the same effects as those of the first embodiment described above can be obtained. That is, since the chiral agent works to prevent the rotation of the liquid crystal molecules LC in a low electric field, the threshold of the VT characteristic when the electric field E is low becomes relatively clear, and a clear black display can be realized in the low electric field. Contrast improvement can be realized.
In addition, since the liquid crystal device 100 employs a normally black mode, a black display is not lifted, a clear black display can be performed, and a high contrast can be obtained.
Further, since the strip electrode 9c is formed in a straight line, the electric field E generated between the adjacent strip electrodes 9c can be generated only in one direction. As a result, the liquid crystal molecules LC can be rotated in only one direction. Therefore, the chiral agent can prevent the rotation of the liquid crystal molecules rotating only in the one direction.

In the above-described embodiment, the normally black mode liquid crystal device has been described. However, the present invention is not limited to the normally black mode, and can be applied to the normally white mode.
The normally white mode is a mode in which white display is performed in a state where no voltage is applied to the liquid crystal layer 50. When the present invention is applied to the normally white mode, the chiral agent works to prevent the rotation of the liquid crystal molecules LC in a low electric field, so that the threshold value of the VT characteristic when the electric field E is low becomes relatively clear, and white display In this case, the occurrence of black color is suppressed, clear white display can be realized in a low electric field, and contrast can be improved.

In the above-described embodiments, the IPS mode and FFS mode liquid crystal devices using TFTs have been described. However, the present invention is not limited to such switching elements, and a TFD (Thin Film Diode) element is provided as a switching element. The present invention can also be applied to other liquid crystal devices.
As a schematic configuration of the TFD element, an insulating film is sandwiched between a lower electrode and an upper electrode. More specifically, the TFD element includes a lower electrode, an element insulating film covering the upper surface of the lower electrode, and a signal line and a pixel electrode (second electrode) provided to face the lower electrode through the element insulating film. ) And. That is, the signal line and the pixel electrode function as the upper electrode of the TFD element as it is.
Note that an upper electrode electrically connected to the signal line or the pixel electrode may be separately provided. Such a TFD element has a so-called back-to-back structure in which two diodes are connected back to back.

  In such a liquid crystal device driven by TFD, a voltage is applied to the liquid crystal layer 50 by a driving method using pulse width modulation. In the TFD liquid crystal device, the liquid crystal layer includes a chiral agent having a spiral in a direction opposite to the rotation direction of the liquid crystal molecules when an electric field is applied. As a result, a liquid crystal device driven with a small data amplitude can be realized.

(Electronics)
FIG. 8 is a perspective configuration diagram of a mobile phone which is an example of an electronic apparatus provided with a liquid crystal device according to the present invention in a display portion. The mobile phone 1300 uses the liquid crystal device of the present invention as a small-size display portion 1301. A plurality of operation buttons 1302, an earpiece 1303, and a mouthpiece 1304.

  The liquid crystal device of the above embodiment is not limited to the mobile phone, but an electronic book, a personal computer, a digital still camera, a liquid crystal television, a viewfinder type or a monitor direct-view type video tape recorder, a car navigation device, a pager, an electronic notebook, It can be suitably used as an image display means for a calculator, a word processor, a workstation, a videophone, a POS terminal, a device equipped with a touch panel, and the like, and the contrast of the display unit 1301 can be improved in any electronic device.

1 is a diagram showing a circuit configuration of a liquid crystal device according to a first embodiment of the present invention. FIG. 2 is a plan configuration diagram of a dot region of the liquid crystal device according to the first embodiment of the present invention. FIG. 3 is a cross-sectional configuration diagram taken along line A-A ′ of FIG. 2. 1 is a schematic cross-sectional view of a liquid crystal device according to a first embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of a liquid crystal device according to a modification of the first embodiment of the present invention. FIG. 6 is a plan configuration diagram of a dot region of a liquid crystal device according to a second embodiment of the present invention. FIG. 7 is a cross-sectional configuration diagram taken along line D-D ′ in FIG. 6. FIG. 11 is a perspective configuration diagram illustrating an example of an electronic device. FIG. 6 is a diagram showing VT characteristics of a conventional liquid crystal device.

Explanation of symbols

9 pixel electrode (second electrode), 10 TFT array substrate (first substrate), 19, 119 common electrode (first electrode), 20 counter substrate (second substrate), 50 liquid crystal layer, 100, 200 liquid crystal device, 1300 Mobile phone (electronic equipment), LC liquid crystal molecules (liquid crystal layer), E electric field.

Claims (6)

A first substrate and a second substrate are provided opposite to each other with a liquid crystal layer interposed therebetween, and a first electrode and a second electrode are provided on the liquid crystal layer side of the first substrate, and the first electrode and the second electrode are provided. A liquid crystal device in which the liquid crystal layer is driven by an electric field generated between two electrodes,
The liquid crystal layer includes a chiral agent that rotates in a direction opposite to a rotation direction of liquid crystal molecules when the electric field is generated between the first electrode and the second electrode;
A liquid crystal device characterized by the above. The first electrode and / or the second electrode are formed in a straight line;
The liquid crystal device according to claim 1. A normally black mode for displaying black when the electric field is not generated;
The liquid crystal device according to claim 1 or 2. The alignment film provided on the first substrate side of the liquid crystal layer and the alignment film provided on the second substrate side are alignment films in which the alignment of liquid crystal molecules is parallel to each other and a pretilt is given in the same direction. That
The liquid crystal device according to claim 1, wherein the liquid crystal device is a liquid crystal device. An alignment film provided on the first substrate side of the liquid crystal layer and an alignment film provided on the second substrate side include an alignment film in which the alignment of liquid crystal molecules is parallel to each other and imparts a pretilt in opposite directions. is being done,
The liquid crystal device according to claim 1, wherein the liquid crystal device is a liquid crystal device. The liquid crystal device according to claim 1 is provided.
Electronic equipment characterized by

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