JP2008122658A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which is thinner than the conventional one. <P>SOLUTION: The liquid crystal display device 50a includes an active matrix 30 and a counter substrate 20a arranged opposite to each other and a liquid crystal layer 25 disposed between the active matrix 30 and the counter substrate 20a, wherein a backlight unit 10a comprising: a light guide plate 3 for planarly emitting light from a light source 1 to the liquid crystal layer 25 side; and a selective reflection type polarizing layer 6 which has a plurality of metal lines 6b extending in parallel with one another on the liquid crystal layer 25 side of the light guide plate 3, reflects polarized light parallel to the direction where respective metal lines 6b are extended and, at the same time, transmits polarized light vertical to the direction where the respective metal lines 6b are extended is integrated on the counter substrate 20a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a thin liquid crystal display device.

  The liquid crystal display device includes, for example, a liquid crystal display panel having an active matrix substrate and a counter substrate which are arranged to face each other, and a liquid crystal layer provided between the two substrates. Further, since the liquid crystal display device is a non-luminous display device, it includes a backlight unit for supplying planar light to the liquid crystal display panel.

  FIG. 6 is a schematic cross-sectional view of a general backlight unit 110.

  As shown in FIG. 6, the backlight unit 110 is provided along an elongated light source 101 and a direction in which the light source 101 extends, and converts linear light from the light source 101 into uniform planar light. A transparent light guide plate 103, a reflective plate 102 for reusing light leaked from the light guide plate 103, and an upper surface side of the light guide plate 103. For example, Sumitomo 3M A brightness enhancement film 105 for improving the front brightness, such as BEF (Brightness Enhancement Film) manufactured by Co., Ltd., is provided on the upper surface side of the brightness enhancement film 105, and transmits only polarized light in one direction and the other directions. A selective reflection type polarizing plate 106 such as DBEF (Dual Brightness Enhancement Film) manufactured by Sumitomo 3M Co., Ltd. The selective reflection type polarizing plate 106 is provided on the upper surface side, and has a function of transmitting only polarized light in one direction and absorbing all polarized light in other directions. Provided on the upper surface side of the polarizing plate 107, and provided with a phase difference plate 108 for improving the viewing angle characteristics, and by adjusting the amount of transmitted light by the selective reflection polarizing plate 106 and the absorption polarizing plate 107, It is configured to display an image.

  For example, Patent Document 1 discloses a liquid crystal display in which a back surface side substrate of a liquid crystal display unit is a surface substrate of an EL (electroluminescence) backlight, and the liquid crystal display unit and the EL backlight are integrally laminated. ing. And according to this, it describes that it becomes thinner than the structure which laminates | stacks the liquid crystal display produced separately and the EL backlight conventionally.

Further, in Patent Document 2, a liquid crystal layer is disposed between a pair of transparent substrates, and a pixel electrode and a counter electrode are provided at least on the inner surfaces of both transparent substrates with the liquid crystal layer sandwiched between the observation side and the opposite side of the observation side. The polarizing means is disposed on the transparent substrate, and the illumination light is incident from the opposite side of the observation side via the one polarizing means, and the one polarizing means is configured as a transparent substrate on the illumination light incident side, on the transparent substrate. Discloses a liquid crystal display device using a wire grid polarizer made of a metal and having a linear grid-like conductive line layer arranged in parallel at a constant period. And according to this, in a liquid crystal display device using a wire grid polarizer, it is described that the use efficiency of illumination light can be further increased, the thickness can be further reduced, and electromagnetic wave noise can be effectively prevented. ing.
JP-A-6-186561 JP 2006-47829 A

  In recent years, liquid crystal display devices having the feature of being thin have been widely used, and the thickness reduction is still in progress. However, in the conventional liquid crystal display device, as shown in FIG. 6, the backlight unit is composed of many optical members (light source 101 to phase difference plate 108), which inevitably increases the housing. End up.

  For example, as a means for reducing the thickness of the liquid crystal display device, it is conceivable to arrange the backlight unit on the counter substrate side and to integrate the backlight unit with the counter substrate. In this case, there is a method in which an optical member such as a polarizing plate is continuously formed on the inner side of the counter substrate, but a general absorption polarizing plate contains iodine with high sublimation properties and has high heat resistance. Low. Moreover, since the conventional selective reflection type polarizing plate also has low heat resistance, there is a concern that it cannot withstand the processing temperature in the manufacturing process and cannot be continuously formed.

  The present invention has been made in view of this point, and an object of the present invention is to realize a liquid crystal display device that is thinner than the conventional one.

  In order to achieve the above object, the present invention provides a backlight including a light guide plate and a selective reflection type polarizing layer having a plurality of metal lines extending in parallel with each other on one of a pair of substrates constituting a liquid crystal display device. The unit is integrated.

  Specifically, a liquid crystal display device according to the present invention is a liquid crystal display device including a pair of substrates disposed opposite to each other, and a liquid crystal layer provided between the pair of substrates. One of the substrates has a light guide plate for emitting light from the light source in a planar manner toward the liquid crystal layer side, and a plurality of metal wires extending in parallel to each other on the liquid crystal layer side of the light guide plate, A backlight unit including a selective reflection type polarizing layer that reflects polarized light parallel to the extending direction of the metal lines and transmits polarized light orthogonal to the extending direction of the metal lines is integrated. To do.

  According to the above configuration, the selective reflection polarizing layer is configured to reflect polarized light parallel to the extending direction of each metal line and to transmit polarized light orthogonal to the extending direction of each metal line. Here, since each metal wire constituting the selective reflection type polarization layer generally has heat resistance, the selective reflection type polarization layer is, for example, a conventional selective reflection type in which a plurality of resin films are laminated. It has higher heat resistance than a polarizing plate (such as DBEF) and can withstand the processing temperature in the manufacturing process. And since the backlight unit including the selective reflection type polarizing layer with high heat resistance and the light guide plate to which the light from the light source is supplied is integrated with one of the pair of substrates constituting the liquid crystal display device. Thus, a liquid crystal display device thinner than the conventional one is realized.

  The backlight unit has a polarization axis formed by orienting a dichroic organic dye in a direction orthogonal to the extending direction of the metal lines, and transmits polarized light parallel to the polarization axis. An absorption-type polarizing layer that absorbs at least a part of polarized light orthogonal to the liquid crystal layer side of the selective reflection type polarizing layer may be provided.

  According to the above configuration, the absorption polarizing layer having a polarization axis formed by orienting the dichroic organic dye has higher heat resistance than the conventional iodine-based polarizing plate. It becomes possible to endure. In addition, since the absorptive polarizing layer is provided on the liquid crystal layer side of the selective reflection polarizing layer, when external light is incident from the liquid crystal layer side, at least one of the polarized lights orthogonal to the polarizing axis of the absorptive polarizing layer. The portion is absorbed by the absorptive polarizing layer, and the remainder of the polarized light passes through the absorptive polarizing layer and then is reflected by the selective reflection polarizing layer and absorbed by the absorptive polarizing layer. For this reason, almost all of the polarized light orthogonal to the polarization axis of the absorbing polarizing layer is absorbed by the absorbing polarizing layer, thereby improving the display contrast. On the other hand, when a wire grid corresponding to each metal wire is used as a polarizing plate as in Patent Document 2, the wire grid functions as a selective reflection type polarizing plate. The light is reflected and the display contrast is lowered.

  The backlight unit includes a plurality of prisms extending in parallel with each other between the light guide plate and the selective reflection type polarizing layer, each having a triangular cross section and having a bottom surface disposed on the light guide plate side. Silica airgel having a refractive index of 1.0 to 1.1 and having a porous skeleton of silica between the light guide plate and each prism, and between the selective reflection type polarizing layer and each prism. May be provided respectively.

  According to the above configuration, since the backlight units extend in parallel with each other and each has a triangular cross section and a plurality of prisms whose bottom surfaces are arranged on the light guide plate side, the backlight units emit light from the light guide plate. A part of the light (for example, S wave: orthogonal polarization) is reflected on the bottom surface of each prism and then recycled back to the light guide plate, and is emitted from the light guide plate and incident through the bottom surface of each prism. The front light in the liquid crystal display device is improved by condensing the light (for example, P wave: parallel polarization) toward the front surface of the liquid crystal display device by a lens formed by a triangular prism.

  Moreover, since the refractive index (1.0-1.1) of the silica airgel provided between the light guide plate and each prism and between the selective reflection type polarizing layer and each prism is close to the refractive index of air, Each prism is formed between the light guide plate and the selective reflection type polarizing layer without reducing the light efficiency.

  The light guide plate may be made of plastic.

  According to the above configuration, since the light guide plate is made of plastic having flexibility, one of a pair of substrates constituting the liquid crystal display device is manufactured by the roll-to-roll method using the light guide plate as a base substrate. It becomes possible.

  The selective reflection type polarizing layer may include a glass substrate and the plurality of metal wires provided on the glass substrate.

  According to said structure, it becomes possible to produce one of a pair of board | substrates which comprises a liquid crystal display device by using the glass substrate which comprises a selective reflection type polarizing layer as a base substrate.

  A common electrode for applying a voltage to the liquid crystal layer is provided on one of the pair of substrates, and a plurality of pixel electrodes for applying a voltage to the liquid crystal layer are provided on the other of the pair of substrates. It may be provided in a shape.

  According to said structure, the effect of this invention is specifically show | played in the liquid crystal display device of an active matrix drive system.

  The light guide plate may be made of plastic, and the other of the pair of substrates may include a color filter layer in which a plurality of colored layers are disposed so as to overlap the pixel electrodes.

  According to the above configuration, since the light guide plate is made of plastic, one of the pair of substrates constituting the liquid crystal display device may be slightly expanded by heating during the manufacturing process, but is disposed so as to overlap each pixel electrode. Since the color filter layer having each colored layer to be formed is provided on the other substrate of the pair of substrates constituting the liquid crystal display device, it is easy to align the pair of substrates constituting the liquid crystal display device become.

  According to the present invention, a backlight unit including a light guide plate and a selective reflection type polarizing layer having a plurality of metal lines extending in parallel with each other is integrated on one of a pair of substrates constituting a liquid crystal display device. Therefore, a liquid crystal display device thinner than the conventional one can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments.

Embodiment 1 of the Invention
1 to 4 show Embodiment 1 according to the present invention. Specifically, FIG. 1 is a schematic cross-sectional view of the liquid crystal display device 50a of the present embodiment, and FIG. 2 is a perspective view of the selective reflection type polarizing layer 6 constituting the liquid crystal display device 50a.

  As shown in FIG. 1, the liquid crystal display device 50a includes a counter substrate 20a, an active matrix substrate 30 disposed to face the counter substrate 20a, and a liquid crystal layer provided between the counter substrate 20a and the active matrix substrate 30. 25.

  The counter substrate 20a is one of a pair of substrates. As shown in FIG. 1, the backlight unit 10a integrated with the substrate, the common electrode 9 provided on the liquid crystal layer 25 side of the backlight unit 10a, It has.

  As shown in FIG. 1, the backlight unit 10 a includes an elongated light source 1, a transparent light guide plate 3 provided along the direction in which the light source 1 extends, and a reflector 2 provided on the lower surface side of the light guide plate 3. The plurality of prisms 5 provided on the upper surface side of the light guide plate 3 and sandwiched between the silica airgels 4a and 4b, the selective reflection type polarizing layer 6 provided on the upper surface side of the silica airgel 4b, and the selective reflection type polarizing layer 6 The absorptive polarizing layer 7 provided on the upper surface side of the first polarizing plate and the retardation layer 8 provided on the upper surface side of the absorbing polarizing layer 7 are provided.

  The light source 1 is composed of, for example, a cold cathode fluorescent tube or a hot cathode fluorescent tube. Here, the light source 1 is accommodated in a half-cylindrical reflector (reflecting plate: not shown) opened on the light guide plate 3 side. The light source 1 may be an LED (Light Emitting Diode) or the like.

  The reflection plate 2 includes, for example, a metal plate such as a stainless plate and a reflection sheet such as a white PET (Polyethylene Terephthalate) film attached to the surface of the metal plate, and reflects light leaked downward from the light guide plate 3. It is for reuse.

  The light guide plate 3 is made of plastic such as acrylic resin, and its lower surface is formed in a step shape. The light guide plate 3 is configured to emit linear light incident on the side surface from the light source 1 in a uniform plane shape from the upper surface to the liquid crystal layer 25 side.

  Each prism 5 extends in parallel with each other, has a triangular cross section, and has a bottom surface disposed on the light guide plate 3 side, for improving the front luminance of the liquid crystal display device 50a. BEF (Brightness Enhancement Film) or prism sheet manufactured by Sumitomo 3M Limited is preferably used.

  The silica airgels 4a and 4b have a refractive index of 1.0 to 1.1 and are constituted by a porous skeleton of silica.

  As shown in FIG. 2, the selective reflection type polarizing layer 6 includes a glass substrate 6a and a plurality of metal wires 6b provided on the glass substrate 6a so as to extend in parallel with each other. As shown in FIG. 3, the selective reflection type polarizing layer 6 transmits polarized light L1 (polarization direction P1) in a direction orthogonal to the extending direction of each metal line 6b and is parallel to the extending direction of each metal line 6b. It is configured to reflect the polarized light L2 (polarization direction P2).

  As shown in FIG. 4, the absorptive polarizing layer 7 has a polarization axis Pa formed by orienting an organic dye having dichroism in a direction orthogonal to the extending direction of each metal line 6b of the selective reflection polarizing layer 6. And transmits the polarized light L1 parallel to the polarization axis Pa (polarization direction P1), and absorbs at least a part of the polarization L2 (polarization direction P2) orthogonal to the polarization axis Pa.

  The retardation layer 8 is an optical element for correcting birefringence of light in the liquid crystal layer 25.

  The active matrix substrate 30 is one of a pair of substrates. As shown in FIG. 1, the glass substrate 11 and a plurality of gate lines (not shown) provided on the glass substrate 11 so as to extend in parallel to each other, A plurality of source lines (not shown) provided so as to extend in parallel to each other in a direction orthogonal to each gate line, and thin film transistors (hereinafter referred to as “TFT”) provided at each gate line and each intersection of the source lines. 13) and a pixel electrode 15 provided corresponding to each TFT 13 in a region surrounded by a pair of adjacent gate lines and a pair of source lines. Here, in the active matrix substrate 30, pixels that are the minimum unit of an image are configured by the pixel electrodes 15, and a display region is configured by arranging these pixels in a matrix.

  In the active matrix substrate 30, a plurality of colored layers (red layer 12R, green layer 12G, and blue layer 12B) are disposed so as to overlap each pixel electrode 15, and a color filter is formed by the colored layers 12R, 12G, and 12B. Layer 12 is constructed. Further, in the active matrix substrate 30, the black matrix 14 is provided between the colored layers 12R, 12G, and 12B and so as to cover the TFTs 13.

  The TFT 13 includes a gate electrode (not shown), a gate insulating film (not shown) provided so as to cover the gate electrode, and a semiconductor layer (island) provided on the gate insulating film at a position corresponding to the gate electrode. (Not shown) and a source electrode and a drain electrode provided to face each other on the semiconductor layer. Here, the gate electrode is a portion protruding to the side of the gate line, and the source electrode is a portion protruding to the side of the source line. The drain electrode is connected to the pixel electrode 15 through a contact hole formed in the color filter layer 12.

  The active matrix substrate 30 has a retardation plate 16 and a polarizing plate 17 laminated on the surface opposite to the surface on which the TFTs 13 and the like are formed. Here, the retardation film 16 is an optical element for correcting the birefringence of light in the liquid crystal layer 25, and the polarizing plate 17 is an iodine-based absorption polarizing plate.

  The liquid crystal layer 25 is made of a nematic liquid crystal material having electro-optical characteristics.

  In the liquid crystal display device 50a configured as described above, in each pixel, when the gate signal is sent from the gate line and the TFT 13 is turned on, the source signal is sent from the source line and passes through the source electrode and the drain electrode of the TFT 13. Thus, a predetermined charge is written in the pixel electrode 15, and a potential difference is generated between the pixel electrode 15 and the common electrode 9, and a predetermined voltage is applied to the liquid crystal capacitor formed of the liquid crystal layer 25. Yes. In the liquid crystal display device 50a, an image is displayed by adjusting the transmittance of light incident from the backlight unit 10a by utilizing the change in the alignment state of the liquid crystal molecules according to the magnitude of the applied voltage. Is done.

  Next, a method for manufacturing the liquid crystal display device 50a of the present embodiment will be described with reference to FIG.

  First, a metal film made of aluminum (Al), silver (Ag), platinum (Pt), palladium (Pd), or the like is formed on the entire substrate on the glass substrate 6a by a sputtering method, and then a pattern is formed by photolithography. Thus, a plurality of metal wires 6b are formed. Here, the plurality of metal lines 6b have, for example, a line width of 100 μm and an interval of 100 μm.

  Subsequently, a polyimide resin film is formed by a silk printing method so as to cover each metal line 6b on the entire substrate on which each metal line 6b is formed, and then a rubbing process is performed on the surface of the resin film.

  Furthermore, an aqueous solution in which a dichroic azo dye for an anisotropic dye film (for example, a tetrakisazo dye) is dissolved as a dichroic organic dye on the entire surface of the rubbed resin film is bar-coater After applying with a coating apparatus such as the above, the absorbing polarizing layer 7 is formed by drying at room temperature.

  Subsequently, the retardation layer 8 is formed by applying or dropping a polymerizable liquid crystal containing an optically active component exhibiting optical rotation on the entire substrate on which the absorption polarizing layer 7 is formed. As the polymerizable liquid crystal, for example, a material reported in Proc. International Display Research Conference, 1994, PP.161-164 (H. Hasebe et al.) Can be used. If necessary, an alignment film may be rubbed on one side of the retardation layer.

  Further, the common electrode 9 is formed by forming an ITO (Indium Tin Oxide) film on the entire substrate on which the retardation layer 8 is formed by sputtering. Thereafter, a polyimide resin is applied to the entire substrate on which the common electrode 9 is formed by spin coating or the like, and then a rubbing process is performed to form an alignment film.

  As described above, the counter substrate forming portion (selective reflection type polarizing layer 6 to common electrode 9) is manufactured.

  Further, a metal film made of titanium or the like is formed on the entire substrate on the glass substrate 11 by a sputtering method, and then a pattern is formed by photolithography to form a gate line and a gate electrode, respectively.

  Subsequently, a gate insulating film is formed by depositing a silicon nitride film or the like by a CVD (Chemical Vapor Deposition) method on the entire substrate on which the gate line and the gate electrode are formed.

  Further, an intrinsic amorphous silicon film and an n + amorphous silicon film doped with phosphorus are continuously formed by CVD on the entire substrate on which the gate insulating film is formed, and then island-shaped on the gate electrode by photolithography. Then, an intrinsic amorphous silicon layer and an n + amorphous silicon layer are formed.

  Then, a metal film made of titanium or the like is formed by sputtering on the entire substrate on the gate insulating film on which the intrinsic amorphous silicon layer and the n + amorphous silicon layer are formed, and then patterned by photolithography to form the source line A source electrode and a drain electrode are formed respectively.

  Subsequently, the n + amorphous silicon layer is removed by etching using the source electrode and the drain electrode as a mask, thereby forming a channel portion. Thereby, a semiconductor layer composed of an intrinsic amorphous silicon layer and an n + amorphous silicon layer is formed, and the TFT 13 is formed.

  Thereafter, a protective insulating film (not shown) is formed by depositing a silicon nitride film or the like on the entire substrate on which the TFT 13 is formed by using a CVD method.

  Further, a black colored photoresist is formed on the entire substrate on which the protective insulating film is formed, and then a pattern is formed by photolithography to form the black matrix 14.

  Subsequently, a red colored photoresist is applied to the entire substrate on which the black matrix 14 is formed, and then a pattern is formed by photolithography to form a red layer 12R.

  And after apply | coating the photoresist colored green on the whole board | substrate with which red layer 12R was formed, pattern formation is carried out by photolithography, and green layer 12G is formed.

  Further, a blue colored photoresist is applied to the entire substrate on which the green layer 12G is formed, and then a pattern is formed by photolithography to form the blue layer 12B.

  When forming the red layer 12R, the green layer 12G, and the blue layer 12B, a contact hole is simultaneously formed on the drain electrode of the TFT 13.

  Then, an ITO film is formed on the entire substrate on which the red layer 12R, the green layer 12G, and the blue layer 12B are formed by sputtering, and then a pattern is formed by photolithography to form the pixel electrode 15.

  Subsequently, after a polyimide resin is applied to the entire substrate on which the pixel electrodes 15 are formed by a spin coating method or the like, a rubbing process is performed to form an alignment film.

  Further, a retardation plate 16 and a polarizing plate 17 are attached to the surface of the glass substrate 11 opposite to the surface on which the TFTs 13 and the like are formed.

  As described above, the active matrix substrate 30 is manufactured.

  Subsequently, for example, a seal material made of a thermosetting epoxy resin or the like is applied to the active matrix substrate 30 by screen printing on a frame-like pattern lacking a liquid crystal injection port so as to surround the display region, thereby forming the seal pattern. After the formation, spherical spacers are dispersed inside the seal pattern.

  Then, the seal pattern is cured by heating after bonding the active matrix substrate 30 on which the spacers are dispersed and the manufactured counter substrate forming portion (selective reflection type polarizing layer 6 to common electrode 9). An empty liquid crystal display pre-panel is produced.

  Further, after injecting a liquid crystal material into an empty liquid crystal display prepanel by a decompression method, a UV curable resin is applied to the liquid crystal injection port, and the liquid crystal material is sealed by UV irradiation. Thereby, the liquid crystal layer 25 is formed, and a liquid crystal display pre-panel is manufactured.

  Subsequently, silica airgel is coated on the glass substrate 6a of the manufactured liquid crystal display prepanel to form a silica airgel layer 4b.

  Furthermore, after each prism 5 is affixed on the silica airgel layer 4b and silica aerogel is coated on each of the affixed prisms 5 to form a silica aerogel layer 4a, the silica aerogel layer 4a thus formed is formed. The light guide plate 3 is pasted on top, and the reflection plate 2 and the light source 1 are attached.

  As described above, the liquid crystal display device 50a of this embodiment can be manufactured. In the above-described manufacturing method of the liquid crystal display device 50a, the method of manufacturing the counter substrate 20a in two stages is exemplified. However, the present invention includes attaching the active matrix substrate 30 after manufacturing the counter substrate 20a as a whole. Thus, the liquid crystal display device 50a may be manufactured.

  As described above, according to the liquid crystal display device 50a of the present embodiment, the selective reflection polarizing layer 6 reflects polarized light parallel to the extending direction of each metal line 6b and is orthogonal to the extending direction of each metal line 6b. Is configured to transmit polarized light. Here, since each metal wire 6b constituting the selective reflection type polarizing layer 6 generally has heat resistance, the selective reflection type polarizing layer 6 is, for example, a conventional one in which a plurality of resin films are laminated. It has higher heat resistance than a selective reflection type polarizing plate (DBEF or the like) and can withstand the processing temperature in the manufacturing process. And the backlight unit 10a provided with the selective reflection type polarizing layer 6 with the high heat resistance and the light guide plate 3 to which the light from the light source 1 is supplied is one of a pair of substrates constituting the liquid crystal display device 50a ( Since it is integrated with the counter substrate 20a), a thinner liquid crystal display device than the conventional one can be realized.

  Further, according to the liquid crystal display device 50a of the present embodiment, the absorptive polarizing layer 7 having the polarization axis Pa formed by aligning the dichroic organic dye is more heat resistant than the conventional iodine-based polarizing plate. Can withstand the processing temperature in the manufacturing process. Further, since the absorption-type polarizing layer 7 is provided on the liquid crystal layer 25 side of the selective reflection-type polarizing layer 6, when external light enters from the liquid crystal layer 25 side, the absorption-type polarizing layer 7 is incident on the polarization axis Pa of the absorption-type polarizing layer 7. At least a part of the orthogonally polarized light is absorbed by the absorptive polarizing layer 7, and the remainder of the polarized light is transmitted through the absorptive polarizing layer 7 and then reflected by the selective reflection polarizing layer 6 and absorbed by the absorptive polarizing layer 7. It will be. Therefore, almost all of the polarized light orthogonal to the polarization axis Pa of the absorption-type polarizing layer 7 is absorbed by the absorption-type polarizing layer 7, so that the display contrast can be improved. On the other hand, when the wire grid corresponding to each metal wire 6b is used as a polarizing plate as in Patent Document 2, the wire grid functions as a selective reflection type polarizing plate, and thus did not pass through the wire grid. External contrast is reflected and display contrast is reduced.

  The reason why the display contrast is improved will be described below with an example.

Here, the polarizing plate 17 has, for example, a light transmittance a ₁ parallel to the polarization axis of 90% and a light transmittance b ₁ perpendicular to the polarization axis of 0.01%. Further, the absorption-type polarizing layer 7 has, for example, a light transmittance a ₂ parallel to the polarization axis of 90% and a light transmittance b ₂ orthogonal to the polarization axis of 0.09%. Further, the selective reflection type polarizing layer 6 has, for example, a light transmittance a ₃ parallel to the polarization axis of 90% and a light transmittance b ₃ orthogonal to the polarization axis of 0.2%.

And when the absorption-type polarizing layer 7 and the polarizing plate 17 are overlapped, the transmittance ratio between when arranged in parallel Nicols and when arranged in crossed Nicols is a ₁ a ₂ + b ₁ b ₂ : a ₁ b ₂ + a ₂ b ₁ and the contrast is about 900.

Moreover, when the selective reflection type polarizing layer 6, the absorption type polarizing layer 7 and the polarizing plate 17 are stacked as in the present embodiment, the transmittance ratio between when arranged in parallel Nicols and when arranged in crossed Nicols. _{There, a 1 a 2 a 3 +} b 1 b 2 b 3: a 2 a 3 b 1 + a 1 b 2 b 3 , and the contrast is about 8800.

  Furthermore, according to the liquid crystal display device 50a of the present embodiment, the backlight unit 10a extends in parallel between the light guide plate 3 and the selective reflection type polarizing layer 6, each having a triangular cross section, Since the bottom surface is provided with the plurality of prisms 5 arranged on the light guide plate 3 side, a part of the light emitted from the light guide plate 3 (for example, S wave: orthogonal polarization) is reflected on the bottom surface of each prism 5. After that, the light is returned to the light guide plate 3 and recycled, and light (for example, P wave: parallel polarization) emitted from the light guide plate 3 and incident through the bottom surface of each prism 5 is formed by the triangular prism 5. By focusing the light toward the front surface (upper side in FIG. 1) of the liquid crystal display device 50a, the front luminance in the liquid crystal display device 50a can be improved.

  Further, the refractive indexes (1.0 to 1.1) of silica airgels 4a and 4b provided between the light guide plate 3 and each prism 5, and between the selective reflection type polarizing layer 6 and each prism 5, respectively, are air. Therefore, each prism 5 can be formed between the light guide plate 3 and the selective reflection type polarizing layer 6 without reducing the light efficiency.

<< Embodiment 2 of the Invention >>
FIG. 5 is a schematic cross-sectional view showing the liquid crystal display device 50b according to the present embodiment. In addition, in the following embodiment, the same code | symbol is attached | subjected about the same part as FIGS. 1-4, and the detailed description is abbreviate | omitted.

  In the first embodiment, the counter substrate 20a is formed by laminating various optical members (1 to 5 and 6 to 9) on the upper and lower surfaces of the glass substrate 6a constituting the selective reflection polarizing layer 6 as a base substrate. Although manufactured, in the liquid crystal display device 50b of the present embodiment, the counter substrate 20b is manufactured using the light guide plate 3 as a base substrate.

  Hereinafter, a method for manufacturing the counter substrate 20b will be specifically described. In addition, about the structure of the opposing board | substrate 20b, since the glass substrate 6a in the selective reflection type polarizing layer 6 of the said Embodiment 1 is abbreviate | omitted, the detailed description is abbreviate | omitted.

  First, silica airgel is coated on the upper surface of the light guide plate 3 (surface not formed in steps) to form a silica airgel layer 4a. The light guide plate 3 as the base substrate may be formed by an imprint technique in which a gel material is pressed into a mold. According to this, the manufacturing method by a roll-to-roll system becomes more effective.

  Subsequently, each prism 5 is pasted on the silica airgel layer 4a, and silica airgel is coated on each of the pasted prisms 5 to form a silica airgel layer 4b.

  Further, a metal film made of aluminum (Al), silver (Ag), platinum (Pt), palladium (Pd), or the like is formed on the entire substrate on which the silica airgel layer 4b is formed by sputtering, and then photolithography is performed. A plurality of metal lines 6b are formed by pattern formation.

  Then, after a polyimide resin film is formed by a silk printing method so as to cover each metal line 6b on the entire substrate on which each metal line 6b is formed, a rubbing process is performed on the surface of the resin film.

  Subsequently, an aqueous solution in which a dichroic azo dye for an anisotropic dye film (for example, a tetrakisazo dye) is dissolved as a dichroic organic dye is applied to the entire surface of the rubbed resin film. After applying with a coating device such as a coater, the absorption polarizing layer 7 is formed by drying at room temperature.

  Furthermore, the retardation layer 8 is formed by applying or dropping a polymerizable liquid crystal containing an optically active component exhibiting optical rotation on the entire substrate on which the absorption-type polarizing layer 7 is formed.

  The common electrode 9 is formed by forming an ITO (Indium Tin Oxide) film on the entire substrate on which the retardation layer 8 is formed by sputtering. Thereafter, a polyimide resin is applied to the entire substrate on which the common electrode 9 is formed by spin coating or the like, and then a rubbing process is performed to form an alignment film.

  Subsequently, the counter substrate forming portion (the light guide plate 3 to the common electrode 9) on which the alignment film is formed is bonded to the active matrix substrate 30 manufactured by the method described in the first embodiment, and a liquid crystal material is injected. After that, the reflector 2 and the light source 1 are attached.

  As described above, the counter substrate 20b and the liquid crystal display device 50b of this embodiment can be manufactured.

  As described above, according to the liquid crystal display device 50b of this embodiment, since the light guide plate 3 that is the base substrate is made of plastic, one of the pair of substrates (the counter substrate 20b) is slightly heated by heating during the manufacturing process. Although there is a risk of expansion, the color filter layer 12 having the colored layers 12R, 12G, and 12R to be disposed so as to overlap the pixel electrodes 15 is the other of the pair of substrates (active matrix substrate) constituting the liquid crystal display device 50b. 30), the counter substrate 20b, that is, the counter substrate forming portion (the light guide plate 3 to the common electrode 9) and the active matrix substrate 30 can be easily aligned.

  Further, according to the liquid crystal display device 50b of the present embodiment, since the light guide plate 3 is made of flexible plastic, the liquid crystal display device 50b is formed in a roll-to-roll manner using the light guide plate 3 as a base substrate. One of the pair of substrates constituting (the counter substrate 20b) can be manufactured.

  In each of the above embodiments, the active matrix drive type liquid crystal display devices 50a and 50b are exemplified, but the present invention can also be applied to a passive matrix drive type liquid crystal display device.

  As described above, the present invention is useful for a thin liquid crystal display device because the backlight unit is integrated with the counter substrate.

3 is a schematic cross-sectional view showing a liquid crystal display device 50a according to Embodiment 1. FIG. It is a perspective view which shows the selective reflection type polarizing layer 6 which comprises the liquid crystal display device 50a. FIG. 5 is a schematic diagram showing the behavior of external light in the selective reflection type polarizing layer 6. It is the schematic diagram which showed the behavior of the external light when the selective reflection type polarizing layer 6 and the absorption type polarizing layer 7 are laminated | stacked. 6 is a schematic cross-sectional view showing a liquid crystal display device 50b according to Embodiment 2. FIG. 2 is a schematic cross-sectional view of a general backlight unit 110. FIG.

Explanation of symbols

Pa Polarization axis 1 Light source 3 Light guide plates 4a, 4b Silica airgel 5 Prism 6 Selective reflection type polarizing layer 6a Glass substrate 6b Metal line 7 Absorption type polarizing layer 9 Common electrodes 10a, 10b Backlight units 12R, 12G, 12B Colored layer 12 Color Filter layer 15 Pixel electrodes 20a and 20b Counter substrate (one of a pair of substrates)
25 Liquid crystal layer 30 Active matrix substrate (the other of a pair of substrates)
50a, 50b liquid crystal display device

Claims (7)

A pair of substrates disposed opposite each other;
A liquid crystal display device comprising a liquid crystal layer provided between the pair of substrates,
One of the pair of substrates has a light guide plate for emitting light from a light source in a planar shape toward the liquid crystal layer, and a plurality of metal wires extending in parallel to each other on the liquid crystal layer side of the light guide plate. And a backlight unit including a selective reflection type polarizing layer that reflects polarized light parallel to the extending direction of each metal line and transmits polarized light orthogonal to the extending direction of each metal line. A liquid crystal display device. The liquid crystal display device according to claim 1,
The backlight unit has a polarization axis formed by orienting a dichroic organic dye in a direction orthogonal to the extending direction of the metal lines, and transmits polarized light parallel to the polarization axis. A liquid crystal display device comprising an absorption polarizing layer that absorbs at least a part of polarized light orthogonal to the liquid crystal layer side of the selective reflection polarizing layer. The liquid crystal display device according to claim 1,
The backlight unit includes a plurality of prisms extending in parallel with each other between the light guide plate and the selective reflection type polarizing layer, each having a triangular cross section and having a bottom surface disposed on the light guide plate side. ,
Between the light guide plate and each prism, and between the selective reflection type polarizing layer and each prism, there is a silica airgel having a refractive index of 1.0 to 1.1 and composed of a porous skeleton of silica. A liquid crystal display device characterized by being provided respectively. The liquid crystal display device according to claim 1,
The liquid crystal display device, wherein the light guide plate is made of plastic. The liquid crystal display device according to claim 1,
The selective reflection type polarizing layer comprises a glass substrate and the plurality of metal wires provided on the glass substrate. The liquid crystal display device according to claim 1,
One of the pair of substrates is provided with a common electrode for applying a voltage to the liquid crystal layer,
A liquid crystal display device, wherein a plurality of pixel electrodes for applying a voltage to the liquid crystal layer are provided in a matrix on the other of the pair of substrates. The liquid crystal display device according to claim 6,
The light guide plate is made of plastic,
The other of the pair of substrates includes a color filter layer in which a plurality of colored layers are provided so as to overlap the pixel electrodes.

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