JP2004258372A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of performing an optimum contrast display from viewing angles in lower and both right and left directions and obtaining a satisfactory visibility. <P>SOLUTION: In each first and second liquid crystal panel, a TN liquid crystal is interposed between a pair of transparent substrates and the TN liquid crystal has 1.5 to 3.0 μm layer thickness d and 300 to 600 nm phase difference value Δnd. The crossing angle of alignment axes of visual confirmation side alignment layers of respective the first and the second liquid crystal panels is specified to be 10° or less, two polarizing plates sandwiching either one of the first or the second liquid crystal panel are specified to be a pair of wide visual field angle polarizing plates, the crossing angle of the polarization axis of the respective wide visual field angle polarizing plates and the alignment axis of the alignment layer on the wide visual field angle polarizing plate disposed side of the one liquid crystal panel is specified to be nearly 90°, and the crossing angle of the polarization axis of the other one polarizing plate and the alignment axis of the alignment layer on the polarizing plate disposed side of the other liquid crystal panel is specified to be 10° or less. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device used for a display using a liquid crystal, and more particularly to a wide field angle liquid crystal display device using a TN (Twisted Nematic) type liquid crystal and a good contrast. The present invention relates to a liquid crystal display device capable of indicating the following.
[0002]
[Prior art]
2. Description of the Related Art In recent years, as a liquid crystal display device capable of high-definition color display, for example, a color liquid crystal display device (hereinafter, referred to as an FS liquid crystal display device) using a field sequential system as disclosed in Patent Document 1 has been widely used. I have.
[0003]
This FS liquid crystal display device has a pair of transparent substrates arranged substantially in parallel at an interval, a pair of transparent electrodes formed on opposing surfaces of each transparent substrate, and a pair of alignments respectively formed on each transparent electrode. A liquid crystal display panel composed of a sealing material for joining and sealing the periphery thereof while maintaining the film and each transparent substrate at a predetermined interval, and a liquid crystal sealed in the sealing space, and sandwiches the liquid crystal display panel. The backlight unit includes a pair of polarizing plates and a backlight unit that selectively emits a plurality of unit colors, for example, three colors of red, green, and blue light source colors.
[0004]
The principle of the color display using the field sequential method is that an optical shutter for selectively opening a specific field so as to be capable of transmitting light in synchronization with light emission of each color of the backlight unit that irradiates the liquid crystal display panel from the back side thereof. In addition, by switching the light emission of the three colors of the backlight unit at a high speed, the display patterns of the three colors are continuously displayed at a high speed in a time-division manner to perform a desired color display. Things. The operation of the liquid crystal display panel as an optical shutter will be described in more detail. A voltage is selectively applied to the transparent electrodes formed on the pair of transparent substrates constituting one pixel of each specific field for performing color display. This changes the molecular arrangement of the liquid crystal in the specific field and acts to change the light transmittance only in the specific field.
[0005]
For example, when one pixel in a certain field is to be displayed in red, light is transmitted when the red backlight unit is turned on and emits light, and light is shielded when the other green and blue backlight units are turned on and emit light. I do.
[0006]
In general, a liquid crystal display device is required to have characteristics such as high-speed response, high contrast, high definition display, and a wide viewing angle. In the FS liquid crystal display device that performs color display as described above, the switching frequency of each color of red, green, and blue of the backlight unit must be switched at 180 Hz, which is three times the normal frequency of 60 Hz. In particular, high-speed response is required.
[0007]
In addition, the FS liquid crystal display device can express three times as many pixels in the same area as a liquid crystal display device that performs color display using three color filters of red, green, and blue, so that high-definition display is possible. Therefore, it is often used as a relatively large display device such as a variety of information display boards and message boards at stations and airports, in which case, it is arranged at a position where a viewer looks up, or the viewer In view of the fact that the screen of the liquid crystal display device is not always visible from the front, a good visibility (high contrast) is exhibited particularly with respect to the viewing angle from below and the viewing angle from both the left and right directions with respect to the screen of the liquid crystal display device. A wide viewing angle is required.
[0008]
In response to these requirements, in recent years, for example, a TN-type liquid crystal has been used as a liquid crystal to be sealed in a liquid crystal display panel, for example, by forming a gap between a pair of transparent substrates in which a liquid crystal is to be sealed with a low gap to achieve high-speed response. In a liquid crystal display device in which two polarizing plates are arranged with their polarization axes orthogonal to each other so as to sandwich the liquid crystal display panel, a liquid crystal display is used to shield light during vertical alignment in which liquid crystals are more regularly arranged. As shown in FIG. 11 (1), which is a simplified view of the panel, when an off-voltage is applied, the liquid crystal is twisted and transmits light, and as shown in FIG. 11 (2), when the on-voltage is applied, the liquid crystal is vertically aligned. In order to increase the contrast, a normally white mode that blocks light is adopted. Note that in FIG. 11 schematically illustrating the liquid crystal display panel, reference numeral 301 denotes a transparent substrate on the viewing side, 302 denotes a transparent substrate on the opposite viewing side, 303 denotes a liquid crystal layer, and 304 denotes a black mask.
[0009]
In the liquid crystal display device adopting the normally white mode, as described above, when one pixel in a specific field is to be displayed in red, and when the red backlight unit is turned on and emits light, the corresponding pixel corresponds to the pixel. Applying an off-voltage to the transparent electrode to transmit light, and applying on-voltage to the transparent electrode corresponding to the one pixel to block light when other green and blue backlight units are turned on and emitting light. It becomes.
[0010]
In response to the demand for a wide viewing angle, for example, a polarizing film (hereinafter, abbreviated as a wide viewing angle polarizing film) for displaying a wide viewing angle has been developed as disclosed in Patent Document 2.・ Research has been conducted to increase the viewing angle of the normally white mode, such as hybrid alignment of a liquid crystal polymer compensation film (WV film) made of Fujifilm's discotic liquid crystal and hybrid alignment of a nematic liquid crystal made by Nippon Oil Corporation. A film (NH film) is known. In the WV film, a wide viewing angle polarizing plate integrated with a polarizing plate is commercially available.
[0011]
Here, the configuration of the polarizing plate and the wide viewing angle polarizing plate will be briefly described.
[0012]
FIG. 12 shows an example of the configuration of a polarizing plate. The polarizing plate is formed by dyeing and adsorbing a dichroic material such as iodine or a dye on polyvinyl alcohol (hereinafter referred to as PVA), and stretching the film to a high degree. -In order to impart polarization characteristics by orienting and impart durability, the PVA film is sandwiched between two films of triacetyl cellulose (hereinafter referred to as TAC). .
[0013]
FIG. 13 shows an example of a configuration of a wide viewing angle polarizing plate. The wide viewing angle polarizing plate has a configuration in which the PVA is sandwiched between a thin film of the TAC and a WV film. ing. The WV film is formed of an optically anisotropic layer in which an alignment film is provided on the TAC, and a discotic compound, which is a negative uniaxial compound, is hybrid-oriented on the orientation film. As the discotic compound, Discotic liquid crystal type compounds are used. The WV film is disposed on one side of the PVA with the optically anisotropic layer positioned on the side opposite to the PVA. In the wide viewing angle polarizing plate having this configuration, the WV film is positioned on the liquid crystal layer side, and is disposed on the liquid crystal display panel via an adhesive layer.
[0014]
[Patent Document 1]
JP 2002-303846 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-22943
[Problems to be solved by the invention]
However, as shown in a comparative example (conventional example) to be described later, simply using the above-mentioned wide-viewing-angle polarizing film or wide-viewing-angle polarizing plate is sufficient for a viewing angle of a liquid crystal display device for public display. I couldn't get it.
[0016]
Accordingly, the present invention has been made in view of the above circumstances, and in a liquid crystal display device employing a field sequential system, it is possible to display an image with an optimum contrast particularly from a viewing angle in both a downward direction and a left and right direction of the liquid crystal display device. It is an object of the present invention to provide a liquid crystal display device capable of obtaining a property.
[0017]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, a feature of the liquid crystal display device according to claim 1 of the present invention is that a first liquid crystal display panel is provided on the opposite side of the first liquid crystal display panel from the first viewing position. A second liquid crystal display panel driven in the same manner as above, a polarizing plate disposed on the viewing side of the first liquid crystal display panel, and a polarization disposed between the first liquid crystal display panel and the second liquid crystal display panel. And a polarizing plate disposed on the anti-viewing side of the second liquid crystal display panel, wherein the first liquid crystal display panel and the second liquid crystal display panel face each other on a surface on which an alignment film is formed and are spaced apart from each other. separated by TN type liquid crystal is sealed between a pair of transparent substrates arranged substantially parallel, the TN-type liquid crystal layer thickness _{d LC} is 1.5-3.0, the retardation value Δn _LC · _{d LC} 300~ 600 nm, and the first liquid crystal display panel is visually recognized. The intersection angle between the alignment axis of the alignment film on the side and the alignment axis of the alignment film on the viewing side of the second liquid crystal display panel is within 10 °, and any one of the first liquid crystal display panel and the second liquid crystal display panel is used. The two polarizing plates sandwiching one of the liquid crystal display panels are a pair of wide viewing angle polarizing plates, and the polarization axes of the wide viewing angle polarizing plates and the wide viewing angle polarizing plates of the one liquid crystal display panel are used. The crossing angle of the alignment film with the alignment axis on the disposition side is approximately 90 °, and the polarization axis of the other one polarizing plate and the alignment film on the other liquid crystal display panel on the disposition side of the polarizing plate are arranged. The intersection angle with the orientation axis is within 10 °.
[0018]
By adopting such a configuration, it is possible to obtain the best contrast with respect to the viewing angle from the downward direction and the left and right directions of the liquid crystal display device, obtain extremely good visibility, and realize a wide viewing angle. be able to.
[0019]
A feature of the liquid crystal display device according to claim 2 is that, in the liquid crystal display device according to claim 1, the first liquid crystal display panel and the second liquid crystal display panel each include a light-shielding film for shielding light between the pixels. It is located.
[0020]
By employing such a configuration, light leakage during color display can be prevented, and contrast can be improved.
[0021]
Further, a feature of the liquid crystal display device according to claim 3 is that, in the liquid crystal display device according to claim 1 or 2, the backlight unit has red, blue, and green light emitting diodes.
[0022]
By employing such a configuration, it is possible to sufficiently secure the luminance during color display.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present embodiment will be described using two examples and three comparative examples.
[0024]
The liquid crystal display device according to the present embodiment includes, for example, two liquid crystal display panels 1 and 2 (FIG. 1 or FIG. 4) in which a TN type liquid crystal having a twist angle of 90 ° is sealed, as shown in FIG. Hereinafter, the liquid crystal display panel disposed on the viewing side is referred to as a first liquid crystal display panel 1, and the liquid crystal display panel disposed on the opposite viewing side is referred to as a second liquid crystal display panel 2.) 1, a first polarizing plate 3 disposed on the viewing side, a second polarizing plate 4 disposed between the first liquid crystal display panel 1 and the second liquid crystal display panel 2, and the second liquid crystal display panel 2 is a liquid crystal display device including a third polarizing plate 5 disposed on the opposite side of the visual recognition side.
[0025]
More specifically, each of the liquid crystal display panels 1 and 2 has two transparent substrates 100, 101, 102 and 103 made of a material such as glass, which are arranged in parallel with a space therebetween. On each of the transparent substrates 100, 101, 102 and 103, the transparent electrodes 104, 105, 106 and 107 are respectively controlled, and the alignment of the liquid crystal molecules is controlled according to the voltage applied to the transparent electrodes 104, 105, 106 and 107. And two transparent substrates 100, 101, 102, 103 constituting each of the liquid crystal display panels 1, 2 are respectively formed by the alignment films 108, 109. , 110, 111 are joined and sealed by sealing materials 112, 113 with their forming surfaces facing each other. In a sealed space surrounded by the transparent substrates 100, 101, 102, and 103 and the sealing materials 112 and 113, the twist angle is 90 °, and the phase difference value Δn _LC · d _LC is 300 to 600 nm, preferably 350 to 500 nm. TN-type liquid crystals 114 and 115 set in the liquid crystal layer are sealed to form a liquid crystal layer.
[0026]
Further, each of the liquid crystal display panel 1, the liquid crystal layer thickness _{d LC} is 1.5-3.0, preferably set to 1.5 to 2.5 [mu] m. It becomes difficult to produce a liquid crystal display panel when the liquid crystal layer thickness d _LC is less than 1.5 [mu] m, is because the response speed exceeds 3.0μm slower.
[0027]
Further, as shown in FIG. 2 or FIG. 5 of the embodiment described later, the alignment axis of the alignment film 108 disposed on the viewing side of the first liquid crystal display panel 1 and the viewing axis of the second liquid crystal display panel 2 The crossing angle of the alignment film 110 with the alignment axis is set within 10 °.
[0028]
Further, inside each of the liquid crystal display panels 1 and 2, light shielding films 116 and 117 for shielding light between pixels of the liquid crystal display panels 1 and 2 are provided. By forming the light-shielding films 116 and 117 between pixels in this manner, light leakage during color display can be prevented, and contrast can be improved.
[0029]
In the present embodiment, the two polarizing plates 3, 4 (4, 5) sandwiching one of the liquid crystal display panels 1 (2) are a pair of wide viewing angle polarizing plates (hereinafter, wide viewing angle polarizing plate). The plates are denoted by reference numerals with “W” added.) 3W, 4W (4W, 5W), the polarization axes of the wide viewing angle polarizing plates 3W, 4W (4W, 5W) and the one liquid crystal display panel 1 (2), the crossing angle with the alignment axis of the alignment films 108, 109 (110, 111) on the side where the wide viewing angle polarizers 3W, 4W (4W, 5W) are disposed is 90 °; Intersecting angle between the polarization axis of the other one polarizing plate 5 (3) and the alignment axis of the alignment film 111 (108) of the other liquid crystal display panel 2 (1) on the side where the polarizing plate 5 (3) is provided. Is within 10 °.
[0030]
Further, the liquid crystal display device of the present embodiment has red, blue, and green light emitting diodes as light sources on the anti-viewing side of the second liquid crystal display panel 2, and selectively selects each unit color of the light emitting diodes. A backlight unit (not shown) that emits light by switching is provided. As described above, by using the light emitting diodes for the backlight unit, it is possible to secure more luminance than when a normal fluorescent display tube (VFD) or the like is used, and to perform favorable color display.
[0031]
Then, the light transmission of each pixel of the first liquid crystal display panel 1 and the second liquid crystal display panel 2 is selectively and identically driven and controlled in synchronization with the emission of each color from the backlight unit, and each unit color is controlled. Are superimposed and displayed in a time-division manner continuously at a high speed to achieve a desired color display.
[0032]
As in the liquid crystal display device of the present embodiment, two polarization plates sandwiching any one of the first liquid crystal display panel 1 and the second liquid crystal display panel 2 in which the TN type liquid crystal is sealed. The plates 3, 4 (4, 5) are a pair of wide viewing angle polarizing plates 3W, 4W (4W, 5W), and the polarizing axes of the wide viewing angle polarizing plates 3W, 4W (4W, 5W) and the one liquid crystal display panel 1 (2), the crossing angle with the alignment axis of the alignment films 108, 109 (110, 111) on the side where the wide-viewing-angle polarizing plates 3W, 4W (4W, 5W) are disposed is set to approximately 90 °, The intersection angle between the polarization axis of one polarizing plate 5 (3) and the alignment axis of the alignment film 111 (108) of the other liquid crystal display panel 2 (1) on the side where the polarizing plate 5 (3) is provided is set to 10 °. With this configuration, the best contrast is obtained with respect to the viewing angle from the lower direction and the left and right directions of the liquid crystal display device. Thus, extremely good visibility can be obtained, and a wide viewing angle can be realized.
[0033]
Hereinafter, specific examples of the above-described liquid crystal display device of the present embodiment will be described, and a description will be given in comparison with a liquid crystal display device of a conventional specification (comparative example).
[0034]
[Example 1]
As shown in FIG. 1, the liquid crystal display device of the present embodiment is a liquid crystal display device having two liquid crystal display panels 1 and 2 stacked in a thickness direction. In the liquid crystal display device, the liquid crystals 114 and 115 are set to have a liquid crystal layer thickness d _LC = 2 μm and a phase difference value Δn _LC · d _LC = 410 nm with a 90 ° left twist, and FIG. As shown, the orientation axis of the orientation film 108 of the transparent substrate 100 arranged on the viewing side of the first liquid crystal display panel 1 and the orientation axis of the orientation film 110 of the transparent substrate 102 arranged on the viewing side of the second liquid crystal display panel 2. The intersection angle with the orientation axis is set to 0 °.
[0035]
As the first polarizing plate 3 and the second polarizing plate 4, a pair of wide-viewing-angle polarizing plates (SKN-18243WL, manufactured by Polatechno) 3W, 4W is used, and the polarization axis of the first polarizing plate 3W is used. And the angle of intersection between the alignment axis of the alignment film 108 on the viewing side of the first liquid crystal display panel 1 and the polarization axis of the second polarizing plate 4W and the alignment of the alignment film 109 on the anti-viewing side of the first liquid crystal display panel 1. The intersection angles with the axes are set to 90 °.
[0036]
As the third polarizing plate 5, a neutral polarizing plate (SKN-18243T manufactured by Polatechno) is used, and the polarizing axis of the third polarizing plate 5 and the alignment film on the opposite side of the second liquid crystal display panel 2 are viewed. The crossing angle of 111 with the orientation axis is set to 0 °.
[0037]
FIG. 3 shows the viewing angle dependence of the contrast when this liquid crystal display device was used as a sample and statically driven at 180 Hz.
[0038]
In FIG. 3, circular lines which are concentric circles and are shown at 0 ° to 50 ° at 10 ° intervals indicate the inclination angle (θ) from the normal to the display surface of the liquid crystal display device. Lines extending radially from the center point and dividing the figure into 12 indicate the counterclockwise angle (φ) when the 3 o'clock direction of the display surface of the liquid crystal display device is assumed to be 0 ° (hereinafter, referred to as “φ”). 6, 8, 9 and 10 in Examples and Comparative Examples.)
[0039]
As a result, the liquid crystal display device of the present embodiment has a range of φ180 to 200 ° (substantially leftward) and φ260 to 280 until the viewer's line of sight is set to θ0 to 50 ° in the region of φ120 to (420) °. ° (almost directly below). A contrast ratio of 200 or more was obtained in a range excluding φ340 to 360 ° (approximately rightward), good visibility of color display could be exhibited, and a wide viewing angle was realized. Also, φ180 to 200 ° (substantially left direction), φ260 to 280 ° (substantially right downward direction). Even at φ340 to 360 ° (substantially right direction), a contrast ratio of 200 or more could be obtained in the range of θ0 to 40 °.
[0040]
In addition, the response speed of the liquid crystal display device of this example was 2 ms.
[0041]
Here, the response speed is a time required for transmitted light to reach a predetermined value when an on / off voltage is applied to the transparent electrode (the same applies to the following Examples and Comparative Examples). .
[0042]
[Example 2]
As shown in FIG. 4, the liquid crystal display device of this embodiment is a liquid crystal display device having two liquid crystal display panels 1 and 2 stacked in a thickness direction. In the liquid crystal display device, the liquid crystals 114 and 115 are set so that the liquid crystal layer thickness d _LC = 2 μm and the phase difference value Δn _LC · d _LC = 410 nm with a 90 ° left twist, and FIG. As shown, the orientation axis of the orientation film 108 of the transparent substrate 100 arranged on the viewing side of the first liquid crystal display panel 1 and the orientation axis of the orientation film 110 of the transparent substrate 102 arranged on the viewing side of the second liquid crystal display panel 2. The intersection angle with the orientation axis is set to 0 °.
[0043]
In the present embodiment, a pair of wide-viewing-angle polarizing plates (SKN-18243WL manufactured by Polatechno) 4W, 5W are used as the second polarizing plate 4 and the third polarizing plate 5, and the second polarizing plate 4 and the third polarizing plate 5 are used. The intersection angle between the polarization axis of the polarizing plate 3W and the alignment axis of the alignment film 110 on the viewing side of the second liquid crystal display panel 2, and the polarization axis of the third polarizing plate 5W and the anti-viewing side of the second liquid crystal display panel 2. Of the alignment film 111 are set to 90 °.
[0044]
Further, as the first polarizing plate 3, a neutral polarizing plate (SKN-18243T manufactured by Polatechno) is used, and the polarizing axis of the first polarizing plate 3 and the alignment film 108 on the viewing side of the first liquid crystal display panel 2 are used. Is set to 0 °.
[0045]
FIG. 6 shows the viewing angle dependence of the contrast when this liquid crystal display device was used as a sample and statically driven at 180 Hz.
[0046]
As a result, the liquid crystal display device of the present embodiment has a range of φ180 to 200 ° (substantially leftward) and φ260 to 280 ° until the viewer's line of sight is set to θ0 to 50 ° in the region of φ120 to (420) °. (Almost right below). A contrast ratio of 200 or more was obtained in a range excluding φ340 to 20 (380) ° (approximately rightward direction), good visibility of color display could be exhibited, and a wide viewing angle was realized. Also, φ180 to 200 ° (substantially left direction), φ260 to 280 ° (substantially right downward direction). Even at φ340 to 20 (380) ° (substantially rightward), a contrast ratio of 200 or more could be obtained in the range of θ0 to 35 °.
[0047]
In addition, the response speed of the liquid crystal display device of this example was 2 ms.
[0048]
[Comparative Example (Conventional Example) 1]
The liquid crystal display device of this comparative example is a liquid crystal display device having one liquid crystal display panel 200 and a pair of polarizing plates 201 and 202 sandwiching the liquid crystal display panel 118. The configuration of the liquid crystal display panel 200 itself is basically the same as the configuration of each of the liquid crystal display panels 1 and 2 in the embodiment. In the liquid crystal display device of the comparative example, the liquid crystal (not shown) is also provided. The liquid crystal layer thickness d _LC = 2 μm and the phase difference value Δn _LC · d _LC = 410 nm are set with a left twist of 90 °, and as shown in FIG. The polarization axes are arranged orthogonally.
[0049]
Further, the polarization axis of the polarizing plate 201 provided on the viewing side of the liquid crystal display panel 200 is orthogonal to the alignment axis of the alignment film (not shown) of the transparent substrate provided on the viewing side of the liquid crystal display panel 200. In addition, the polarization axis of the polarizing plate 202 provided on the anti-viewing side is orthogonal to the alignment axis of the alignment film (not shown) of the transparent substrate provided on the anti-viewing side of the liquid crystal display panel. Is established.
[0050]
As the pair of polarizing plates 201 and 202, neutral polarizing plates (SKN-18243T manufactured by Polatechno) were used.
[0051]
FIG. 8 shows the viewing angle dependence of the contrast when this liquid crystal display device was used as a sample and statically driven at 180 Hz.
[0052]
As a result, in the liquid crystal display device of this comparative example, the viewing angle range in which a contrast ratio of 200 or more can be obtained is in the range of θ0 to 30 ° around φ30 °, in the range of θ0 to 40 ° near φ160 °, and in the range of φ180. It was almost limited to the range of φ0 to 15 to 20 ° at 〜360 °, and the viewing angle was very narrow.
[0053]
[Comparative Example (Conventional Example) 2]
The liquid crystal display device of this comparative example has substantially the same configuration as that of the liquid crystal display device of Comparative Example 1 described above. However, as the pair of polarizing plates 201 and 202, both have a wide viewing angle polarizing plate (manufactured by Polatechno: SKN-18243WL).
[0054]
FIG. 9 shows the viewing angle dependency of the contrast when the liquid crystal display device was used as a sample and was statically driven at 180 Hz.
[0055]
As a result, in the liquid crystal display device of this comparative example, the viewing angle region in which a contrast ratio of 200 or more can be obtained is wider than that of the comparative example 1, but, for example, in the case of θ50 °, φ37 to 45 ° In one direction, in the case of θ40 °, it can be obtained in only four directions of φ30 to 50 °, φ135 to 150 °, φ215 to 250 ° and φ300 to 330 °, and the viewing angle is still not enough. .
[0056]
[Comparative Example (Conventional Example) 3]
The liquid crystal display of this comparative example has substantially the same configuration as the liquid crystal display of Example 2 described above, but as the first polarizing plate 3 to the third polarizing plate 5, all are neutral polarizing plates (Polartechno). (Manufactured product: SKN-18243T).
[0057]
FIG. 10 shows the viewing angle dependence of the contrast when the liquid crystal display device was used as a sample and statically driven at 180 Hz.
[0058]
As a result, in the liquid crystal display device of this comparative example, the viewing angle region in which a contrast ratio of 200 or more can be obtained is wider than that of the comparative examples 1 and 2, It could only be obtained in the range of ４５45 °, １４０140-180 ° and ２３０230-315 °, and the viewing angle was not yet sufficient. Further, the viewing angle range in which a contrast of 1000 or more can be obtained is also narrower than in the case of Examples 1 and 2 described above.
[0059]
From these experiments, it is found that the alignment axis of the alignment film on the viewing side of the first liquid crystal display panel in which the TN type liquid crystal is sealed, and the alignment of the alignment film on the viewing side of the second liquid crystal display panel in which the TN type liquid crystal is also sealed. The angle of intersection with the axis is within 10 °, the two polarizing plates sandwiching one of the liquid crystal display panels are a pair of wide viewing angle polarizing plates, and the polarizing axis of each wide viewing angle polarizing plate and the one liquid crystal. The crossing angle between the orientation axis of the orientation film on the side where the wide viewing angle polarizers of the display panel are disposed is set to approximately 90 °, and the polarization axis of the other one polarizer and the polarizer of the other liquid crystal display panel are set. It was found that by setting the crossing angle with the alignment axis of the alignment film on the arrangement side within 10 °, it was possible to improve the contrast particularly from the viewing angles in both the downward direction and the left and right directions. .
[0060]
If the liquid crystal display device has a wide viewing angle in this way, it is arranged at a position where a viewer can look up as a relatively large display device such as various information display boards and message boards at stations and airports. Even in such a case, good visibility of color display (high contrast) can be exhibited.
[0061]
Note that the present invention is not limited to the above-described embodiments and examples, and various changes can be made as necessary.
[0062]
【The invention's effect】
As described above, according to the present invention, in a field sequential type liquid crystal display device, it is possible to display an optimal contrast from the viewing angle even in a downward direction or in both left and right directions, and to achieve high definition and good This provides an effect that a high visibility can be obtained.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a laminated structure of a liquid crystal display device of Example 1 of the present embodiment; FIG. 2 is a view showing polarization axes of respective polarizing plates and liquid crystal display panels constituting the liquid crystal display device of Example 1; FIG. 3 is a view showing the viewing angle dependence of the contrast of the liquid crystal display device of Example 1; FIG. 4 is a view showing the viewing angle dependence of the contrast of the liquid crystal display device of Example 1; FIG. 5 is a vertical cross-sectional view illustrating a laminated structure of a display device. FIG. 6 is a view showing the viewing angle dependence of the contrast of the liquid crystal display device of Example 2. FIG. 7 is a diagram showing the polarization axes of the polarizing plates constituting the liquid crystal display devices of Comparative Examples 1 and 2 (conventional examples). FIG. 8 is a view showing an arrangement of alignment axes of alignment films on a viewing side and a non-viewing side of a liquid crystal display panel. FIG. 9 is a diagram showing the viewing angle dependence of the contrast of the liquid crystal display device of FIG. 1; FIG. 9 is a diagram showing the viewing angle dependence of the contrast of the liquid crystal display device of Comparative Example (conventional example); FIG. FIG. 11 is a view showing the viewing angle dependence of the contrast of the liquid crystal display device of FIG. 3. FIG. 11 is an explanatory view showing the arrangement of liquid crystals and the transmission state of light when an on / off voltage is applied. FIG. 13 is a cross-sectional view illustrating an example of a configuration of a wide-viewing-angle polarizing plate.
DESCRIPTION OF SYMBOLS 1 1st liquid crystal display panel 2 2nd liquid crystal display panel 3 1st polarizing plate 3W 1st polarizing plate 4 (using a wide viewing angle polarizing plate) 2nd polarizing plate 4W (using a wide viewing angle polarizing plate) 2nd Polarizing plate 5 Third polarizing plate 5W Third polarizing plate 100 (using a wide viewing angle polarizing plate) Viewing-side transparent substrate 101 of first liquid crystal display panel Anti-viewing side transparent substrate 102 of first liquid crystal display panel 102 Second liquid crystal display The transparent substrate 103 on the viewing side of the panel 103 The transparent substrate 108 on the opposite side of the liquid crystal display panel 108 The alignment film 109 of the transparent substrate on the viewing side of the first liquid crystal display panel 109 The alignment film 110 of the transparent substrate on the opposite side of the first liquid crystal display panel Alignment film of transparent substrate on viewing side of liquid crystal display panel 111 Alignment film of transparent substrate on the opposite viewing side of second liquid crystal display panel

Claims (3)

A backlight unit is provided on the anti-viewing side of the liquid crystal display panel for selectively switching a plurality of unit colors to emit light, and light transmission of each pixel of the liquid crystal display panel is synchronized with light emission of each unit color from the backlight unit. A liquid crystal display device which selectively controls the display pattern of each unit color, and superimposes and displays the respective display patterns of each unit color continuously in a time-division manner to perform a desired display,
A first liquid crystal display panel, a second liquid crystal display panel disposed on a non-viewing side of the first liquid crystal display panel and driven in the same manner as the first liquid crystal display panel, and a second liquid crystal display panel on the viewing side of the first liquid crystal display panel. A polarizing plate provided, a polarizing plate provided between the first liquid crystal display panel and the second liquid crystal display panel, and a polarizing plate provided on the opposite viewing side of the second liquid crystal display panel.
In the first liquid crystal display panel and the second liquid crystal display panel, a TN type liquid crystal is sealed between a pair of transparent substrates disposed so as to be substantially parallel to each other with a surface on which an alignment film is formed facing each other. type liquid crystal layer thickness _{d LC} is 1.5-3.0, the retardation value Δn _LC · _{d LC} is the 300 to 600 nm, and the the orientation axis of the viewing side of the alignment film of the first liquid crystal display panel The angle of intersection with the alignment axis of the alignment film on the viewing side of the second liquid crystal display panel is within 10 °,
The two polarizing plates sandwiching one of the first liquid crystal display panel and the second liquid crystal display panel are a pair of wide viewing angle polarizing plates, and the polarizing axis of each wide viewing angle polarizing plate and The cross angle of the liquid crystal display panel with the alignment axis of the alignment film on the side where the wide viewing angle polarizers are disposed is approximately 90 °,
A liquid crystal display device wherein the crossing angle between the polarization axis of the other one polarizing plate and the alignment axis of the alignment film of the other liquid crystal display panel on the side where the polarizing plate is provided is within 10 °. . 2. The liquid crystal display device according to claim 1, wherein the first liquid crystal display panel and the second liquid crystal display panel each include a light shielding film that shields light between the pixels. The liquid crystal display device according to claim 1, wherein the backlight unit includes red, blue, and green light emitting diodes.

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