JP2005128171A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To resolve bluing effect when black is displayed in an OCB liquid crystal display device. <P>SOLUTION: The liquid crystal display device has: a liquid crystal cell 110 provided with a bend aligned liquid crystal layer 140 interposed between a counter substrate 130 and an array substrate 120 wherein filters with respective colors of red, green and blue, are equipped on one of the substrates; retardation plates 200a, 200b, 210a and 210b disposed at least on one side of the liquid crystal cell; two sheets of polarizing plates 220a and 220b disposed with the liquid crystal cell and the retardation plates interposed in between; and a dichroic pigment element 400 disposed on an optical path L of light passing through the liquid crystal cell, the retardation plates and the polarizing plates and absorbing blue light at a specified angle of view. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using an OCB (Optically Compensated Birefringence) technique capable of realizing a wide viewing angle and a high-speed response.

  Liquid crystal display devices have been applied to various uses by taking advantage of light weight, thinness, and low power consumption.

  Currently, a twisted nematic (TN) type liquid crystal display device widely used in the market is composed of a liquid crystal material having an optically positive refractive index anisotropy arranged approximately 90 ° between substrates, The optical rotation of incident light is adjusted by controlling the twisted arrangement. Although this TN liquid crystal display device can be manufactured relatively easily, its viewing angle is narrow and its response speed is slow, so that it is not particularly suitable for displaying moving images such as TV images.

  On the other hand, an OCB type liquid crystal display device has attracted attention as an improvement in viewing angle and response speed. The OCB type liquid crystal display device is formed by sealing a liquid crystal material capable of bend alignment between substrates, and the response speed is improved by an order of magnitude compared to the TN type liquid crystal display device. Since this is self-compensated, there is an advantage that the viewing angle is wide. When an image is displayed using such an OCB type liquid crystal display device, light is blocked (black display) in a high voltage application state by controlling birefringence and combining with a polarizing plate, for example. It is conceivable to transmit light (display white) in a state.

However, in the black display state, the liquid crystal molecules are aligned along the electric field direction by applying a high voltage (aligned in the normal direction to the substrate), but the liquid crystal molecules near the substrate are in the normal direction due to the interaction with the alignment film. The light is influenced by the phase difference in a predetermined direction. For this reason, when observed from the normal direction of the substrate, the transmittance during black display cannot be sufficiently reduced, leading to a decrease in contrast. Thus, for example, it is known to combine the uniaxial retardation plate to compensate for the retardation of the liquid crystal layer during black display and to sufficiently reduce the transmittance. In addition, as a method of sufficiently compensating for black display or gradation characteristics even when observed from an oblique direction, a hybrid array of optical negative retardation plates is combined as disclosed in Patent Document 1, for example. Is also known.
Japanese Patent Laid-Open No. 10-197862

  By the way, a color liquid crystal display device reflects or transmits incident light such as natural light or a backlight having high color rendering properties and displays it through each color filter, and selects light over the entire light wavelength region in the wavelength pass band of each filter. ing.

    Since the TN liquid crystal display device uses optical rotation for display, even if light is internally reflected between the substrates, there is almost no influence on the display. However, in the OCB liquid crystal display device, the retardation received by the incident light passing through the liquid crystal layer and the retardation of the retardation plate are shifted due to the number of internal reflections, thereby causing a problem that the color balance of the image is lost. . Furthermore, since the internally reflected reflected light also has wavelength dispersion, the color balance is further disrupted. This color tone can be generated at any wavelength of light, but the wavelength range shared by the blue filter for blue, which is recognized as blue-violet-blue-blue-green, is wider than other colors, and the blue filter characteristics have a wide passband. Therefore, there is a possibility that the image is bluish when displaying black.

  An object of the present invention is to provide a liquid crystal display device having a high response speed and an excellent color balance.

  The present invention provides filter means for absorbing the blue component of the light components that pass through the liquid crystal cell, and adjusts the color balance by attenuating unnecessary light leaking from the blue filter.

  In the present invention, a dichroic dye element is disposed as a filter means in the light path controlled by the liquid crystal cell. A typical dichroic dye element is an element that maximizes the transmittance of light of a predetermined wavelength selected in the direction perpendicular to the liquid crystal cell surface, and reduces the transmittance as it is tilted from the vertical direction, that is, increases the absorption. Prevents unwanted light leakage in the oblique direction.

According to the present invention, an array substrate and a counter substrate each having an electrode, the electrodes facing each other, a liquid crystal layer sandwiched between the substrates and arranged in a bend, and a red provided on one of the substrates A liquid crystal cell comprising green, blue and blue color filters,
A phase difference plate disposed on at least one of the liquid crystal cells;
Two polarizing plates disposed across the liquid crystal cell and the retardation plate,
A dichroic dye disposed on a path of light passing through the liquid crystal cell, the retardation plate and the polarizing plate and having an arrangement with anisotropic visible light transmittance, and perpendicular to the liquid crystal cell surface; A dichroic dye element that selectively maximizes the transmittance of light of a predetermined wavelength in the direction;
A liquid crystal display device characterized by comprising:

  Here, the predetermined wavelength light is preferably light in a range of 300 nm to 500 nm. That is, the light in the oblique direction on the blue light side is suppressed.

  Further, the dichroic dye element comprises two substrates, a liquid crystal sandwiched between these substrates, and a mixture layer of the dichroic dye.

  Using a dichroic dye element as a guest-host liquid crystal structure, selective absorption in an oblique direction of a specific wavelength light region is uniformly and efficiently performed.

  Here, it is preferable that the two substrates of the dichroic dye element each have an electrode to which a voltage can be applied to the mixture layer, and the arrangement of the dichroic dye is changed by applying the voltage.

  Furthermore, it is preferable that a control circuit for changing the arrangement of dichroic dyes according to the display image of the liquid crystal cell is connected to the electrode.

  In addition, the dichroic dye element includes a dichroic dye layer having an anisotropic arrangement in visible light transmittance, and is disposed between the polarizing plate on the light path and the liquid crystal cell. A liquid crystal display device in which the transition dipole moment of the chromatic dye and the absorption axis of the polarizing plate are arranged substantially in parallel is obtained.

  Furthermore, a liquid crystal display device in which the predetermined wavelength light is blue light is obtained.

  In the present invention, a dichroic dye element is arranged on the light path passing through the liquid crystal cell to selectively inhibit transmission of a blue component at a specific viewing angle, thus preventing light leakage of blue light and black display. The blueness of the image that sometimes occurs can be eliminated.

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

(Embodiment 1)
FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to the OCB mode system of the present embodiment.

  This liquid crystal display device 1 has an aspect ratio of 16: 9 and a diagonal type of 22. The light-transmitting active matrix type liquid crystal panel 100 and a plurality of tubular light sources 310 (see FIG. 10) are juxtaposed. A backlight 300 configured and disposed on the back of the liquid crystal panel, a dichroic dye element 400 disposed between the liquid crystal panel 100 and the backlight 300, and a liquid crystal cell 110 in the liquid crystal panel 100, which is built in the scanning line Yj A signal line driving circuit 500 configured by scanning line driving circuits Ydr1 and Ydr2 (see FIG. 3) for supplying the signal Vg and TCP (Tape Carrier Package) for supplying the signal voltage Vsig to the signal line Xi (see FIG. 3); A common electrode drive circuit 700 for supplying the common electrode voltage Vcom to the common electrode Ecom (see FIG. 2), a scanning line drive circuit Ydr1, Ydr2, a signal line drive circuit 500, and a control circuit 900 for controlling the common electrode drive circuit 700; LCD panel 100 with backlight 300 And a bezel 1000 having a frame shape.

As shown in FIG. 2, the liquid crystal panel 100 includes a liquid crystal cell 110, a front hybrid phase difference plate 200a on the outgoing light side, a front biaxial phase difference plate 210a, a front polarizing plate 220a, a rear hybrid phase difference plate 200b, and a rear surface 2. It comprises an axial phase difference plate 210b and a rear polarizing plate 220b on the incident light side. The front hybrid phase difference plate 200a, the front biaxial phase difference plate 210a and the front polarization plate 220a are integrally formed. Similarly, the rear hybrid phase difference plate 200b, the rear biaxial phase difference plate 210b and the rear polarization plate 220b are also formed. The liquid crystal cells 110 are integrally formed and attached to the main surface.
The liquid crystal cell 110 includes an array substrate 120 having display pixel electrodes, a counter substrate 130 disposed so that the counter electrode is opposed to the display pixel electrodes of the array substrate, and the array substrate 120 and the counter substrate 130, respectively. The liquid crystal layer 140 is sandwiched between alignment films 151 and 153.

<Configuration of array substrate>
The array substrate 120 will be described with reference to FIGS.
The array substrate 120 includes a silicon oxide (a signal line Xi composed of a plurality of aluminum (Al) and a scanning line Yj composed of a plurality of molybdenum-tungsten alloys (MoW) on a transparent glass substrate GLS1. They are arranged in a matrix via an interlayer insulating film INS2 made of a (SiO2) film. In addition, an auxiliary capacitance line Cj created in the same process as the scanning line Yj is arranged in parallel with the scanning line Yj.
In the vicinity of the intersection of the signal line Xi and the scanning line Yj, an ITO (Indium Tin Oxide) is formed as a transparent electrode through a passivation film INS3 on a top gate thin film transistor TFT having a polycrystalline silicon (p-Si) film as an active layer. The display pixel electrode Dpix is formed. More specifically, this TFT is configured in a double gate structure in order to reduce off-leakage current, and includes p-type source / drain regions p-Si (s), p-Si (d), channel region p-Si (c1 ), P-Si (c2), the channel region p-Si (c1), and the p-Si (c2) connecting region p-Si (i) is included in the p-Si film, and the drain region p- Si (d) is connected to the signal line Xi through the contact hole CH1, and the source region p-Si (s) is routed by the source wiring EXT made of Al through the contact hole CH2, and through the contact hole CH3. It is connected to the display pixel electrode Dpix.
A gate insulating film INS1 made of TEOS is disposed on the p-Si film, a first gate electrode G1 extending from the scanning line Yj is disposed thereon, and a part of the scanning line Yj is a second gate. Wired as electrode G2. The first gate electrode G1 corresponds to the first channel region p-Si (c1), and the second gate electrode G2 corresponds to the second channel region p-Si (c2).
Further, the source region p-Si (s) of this TFT includes the source region extension portion p-Si (se) (FIGS. 5 and 6A) and extends from the auxiliary capacitance line Cj and is identical to the auxiliary capacitance line Cj. The first auxiliary capacitance electrode EC1 made of MoW formed in the process is electrically connected to the second auxiliary capacitance electrode EC2 disposed via the interlayer insulating film INS2 via the contact hole CH4. The second auxiliary capacitance electrode EC2 is made of Al formed in the same process as the signal line Xi. Further, a phase change pixel electrode Tpix formed in the same process as the display pixel electrode Dpix is disposed on the second auxiliary capacitance electrode EC2 via the passivation film INS3, and the phase change pixel electrode Tpix is formed in the contact hole CH5. Is electrically connected to the second auxiliary capacitance electrode EC2.
With such a configuration, the storage capacitor Cs (FIG. 3) is formed between the first storage capacitor electrode EC1 and the second storage capacitor electrode EC2, and the phase change pixel electrode Tpix is disposed on the storage capacitor Cs. Therefore, it is possible to effectively secure a large storage capacity Cs without impairing the aperture ratio.
Further, in this embodiment, the display pixel electrode Dpix and the phase transition pixel electrode Tpix are arranged across the scanning line Yj, and the source region extension portion p− independent of the TFT source region p-Si (s). Since it is connected by Si (se), even if there is a short circuit etc. in the storage capacitor Cs, it is easy to electrically disconnect the source region extension part p-Si (se) by means such as laser irradiation. Can be rescued.
In addition, the display pixel electrode Dpix and the phase transition pixel electrode Tpix of the next horizontal line adjacent on the storage capacitor line Cj are configured in a comb-teeth shape in which opposite ends are engaged with each other. By applying a twisted lateral electric field between the display pixel electrode Dpix and the phase transition pixel electrode Tpix, it becomes possible to uniformly nucleate the bend, which is uniform from the initial spray arrangement state. It is possible to lead to a bend arrangement state. The comb tooth pitch can be led to a uniform arrangement at a low voltage by making it smaller than 50 μm, for example.
Incidentally, as shown in FIG. 3, both ends of the scanning line Yj are electrically connected to scanning line driving circuits Ydr1 and Ydr2 integrally formed on the glass substrate GLS1, respectively. The vertical scanning clock signal YCK and the vertical start signal YST are input to the scanning line driving circuits Ydr1 and Ydr2, respectively. The auxiliary capacitance line Cj is connected to the connection wiring Ccs at both ends, and the auxiliary capacitance voltage Vcs is input through the connection wiring Ccs. The signal line Xi is connected to the signal input line xk (k = i / 2) via the selection switch SEL. Specifically, the signal line Xi is divided into an odd signal line Xi (i = 1, 3, 5,...) And an even signal line Xi (i = 2, 4, 6,. A pair of odd signal lines Xi and Xi + 2 are connected to the same signal input line xk via selection switches SEL1 and SEL3, and a pair of adjacent even signal lines Xi + 1 and Xi + 3 are connected to selection switches SEL2 and SEL4. To the same signal input line xk + 1. The selection switch SEL1 connected to one of the odd signal line pairs and the selection switch SEL4 connected to one of the even signal line pairs are selected by the first selection signal Vsel1 and connected to the other of the odd signal line pairs. The selection switch SEL3 and the selection switch SEL2 connected to the other of the even signal line pair are wired so as to be selected by the second selection signal Vsel2.

  For example, as shown in FIG. 7A, the signal voltage Vsig1 having a positive polarity (+) with respect to the counter electrode voltage Vcom is applied to the display pixel electrode Dpix corresponding to the signal line X1 in the first half of one horizontal scanning period (1H). The negative (−) signal voltage Vsig4 with respect to the counter electrode voltage Vcom is written to the display pixel electrode Dpix corresponding to the signal line X4. Then, in the latter half of one horizontal scanning period (1H), the display pixel electrode Dpix corresponding to the signal line X2 has a negative (−) signal voltage Vsig2 with respect to the counter electrode voltage Vcom, and the display pixel electrode corresponding to the signal line X3. A signal voltage Vsig3 having a positive polarity (+) with respect to the counter electrode voltage Vcom is written in Dpix. Further, as shown in FIG. 7B, a negative (−) signal with respect to the counter electrode voltage Vcom is applied to the display pixel electrode Dpix corresponding to the signal line X1 in the first half of one horizontal scanning period (1H) of the next frame. The voltage Vsig1 is written into the display pixel electrode Dpix corresponding to the signal line X4 as a positive (+) signal voltage Vsig4 with respect to the counter electrode voltage Vcom. Then, in the second half of one horizontal scanning period (1H), the display pixel electrode Dpix corresponding to the signal line X2 has a positive (+) signal voltage Vsig2 with respect to the counter electrode voltage Vcom, and the display pixel electrode corresponding to the signal line X3. A negative (−) signal voltage Vsig3 is written in Dpix with respect to the counter electrode voltage Vcom.

In this way, frame inversion driving and dot inversion driving are performed, thereby preventing the application of an undesired DC voltage and effectively preventing the occurrence of flicker. Furthermore, the number of connections between the signal line driving circuit 500 and the liquid crystal panel 100 is reduced to i / 2 with respect to the number i of the signal lines Xi, so the connection process is greatly reduced and the number of connection points is small. As a result, improvement in manufacturing yield, improvement in impact resistance, and the like are achieved. In addition, the connection pitch limit associated with higher definition can be expanded, and for example, high definition of 80 μm or less can be achieved.
In the above embodiment, the signal voltage Vsig input from a certain signal input line xk is serially distributed to every other two signal lines Xi and Xi + 2 within one horizontal scanning period (1H). However, it is also possible to distribute to three signal lines or four signal lines, and by doing so, the number of connections can be further reduced. However, increasing the number of distributions shortens each writing time, so it is necessary to design appropriately according to the capability of the TFT.
<Configuration of counter substrate>
The counter substrate 130 is a matrix-shaped light-shielding film BM that blocks unwanted leakage light on the glass substrate GLS2, and red R, green G, and blue B provided corresponding to each display pixel electrode Dpix for color display. A transparent counter electrode Ecom made of each color filter CF (R), CF (G), CF (B) and ITO is provided. Although not shown here, CF (G) and CF (B) are sequentially arranged adjacent to CF (R).

  Although not shown, resinous column spacers are arranged on the counter electrode Ecom, and are regularly arranged at a ratio of one to a plurality of pixels so as to maintain a gap with the array substrate 110. . The spacer corresponding position on the array substrate is the wide area Xa of the signal line shown in FIG.

<Configuration of LCD panel>
Next, the configuration of the liquid crystal panel 100 will be described in more detail.
As shown in FIG. 2, the alignment films 151 and 153 arranged on the respective main surfaces of the arrays and the counter substrates 120 and 130 are substantially in the rubbing direction Ra and Rb (see FIGS. 8 and 9) in the vertical direction of the screen. The rubbing process is performed in the parallel direction and in the same direction. The pretilt angle (θ) is set to approximately 10 °. A liquid crystal layer 140 is sandwiched between the two substrates 120 and 130. As the liquid crystal layer 140, a p-type nematic liquid crystal having positive dielectric anisotropy in which liquid crystal molecules are bend-aligned in a state where a predetermined voltage is applied to the display pixel electrode Dpix and the counter electrode Ecom is used.

By the way, as shown in FIG. 9A, the liquid crystal molecules 140a of the liquid crystal layer 140 are in a splay alignment state when no voltage is applied between the display pixel electrode Dpix and the counter electrode Ecom. For this reason, when the power is turned on, a high voltage of about several tens of volts is applied between the display pixel electrode Dpix and the counter electrode Ecom to shift to the bend arrangement state. In order to reliably perform this phase transition, when applying a high voltage, a reverse polarity voltage is sequentially written for each adjacent horizontal pixel line, so that a horizontal direction is applied between the adjacent display pixel electrode Dpix and the phase transition pixel electrode Tpix. Nucleation is performed by giving a torsional potential difference of, and phase transition is performed around this nucleus. By performing such an operation for about 1 second, the splay arrangement state is shifted to the bend arrangement state, and the potential difference between the display pixel electrode Dpix and the counter electrode Ecom is made the same potential to once create an undesired history. to erase.
After making the bend alignment state in this way, during operation, a voltage equal to or higher than the low off voltage Voff at which the bend alignment state is maintained is applied to the liquid crystal molecules 140a as shown in FIG. 9B. By changing the voltage between the off-voltage and the on-voltage Von higher than this, the alignment state is changed between (b) to (c) in the figure, and the retardation value of the liquid crystal layer 140 is changed to λ / 2 Change the transmittance to control.

In order to achieve such an operation, as shown in FIG. 8, the absorption axes Aa and Ab of the pair of polarizing plates 220a and 220b are orthogonal to each other so as to display black when the on-voltage Voff is applied, and the rubbing directions Ra, The arrangement is shifted from Rb by π / 4.
Further, the front hybrid phase difference plate 200a and the rear hybrid phase difference plate 200b attached between the outer surfaces of the array substrate 120 and the counter substrate 130 and the polarizing plates 220a and 220b are liquid crystal at the time of on-voltage (when black is displayed). It compensates for the retardation value RLCon of the layer 140, for example, 80 nm, and further prevents unwanted light leakage from the front and oblique directions during black display. That is, the discotic liquid crystal constituting the hybrid phase difference plates 200a and 200b is an optically negative material in which the refractive indexes nx and ny are equal and the refractive index nz in the optical axis direction is smaller than nx and ny. As shown in FIGS. 2 and 8, the molecular optical axis Dopt is inclined in the opposite direction to the inclination direction of the optical axis of the liquid crystal molecules 140a of the liquid crystal layer 140, and the inclination angle is gradually changed in the film thickness direction. Each of the retardation values RD is -40 nm. Accordingly, since the retardation RLCon of the liquid crystal layer 140 at the time of black display is 80 nm, the phase difference at the time of black display is canceled, thereby preventing undesired light leakage.
Further, biaxial retardation plates 210a and 210b are disposed between the hybrid retardation plates 200a and 200b and the polarizing plates 220a and 220b, respectively. The biaxial retardation plates 210a and 210b prevent light leakage due to the optical rotation of the liquid crystal layer 140 in an oblique direction. The biaxial retardation plates 210a and 210b are respectively connected to the absorption axes Aa and Ab of the polarizing plates 220a and 220b. Are matched. Therefore, the phase difference from the front direction can be made substantially zero by the combination with the polarizing plates 220a and 220b, and only the wavelength dispersion in the oblique direction can be selectively improved.

<Backlight configuration>
The backlight 300 disposed facing the back polarizing plate 220b will be described with reference to FIG.

  The backlight 300 includes, for example, a plurality of tubular light sources 310 arranged side by side as shown in FIG. 5A, and a resin that efficiently emits light from the tubular light sources 310 to the front surface and accommodates the tubular light sources 310. A reflector 320 made of light, and an optical sheet disposed between the polarizing plate 220b (see FIG. 2) and the tubular light source 310 are configured.

  The optical sheet is, for example, a diffuser plate 340 such as TDX manufactured by Asahi Kasei Co., Ltd. for ensuring luminance uniformity, a BEFIII manufactured by 3M, for example, in which a plurality of prism rows that condense light source light emitted from the tubular light source 310 are arranged, and the like. Prism sheet 350,360.

The tubular light source 310 is composed of a high color rendering lamp typified by a three-wavelength cold cathode fluorescent tube. As an example, the tubular light source 310 has a light emission spectrum as shown by a curve A in FIG. The region has a green light region having a peak at 540 nm and a blue light region having a peak at 435 nm. As a light emitting phosphor excited by 147 nm ultraviolet rays when xenon gas is used as a discharge gas of a lamp, Y ₂ O ₃ : Eu phosphor for red, LaPO ₄ : Ce, Tb phosphor for green, and blue Although a BAM phosphor is used, other phosphors are often used, and there is no great difference in the emission spectrum for obtaining high color rendering properties.

FIG. 4B shows a modification of the present embodiment, in which a side light type surface light source is used as a backlight, and a light guide plate 370 made of acrylic resin or the like, and a tubular tube disposed on the side surface of the light guide plate 370. The light source 310, the reflector 380 that efficiently guides the light source light from the tubular light source 310 to the light guide plate 370, the diffuser plate 340 disposed thereon, and the prism sheets 350 and 360 disposed thereon. Even with such a configuration, the same effects as described above can be achieved.
Each color filter CF (R), CF (G), CF (B) of the liquid crystal cell 110 has a transmission characteristic that shares these light wavelengths, the red filter CF (R) is 580 nm or more, and the green filter CF (G ) Has a transmission characteristic of 580 to 510 nm, and the blue filter CF (B) has a transmission characteristic of 550 to 400 nm. The blue filter CF (B) has a wide passband, that is, the pass region of the blue filter CF (B) contains a sharp peak at 435 nm, a broad peak at 450 nm, and a low sharp peak at 490 nm in the emission spectrum of the lamp. .

<Configuration of dichroic dye element>
As shown in FIG. 2, the dichroic dye element 400 is composed of two transparent substrates 410, 420 with electrodes 411, 421 facing each other with a gap therebetween, and a mixture layer of the dichroic dye 431 and the liquid crystal 432. This is a dichroic dye liquid crystal cell having a guest-host liquid crystal structure with 430 sandwiched therebetween. A voltage circuit 440 is connected to each of the electrodes 411 and 421, and a voltage is applied between the electrodes.

  When the liquid crystal 432 is arranged in a direction perpendicular to the substrate surface, the dichroic dye 431 is also arranged in the same manner, and does not absorb light transmitted through the element in the vertical direction. On the other hand, light transmitted through the element in an oblique direction with respect to the direction perpendicular to the substrate surface is absorbed by the dichroic dye 431. The degree of absorption depends on the arrangement of the dichroic dyes. In the vertical arrangement, the absorption is the smallest in the direction perpendicular to the substrate surface, and the transmittance is maximum. In the present embodiment, a yellow dye that transmits red and green light and absorbs blue light is used as the dichroic dye, and blue light is selectively absorbed according to the transmission direction of the substrate.

  Furthermore, when a voltage is applied from the voltage circuit 440 connected to the electrodes 411 and 421, the arrangement direction of the mixture layer 430 changes. By changing the arrangement of the dye from the direction perpendicular to the substrate surface to the direction inclined, the absorption rate in a specific direction increases, so by selecting the blue light leakage in a certain direction on the display screen by controlling the applied voltage Can be suppressed.

  Further, when the voltage is controlled according to the display image, the blueness of the screen can be effectively prevented. On a screen with many black displays, even a slight bluish color is noticeable. Therefore, an image without a bluish color can be obtained by enhancing the action of the dichroic dye element on such a screen.

  This element is manufactured as follows. First, two glass substrates having electrodes formed of ITO films are prepared, a vertical alignment film is applied on these electrodes, and cured at 200 ° C. for 1 hour. Thereafter, the surface of the alignment film is rubbed with a rayon cloth. A gap of about 5.0 μm is provided between the two glass substrates so that the alignment films face each other and come inside, and the periphery is sealed and fixed with an adhesive. Thereafter, a mixture of vertically aligned liquid crystal and dichroic dye (C.I.Direct Yellow 12) in a weight ratio of 100: 1 is vacuum-injected and sealed to obtain a dichroic dye liquid crystal cell.

<Display operation>
As shown in FIG. 8, the light emitted from the tubular light source 310 passes through the polarizing plate 220b through the dichroic dye element 400 on the light path L. Here, only polarized light that has passed through transmission axes orthogonal to the absorption axes Aa and Ab of the polarizing plate 220b is emitted and passes through the dichroic dye element 400, the rear biaxial retardation plate 210b, and the rear hybrid retardation plate 200b. The light enters the liquid crystal cell 110.

  Since the total retardation of the liquid crystal layer 140 and all the retardation plates at the on-voltage in the normal direction is substantially zero, the polarized light passes through as it is and reaches the polarizing plate 220a on the front side. Since the polarizing plates 220a and 220b have a crossed Nicols arrangement, the polarized light is absorbed and blocked by the front polarizing plate 220a to obtain a black display.

  Since the retardation of the liquid crystal layer 140 changes depending on the voltage application state between the on-voltage and the off-voltage, and the difference from the retardation of all the retardation plates changes, the incident light emitted from the front biaxial retardation plate 210a is elliptically polarized. Thus, the light reaches the front polarizing plate 220a, and light is transmitted corresponding to the polarization state. By varying the applied voltage in this way, gradation display is possible.

  Focusing on the blue light, the light emitted from the tubular light source 310 passes through the dichroic dye element 400, so that 300-500 nm of the light reaching the incident light side polarizing plate 220b on the backlight side by this element. A part of the blue light in the range is selectively absorbed corresponding to the passing direction. That is, since it functions as a yellow filter in a direction that is colorless with respect to the direction perpendicular to the liquid crystal cell and that is inclined from this direction, it is possible to prevent light leakage of blue light in the inclined direction.

  When the dichroic dye element 400 is disposed between the backlight 300 and the polarizing plate 220b on the backlight side as described above, for example, the u′v ′ coordinate at 60 ° on the screen right field when there is no dichroic dye element. The chromaticity which was (u′v ′) = (0.185, 0.300) in the system became (u′v ′) = (0.200, 0.400) by insertion.

(Embodiment 2)
In this embodiment, a dichroic dye film 450 is used as a dichroic dye element. 8 denote the same parts, and a description thereof will be omitted. The dichroic dye film 450 has the transition dipole moment axes 452 of the dichroic dye 451 arranged uniformly in the uniaxial direction 453, and the polarizing plate 220b on the backlight 300 side, that is, the incident light side, the liquid crystal cell 110, and the like. Place between. Actually, it is inserted between the polarizing plate 220b and the biaxial retardation plate 210b. The axis 452 of the transition dipole moment is made substantially parallel to the absorption axis Ab of the polarizing plate 220b. In this embodiment, a yellow dye is used as the dichroic dye.

  The dichroic dye film 450 is a polarizing plate that produces a polarizing effect for light of a specific wavelength. When a yellow dye is used, it absorbs blue light with respect to vibration light in the direction of the axis 452 of the transition dipole moment. Specifically, the vibration light component of the transmission axis orthogonal to this is not absorbed. However, the polarization degree of the dichroic dye film can be arbitrarily selected, and it is easy to have an absorbing action even for vibration light slightly deviated from the absorption axis. Therefore, even if the transition dipole moment axis 452 of the dichroic dye film 450 is arranged in parallel with the absorption axis of the polarizing plate 220b, blue light is absorbed even for a polarized component slightly deviated from the absorption axis of the polarizing plate. To do. When a dichroic dye film having a high degree of polarization is used, it is preferable to shift the transition dipole moment axis by a slight angle from the absorption axis Ab of the polarizing plate on the incident light side. If the range is set to a maximum of 5 °, the visibility in the vertical direction of the liquid crystal cell is not affected. In this case, the angle of deviation may be adjusted according to the polar angle where the degree of bluishness due to light leakage is large in the field of view. Here, the fact that the axis 452 of the transition dipole moment and the absorption axis Ab of the polarizing plate 220b are substantially parallel to each other includes a shift in the range of 5 ° at the maximum.

  The dichroic dye film can be produced as follows. The PVA film was dyed for 5 minutes in a dyeing bath in which 1 g of dichroic dye (C.I.Direct Yellow 12) was dissolved in 1 L of water. Subsequently, the dyed film was stretched 4 times in a certain direction and immersed in a 5% boric acid aqueous solution for 3 minutes. This was air-dried at room temperature. As a protective film, triacetyl cellulose (TAC) was bonded to a stretched and dried PVA film from both sides to obtain a dichroic dye film.

  In the present embodiment, the polarizing plate 220b is bonded in such a manner that the absorption axis Ab of the polarizing plate and the stretching direction (transition dipole moment axis) 452 of the dichroic dye film 450 are parallel, and two retardation films 210b and 200b are further bonded. Affix to the chromatic dye film 450 side. The polarizing plate 220b, the dichroic dye film 450, and the retardation films 210b and 200b are disposed on the surface of the array substrate 120 on the incident light side of the liquid crystal cell 110 with bend alignment. Similarly, the polarizing plate 220a and the retardation films 210a and 200a are bonded to the surface of the counter substrate 130 on the outgoing light side of the liquid crystal cell.

  As a result, the chromaticity that was (u′v ′) = (0.185, 0.300) in the u′v ′ coordinate system at the right visual field of 60 ° with the structure without the dichroic dye film was obtained by inserting the film. (U′v ′) = (0.210, 0.405).

  As a modification of the present embodiment, a dichroic dye film 450 is disposed between the front emission light side polarizing plate 220 a and the liquid crystal cell 110. Blue light leakage is noticeable during black display, and this light leakage is caused by the fact that the polarization component of blue light transmitted through the phase difference plates 220a and 210a does not coincide with the absorption axis of the polarizing plate 220a. As a result, the undesired polarization component is absorbed together with the transition dipole moment of the dichroic dye film to eliminate light leakage. By keeping the angle of the transition dipole moment axis within 5 ° with respect to the absorption axis of the polarizing plate, the color balance in the vertical direction of the liquid crystal cell surface is not impaired.

  As mentioned above, although this invention was demonstrated by embodiment, it includes various deformation | transformation, for example, a phase difference plate can also be arrange | positioned to the one side of a liquid crystal cell, and also a polarizing plate has one reflection type liquid crystal display device. It can be similarly applied to.

1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment of the present invention. 1 is a partially enlarged schematic cross-sectional view of a liquid crystal cell according to an embodiment. 1 is a schematic equivalent circuit diagram of a liquid crystal cell according to an embodiment. The partial schematic front view of the array substrate of one Embodiment. The partial schematic front view of the array substrate of one Embodiment. (A) is a partial schematic cross-sectional view of the array substrate cut along the line BB in FIG. 5, and (b) is a partial schematic cross-sectional view of the array substrate cut along the line CC. The figure for demonstrating the display state of one Embodiment. 1 is a schematic configuration diagram of a liquid crystal display device according to an embodiment. (A), (b), (c) is the schematic explaining operation | movement of one Embodiment. (A), (b) is a schematic sectional drawing of the backlight of Embodiment 1. FIG. The schematic block diagram of the liquid crystal display device of other embodiment.

Explanation of symbols

110: Liquid crystal cell
120: Array substrate
130: Counter substrate
CF (R), CF (G), CF (B): Color filter
140: Liquid crystal layer
200a, 200b: Hybrid phase difference plate
210a, 210b: Biaxial retardation plate
220a, 220b: Polarizing plate
300: Backlight
400, 450: Dichroic dye element

Claims (7)

An array substrate and an opposing substrate each having an electrode, the electrodes facing each other, a liquid crystal layer sandwiched between the substrates and arranged in a bend, and red, green, and blue colors provided on one of the substrates A liquid crystal cell comprising a filter;
A phase difference plate disposed on at least one of the liquid crystal cells;
Two polarizing plates disposed across the liquid crystal cell and the retardation plate,
A dichroic dye disposed on a path of light passing through the liquid crystal cell, the retardation plate and the polarizing plate and having an arrangement with anisotropic visible light transmittance, and perpendicular to the liquid crystal cell surface; A dichroic dye element that selectively maximizes the transmittance of light of a predetermined wavelength in the direction;
A liquid crystal display device comprising:   The liquid crystal display device according to claim 1, wherein the predetermined wavelength light is light in a range of 300 nm to 500 nm.   3. The liquid crystal display device according to claim 1, wherein the dichroic dye element comprises two substrates, a liquid crystal sandwiched between the substrates, and a mixture layer of the dichroic dye.   4. The two substrates of the dichroic dye element each have an electrode to which a voltage can be applied to the mixture layer, and the arrangement of the dichroic dye changes by applying the voltage. The liquid crystal display device described.   The liquid crystal display device according to claim 4, wherein a control circuit for changing an arrangement of dichroic dyes according to a display image of the liquid crystal cell is connected to the electrode. An array substrate and an opposing substrate each having an electrode, the electrodes facing each other, a liquid crystal layer sandwiched between the substrates and arranged in a bend, and red, green, and blue colors provided on one of the substrates A liquid crystal cell comprising a filter;
A phase difference plate disposed on at least one of the liquid crystal cells;
Two polarizing plates disposed across the liquid crystal cell and the retardation plate,
A dichroic dye disposed on a passage of light passing through the liquid crystal cell, the retardation plate and the polarizing plate and having an anisotropic arrangement in visible light transmittance; A liquid crystal display device, which is disposed between one polarizing plate and the liquid crystal cell, wherein the transition dipole moment of the dichroic dye and the absorption axis are disposed substantially in parallel.   The liquid crystal display device according to claim 1, wherein the predetermined wavelength light is blue light.

Images