JP5491892B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device.

  A liquid crystal display device is a non-luminous display device, unlike a self-luminous display device typified by a CRT (Cathode Ray Tube) or a PDP (Plasma Display Panel), or the like. Images and images are displayed by adjusting the amount of reflected external light or both.

  In addition, the liquid crystal display device has features such as thinness, light weight, and low power consumption, and has recently been widely used for a display unit of a portable electronic device such as a liquid crystal television, a display for a personal computer, and a mobile phone terminal. .

  The liquid crystal display device includes a liquid crystal display panel and a drive circuit that drives the liquid crystal display panel. A liquid crystal display panel is a display panel in which a liquid crystal material is sealed between a pair of substrates, and has a display region constituted by a set of a large number of pixels. Each pixel includes a pixel electrode and a common electrode, and changes the amount of transmitted light and / or the amount of reflected light by changing the orientation of the liquid crystal layer (liquid crystal molecules) according to the potential difference between the pixel electrode and the common electrode.

  The arrangement of the pixel electrode and the common electrode is roughly classified into a configuration in which the pixel electrode and the common electrode are arranged on different substrates and a configuration in which the pixel electrode and the common electrode are arranged on the same substrate. A liquid crystal display panel in which a pixel electrode and a common electrode are arranged on the same substrate is generally referred to as an IPS (In Plane Switching) method, and the amount of transmitted light or the amount of transmitted light can be reduced by rotating liquid crystal molecules in a plane parallel to the substrate. Adjust the amount of reflected light or both. In the IPS liquid crystal display panel, the alignment direction of the liquid crystal layer is nearly horizontal, so that the change in retardation of the liquid crystal layer due to the change in viewing angle is small. Therefore, the liquid crystal display device adopting the IPS method can achieve a wide viewing angle. On the other hand, the VA (Vertical Alignment) method employs a configuration in which the pixel electrode and the common electrode are arranged on different substrates.

  In recent years, a liquid crystal display method using a substance that changes from optical isotropy to optical anisotropy by applying an electric field has been proposed (see, for example, Patent Document 1). In the liquid crystal display method, a liquid crystal material having a blue phase or a liquid crystal material having cubic symmetry is used (for example, see Non-Patent Document 1), and has a comb-like electrode portion as in the IPS method. An electric field parallel to the substrate is applied by the comb electrode. These liquid crystal display devices can achieve response characteristics of several microseconds to several hundred microseconds, and can operate much faster than the IPS method using the conventional nematic phase. It can be expected to improve.

Japanese Patent No. 3504159 JP 2006-003840 A

Yoshiaki Hisakado etc. “Large Electro-optic Kerr Effect in Polymer-Stabilized Liquid-Crystalline Blue Phases”, Advanced Materials, Vol. 17, No. 1, 96 (2005)

  For example, in a liquid crystal display device using a blue phase liquid crystal as a liquid crystal material and driving a pixel electrode composed of comb-shaped electrodes and a common electrode on the same substrate, even if these electrodes are formed of a transparent electrode material, Light is not transmitted. One cause is that when the pixel electrode and the common electrode are arranged on the same substrate, the electric field strength is usually weak on the electrodes and no optical anisotropy is imparted. Another reason is that there are few electric field components parallel to the substrate surface on the electrodes and many electric field components perpendicular to the substrate surface.

  Here, if the electrode is arranged not only on one of the pair of substrates sandwiching the liquid crystal layer but also on both, an electric field having a component parallel to the substrate surface can be generated also on the electrode. The above problem can be solved by the configuration. Further, in this configuration, the potential of the electrode on the other substrate can be arbitrarily set as compared with the configuration in which the pixel electrode to which the voltage corresponding to the image signal is applied is disposed only on one of the pair of substrates and the potential of the electrode on the other substrate is fixed. In the configuration in which the adjustment is possible and the configuration in which the pixel electrode is also provided on the other substrate, it is possible to improve the transmittance by applying a suitable electric field to the liquid crystal.

  However, the configuration in which the pixel electrodes and the like are arranged on both of the pair of substrates requires that a thin film transistor (TFT) is provided for each pixel on both substrates, and a signal wiring to each pixel needs to be installed. There was a problem that the rate decreased and the manufacturing cost increased.

  The present invention solves the above problems, and its purpose is to improve transmittance and drive voltage in a liquid crystal display device using a liquid crystal that generates optical anisotropy by applying a voltage typified by a blue phase liquid crystal. In other words, the aperture ratio is improved and the manufacturing cost is reduced.

  The above-described object, other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  A liquid crystal display device according to the present invention opposes a first substrate on which a signal wiring to which an image signal is applied and a switching element disposed in each of a plurality of pixels is formed, with a spacing from the first substrate. A second substrate disposed; a liquid crystal layer sandwiched between the first substrate and the second substrate; and a surface of the first substrate in contact with the liquid crystal layer, provided for each pixel, A first pixel electrode connected to a signal line through the switch element and generating a driving electric field for driving the liquid crystal layer; and a surface of the second substrate that is in contact with the liquid crystal layer; A second pixel electrode that generates a driving electric field and the gap between the first and second pixel electrodes that are arranged at positions facing each other are electrically connected to each other, and the second pixel electrode is connected to the second pixel electrode. An interconnection for applying a voltage according to the image signal; A. In the liquid crystal display device, the liquid crystal layer may be a substance that exhibits optical isotropy when the driving electric field is not applied and exhibits optical anisotropy when the driving electric field is applied.

  In another liquid crystal display device according to the present invention, a reference voltage is further applied, and the drive electric field is generated between the pixel electrode and the liquid crystal display device. The liquid crystal display device is provided on a surface in contact with the liquid crystal layer of the first substrate. The first common electrode and the second common electrode provided on the surface of the second substrate in contact with the liquid crystal layer, and the first common electrode and the second common electrode are disposed at the interval between the first common electrode and the second common electrode. And an interconnection part for electrically connecting the common electrodes.

  Another liquid crystal display device according to the present invention includes a light source that irradiates light to a back surface of a liquid crystal panel including the first and second substrates, wherein the liquid crystal panel emits light from the light source to the mutual light source. It has a light-shielding part that prevents light from passing through the vicinity of the connection part.

  In the liquid crystal display device according to the present invention, the interconnect portion may have a substantially spherical conductor. The interconnecting portion may be a columnar conductor or a columnar member having a surface formed with a conductor. Further, the interconnect portion can also serve as a function of keeping the distance between the substrates uniform in the plane of the substrate.

  In the liquid crystal display device according to the present invention, when the image signal is applied to the first pixel electrode, the interconnection between the first and second pixel electrodes is connected to the first pixel electrode and the first pixel electrode. A potential difference may be generated between the second pixel electrode and the second pixel electrode.

  The interconnect portion having the substantially spherical conductor further includes a conductive support for retaining the substantially spherical conductor between the substantially spherical conductor and the first or second pixel electrode. You may have. The support may be a member having a structure in which a surface in contact with the substantially spherical conductor is a concave surface having a smaller curvature than the conductor or a member having adhesiveness to the substantially spherical conductor.

  At least one of the first pixel electrode and the second pixel electrode may have a comb-like planar shape. In addition, at least one of the first common electrode and the second common electrode may have a comb-like planar shape. A preferred aspect of the liquid crystal display device according to the present invention in which the first pixel electrode, the second pixel electrode, the first common electrode, and the second common electrode have a comb-like planar shape, The comb teeth of each electrode are substantially parallel to each other and are arranged so as not to overlap each other when viewed from the normal direction of the substrate.

  In the liquid crystal display device according to the present invention, the liquid crystal layer may be a liquid crystal material that exhibits a blue phase.

  In addition, each of the first and second substrates may have a polarizing plate disposed on the surface opposite to the side facing the liquid crystal layer with the polarization directions being shifted from each other.

  According to the liquid crystal display device of the present invention, the aperture ratio is improved while improving the transmittance. Further, according to the liquid crystal display device of the present invention, the manufacturing cost can be reduced.

It is typical sectional drawing of the liquid crystal display device which is embodiment of this invention. It is a figure which shows the equivalent circuit of the pixel arranged in the pixel display area. 2 is a schematic plan view of a first substrate in one pixel of the liquid crystal display device according to the first embodiment. FIG. FIG. 4 is a schematic plan view of a second substrate in one pixel of the liquid crystal display device according to the first embodiment. FIG. 5 is a schematic cross-sectional view of the liquid crystal cell of the liquid crystal display device according to the first embodiment, taken along line AA in FIGS. 3 and 4. 5 is a schematic cross-sectional view of the liquid crystal cell of the liquid crystal display device according to the first embodiment, taken along the line BB in FIGS. 3 and 4. FIG. It is a schematic plan view of the 1st board | substrate in one pixel of the conventional common liquid crystal display device using a comb-shaped electrode. It is a schematic plan view of the 2nd board | substrate in one pixel of the conventional common liquid crystal display device using a comb-shaped electrode. FIG. 9 is a schematic cross-sectional view of a liquid crystal cell of a conventional liquid crystal display device taken along a line CC in FIGS. 7 and 8. FIG. 9 is a schematic cross-sectional view of a liquid crystal cell of a conventional liquid crystal display device taken along a line DD in FIGS. 7 and 8. 4 is a graph showing voltage-transmittance characteristics of a liquid crystal display device according to an embodiment of the present invention and a conventional liquid crystal display device. FIG. 5 is a schematic cross-sectional view of the liquid crystal display device according to the second embodiment taken along the line BB in FIGS. 3 and 4. It is typical sectional drawing which followed the straight line BB of FIG. 3, FIG. 4 of the liquid crystal display device which concerns on 3rd Embodiment. It is typical sectional drawing which followed the straight line BB of FIG. 3, FIG. 4 of an example of the liquid crystal display device which concerns on 4th Embodiment. It is typical sectional drawing which followed the straight line BB of FIG. 3, FIG. 4 of another example of the liquid crystal display device which concerns on 4th Embodiment. FIG. 9 is a schematic plan view of a first substrate in one pixel of a liquid crystal display device according to a fifth embodiment. FIG. 10 is a schematic plan view of a second substrate in one pixel of a liquid crystal display device according to a fifth embodiment. It is typical sectional drawing which followed the straight line BB of FIG. 3, FIG. 4 of the liquid crystal display device which concerns on 6th Embodiment.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings. In addition, in the following description and drawings, what has the same function attaches | subjects the same code | symbol, and avoids the overlapping description. The liquid crystal display device according to each embodiment can be used for, for example, a display unit of a mobile phone or a display unit of a television.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view of a liquid crystal display device 2 according to this embodiment. The liquid crystal display device 2 includes a liquid crystal panel 4 and a backlight unit 6. The liquid crystal panel 4 includes a pair of substrates 8 and 10, a liquid crystal layer 12, and polarizing plates 14a and 14b. The pair of substrates 8 and 10 are opposed to each other in parallel with a gap, and the liquid crystal layer 12 is sandwiched between them. Hereinafter, the laminate of the substrates 8 and 10 and the liquid crystal layer 12 is referred to as a liquid crystal cell.

  The polarizing plates 14a and 14b are disposed on the outer surface of the liquid crystal cell. That is, the polarizing plates 14a and 14b are laminated on the surfaces of the substrates 8 and 10 opposite to the side facing the liquid crystal layer 12, respectively. In order to achieve normally closed, the polarization directions of the polarizing plates 14a and 14b are basically orthogonal to each other. The polarizing plates 14a and 14b are composed of a polyvinyl alcohol (Poly-Vinyl Alcohol, hereinafter referred to as PVA) layer that has been adsorbed and stretched with iodine, and a protective film that protects it.

  In the liquid crystal panel 4, the side of the substrate 10 and the polarizing plate 14b is the display surface side, and the side of the substrate 8 and the polarizing plate 14a is the back side. The backlight unit 6 is disposed on the back surface of the liquid crystal panel 4 and irradiates the back surface with light. The backlight unit 6 includes a light guide plate, a diffusion plate, and the like in addition to the light source.

  Any light source may be used as long as it can irradiate the liquid crystal cell from the back surface, and various types and structures of light sources can be employed. For example, a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), an organic EL (Electro-Luminescence), or the like can be used as a light source.

  The backlight unit 6 is necessary only when the liquid crystal cell is used in the transmissive mode, and is not necessary when used in the reflective mode.

  The first substrate 8 and the second substrate 10 are transparent to transmit light, and are made of, for example, glass or a polymer film. As the polymer film, plastics and polyethersulfone (hereinafter referred to as PES) are particularly suitable in various characteristics. However, since plastic and PES allow air to pass, it is desirable to form a gas barrier on the substrate surface. The gas barrier can be formed by a silicon nitride film.

  Various members such as wiring are added to the first substrate 8 and the second substrate 10, but the illustration is omitted in FIG. 1. The structure of the substrates 8 and 10 will be further described later.

  The liquid crystal layer 12 is made of a medium that has substantially optical isotropy when no electric field is applied and exhibits optical anisotropy when the electric field is applied. Examples of such a medium include a blue phase liquid crystal material and a medium having cubic symmetry.

  The blue phase liquid crystal material is a material in which a monomer is contained in a nematic liquid crystal composition containing a chiral agent, and the temperature range of the blue phase is expanded by polymerizing the monomer in the blue phase of the liquid crystal. For nematic liquid crystals, organic compounds having a ring structure substituted with a polar group and a long chain structure, which are generally used for liquid crystal displays, are used. As the chiral agent, an organic compound having an asymmetric carbon in the molecule is used. A typical polymerizable monomer includes an acrylic monomer. In the case of photopolymerization, a polymerization initiator such as an acetophenone derivative is used in combination.

  A plurality of pixels are arranged in a matrix in the pixel display area of the liquid crystal display device 2. FIG. 2 is a diagram showing an equivalent circuit of the pixels arranged in the pixel display area. In the pixel display area, a plurality of scanning lines 16 extending in the horizontal direction of the screen and a plurality of signal lines 18 extending in the vertical direction of the image are arranged. The scanning wiring 16 and the signal wiring 18 are preferably formed of a low-resistance conductive material, for example, chromium, tantalum-molybdenum, tantalum, aluminum, copper, or the like.

  The pixel area is an area surrounded by the scanning wiring 16 and the signal wiring 18. At least one TFT 20 is provided corresponding to each pixel region. The TFT 20 is provided at the intersection of the scanning wiring 16 and the signal wiring 18 that are substantially orthogonal to each other. The gate electrode of the TFT 20 is connected to the scanning wiring 16, the drain electrode is connected to the signal wiring 18, and the source electrode is connected to the contact hole 22. Although not shown in FIG. 2, the contact hole 22 is connected to the pixel electrode of each pixel. In order to prevent the image signal held in the pixel from leaking, a storage capacitor 24 may be arranged in parallel with the pixel electrode on the source electrode of the TFT 20. The TFT 20 has an inverted stagger structure, and has a semiconductor layer in its channel portion.

  A signal for controlling on / off of the TFT 20 is applied to the scanning wiring 16, and a voltage signal for controlling the liquid crystal layer 12 is applied to the signal wiring 18. The TFT 20 functions as a switch element that controls the intermittent connection between the signal wiring 18 and the pixel electrode according to the signal of the scanning wiring 16. When the TFT 20 is turned on, a voltage signal corresponding to the image signal is applied from the signal wiring 18 to the pixel electrode. The

  FIG. 3 is a schematic plan view of the first substrate 8 in one pixel of the liquid crystal display device 2. FIG. 4 is a schematic plan view of the second substrate 10 in one pixel of the liquid crystal display device 2. 5 and 6 are schematic cross-sectional views between AA and BB of the liquid crystal cell of the liquid crystal display device 2.

  In one pixel region of the first substrate 8, the first pixel electrode 26a, the first common electrode 28a, the TFT 20, the contact hole 22, the scanning wiring 16, the signal wiring 18, the first insulating film 30a, the second An insulating film 30b is disposed.

  The scanning wiring 16 is formed on the surface of the first substrate 8 on the liquid crystal layer 12 side, and after the first insulating film 30a is laminated thereon, the signal wiring 18 is formed. Further, after the second insulating film 30b is stacked thereon, the first pixel electrode 26a and the first common electrode 28a are formed.

  The first insulating film 30a and the second insulating film 30b are provided in order to prevent contact of each wiring, and the material is not particularly limited as long as it can be electrically insulated. For example, a silicon nitride film or the like is used.

  The contact hole 22 is formed in the insulating films 30 a and 30 b in the overlapping region between the first pixel electrode 26 a and the signal wiring 18, and the first pixel electrode 26 a is sourced to the semiconductor layer 32 of the TFT 20 through the contact hole 22. Contact as an electrode.

  On the other hand, in one pixel region of the second substrate 10, a second pixel electrode 26b, a second common electrode 28b, a light shielding layer 34, a color filter 36, a planarizing layer 38, and the like are disposed.

  A color filter 36 and a planarizing layer 38 are sequentially stacked on the surface of the second substrate 10 on the liquid crystal layer 12 side, and a second pixel electrode 26b and a second common electrode 28b are formed on the surface. For example, the light shielding layer 34 can be formed on the outer surface of the second substrate 10.

  As the color filter 36, a colored film that transmits red (R), green (G), or blue (B) light is disposed for each pixel. The arrangement of the colored films corresponds to the arrangement of R pixels, G pixels, and B pixels on the display screen, and examples of the arrangement include a stripe arrangement and a delta arrangement.

  The flattening layer 38 is provided for flattening irregularities generated during the production of the color filter. For example, an acrylic resin or the like is used for the planarizing layer 38.

  The light shielding layer 34 is disposed along the pixel boundary in order to improve the resolution and prevent color mixing by blocking light leakage from adjacent pixels. The light shielding layer 34 can be formed using an opaque material such as metal or resin, and is preferably formed of chromium, tantalum-molybdenum, tantalum, aluminum, copper, or the like. In FIG. 4, the light shielding layer 34 is arranged only at the pixel boundary extending in the vertical direction. However, for example, in the pixel arrangement method in which different colors are arranged in the vertical direction, the light shielding layer 34 may be arranged at the pixel boundary extending in the horizontal direction. Good.

  A space between the first substrate 8 and the second substrate 10 is filled with the liquid crystal layer 12. The pixel electrodes 26 a and 26 b and the common electrodes 28 a and 28 b are in contact with the liquid crystal layer 12.

  The pixel electrodes 26 a and 26 b and the common electrodes 28 a and 28 b are arranged for applying an electric field to the liquid crystal layer 12. The pixel electrode and the common electrode may be transparent or opaque as long as they are low-resistance conductive materials. For example, indium tin oxide (ITO), zinc oxide (ZnO), chromium, tantalum-molybdenum, tantalum, aluminum, copper, or the like is used.

  For example, the first pixel electrode 26a is formed in a comb shape, and, for example, comb teeth extending in the vertical direction and arranged in the horizontal direction in the pixel and the comb teeth extending in the horizontal direction are connected to each other. Has a bridging part. Although the second pixel electrode 26b can also be a general comb shape having a plurality of comb-tooth portions, this embodiment shows an example in which the comb-electrode has only one comb-tooth portion as a special case. ing.

  In the example shown in FIG. 3, the first common electrode 28 a has a comb portion that extends in the horizontal direction across a plurality of pixels along the pixel boundary, and a comb portion that extends in the vertical direction from the portion. Formed into a shape. In the example shown in FIG. 4, the second common electrode 28b is formed as a plurality of linear electrodes extending in the vertical direction. In the range shown in FIG. 4, the second common electrode 28 b has a shape having only comb-tooth portions extending in the vertical direction and no bridging portion. This is taken as a special form of comb. Also in the shape of the second common electrode 28b shown in FIG. 4, in order to reduce the resistance, for example, a portion extending in the horizontal direction, that is, the same direction as the scanning wiring is provided in a place other than the display portion in FIG. It is also possible to bridge a plurality of comb teeth shown.

  The comb-tooth portions of each pixel electrode and each common electrode described above are substantially parallel to each other and are arranged so as not to overlap each other when viewed from the normal direction of the substrates 8 and 10. By arranging in this way, an oblique electric field can be generated between the pixel electrode and the common electrode on the upper and lower substrates. As a result, an electric field having a component parallel to the substrate surface is generated on the electrode, and the transmittance can be improved.

  Note that the comb-tooth portion extending in the vertical direction of the pixel electrode and the common electrode shown in FIGS. 3 and 4 can be bent in the pixel to form a multi-domain, thereby improving the viewing angle.

  In the present liquid crystal display device 2, conductive beads 40 are provided between the substrates 8 and 10 as interconnecting portions that electrically connect the first pixel electrode 26 a and the second pixel electrode 26 b for each pixel. Be placed. The second pixel electrode 26b is provided with a portion overlapping the comb-shaped bridging portion of the first pixel electrode 26a described above. The conductive beads 40 can be disposed in the overlapping portion.

  As described above, the conductive beads 40 have a function of making contact between the upper and lower pixel electrodes for each pixel, and at the same time, a function of maintaining the gap of the liquid crystal layer 12 between the first substrate 8 and the second substrate 10. Can bear.

  The conductive beads 40 can be made by, for example, using glass beads or resin beads as a base and plating the surface thereof with silver or gold. The conductive beads 40 only have to be conductive, and may be metal particles. Further, the material may be a low resistance material, and for example, aluminum, gold, silver, or the like is used.

  In the prior art, when the pixel electrodes are provided on the upper and lower substrates, it is necessary to arrange the TFT, the scanning wiring, and the signal wiring on each substrate. On the other hand, according to the present invention, the pixel electrode 26b on the second substrate 10 side is changed to the pixel electrode 26a on the first substrate 8 side by using the conductive beads 40 for each pixel as in the above-described embodiment. Therefore, it is not necessary to provide TFTs, scanning wirings, and signal wirings on the second substrate 10, so that the liquid crystal display device can be easily manufactured and the manufacturing cost can be reduced. Further, since the TFT, the scanning wiring, and the signal wiring are not provided on the second substrate 10, the aperture ratio can be improved.

  An alignment film is essential in a conventional liquid crystal panel using nematic liquid crystal. The alignment film is often formed of an insulating material such as polyimide. Therefore, when applying the present invention in which the above-described conductive beads contact the upper and lower pixel electrodes, the alignment film at the contact position of the conductive beads is removed. On the other hand, since the liquid crystal panel using the blue phase liquid crystal of this embodiment does not require an alignment film, it is not necessary to remove the alignment film when arranging conductive beads, and the present invention can be applied more easily. .

  In the drawing, only one conductive bead 40 is arranged in one pixel. However, the conductive beads 40 may be arranged in a plurality of places in one pixel in order to prevent defects due to poor arrangement.

  Here, for comparison with the present embodiment, the configuration of a conventional pixel using comb-shaped electrodes will be described. FIGS. 7 and 8 are schematic plan views of the first and second substrates in one pixel of a conventional general liquid crystal display device using comb electrodes. 9 and 10 are schematic cross-sectional views between CC and DD of the liquid crystal cell of the conventional liquid crystal display device. In this configuration, only the pixel electrode 26 a and the common electrode 28 a are formed on the first substrate 8, and the pixel electrode and the common electrode are not formed on the second substrate 10. In this case, conductive beads are not required, and a configuration such as a TFT is not required on the second substrate 10 side, but the transmittance of the pixel electrode 26a and the common electrode 28a on the first substrate 8 side is reduced. The aforementioned problem of reduction occurs. FIG. 11 is a graph showing voltage-transmittance characteristics of the liquid crystal display device 2 of the present embodiment and the conventional liquid crystal display device. FIG. 11 shows that the transmittance (curve T1) obtained with the electrode structure of the present embodiment is 1.5 times higher than the transmittance (curve T2) of the prior art. According to the present invention, the transmittance and the aperture ratio are improved as compared with the prior art, and as a result, the liquid crystal driving voltage necessary for obtaining the same luminance is lowered.

  The shape of the pixel electrode and the common electrode shown in this embodiment is an example. In the present invention, regardless of the shape of each electrode, the first pixel electrode is disposed on the first substrate, the second pixel electrode is disposed on the second substrate, and the first pixel electrode and the second pixel are disposed. This is effective when controlling the electrode to the same potential.

[Second Embodiment]
The second embodiment of the present invention is fundamentally different from the first embodiment in that the interconnect portion that electrically connects the first pixel electrode 26a and the second pixel electrode 26b is the first. It is a point which replaces with the substantially spherical conductive bead 40 in this embodiment, and is a columnar spacer. Since other points are basically the same as those in the first embodiment, only the differences will be described below.

  The planar structures of the first and second substrates in one pixel of the liquid crystal display device 2 of the second embodiment are the same as those shown in FIGS. FIG. 12 is a schematic cross-sectional view of the liquid crystal display device 2 of the present embodiment taken along the line BB in FIGS. 3 and 4. As shown in FIG. 12, the liquid crystal display device 2 of this embodiment includes a columnar spacer 42 between the first pixel electrode 26a and the second pixel electrode 26b. A conductive layer 44 is formed on the surface of the columnar spacer 42.

  The columnar spacer 42 has a function of maintaining the gap of the liquid crystal layer 12 between the first substrate 8 and the second substrate 10. The columnar spacer 42 may be of any shape or material as long as the gap of the liquid crystal layer 12 can be maintained. For example, a resist material or an acrylic resin is used.

  The columnar spacer 42 has a function of electrically connecting the first pixel electrode 26 a and the second pixel electrode 26 b through the conductive layer 44. The conductive layer 44 may be transparent or opaque as long as it is a low resistance conductive material. For example, indium tin oxide (ITO), zinc oxide (ZnO), chromium, tantalum-molybdenum, tantalum, aluminum, copper, or the like is used.

  This embodiment also exhibits the effects of the present invention such as the improvement of the transmittance and the aperture ratio, the manufacturing cost, and the reduction of the driving voltage described in the first embodiment.

  The same effect can be obtained even if the columnar spacer 42 itself is made of a conductive material such as metal.

[Third Embodiment]
The third embodiment of the present invention is basically different from the first embodiment in that it includes a light shielding portion 46. Since other points are basically the same as those in the first embodiment, only the differences will be described below.

  FIG. 13 is a schematic cross-sectional view of the liquid crystal display device 2 of the third embodiment along the line BB in FIGS. 3 and 4. The light shielding portion 46 is provided to prevent useless light from leaking out due to the alignment disorder generated by the conductive beads 40. The alignment disorder is caused by the loss of isotropicity of the blue phase due to liquid crystal alignment on the surface of the conductive beads or columnar spacers. Further, in addition to the electric field generated by the first pixel electrode 26a and the second pixel electrode 26b, an electric field is also generated by the interconnecting portion such as the conductive beads 40, and the electric field is affected in a complicated manner near the interconnecting portion. This also causes disorder of orientation.

  The light shielding part 46 is formed so as to prevent the irradiation light from the backlight unit 6 from passing through the vicinity of the conductive beads 40 that are the interconnection parts. The shape and material of the light shielding part 46 are not limited as long as light can be shielded. For example, an opaque material such as metal or resin can be used, and chromium, tantalum-molybdenum, tantalum, aluminum, copper, or the like can be used.

  In FIG. 13, the light shielding portion 46 is disposed between the first insulating film 30a and the second insulating film 30b. However, the light shielding portion 46 only needs to be able to block light leakage generated by the conductive beads 40. Even if the light shielding portion 46 is arranged on the surface of the substrate 8, the first pixel electrode 26a, or the second substrate 10 side, the same effect can be obtained.

  According to the present embodiment, the blue phase is used, the first substrate 8 and the second substrate 10 have the pixel electrodes 26a and 26b, respectively, and the first pixel electrode 26a and the second pixel electrode 26b are provided. In the liquid crystal display device 2 in which the conductive beads 40 and the like to be conducted are arranged for each pixel, it is possible to obtain the effects of improving the transmittance and aperture ratio, reducing the manufacturing cost, and the driving voltage described in the first embodiment. Furthermore, by providing the light shielding part 46, it is possible to prevent a decrease in contrast ratio.

[Fourth Embodiment]
The fourth embodiment of the present invention is basically different from the first embodiment in that the interconnect portion that electrically connects the first pixel electrode 26a and the second pixel electrode 26b is electrically conductive. A conductive support is provided between the bead 40 and the first or second pixel electrode 26a, 26b to hold the conductive bead 40 at a predetermined position in the substrate surface. Since other points are basically the same as those in the first embodiment, only the differences will be described below.

  Installation of the conductive beads 40 can be achieved by, for example, a fixed point arrangement applying the principle of an ink jet printer, but may move after the arrangement. Therefore, a support for fixing the conductive beads 40 is provided.

  FIG. 14 is a schematic cross-sectional view of an example of the liquid crystal display device 2 of the fourth embodiment along the line BB in FIGS. 3 and 4. In the configuration shown in FIG. 14, the liquid crystal display device 2 includes a pedestal 48 as a support. The pedestal 48 is arranged to prevent the conductive beads 40 from moving to a location outside the pixel electrode where the conductive beads are to be brought into contact. Further, the shape of the pedestal portion 48 is determined so that the object can be achieved. For example, in the example shown in FIG. 14, the pedestal portion 48 has a curvature that is larger than that of the conductive bead 40 whose surface is in contact with the conductive bead 40. Has a small concave surface. The material of the pedestal portion 48 may be any conductive material having a low resistance, and is not particularly limited to being transparent or opaque. For example, indium tin oxide (ITO), zinc oxide (ZnO), chromium, tantalum-molybdenum, tantalum, aluminum, or copper is processed by etching or the like.

  In the configuration shown in FIG. 14, the pedestal portion 48 is disposed on the first pixel electrode 26a. This configuration is particularly effective in a manufacturing method in which the conductive beads 40 are installed with the first substrate 8 side down. On the contrary, when the conductive beads 40 are installed with the second substrate 10 facing down, it is preferable to dispose the pedestal 48 on the second pixel electrode 26b side. Further, the pedestal portion 48 may be provided on both the first pixel electrode 26a side and the second pixel electrode 26b side.

  FIG. 15 is a schematic cross-sectional view of another example of the liquid crystal display device 2 of the fourth embodiment along the line BB in FIGS. 3 and 4. In the configuration shown in FIG. 15, the liquid crystal display device 2 includes an adhesive portion 50 as a support. Similar to the pedestal portion 48, the adhesive portion 50 is also arranged to prevent the conductive beads 40 from moving to a location outside the pixel electrode where the conductive beads are to be brought into contact. As long as the adhesive part 50 is a conductive adhesive, a shape and a material will not be ask | required. For example, a copper foil pressure-sensitive adhesive tape, an aluminum foil pressure-sensitive adhesive tape, or a material having conductivity in the pressure-sensitive adhesive itself can be used.

  In the configuration shown in FIG. 15, the adhesive portion 50 is disposed on the first pixel electrode 26a. This configuration is particularly effective in a manufacturing method in which the conductive beads 40 are installed with the first substrate 8 side down. Conversely, when the conductive beads 40 are installed with the second substrate 10 facing down, it is preferable to dispose the adhesive portion 50 on the second pixel electrode 26b side. Further, the adhesive portion 50 may be provided on both the first pixel electrode 26a side and the second pixel electrode 26b side.

  According to the present embodiment, the blue phase is used, the first substrate 8 and the second substrate 10 have the pixel electrodes 26a and 26b, respectively, and the first pixel electrode 26a and the second pixel electrode 26b are provided. In the liquid crystal display device 2 in which the conductive beads 40 to be conducted are arranged for each pixel, the effects of improving the transmittance and aperture ratio, reducing the manufacturing cost and driving voltage described in the first embodiment can be obtained. Furthermore, by providing a support such as the pedestal portion 48 and the adhesive portion 50, it is possible to dispose the conductive beads 40 on the substrate in a random manner on the substrate, instead of the fixed point placement using the ink jet technology. It becomes. Thereby, the process of installing the conductive beads 40 can be simplified, and the production of the liquid crystal panel can be facilitated.

[Fifth Embodiment]
The fifth embodiment of the present invention is basically different from the first embodiment in that an interconnecting portion is provided not only for the pixel electrode but also for the common electrode. Since other points are basically the same as those in the first embodiment, only the differences will be described below.

  FIG. 16 is a schematic plan view of the first substrate 8 in one pixel of the liquid crystal display device of the present embodiment. FIG. 17 is a schematic plan view of the second substrate 10 in one pixel of the liquid crystal display device of the present embodiment. In this embodiment, two conductive beads 40 are disposed between the substrates. One conductive bead is disposed between the first pixel electrode 26a and the second pixel electrode 26b, as in the first embodiment. Another conductive bead 40 is disposed between the first common electrode 28a and the second common electrode 28b and electrically interconnects both the common electrodes. The conductive beads 40 between the common electrodes are arranged at positions where the first common electrode 28a and the second common electrode 28b are opposed to each other.

  In the first embodiment, the second common electrode 28b in each pixel is mutually connected between all the pixels, and is set to a common potential in each pixel. On the other hand, the second common electrode 28b in each pixel in this embodiment is connected to the first common electrode 28a in the pixel, and the potential is set via the first common electrode 28a. . Therefore, the second common electrode 28b of each pixel does not necessarily have to be connected to each other on the second substrate 10, and can be, for example, an electrode shape separated for each pixel.

  Specifically, as in the first embodiment, the second common electrode 28b is a linear electrode extending across a plurality of pixels arranged in the vertical direction as shown in FIG. 4, and further arranged in the horizontal direction. The plurality of on-line electrodes can be interconnected at places other than the display unit. In contrast, the second common electrode 28b of the present embodiment has an electrode shape separated for each pixel as shown in FIG.

  On the other hand, scanning wirings 16 and signal wirings 18 are arranged at pixel boundaries of the first substrate 8 located on the back side of the liquid crystal panel, and a first common electrode 28a is further provided between the pixels at such pixel boundaries. Even if interconnects are provided, the influence on the aperture ratio of the liquid crystal panel is small. Therefore, for example, as shown in FIGS. 3 and 16, it is possible to interconnect the first common electrodes 28a in units of rows in the display portion by wiring in the horizontal direction along the pixel boundary. In addition, the first common electrode 28a may be connected to each other as a linear electrode extending in the column direction like the second common electrode 28b in FIG. 4 as the first common electrode 28a. It is. Therefore, the first common electrode 28a can be set to a different potential for each row and column.

  In this embodiment, by connecting the second common electrode 28b to the first common electrode 28a via the conductive beads 40, the potential of the second common electrode 28b is also set in units of rows and columns. Is possible. This makes it possible to apply a driving method in which the common potential is inverted for each partial region of the display unit such as for each row or for each column. By adopting the common inversion method, the voltage amplitude of the liquid crystal driving circuit can be halved.

  Note that the connection by the conductive beads 40 between the first common electrode 28a and the second common electrode 28b is not necessarily performed in all pixels. For example, when the common potential is inverted for each column, all the second common electrodes 28b of the pixels in each column are connected in the vertical direction, and the first common electrode 28a and the second common electrode 28b are only in a certain column. Can be conducted. Further, if it is only for common inversion, only the first common electrode 28a and the second common electrode 28b are connected by conductive beads, and the first pixel electrode 26a and the second pixel electrode 26b are electrically conductive. A voltage may be supplied separately without connecting with the bead 40.

  In the present embodiment, an example in which the conductive beads 40 are arranged between the pixel electrodes and between the common electrodes as the interconnection part has been shown. However, the function of the interconnection part that electrically connects the pixel electrodes and between the common electrodes, respectively. As long as it can perform, it does not have to be a substantially spherical shape like the conductive beads 40.

  According to the present embodiment, as in the first embodiment, the effects of improving the transmittance and the aperture ratio, reducing the manufacturing cost, and the driving voltage can be obtained. Further, the second substrate 10 is manufactured by providing two interconnect portions in the pixel and connecting the pixel electrodes and the common electrode to each other between the first substrate 8 and the second substrate 10. It can be made easier. In addition, the drive voltage can be further reduced by enabling the common inversion drive.

[Sixth Embodiment]
The sixth embodiment of the present invention is fundamentally different from the first embodiment in that an interconnect portion is formed when an image signal is applied from the signal wiring 18 to the first pixel electrode 26a via the TFT 20. This is in that a potential difference is generated between the first pixel electrode 26a and the second pixel electrode 26b. Since other points are basically the same as those in the first embodiment, only the differences will be described below.

  FIG. 18 is a schematic cross-sectional view of the liquid crystal display device 2 of the sixth embodiment at the position of the straight line BB in FIGS. 3 and 4. In the configuration shown in FIG. 18, a voltage dividing unit 52 is disposed as an interconnection between the first pixel electrode 26 a and the second pixel electrode 26 b.

  In the first embodiment, in order to set the first pixel electrode 26a and the second pixel electrode 26b to a common potential corresponding to an image signal in each pixel, It is formed using a low resistance metal or the like. On the other hand, in the present embodiment, the voltage divider 52 gives a potential difference between the first pixel electrode 26a and the second pixel electrode 26b. As a result, variations in the electric field generated in the liquid crystal layer 12 can be increased, and an improvement in transmittance and an improvement in viewing angle can be achieved.

  A resistive material or a dielectric material can be used as the material of the voltage dividing section 52. For example, although a resin, an organic substance, etc. can be used, if the same objective can be achieved, it will not be restricted to this. Further, since the potential difference between the first pixel electrode 26a and the second pixel electrode 26b is determined by the resistance value and the capacitance value of the voltage divider 52, an optimal value can be selected according to the application.

  For example, if the voltage dividing unit 52 has a high resistance, the voltage dividing unit 52 and the second pixel electrode 26b constitute a CR circuit, and the second pixel electrode is compared with the potential change of the first pixel electrode 26a. The potential of 26b is gradually changed according to the time constant of the CR circuit. As a result, when the TFTs 20 in each row are sequentially turned on to write image signals to the pixels, a potential difference is generated between the first pixel electrode 26a and the second pixel electrode 26b at the end of the on period of the TFT 20. be able to.

  With the configuration of this embodiment, the potentials of the first pixel electrode 26a, the second pixel electrode 26b, and the common electrodes 28a and 28b can be made different from each other. By properly using these three kinds of potentials, it becomes possible to adjust the driving conditions so as to further increase the transmittance.

  Although the present invention has been specifically described with reference to the first to sixth embodiments, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the present invention. Of course there is.

  For example, although the transmissive liquid crystal display panel has been described as an example in the above embodiment, the present invention is not limited to this and can be applied to a transflective liquid crystal display panel.

  The liquid crystal display device according to the present invention can be used for, for example, an active matrix type liquid crystal display, and can be used for a television, a car navigation system, a PC monitor, a notebook PC, a mobile phone, a DSC, a PDA, and the like. .

  2 liquid crystal display device, 4 liquid crystal panel, 6 backlight unit, 8 first substrate, 10 second substrate, 12 liquid crystal layer, 14a, 14b polarizing plate, 16 scanning wiring, 18 signal wiring, 20 TFT, 22 contact hole 24 storage capacitor 26a first pixel electrode 26b second pixel electrode 28a first common electrode 28b second common electrode 30a first insulating film 30b second insulating film 32 semiconductor layer , 34 Light-shielding layer, 36 Color filter, 38 Flattening layer, 40 Conductive beads, 42 Columnar spacer, 44 Conductive layer, 46 Light-shielding part, 48 Base part, 50 Adhesive part, 52 Pressure dividing part

Claims (13)

A first substrate on which a signal wiring to which an image signal is applied and a switch element disposed in each of the plurality of pixels are formed;
A second substrate disposed opposite to the first substrate at an interval;
A liquid crystal layer sandwiched between the first substrate and the second substrate;
A first pixel electrode provided for each pixel on a surface of the first substrate in contact with the liquid crystal layer, connected to the signal wiring via the switch element, and generating a drive electric field for driving the liquid crystal layer;
A second pixel electrode provided for each of the pixels on a surface of the second substrate in contact with the liquid crystal layer and generating the driving electric field;
An interconnection that is disposed at the interval between the first and second pixel electrodes and is electrically connected between the two pixel electrodes and applies a voltage corresponding to the image signal to the second pixel electrode. And
Each electrode is applied with a reference voltage and generates the driving electric field between the pixel electrode and the first common electrode and the second substrate provided on the surface of the first substrate in contact with the liquid crystal layer. A second common electrode provided on a surface in contact with the liquid crystal layer;
Have a, and interconnects for electrically connecting the corresponding disposed in the gap both common electrodes in said first and second common electrodes mutually opposing positions,
The first pixel electrode, the second pixel electrode, the first common electrode, and the second common electrode have a comb-shaped planar shape,
The comb portions of each electrode are substantially parallel to each other and arranged so as not to overlap each other when viewed from the normal direction of the substrate,
A liquid crystal display device. The liquid crystal display device according to claim 1.
The liquid crystal display device, wherein the liquid crystal layer exhibits optical isotropy when the driving electric field is not applied, and exhibits optical anisotropy with the application of the driving electric field. The liquid crystal display device according to claim 1 or 2 ,
A light source for irradiating light to the back surface of the liquid crystal panel including the first and second substrates;
The liquid crystal panel has a light-shielding portion that prevents irradiation light from the light source from passing near the interconnecting portion;
A liquid crystal display device. The liquid crystal display device according to claim 1 or 2 ,
The liquid crystal display device, wherein the interconnect portion has a substantially spherical conductor. The liquid crystal display device according to claim 1 or 2 ,
The liquid crystal display device, wherein the interconnecting portion is a columnar conductor. The liquid crystal display device according to claim 1 or 2 ,
The liquid crystal display device according to claim 1, wherein the interconnecting portion is a columnar member having a surface formed with a conductor. The liquid crystal display device according to claim 1 or 2 ,
The liquid crystal display device, wherein the interconnect portion keeps the distance between the substrates uniform in a plane of the substrate. The liquid crystal display device according to claim 1 or 2 ,
The interconnect between the first and second pixel electrodes is provided between the first pixel electrode and the second pixel electrode when the image signal is applied to the first pixel electrode. A liquid crystal display device characterized by producing a potential difference. The liquid crystal display device according to claim 4 .
The interconnect portion further includes a conductive support for retaining the substantially spherical conductor between the substantially spherical conductor and the first or second pixel electrode. Liquid crystal display device. The liquid crystal display device according to claim 9 .
The liquid crystal display device, wherein the support is a concave surface having a curvature smaller than that of the conductor in contact with the substantially spherical conductor. The liquid crystal display device according to claim 9 .
The said support body has adhesiveness with respect to the said substantially spherical conductor, The liquid crystal display device characterized by the above-mentioned. The liquid crystal display device according to claim 1 or 2 ,
The liquid crystal layer is made of a liquid crystal material that develops a blue phase. The liquid crystal display device according to claim 1 or 2 ,
Each of the first and second substrates has a polarizing plate disposed on a surface opposite to the side facing the liquid crystal layer, the polarization directions of which are shifted from each other.

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