JP2018077419A - In-plane field control type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-plane field control type liquid crystal display device that provides a new display region.SOLUTION: The in-plane field control type liquid crystal display device includes: first and second substrates disposed opposing to each other; first and second stripe electrode groups parallel and alternately disposed and extending in one orientation on an opposing surface of the first substrate; third and fourth stripe electrode groups parallel and alternately disposed and extending in one orientation on an opposing surface of the second substrate; first and second ridge-like wiring parts connected to opposing ends of the first and second stripe electrode groups and cooperatively constituting first and second comb-like electrodes in an interdigital arrangement; third and fourth ridge-like wiring parts connected to opposing ends of the third and fourth strip electrode groups and cooperatively constituting third and fourth comb-like electrodes in an interdigital arrangement; a liquid crystal layer housed in a region between the first and second substrates; and first and second polarizers disposed outside the first and second substrates.SELECTED DRAWING: Figure 1-1

Description

  The present invention relates to an in-plane electric field control type liquid crystal display device, and more particularly to an in-plane electric field control type liquid crystal display device having an improved aperture ratio.

  In a general liquid crystal display device, an electrode is provided on each of a pair of substrates arranged opposite to each other with a liquid crystal layer interposed therebetween, and an electric field is generated in a direction perpendicular to the substrate surface by using these electrodes. Bright and dark display is realized by changing the alignment state of the liquid crystal molecules. In such a liquid crystal display device, the liquid crystal molecules in the liquid crystal layer are aligned in a certain direction with respect to the substrate surface when an electric field is applied, so that viewing angle dependence occurs in bright and dark display.

  There is also a liquid crystal display device that can reduce the viewing angle dependency and realize good viewing angle characteristics. First and second striped electrodes (also referred to as teeth or finger-like portions) are alternately arranged in parallel on the opposing surfaces of one side of a pair of substrates arranged opposite to each other with a liquid crystal layer interposed therebetween. One end of the first and second stripe-shaped electrodes is connected to a common ridge-shaped wiring portion to form a comb-shaped electrode, and the two ridge-shaped wiring portions are arranged on the outside, and the tooth portions are bitten together. A combined interdigital arrangement (in which each finger-like portion is inserted between the opposite finger-like portions) is adopted.

  A voltage is applied between the first and second comb electrodes to generate an electric field in a direction substantially horizontal to the substrate surface in the inter-electrode region. Bright and dark display is realized by changing the in-plane alignment state of the liquid crystal molecules in the liquid crystal layer by an electric field in the in-plane direction. Such a liquid crystal display device can change the orientation of the liquid crystal molecules in the liquid crystal layer while being horizontal with respect to the substrate surface when an electric field is applied, and is less likely to cause viewing angle dependence in bright and dark displays, thereby realizing good viewing angle characteristics. Such a liquid crystal display device is called an in-plane switching (IPS) mode liquid crystal display device.

  FIG. 4A is a plan view showing a simplified electrode shape example formed on the surface of one substrate of the IPS mode liquid crystal display device. Two types of stripe electrodes E1 and E2 are alternately arranged in parallel to define a stripe-shaped interelectrode region. In order to apply a voltage to the two types of striped electrodes E1 and E2, the striped electrodes E1 and E2 are extended in opposite directions to each other, and ridged wiring portions W1 and W2 serving as connection portions are connected to the extended ends. A comb-like electrode is used. The stripe-shaped electrode E1 is connected by the ridge-shaped wiring portion W1, the stripe-shaped electrode E2 is connected by the ridge-shaped wiring portion W2, and the first and second comb-shaped electrodes are formed. The stripe-shaped electrode E1 and the stripe-shaped electrode are formed. E2 is arranged in an interdigital manner (alternately). When a voltage is applied between the ridged wiring portions W1 and W2, an electric field is formed in the interelectrode region between the striped electrodes E1 and E2, and the alignment of liquid crystal molecules is controlled. The electrode width and the inter-electrode region width are set to be sufficiently narrow, and the display region is configured by the region where the striped electrodes E1 and E2 are distributed visually.

  As a liquid crystal display device, there are a dot matrix display type in which a display surface is configured by a large number of dots and a segment display type in which a predetermined character, pattern, and the like are displayed. In a dot matrix display type IPS mode liquid crystal display device, a large number of dots of, for example, 0.5 mm square or less are distributed in a matrix on the display surface, and a uniform comb-like electrode is disposed in each dot. Since the length of the striped electrode included in the comb-like electrode is short, a thin electrode width can be realized even with a transparent electrode having a relatively high sheet resistance. In the segment display type IPS liquid crystal display device, the length of the striped electrode changes according to the pattern to be displayed. The length of the electrode may become long, and it is desirable to reduce the resistance of the electrode in order to maintain display uniformity.

  There is a possibility that the resistance value is lowered by increasing the thickness of the electrode. However, when the electrode is thickened, there is a possibility that the level difference is increased and the display quality is lowered. From the viewpoint of ensuring display uniformity, it is desirable to increase the width and lower the resistance value without increasing the thickness of the electrode. In some cases, the electrode width is set to be wide to reduce the aperture ratio.

  FIG. 4B is a plan view showing a specific electrode configuration showing a part of a 7-segment display element capable of displaying the numeral 8. In the lower triangular area, two types of stripe-shaped electrodes E1 and E2 arranged on the average in the vertical direction are alternately arranged in the horizontal direction to form a display area. The stripe-like electrode extends in the vertical direction while slightly bending left and right. The angle of bending is, for example, an angle of about 1 to 5 degrees. The striped electrode E1 is connected to the ridge-shaped wiring portion W1 disposed on the upper side. The other striped electrode E2 is connected to the ridged wiring portion (W2) in the lower part outside the drawing. In order to reduce the resistance of the electrodes, for example, both the electrode width and the inter-electrode region width are set to about 5 μm to 30 μm.

  In the IPS mode liquid crystal display device, the active display area is an inter-electrode area, and the electrode area itself is a non-display area. The ratio occupied by the inter-electrode region which is the display region in the entire area is called the aperture ratio. In order to realize a bright display, it is desirable to improve the aperture ratio. Since the interelectrode region forms a sufficient electric field, the width is limited. In order to apply a uniform voltage to the entire length of the electrode, it is desired to form a low-resistance electrode. If the electrode width is increased in order to obtain a low-resistance electrode, the area of the electrode region in the total area increases and the aperture ratio decreases.

  The electrodes required from the functional aspect of the IPS mode liquid crystal display device are two types of striped electrodes formed on the surface of one substrate. An alignment film is formed on the opposing surfaces of the pair of substrates, and an alignment process such as rubbing is performed in a predetermined direction. The alignment treatment such as rubbing must be performed in a certain relationship with the direction of the striped electrodes arranged in parallel. A pair of polarizers such as crossed Nicols are disposed outside the pair of substrates. The transmission axis direction of the polarizer must have a certain relationship with the striped electrode direction. In order to satisfy such a requirement in the manufacturing process, some kind of electrode is formed so as to function as an aligner on a substrate on which a display electrode is not formed.

  Note that a liquid crystal display device that controls display by an electric field between parallel electrodes formed on a substrate without regard to the orientation direction of liquid crystal molecules is referred to as an in-plane electric field control type liquid crystal display device.

JP-A-56-91277 (Japanese Examined Patent Publication No. 63-21907) JP 2014-29382 A

  One object of the embodiment is to provide an in-plane electric field control type liquid crystal display device that provides a new display area.

  Another object of the embodiment is to provide an in-plane electric field control type liquid crystal display device having an improved aperture ratio.

  Still another object of the embodiment is to provide an in-plane electric field control type liquid crystal display region having a novel function.

  According to the embodiment, the first and second substrates arranged opposite to each other, and the first and second striped electrode groups alternately arranged in parallel on the opposite surface of the first substrate and extending to one position, The third and fourth stripe electrode groups alternately arranged in parallel on the opposite surface of the second substrate and extending to one position are connected to the opposite ends of the first and second stripe electrode groups. , Connected to the opposing ends of the first and second ridge-like wiring portions and the third and fourth stripe-like electrode groups constituting the first and second comb-like electrodes jointly arranged in an interdigital manner Liquid crystal housed in a region between the first and second substrates and the third and fourth ridge-like wiring portions constituting the third and fourth comb-like electrodes jointly interdigitally arranged An in-plane electric field control type liquid crystal display device including a layer and first and second polarizers arranged outside the first and second substrates is provided.

  In the first configuration, in the projection onto the substrate, the extending direction of the first and second striped electrode groups and the extending direction of the third and fourth striped electrode groups are arranged in parallel. The

  In the second configuration, in the projection onto the substrate, the extending direction of the first and second striped electrode groups intersects with the extending direction of the third and fourth striped electrode groups. Be placed.

  The inter-electrode regions of the third and fourth stripe electrode groups can form a display region when an electric field is formed. When the inter-electrode regions of the third and fourth stripe electrode groups are arranged in the electrode regions of the first and second stripe electrode groups, the display region can be configured in the non-display region.

,as well as FIG. 1A is a schematic cross-sectional view of an in-plane electric field control type liquid crystal display device according to the first embodiment, and FIG. 1B is a comb-like electrode SW1, SW2 on the lower substrate 1 and a comb-like electrode SW3 on the upper substrate 2. FIG. 1C shows the stripe electrodes E1 and E2 of the first and second comb-like electrodes and the stripe electrode E3 of the third and fourth comb-like electrodes. , E4 and the sum of the inter-electrode regions. 2A and 2B are plan views of electrodes showing a modification of the first embodiment. FIG. 3A is a plan view showing the stripe electrode group on the lower substrate and the stripe electrode group on the upper substrate in an in-plane electric field control type liquid crystal display device according to the second embodiment, and FIG. 3B is mainly between the electrodes. FIG. 3C is a cross-sectional view schematically showing a liquid crystal layer containing vertically aligned liquid crystal molecules. 4A is a plan view schematically showing the shape of a comb-like electrode of an IPS mode liquid crystal display device according to the prior art, and FIG. 4B is a plan view showing a specific electrode shape of a part of a 7-segment display element.

1, 2 transparent substrate, 3, 4 orientation layer, 5 seal,
6 liquid crystal layer, 8, 9 polarizer, W1, W2 ridged wiring section,
E1, E2 (on the substrate 1) stripe electrodes (tooth electrodes of comb-like electrodes),
E3, E4 (on the substrate 2) striped electrode (tooth electrode of comb-like electrode),
B1, B2, B3, B4 ridged wiring portions of comb-like electrodes,
SW1, SW2, SW3, SW4 comb-teeth electrodes,
D1 Interelectrode region on the substrate 1, D2 Interelectrode region on the substrate 2,
F1, F2 Electric field formed by the intersecting electrode group in the inter-electrode region.

  An in-plane electric field control type liquid crystal display device according to the first embodiment will be described with reference to FIGS. As shown in FIG. 1A, stripe electrodes E1, E2, E3, and E4 are formed of transparent electrodes on the opposing surfaces of the transparent substrates 1 and 2 that are arranged to face each other, and the alignment films 3 and 4 cover the transparent electrodes. It is formed on a substrate. The periphery of the display surface is sealed with a seal 5 and accommodates a liquid crystal layer 6. The liquid crystal layer 6 includes horizontally aligned liquid crystal molecules. Polarizer pairs 8 and 9 are arranged outside the pair of substrates 1 and 2.

  Conventionally, as a product, a striped electrode is disposed only on one substrate and no electrode is disposed on the other substrate, but an electrode is also formed on the other substrate during the process. Therefore, even if a striped electrode is formed on the other substrate, no new process is added.

  FIG. 1B is a combination of a plan view and a cross-sectional view showing a schematic configuration of electrodes on the upper substrate and the lower substrate. The striped electrode groups E1, E2, E3, and E4 are connected by wiring of the ridge-shaped wiring portions B1, B2, B3, and B4 to form comb-shaped electrodes SW1, SW2, SW3, and SW4. On the lower substrate 1, the comb-like electrodes SW1 and SW2 form an interdigital arrangement, and an electric field can be formed between the striped electrodes E1 and E2. On the upper substrate 2, the comb-like electrodes SW3 and SW4 form an interdigital arrangement, and an electric field can be formed between the striped electrodes E3 and E4. The sectional view in the figure schematically shows an electric field when the electrodes E2 and E4 are grounded and a positive voltage is applied to the electrodes E1 and E3, for example. The alignment of liquid crystal molecules is controlled by these electric fields.

  The upper part of FIG. 1C is a plan view showing the arrangement of the electrodes E1 and E2 on the lower substrate and the arrangement of the interelectrode region D1 formed therebetween. The middle part of FIG. 1C is a plan view showing the arrangement of the electrodes E3 and E4 on the upper substrate and the arrangement of the interelectrode region D2 formed therebetween. The electrodes E1 and E2 on the lower substrate constitute a non-display area, and the interelectrode area D1 therebetween is the display area. The electrodes E3 and E4 on the upper substrate are arranged so as to overlap with the interelectrode region D1 of the lower substrate, and the interelectrode region D2 is defined so as to overlap with the electrode regions E1 and E2 of the lower substrate.

  When a voltage is applied between the comb-like electrode pairs SW3 and SW4 on the upper substrate and the inter-electrode region D2 is set as a display region, the display region overlaps with the electrode regions E1 and E2 which were non-display regions on the lower substrate. Is formed.

  1C is a plan view showing the inter-electrode region D1 of the lower substrate and the inter-electrode region D2 of the upper substrate together. Since the sides of the striped electrode groups E1 and E2 and the sides of the striped electrode groups E3 and E4 are arranged to coincide with each other, the interelectrode region D2 can completely fill the gap between the interelectrode regions D1. Placed in. An extremely high aperture ratio can be provided.

  1A to 1C can provide an extremely high aperture ratio, but the position of the side of the striped electrode on the upper substrate is adjusted to the position of the side of the striped electrode on the lower substrate with high accuracy. There is a need. There is a case where a configuration that can be manufactured even by a manufacturing process with lower accuracy is desired.

  FIG. 2 shows a modification in which the accuracy required for the manufacturing process can be relaxed. FIG. 2A shows a pattern in which, for example, the striped electrodes E1 and E2 on the lower substrate and the striped electrodes E3 and E4 on the upper substrate overlap at the ends. The inter-electrode region between the striped electrodes E3 and E4 on the upper substrate is formed inside the electrode region of the striped electrodes E1 and E2 on the lower substrate. Of the electrode area of the striped electrodes E1 and E2 on the lower substrate, a part of the region overlapping the stripe electrodes E3 and E4 on the upper substrate cannot be a display region, but the lower substrate overlapping the interelectrode region D2 on the upper substrate The electrode region can be used as a display region, and the aperture ratio can be improved.

  FIG. 2B shows a pattern in which the striped electrodes E1 and E2 on the lower substrate and the striped electrodes E3 and E4 on the upper substrate are separated from each other. A pattern in which the inter-electrode region of the striped electrodes E3 and E4 on the upper substrate includes the striped electrodes E1 and E2 of the lower substrate and regions on both sides thereof (part of the inter-electrode region of the lower substrate). It is. Two types of electric fields are formed in regions that are not electrode regions of the upper and lower substrates. Most of the display area can be displayed stably. The aperture ratio can be improved.

  When the liquid crystal molecules are horizontally aligned and a liquid crystal material having a negative dielectric anisotropy is used as the liquid crystal material, the liquid crystal molecules are aligned so that the axial direction of the liquid crystal molecules is substantially orthogonal to the extending direction of the striped electrode. When an electric field is generated between the stripe electrodes, the dipoles of the liquid crystal molecules are along the electric field direction, and the axial direction of the liquid crystal molecules is along the extending direction of the stripe electrodes.

  When the liquid crystal molecules are aligned horizontally and the liquid crystal material uses a liquid crystal material with positive dielectric anisotropy, the axis direction of the liquid crystal molecules is set to be approximately parallel to the extending direction of the striped electrode To do. When an electric field is generated between the striped electrodes, the axial direction of the liquid crystal molecules is along the direction of the electric field and along the direction orthogonal to the extending direction of the striped electrodes. It is also possible to use a liquid phase layer in which liquid crystal molecules having positive dielectric anisotropy are vertically aligned with respect to the substrate surface.

  3A, 3B, and 3C show the in-plane electric field control type liquid crystal display device according to the second embodiment. For example, liquid crystal molecules having positive dielectric anisotropy are used, and an alignment film that vertically aligns the liquid crystal molecules is used. As shown in FIG. 3A, the striped electrodes E1 and E2 on the lower substrate are arranged parallel to each other along one direction (vertical direction in the figure), and the striped electrodes E3 and E4 on the upper substrate are connected to the electrode E1. , E2 are arranged in parallel to each other along a direction intersecting with E2 (lateral direction in the figure). Note that the intersection region of the electrodes E1, E2 and the electrodes E3, E4 is CR.

  As shown in FIG. 3B, when a voltage is applied between the striped electrodes E1 and E2 of the lower substrate, an electric field in the horizontal direction in the drawing is generated in the interelectrode region D1, thereby constituting a display region. When a voltage is applied between the striped electrodes E3 and E4 of the upper substrate, an electric field in the vertical direction in the figure is generated in the interelectrode region D2, and a display region can be configured. Considering one crossing region CR1, a vertical electric field is present in the interelectrode region D2 of the upper substrate adjacent vertically, and a horizontal electric field is present in the interelectrode region D1 of the lower substrate adjacent in the horizontal direction. Electric fields in two vertical and horizontal directions are formed in the intersecting regions of the interelectrode regions D1 and D2 that are formed and are obliquely adjacent to each other. The liquid crystal molecules are aligned while interacting. An alignment of liquid crystal molecules whose in-plane direction changes is formed around the intersection region CR1.

  As shown in FIG. 3C, an electric field whose in-plane direction changes can be applied to the liquid crystal molecules in the vertically aligned liquid crystal layer. Depending on the electric field component, the alignment direction of the liquid crystal molecules also changes. The upper and lower polarizers are more preferably clockwise and counterclockwise circular polarizers.

  Note that the opposed striped electrode groups exemplified in (E1-E2), (E3-E4), etc. are arranged so as to extend in one direction as a whole as shown in FIG. 4B. From the viewpoint of accuracy required for the process, it is preferable to bend it slightly on both sides in the extending direction.

  Although the present invention has been described with reference to the embodiments, the above description is not restrictive. It will be apparent to those skilled in the art that various modifications, additions, improvements, combinations, and the like can be made.

Claims (10)

First and second substrates disposed opposite to each other;
First and second stripe-shaped electrode groups alternately arranged in parallel on the opposing surface of the first substrate and extending to one position;
Third and fourth striped electrode groups alternately arranged in parallel on the opposing surface of the second substrate and extending to one position;
First and second ridge wiring portions connected to opposing ends of the first and second stripe electrode groups and constituting first and second comb-like electrodes jointly interdigitally arranged When,
Third and fourth ridge wiring portions connected to opposite ends of the third and fourth striped electrode groups and constituting third and fourth comb-like electrodes jointly arranged in an interdigital manner When,
A liquid crystal layer housed in a region between the first and second substrates;
First and second polarizers disposed outside the first and second substrates;
In-plane electric field control type liquid crystal display device.   At least one of the first and second striped electrode groups and / or the third and fourth striped electrode groups, or both sets of electrode edge portions are bent with respect to the extending direction of the striped electrodes. The in-plane electric field control type liquid crystal display device according to claim 1.   The projection direction onto the substrate is arranged such that the extending direction of the first and second stripe electrode groups and the extending direction of the third and fourth stripe electrode groups are arranged in parallel. 3. An in-plane electric field control type liquid crystal display device according to 1 or 2.   The in-plane electric field control type liquid crystal display device according to claim 3, wherein the liquid crystal layer includes liquid crystal molecules horizontally aligned with respect to a substrate surface.   In the projection onto the substrate, the inter-electrode region at the center of the third and fourth striped electrode groups is disposed on the electrode region excluding both ends of the first and second striped electrode groups. The in-plane electric field control type liquid crystal display device according to claim 1, comprising a portion.   In the projection onto the substrate, the position of the electrode side end of the central portion of the third and fourth stripe electrode groups overlaps the position of the electrode side edge of the first and second stripe electrode groups. Item 6. The in-plane electric field control type liquid crystal display device according to Item 5.   In the projection onto the substrate, the position of the electrode side end at the center of the third and fourth stripe electrode groups is determined from the position of the electrode side edge of the first and second stripe electrode groups to the inside of the electrode. The in-plane electric field control type liquid crystal display device according to claim 5, wherein the in-plane electric field control type liquid crystal display device is separated in a direction of the direction of the electrode or outside the electrode.   In the projection onto the substrate, the extending direction of the first and second striped electrode groups and the extending direction of the third and fourth striped electrode groups are arranged to intersect. The in-plane electric field control type liquid crystal display device according to claim 1.   The in-plane electric field control type liquid crystal display device according to claim 8, wherein the liquid crystal layer includes liquid crystal molecules vertically aligned with respect to a substrate surface. The in-plane electric field control type liquid crystal display device according to claim 8, wherein the first and second polarizers are circular polarizers having opposite directions.

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