JP2008089966A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display whose visual field angle characteristics are further enhanced, despite the liquid crystal display having a simple and inexpensive constitution. <P>SOLUTION: The liquid crystal display includes a first substrate, a second substrate, polarizing plates provided to the first substrate and the second substrate, a liquid crystal layer, disposed between the first substrate and the second substrate, a first electrode provided to the first substrate and a second electrode applying an electric field to the liquid crystal layer by the potential difference generated between the first and the second electrodes, the liquid crystal layer has properties where the optical anisotropy is generated by voltage application from optically isotropic state, and the polarizing plate is constituted of an E (extraordinary)-type polarizer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device called a so-called lateral electric field method.

  When a liquid crystal display device is used as a television monitor, the liquid crystal display device is desired to have a so-called wide viewing angle characteristic.

  In this case, a liquid crystal display device called a horizontal electric field method can obtain a larger viewing angle characteristic than, for example, a conventional twisted nematic (TN) display method.

  A horizontal electric field type liquid crystal display device is configured to have a pair of electrodes in each pixel region on the liquid crystal side surface of one of the substrates facing each other with a liquid crystal layer interposed therebetween, and applied to these electrodes. This is because the behavior of the liquid crystal molecules according to the electric field generated by the potential difference is such that light incident on the liquid crystal layer is emitted at a wide angle.

  In a conventional horizontal electric field type liquid crystal display device, an optically uniaxial liquid crystal material has been used.

  However, in recent years, liquid crystal materials that are optically isotropic and so-called isotropic liquid crystals have been known.

  Such a liquid crystal has the property that the alignment of liquid crystal molecules is optically three-dimensional or two-dimensionally isotropic when no voltage is applied to the liquid crystal layer, and birefringence is induced in the voltage application direction by applying a voltage. Have.

Such an isotropic liquid crystal is described in detail, for example, in Patent Document 1 below.
JP 2006-3840 A

  As described above, the conventional lateral electric field type liquid crystal display device uses an optically uniaxial liquid crystal material, so that the transmittance depends on the viewing angle, and when no voltage is applied. In the case of black display, it was confirmed that a decrease in contrast is inevitable due to light leakage based on light scattering caused by thermal fluctuation of the liquid crystal.

  Therefore, the present applicant has attempted to use the isotropic liquid crystal as a material of the liquid crystal display device of the horizontal electric field type, and has solved the above-described disadvantages.

  Further, by using the isotropic liquid crystal as the liquid crystal material in this way, it has been found that the viewing angle can be further expanded in spite of a simple and inexpensive configuration.

  An object of the present invention is to provide a liquid crystal display device having a further improved viewing angle characteristic despite a simple and inexpensive configuration.

   Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.

(1) A liquid crystal display device according to the present invention includes, for example, a first substrate, a second substrate,
A polarizing plate provided on the first substrate and the second substrate;
A liquid crystal layer disposed between the first substrate and the second substrate;
A first electrode provided on the first substrate and a second electrode for applying an electric field to the liquid crystal layer due to a potential difference generated between the first electrode, and
The liquid crystal layer has a property of causing optical anisotropy by applying voltage from an optically isotropic state,
The polarizing plate is composed of an E-type polarizer.

(2) The liquid crystal display device according to the present invention is based on, for example, the configuration of (1), and the polarizing plate is formed on the surface opposite to the liquid crystal layer of the first substrate and the second substrate. It is characterized by that.

(3) The liquid crystal display device according to the present invention is, for example, on the premise of the configuration of (2), wherein the polarizing plate is protected by a protective film or a protective plate.

(4) The liquid crystal display device according to the present invention is, for example, on the premise of the configuration of (2), wherein the polarizing plate is formed by applying an E-type polarizer on the film surface.

(5) The liquid crystal display device according to the present invention is premised on the configuration of (1), for example, and the polarizing plate is formed on the liquid crystal layer side surface of the first substrate and the second substrate. Features.

(6) The liquid crystal display device according to the present invention is based on, for example, the configuration of (1), and the electrode is formed through a planar electrode formed on the first substrate and an insulating film formed covering the electrode. The first electrode and the second electrode are constituted by an electrode group formed so as to overlap with each other.

(7) The liquid crystal display device according to the present invention is premised on the configuration of (1), for example, through a gate signal line, a thin film transistor that is turned on by a scanning signal from the gate signal line, and a thin film transistor that is turned on A drain signal line for supplying a video signal to one of the first electrode and the second electrode, and the other electrode of the first electrode and the second electrode with respect to the video signal And a common signal line for supplying a reference signal as a reference.

(8) The liquid crystal display device according to the present invention includes, for example, a liquid crystal display panel, and a backlight disposed on the back surface of the liquid crystal display panel via an optical sheet,
The liquid crystal display panel includes a first substrate, a second substrate, a polarizing plate provided on the first substrate and the second substrate, and between the first substrate and the second substrate. And a second electrode for applying an electric field to the liquid crystal layer by a potential difference generated between the first electrode provided on the first substrate and the first electrode,
The liquid crystal layer has a property of causing optical anisotropy by applying voltage from an optically isotropic state, and the polarizing plate is composed of an E-type polarizer,
The optical sheet is configured such that an emission angle of light emitted to the liquid crystal display panel is increased with respect to incident light from the backlight side.

(9) The liquid crystal display device according to the present invention is based on, for example, the configuration of (8), and the polarizing plate is formed on the surface opposite to the liquid crystal layer of the first substrate and the second substrate. It is characterized by that.

(10) The liquid crystal display device according to the present invention is, for example, on the premise of the configuration of (9), wherein the polarizing plate is protected by a protective film or a protective plate.

(11) The liquid crystal display device according to the present invention is, for example, on the premise of the configuration of (9), wherein the polarizing plate is formed by applying an E-type polarizer on the film surface.

(12) The liquid crystal display device according to the present invention is based on, for example, the configuration of (8), and the polarizing plate is formed on the liquid crystal layer side surface of the first substrate and the second substrate. Features.

(13) The liquid crystal display device according to the present invention, for example, on the premise of the configuration of (8), the electrode is formed through a planar electrode formed on the first substrate and an insulating film formed covering the electrode. The first electrode and the second electrode are constituted by an electrode group formed so as to overlap with each other.

(14) The liquid crystal display device according to the present invention is based on, for example, the configuration of (8), and includes a gate signal line, a thin film transistor that is turned on by a scanning signal from the gate signal line, and a thin film transistor that is turned on. A drain signal line for supplying a video signal to one of the first electrode and the second electrode, and the other electrode of the first electrode and the second electrode with respect to the video signal And a common signal line for supplying a reference signal as a reference.

(15) The liquid crystal display device according to the present invention is premised on, for example, the configuration of (8), and the optical sheet is formed with a convex lens assembled on the surface on the liquid crystal display panel side, and a skirt of the convex lens on the back surface. In this part, a window through which light can be transmitted is formed.

  In addition, this invention is not limited to the above structure, A various change is possible in the range which does not deviate from the technical idea of this invention.

  The liquid crystal display device configured as described above can further improve the viewing angle characteristics despite the simple and inexpensive configuration.

  Hereinafter, embodiments of a liquid crystal display device according to the present invention will be described with reference to the drawings.

<Overall configuration diagram>
FIG. 2 is a perspective view schematically showing the entire liquid crystal display device according to the present invention. In the figure, the liquid crystal display device is configured by sequentially arranging a liquid crystal display panel PNL, an optical sheet OST, a diffusion plate DBD, and a backlight BL from the observer side.

  The liquid crystal display panel PNL includes a pair of transparent substrates SUB1 and SUB2 with liquid crystal interposed therebetween as an envelope. The transparent substrate SUB2 is formed to have a slightly smaller area than the transparent substrate SUB1, and is disposed so as to face the transparent substrate SUB1 with the left side portion and the upper side portion in the figure exposed, for example. A scanning drive circuit V made up of a plurality of semiconductor chips faced down is mounted in parallel on the left side of the transparent substrate SUB1, and a video signal made up of a plurality of semiconductor chips faced down on the upper side. A drive circuit He is mounted side by side.

  The transparent substrate SUB2 is fixed to the transparent substrate SUB1 by a sealing agent SL formed around the periphery thereof, and the sealing agent SL seals the liquid crystal interposed between the transparent substrate SUB1 and the transparent substrate SUB2. It also functions as a sealant. And the area | region where this liquid crystal was sealed, ie, the area | region enclosed by the sealing agent SL, is comprised as liquid crystal display part AR.

  A gate signal line GL and a common signal line CL that extend in the x direction and are arranged in parallel in the y direction are formed on the surface of the liquid crystal display portion AR of the transparent substrate SUB1 on the liquid crystal side. These gate signal line GL and common signal line CL are, for example, from above in FIG. 2, the gate signal line GL, the common signal line CL disposed with a relatively large distance from the gate signal line GL, and the common signal line. The gate signal line GL arranged with a slight distance from the line CL, the common signal line CL arranged with a relatively large distance from the gate signal line GL,... Yes.

  A drain signal line DL that is electrically insulated from the gate signal line GL and the common signal line CL is extended in the y direction in FIG. Has been placed.

  Pixels are formed in regions surrounded by a pair of gate signal lines GL adjacent to each other and a pair of drain signal lines DL adjacent to each other. Are arranged in a matrix. The configuration of each pixel will be described in detail later.

  Each gate signal line GL extends beyond the sealant SL on the left side of the drawing, for example, and is connected to a corresponding electrode (not shown) of the scanning signal drive circuit V. The scanning signal drive circuit V sequentially supplies, for example, a gate signal composed of, for example, a rectangular pulse from the upper side to the lower side in the drawing to each gate signal line GL. The gate signal line to which the gate signal is supplied A pixel column composed of each pixel formed along the GL can be selected.

  Each drain signal line DL extends beyond the sealant SL, for example, on the upper side of FIG. 2, and is connected to a corresponding electrode (not shown) of the video signal drive circuit He. The video signal drive circuit He supplies a video signal to each drain signal line DL in accordance with the timing of each output of the gate signal from the scanning signal drive circuit V. A video signal is applied to each pixel in the pixel row.

  Further, each of the common signal lines CL is connected to the common signal supply terminal CST, for example, at the right end in FIG. The common signal supply terminal CST is supplied with a common signal that is a reference voltage with respect to the voltage of the video signal, and the common signal is supplied to each pixel through a common signal line CL. It has become.

  Thus, an electric field corresponding to the voltage difference of the video signal with respect to the common signal is applied to the liquid crystal of each pixel to which the common signal and the video signal are supplied, and the molecules of the liquid crystal correspond to the strength of the electric field. It behaves and changes the light transmittance.

  A backlight BL is disposed on the back surface (surface opposite to the observer) of the liquid crystal display panel PNL via an optical sheet OST and a diffusion plate DBD, and the light from the backlight BL is transmitted through the diffusion plate DBD. The light passes through each pixel of the liquid crystal display panel PNL through the optical sheet OST and reaches the eyes of the observer.

  Although not shown in FIG. 2, in the liquid crystal display panel PNL, polarized light is respectively applied to the surface of the transparent substrate SUB1 opposite to the liquid crystal side and the surface of the transparent substrate SUB2 opposite to the liquid crystal side. A plate is formed. These polarizing plates are provided so that the change in the behavior of the liquid crystal can be visually observed. For this reason, each polarizing plate is formed so as to cover at least the liquid crystal display portion AR. FIG. 3 shows a polarizing plate PL1 formed on the surface of the transparent substrate SUB1 opposite to the liquid crystal side and a polarizing plate PL2 formed on the surface of the transparent substrate SUB2 opposite to the liquid crystal side. The transmission axis (absorption axis) PLA1 of the polarizing plate PL1 and the transmission axis (absorption axis) PLA2 of the polarizing plate PL2 are arranged in a Nicols arrangement orthogonal to each other. These polarizing plates PL1 and PL2 will be described in detail later.

  The backlight BL is, for example, a so-called direct type, and is configured by arranging a plurality of cold cathode ray tubes CDR, for example, facing the liquid crystal display part AR of the liquid crystal display panel PNL. Each of the cold cathode ray tubes CDR is arranged on the inner surface side of the outer frame of the backlight BL, which includes the reflector RFB, with the longitudinal direction thereof aligned with the x direction in FIG.

  The direct type backlight BL is suitable when the liquid crystal display panel PNL is large. Therefore, the backlight BL may be composed of a light guide plate that is substantially the same shape as the liquid crystal display panel PNL and a cold cathode ray tube disposed on the side surface of the light guide plate. Further, the light source may be a direct type using a light emitting diode (LED), a backlight having LEDs arranged on the side surface, or an organic electroluminescence (OLED) as a light source.

<Equivalent circuit of pixels>
FIG. 4 is a diagram showing one embodiment of an equivalent circuit of pixels in the liquid crystal display portion AR of the liquid crystal display device according to the present invention, and shows a circuit formed on the liquid crystal side surface of the transparent substrate SUB1. FIG. 4 shows 2 × 3 pixels that are adjacent to each other among the pixels shown in FIG.

  As described above, each pixel has a region adjacent to another adjacent pixel by a pair of adjacent drain signal lines DL and a pair of adjacent gate signal lines GL.

  At one corner of the pixel, a thin film transistor TFT having an MIS structure is formed, the gate electrode thereof is connected to the adjacent gate signal line GL, and the drain electrode is connected to the adjacent drain signal line DL.

  In addition, a pixel electrode PX and a counter electrode CT configured as a pair of electrodes are formed in the pixel region, the pixel electrode PX is connected to a source electrode of the thin film transistor TFT, and the counter electrode CT is connected to the common signal line. Connected to CL.

  In such a circuit configuration, a reference voltage (a voltage serving as a reference for the video signal) is applied to the counter electrode CT of each pixel via the common signal line CL, and gates are sequentially applied to the gate signal line GL from the upper side in the figure, for example. A pixel row is selected by applying a voltage, and a thin film transistor TFT that is turned on by the gate voltage to each pixel of the pixel row by supplying a video signal to each drain signal line DL according to the selection timing. Then, the voltage of the video signal is applied to the pixel electrode PX. A so-called lateral electric field having an intensity corresponding to the voltage of the video signal is generated between the pixel electrode PX and the counter electrode CT, and the liquid crystal behaves according to the intensity of the lateral electric field.

  In the circuit shown in this manner, the gate signal line GL, the drain signal line DL, and the thin film transistor TFT have a geometrically similar arrangement in a pixel having a configuration to be described later. The pixel electrode PX is formed of a plurality of band-shaped electrodes that are superimposed on the counter electrode CT with an insulating film interposed therebetween.

  For this reason, a capacitive element using the insulating film as a dielectric film is formed between the pixel electrode PX and the counter electrode CT, and when a video signal is applied to the pixel electrode PX, the application of the video signal is applied. Is stored for a relatively long time by the capacitive element.

<Pixel configuration>
FIG. 5 is a diagram showing the configuration of the pixels formed on the liquid crystal side surface of the transparent substrate SUB1. 5A is a plan view, FIG. 5B is a cross-sectional view taken along line bb in FIG. 5A, and FIG. 5C is a cross-sectional view taken along line cc in FIG.

  First, the gate signal line GL and the common signal line CL are formed in parallel with a relatively large distance on the liquid crystal side surface (front surface) of the transparent substrate SUB1.

  In a region between the gate signal line GL and the common signal line CL, a counter electrode CT made of, for example, an ITO (Indium-Tin-Oxide) transparent conductive material is formed. The counter electrode CT is formed so as to be superimposed on the common signal line CL at a side portion on the common signal line CL side, and is thereby electrically connected to the common signal line CL.

  An insulating film GI is formed on the surface of the transparent substrate SUB1 so as to cover the gate signal line GL, the common signal line CL, and the counter electrode CT. This insulating film GI functions as a gate insulating film of the thin film transistor TFT in a formation region of the thin film transistor TFT described later, and the film thickness and the like are set accordingly.

  On the upper surface of the insulating film GI, a semiconductor layer AS made of, for example, amorphous silicon is formed at a portion overlapping with a part of the gate signal line GL. The semiconductor layer AS is a semiconductor layer of the thin film transistor TFT.

  Then, a drain signal line DL is formed extending in the y direction in the figure, and this drain signal line DL is formed with an extension portion laminated on the semiconductor layer AS at a part of the drain signal line DL. It functions as the drain electrode DT of the TFT.

  Further, the source electrode ST formed simultaneously with the formation of the drain signal line DL and the drain electrode DT is opposed to the drain electrode DT on the semiconductor layer AS, and from the semiconductor layer AS to the pixel region. It is formed with an extending portion that extends slightly to the side. This extending portion constitutes a pad portion connected to a part of the pixel electrode PX described later.

  Here, when the semiconductor layer AS is formed on the insulating film GI, the surface thereof is formed by doping a high concentration impurity, and the drain electrode DT and the source electrode ST are formed by patterning. After that, the high-concentration impurity layer formed in a region other than the region where the drain electrode DT and the source electrode ST are formed is etched using the drain electrode DT and the source electrode ST as a mask. This is because a high-concentration impurity layer remains between the semiconductor layer AS, the drain electrode DT, and the source electrode ST, and this impurity layer is formed as an ohmic contact layer.

  By doing so, the thin film transistor TFT is configured as a so-called inverted staggered MIS transistor having the gate signal line GL as a gate electrode.

  Note that the MIAS structure transistor is driven so that the drain electrode DT and the source electrode ST are switched by application of the bias. However, in the description of this embodiment, the transistor is connected to the drain signal line DL for convenience. The side connected to the drain electrode DT and the side connected to the pixel electrode PX are called the source electrode ST.

  A first protective film PAS1 is formed on the surface of the transparent substrate SUB1 so as to cover the thin film transistor TFT. The first protective film PAS1 is provided in order to prevent the thin film transistor TFT from coming into direct contact with the liquid crystal. The first protective film PAS1 is provided as an intervening layer between the counter electrode CT and a pixel electrode PX described later, and is provided between the counter electrode CT and the pixel electrode PX together with the insulating film GI. It also functions as a dielectric film for the capacitive element.

  A pixel electrode PX is formed on the upper surface of the first protective film PAS1. The pixel electrode PX is made of a transparent conductive material such as ITO (Indium-Tin-Oxide), for example, and is formed so as to overlap with the counter electrode CT over a wide area.

  The pixel electrode PX is formed so as to have an electrode group composed of a large number of strip-shaped electrodes in which a large number of slits are juxtaposed in a direction crossing the longitudinal direction thereof, and both ends thereof are connected to each other. Has been.

  A second protective film PAS2 is formed on the surface of the transparent substrate SUB1 so as to cover the pixel electrode PX. The second protective film PAS2 is provided, for example, to prevent conduction between the pixel electrode PX and the liquid crystal. As will be described later, the liquid crystal display device shown in this embodiment uses an isotropic liquid crystal as the liquid crystal, and thus can be configured not to form an alignment film. 2 It is necessary to provide an insulating film such as the protective film PAS2.

  As shown in FIG. 5A, each electrode of the pixel electrode PX divides the pixel region into two parts, for example, in the upper and lower parts in the figure, and one of the regions is, for example, in the traveling direction of the gate signal line GL. It is formed so as to extend in the + 45 ° direction, and is formed so as to extend in the −45 ° direction in the other region. A so-called multi-domain method is adopted, and when the direction of the slit provided in the pixel electrode PX in one pixel (the direction of the electrode group of the pixel electrode PX) is single, the problem of coloring due to the viewing direction is eliminated. It has become the composition. In addition, the slit structure suitable for isotropic liquid crystal has an angle of ± 45 °, but is not necessarily limited to such a configuration.

  In the embodiment described above, the semiconductor layer of the thin film transistor TFT is formed of amorphous silicon, but may be formed of polysilicon.

<Configuration of transparent substrate SUB2>
FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5A, in which the transparent substrate SUB1 and the transparent substrate SUB2 disposed to face each other through the liquid crystal QL are also drawn.

  A black matrix BM is formed on the liquid crystal side surface of the transparent substrate SUB2. This black matrix BM is provided to delineate each pixel PIX with other adjacent pixels PIX, and is superimposed on the gate signal line GL, common signal line CL, and drain signal line DL on the transparent substrate SUB1 side. Is formed. Thus, the black matrix BM is formed in a pattern in which an opening is formed in the central portion excluding the peripheral region of each pixel PIX. Further, the black matrix BM is formed so as to cover the thin film transistor TFT with a liquid crystal, thereby avoiding a change in characteristics of the semiconductor layer due to light irradiation.

  A color filter CF is formed in a portion where the opening of the black matrix BM is formed, and its periphery is formed so as to overlap the black matrix BM. In this color filter CF, a red (R) color filter CF, a green (G) color filter CF, and a blue (B) color filter are formed in three adjacent pixels, respectively. The pixel is configured as one pixel for color display.

  Then, a planarizing film OC made of, for example, a resin is formed so as to cover these color filters CF. The alignment film is not formed on the transparent substrate SUB2 side as in the case of the transparent substrate SUB1 side.

  A polarizing plate PL2 is formed on the surface of the transparent substrate SUB2 opposite to the liquid crystal LQ. Details of the polarizing plate PL2 will be described later.

  Further, the color filter CF is formed, for example, by containing a pigment in the resin layer, and configured to exhibit a predetermined color by the pigment. However, in this embodiment, for example, it may be configured to contain a dye instead of the pigment as necessary. This is because black display closer to achromatic color can be realized, and a large color tone difference between black display and white display can be suppressed. Here, the pigment is composed of particles having a diameter of several tens to several hundreds of nanometers, and the dye is grasped as a small molecule of about several nanometers even if the diameter is large.

  Each pixel PIX configured in this manner is configured as a so-called normally black mode in which black display is performed when an electric field is not generated between the pixel electrode PX and the counter electrode CT.

<Configuration of liquid crystal material>
As a material of the liquid crystal LQ, for example, a so-called isotropic liquid crystal that becomes optically isotropic when no voltage is applied is used.

  By using the isotropic liquid crystal in this way, it is possible to avoid the viewing angle dependency of the transmittance of the liquid crystal LQ, and when the black color is displayed when no voltage is applied, the thermal properties of the liquid crystal LQ are reduced. This is because light scattering due to fluctuations can be avoided and a decrease in contrast due to light leakage can be avoided.

Various materials can be selected as the isotropic liquid crystal. For example, a polymer-stable blue phase is known. The polymer-stabilized blue phase uses a non-liquid crystalline monomer represented by Chemical Formula 1 to Chemical Formula 3, a liquid crystalline monomer represented by Chemical Formula 4, a cross-linking agent represented by Chemical Formula 5, and a photopolymerization initiator represented by Chemical Formula 6, and these are converted into ultraviolet rays. A final isotropic liquid crystal material is obtained by (UV) irradiation and photocrosslinking.

<Polarizer>
As the polarizing plate PL1 and the polarizing plate PL2, a so-called E-type polarizer is used. Such a polarizing plate is called an E (Extraordinary) type because it transmits extraordinary light and absorbs ordinary light, and is generally called an O (Ordinary) type polarizing plate (transmits ordinary light). In contrast, abnormal light is absorbed).

  The polarizing plate PL1 and the polarizing plate PL2 made of such an E-type polarizer have a good viewing angle characteristic by themselves and can obtain an extremely wide viewing angle as compared with a polarizing plate made of an O-type polarizer. become able to.

  In the liquid crystal display device using the optically isotropic liquid crystal as described above, when such an E-type polarizer is used as the polarizing plates PL1 and PL2, the liquid crystal is displayed in the normal black display. Therefore, it is confirmed that an effect of obtaining a high contrast can be obtained.

  By the way, in other liquid crystal display devices using liquid crystals that are not optically isotropic, when this E-type polarizer is used as a polarizing plate, light leakage increases, and the contrast is greatly attenuated. Thus, the polarizing plate made of the E-type polarizer has not been used in conventional liquid crystal display devices.

  FIG. 1A is an enlarged view showing that the polarizing plate LP1 formed on the surface of the transparent substrate SUB1 opposite to the liquid crystal LQ is composed of an E-type polarizer, for example.

  In FIG. 1A, the polarizing plate LP1 is composed of a pigment PG that forms a chromonic liquid crystal phase and has a disk-like skeleton, for example. Here, the pigment PG having a disk-like skeleton has a structure in which aromatic rings are connected, and is made of, for example, perylene, naphthalene, or the like.

  The transmission axis PLA1 of the polarizing plate LP1 composed of the E-type polarizer configured as described above is shown in the direction shown in the drawing, and this direction is made to coincide with the coating direction A of the material performed when the polarizing plate LP1 is formed. It has become.

  That is, FIG. 1B shows, for example, that a dichroic dye lyotropic liquid crystal (water-soluble) is dropped on the transparent substrate SUB1 and the roller R is moved in the application direction A, whereby the dye PG is applied during the application. The self-alignment is caused by the shear stress, and the transmission axis PLA1 of the alignment plate LP1 formed thereby is formed to coincide with the coating direction A.

  And the polarizing plate PL1 which consists of such an E-type polarizer is grasped | ascertained as a thin film which consists of several supramolecular complex of the 1 type or several types of organic material uniformly oriented in order to polarize light.

  FIG. 7 is a diagram showing a configuration of a polarizing plate made of an O-type polarizer. In FIG. 7, the polarizing plate LP 'is formed by stretching polyvinyl alcohol PVA dyed with iodine IO in the B direction in the figure, and in this case, the transmission axis PLA' is in a direction perpendicular to the B direction. It can be confirmed that the polarizing plate LP ′ having such a configuration has poor viewing angle characteristics as compared with the polarizing plates LP1 and LP2 made of the E-type polarizer.

  In the above description, only the polarizing plate LP1 has been described, but the polarizing plate LP2 formed on the transparent substrate SUB2 side has the same configuration as the polarizing plate LP1. In this case, the polarizing plate LP1 formed on the transparent substrate SUB1 and the polarizing plate LP2 formed on the transparent substrate SUB2 have a relationship in which the directions of the transmission axes PLA1 and PLA2 are orthogonal to each other as shown in FIG. is there.

The polarizing plates PL1 and PL2 described above are each formed directly on one surface of the transparent substrates SUB1 and SUB2. However, the present invention is not limited to this. For example, an E-type polarizer is formed on one surface of a film made of polyethylene terephthalate (PET) or polyolefin through the above-described polarizer coating process, and the polarizing plate includes the film. May be used as the polarizing plates PL1 and PL2 described above. When forming on a film having birefringence such as a PET film, problems such as coloring due to the birefringence of the film can be avoided if the polarizing plane is disposed on the panel side and the film is disposed on the outside. When forming on the polyolefin film which does not have birefringence, you may arrange | position the film side to the panel side. In this case, when the polarizer to be applied to the film is water-soluble, the film surface is previously made hydrophilic by using, for example, a UV cleaner called a UV / O ₃ device, thereby applying the polarizer. Can be ensured, and the polarization performance can be improved.

  Similarly, an E-type polarizer is formed on one surface of a film made of triacetyl cellulose (TAC) through the above-described polarizer coating step, and the polarizing plate provided with the film is used as the polarizing plate PL1, described above. You may make it use as PL2. In this case, the film has a property of easily making the surface hydrophilic, and therefore, the reliability of the application of the polarizer can be secured and the polarization performance can be improved. When the polarizing plates PL1 and PL2 thus configured are attached to the transparent substrates SUB1 and SUB2, respectively, the film and the transparent substrates SUB1 and SUB2 are arranged with the film facing outside of the transparent substrates SUB1 and SUB2. By adopting an arrangement configuration in which the E-type polarizer is positioned between the films, the anisotropy of the film can be prevented from being affected.

  Further, when the polarizing plates PL1 and PL2 each having a polarizer applied to a film are attached to the transparent substrates SUB1 and SUB2, respectively, the films may be attached to the transparent substrates SUB1 and SUB2. In this case, you may make it comprise the said polarizing plates PL1 and PL2 by forming a protective film on the upper surface of the polarizer apply | coated to the film. The polarizers PL1 and PL2 thus configured can be made to have a robust configuration because the polarizer is protected from an external failure by the protective film. Similarly, protection from external obstacles can be achieved by arranging a protective plate forward without forming the protective film.

<Optical sheet OST>
FIG. 8A shows an example in which the optical sheet OST shown in FIG. 2 has a characteristic with a large radiation angle with respect to the incident angle, and the optical sheet OST is used as the backlight BL. And a diffusion plate DBD. Fig.8 (a) is a figure corresponded in the cross section in the VIII-VIII line of FIG.

  The optical sheet OST is formed by a collection of convex lenses LNS made up of a large number of hemispherical projections on the surface on the liquid crystal display panel PNL side, and a window WD through which light can be transmitted to the hem of the convex lens LNS on the back surface Is formed. The window WD can be configured, for example, by providing an opening in a light shielding film formed on the back surface of the optical sheet OST.

  The optical sheet OST configured as described above has the light emitted from the backlight BL side through the optical sheet OST when the direction of the arrow Q shown in FIG. As shown in the graph, the intensity increases at the emission angle in the direction from 0 ° to 45 ° (−45 °), and the emission angle in the direction from 45 ° (−45 °) to 90 ° (−90 °). It has the characteristic that the strength decreases at.

  This can greatly increase the radiation angle of light incident on the liquid crystal display panel PNL from the backlight BL side by interposing the optical sheet OST having the above-described configuration.

  As described above, the liquid crystal display device according to the present invention uses a so-called horizontal electric field type liquid crystal display panel PNL excellent in viewing angle characteristics, and is an E type having excellent viewing angle characteristics as the polarizing plates LP1 and LP2. Since a polarizing plate made of a polarizer is used, the radiation angle of light from a light source (a concept including a backlight BL, a diffusion plate DBD, and an optical sheet OST) is followed, in other words, to the liquid crystal display panel PNL. It is intended to increase the radiation angle of the incident light. The optical sheet described above is a sheet that controls the radiation angle of incident light to a specific angle, but may be configured to use a diffusion sheet that has radiation characteristics of incident light evenly in almost all directions. .

  The optical sheet OST of the above-described embodiment is configured by including a large number of lenses made of hemispherical protrusions. However, for example, the lens may be configured such that lenses made of kamaboko-shaped protrusions extending in the x direction or the y direction are arranged in parallel in a direction orthogonal to the longitudinal direction. This is because there may be a case where the viewing angle is widened only in the x direction or the y direction.

  FIG. 9 is a block diagram showing another embodiment of the liquid crystal display device described above, and corresponds to FIG.

  Compared to the configuration in FIG. 6, the polarizing plate PL1 is formed on the liquid crystal LQ side surface of the transparent substrate SUB1, and the polarizing plate PL2 is formed on the liquid crystal LQ side surface of the transparent substrate SUB2. Have

  The polarizing plates PL1 and PL2 made of E-type polarizers can be made much smaller in thickness than the polarizing plates made of O-type polarizers, and can easily be built in the liquid crystal display panel PNL. .

  Further, this makes it possible to avoid the damage caused by the external failure of the polarizing plates PL1 and PL2.

  In FIG. 9, the polarizing plate PL1 is formed as a layer formed on the liquid crystal side from the pixel electrode PX, for example. That is, the second protective film PSV2 covering the pixel electrode PX is also formed as a planarizing film, and the polarizing plate PL1 is formed on the upper surface of the second protective film PSV2. Then, for example, a surface film SFL1 is formed so as to cover this polarizing plate PL1. The surface film SFL1 has a periodic structure formed on the surface on the liquid crystal side, and the interaction at the interface with the liquid crystal LQ has a function of increasing the retention of the periodic structure of the isotropic liquid crystal and reducing the alignment defect. Yes. However, the configuration is not necessarily limited to this, and the pixel electrode PX may be formed on the transparent substrate SUB1 side with respect to the counter electrode CT.

  In FIG. 9, the polarizing plate PL2 is formed as a layer formed on the liquid crystal side from the color filter CF. That is, the polarizing plate PL2 is formed on the upper surface of the planarizing film OC that covers the color filter CF. A surface film SF2 having the same function as the surface film SFL1 is formed so as to cover the polarizing plate PL2. However, it is not necessarily limited to such a configuration as described above.

  Of course, the surface films SFL1 and SFL2 having the above-described functions are not only applicable to the configuration shown in FIG. 8, but can be applied to the configuration shown in FIG. 6, for example.

  The above-described liquid crystal display device is a so-called transmissive type as an example. However, it goes without saying that the present invention can also be applied to a so-called transflective or reflective type liquid crystal display device. In this case, the pixel electrode PX or the counter electrode CT may be made of a material other than the transparent conductive material according to the type. For example, in the case of a transflective liquid crystal display device, the pixel electrode PX is made of a material having good light reflection efficiency made of, for example, aluminum. In the case of a reflective liquid crystal display device, the counter electrode CT is made of, for example, aluminum. It seems to be made of a material having a good light reflection efficiency.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically.

It is a block diagram which shows one Example of the polarizing plate used for the liquid crystal display device by this invention. It is a schematic perspective view which shows one Example of the liquid crystal display device by this invention. It is a figure which shows the relationship of the transmission axis of each polarizing plate used for the liquid crystal display device by this invention. It is a figure which shows one Example of the equivalent circuit of the pixel of the liquid crystal display device by this invention. It is a figure which shows one Example of a structure of the pixel of the liquid crystal display device by this invention. It is sectional drawing in the VI-VI line of Fig.5 (a). It is the figure which showed the structure of the O-type polarizer. It is a figure which shows one Example of a structure of the optical sheet used for the liquid crystal display device by this invention. It is sectional drawing which shows the other Example of the liquid crystal display device by this invention.

Explanation of symbols

PNL: Liquid crystal display panel, SUB1, SUB2: Transparent substrate, V: Scanning signal driving circuit, He: Video signal driving circuit, SL: Sealing agent, AR: Liquid crystal display, OST: Optical sheet, DBD ... Diffusion plate, BL ... Backlight, CDR ... Cold cathode ray tube, RFB ... Reflection plate, PL1, PL2 ... Polarizing plate, PLA1, PL2 ... Transmission axis, GL ... Gate signal, CL ... Common signal line, DL ... Drain signal line, TFT ... Thin film transistor, AS ... Semiconductor layer, DT ... Drain electrode, ST ... Source electrode, CT ... Counter electrode, PX ... Pixel electrode, GI ... Insulation Film, PAS1, PAS2 ... Protective film, PIX ... Pixel, BM ... Black matrix, CF ... Color filter, OC ... Planeization film, LQ ... Liquid crystal, PG ... Dye, IO ... Yo , LES ...... convex lens, WD ...... window, SFL1, SFL2 ...... surface film.

Claims (15)

A first substrate, a second substrate,
A polarizing plate provided on the first substrate and the second substrate;
A liquid crystal layer disposed between the first substrate and the second substrate;
A first electrode provided on the first substrate and a second electrode for applying an electric field to the liquid crystal layer due to a potential difference generated between the first electrode, and
The liquid crystal layer has a property of causing optical anisotropy by applying voltage from an optically isotropic state,
The liquid crystal display device, wherein the polarizing plate is composed of an E-type polarizer.   The liquid crystal display device according to claim 1, wherein the polarizing plate is formed on a surface of the first substrate and the second substrate opposite to the liquid crystal layer.   The liquid crystal display device according to claim 2, wherein the polarizing plate is protected by a protective film or a protective plate.   The liquid crystal display device according to claim 2, wherein the polarizing plate is formed by applying an E-type polarizer on a film surface.   The liquid crystal display device according to claim 1, wherein the polarizing plate is formed on a surface of the first substrate and the second substrate on a liquid crystal layer side.   A planar electrode formed on the first substrate and an electrode group formed so as to overlap the electrode via an insulating film formed over the electrode, the first electrode and the second electrode; The liquid crystal display device according to claim 1, comprising:   A gate signal line, a thin film transistor that is turned on by a scanning signal from the gate signal line, and a video signal is supplied to one of the first electrode and the second electrode through the turned on thin film transistor 2. A drain signal line and a common signal line for supplying a reference signal serving as a reference for the video signal to the other one of the first electrode and the second electrode. A liquid crystal display device according to 1. A liquid crystal display panel, and a backlight disposed on the back surface of the liquid crystal display panel via an optical sheet,
The liquid crystal display panel includes a first substrate, a second substrate, a polarizing plate provided on the first substrate and the second substrate, and between the first substrate and the second substrate. And a second electrode for applying an electric field to the liquid crystal layer by a potential difference generated between the first electrode provided on the first substrate and the first electrode,
The liquid crystal layer has a property of causing optical anisotropy by applying voltage from an optically isotropic state, and the polarizing plate is composed of an E-type polarizer,
The liquid crystal display device, wherein the optical sheet is configured such that an emission angle of light emitted to the liquid crystal display panel is increased with respect to incident light from the backlight side.   The liquid crystal display device according to claim 8, wherein the polarizing plate is formed on a surface of the first substrate and the second substrate opposite to the liquid crystal layer.   The liquid crystal display device according to claim 9, wherein the polarizing plate is protected by a protective film or a protective plate.   The liquid crystal display device according to claim 9, wherein the polarizing plate is formed by applying an E-type polarizer on a film surface.   The liquid crystal display device according to claim 8, wherein the polarizing plate is formed on a surface on the liquid crystal layer side of the first substrate and the second substrate.   A planar electrode formed on the first substrate and an electrode group formed so as to overlap the electrode via an insulating film formed over the electrode, the first electrode and the second electrode; The liquid crystal display device according to claim 8, comprising:   A gate signal line, a thin film transistor that is turned on by a scanning signal from the gate signal line, and a video signal is supplied to one of the first electrode and the second electrode through the turned on thin film transistor 9. A drain signal line and a common signal line for supplying a reference signal serving as a reference for the video signal to the other electrode of the first electrode and the second electrode. A liquid crystal display device according to 1.   The optical sheet is formed by collecting convex lenses on a surface on the liquid crystal display panel side, and a window through which light can be transmitted is formed on the bottom surface of the convex lens. The liquid crystal display device according to claim 8.

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