JP2004325795A - Liquid crystal display - Google Patents

Abstract

Provided is a TN-type liquid crystal display device having a wide viewing angle, little change in black display color due to a viewing angle, and capable of observing a color image having substantially the same contrast and hue over a wide viewing angle. .
A liquid crystal element (1) having a liquid crystal layer (10) in which liquid crystal molecules (11) are twisted at a twist angle of 90 ° is provided, and front and rear polarizers (12, 13) whose transmission axes are orthogonal to each other. Are arranged, and the average tilt angles α of the discotic liquid crystal molecules 19 of both the viewing angle improving elements 14 and 15 are respectively set to those of the liquid crystal element 1. The average tilt angle θ of the liquid crystal molecules 11 when a black display voltage was applied between the electrodes 4 and 5 was set to a value satisfying the relationship α = 90−θ.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display device provided with a viewing angle improving element having a discotic liquid crystal layer.
[0002]
[Prior art]
In the liquid crystal display device, electrodes forming a plurality of pixels are provided on regions facing each other on inner surfaces of a pair of substrates arranged opposite to each other, and liquid crystal molecules are substantially provided between the pair of substrates. A TN (twisted nematic) type liquid crystal element comprising a liquid crystal element provided with a liquid crystal layer twisted at a twist angle of 90 ° and a pair of polarizing plates interposed therebetween. Widely used.
[0003]
However, this TN type liquid crystal display device has a problem that a viewing angle of display (an observation angle range in which display can be observed with good contrast) is narrow.
[0004]
Therefore, conventionally, the discotic liquid crystal molecules are arranged between the liquid crystal element and the pair of polarizing plates, the tilt directions of the discotic liquid crystal molecules are aligned in one direction, and the surface facing the polarizing plate and the surface facing the liquid crystal element. There has been proposed a liquid crystal display device having a wide viewing angle by arranging a viewing angle improving element having a discotic liquid crystal layer which is sequentially oriented with different tilt angles from one side to the other (Patent Document 1). reference).
[0005]
[Patent Document 1]
JP 2000-338489 A
[0006]
[Problems to be solved by the invention]
However, in the liquid crystal display device having the viewing angle improving element, the optical characteristics of the liquid crystal layer of the liquid crystal element and the discotic liquid crystal layer of the viewing angle improving element have wavelength dependence, and the optical action is the viewing angle (display). In the viewing direction), the hue of the display changes according to the change in the viewing angle.
[0007]
This change in hue is such that in a normally white mode liquid crystal display device in which a pair of polarizing plates are arranged with their transmission axes substantially orthogonal to each other, the color of black display changes significantly according to the viewing angle.
[0008]
In a color liquid crystal display device in which a liquid crystal element is provided with three color filters of red, green, and blue respectively corresponding to the plurality of pixels, the transmission intensity of light of each color according to the viewing angle changes depending on the viewing angle. Therefore, the hue of the observed color image changes according to the viewing angle, and the contrast also decreases.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device having a wide viewing angle, little change in display color due to the viewing angle, and capable of observing a color image having substantially the same contrast and hue over a wide viewing angle. It is what it was.
[0010]
[Means for Solving the Problems]
In the liquid crystal display device of the present invention, electrodes forming a plurality of pixels are provided on regions facing each other on inner surfaces of a pair of substrates arranged opposite to each other, and an inner surface of one substrate corresponds to each of the plurality of pixels. A liquid crystal layer provided with three color filters of red, green, and blue, and a liquid crystal layer in which liquid crystal molecules are twisted at a twist angle of substantially 90 ° between the substrates, between the pair of substrates. A discotic liquid crystal disposed between the liquid crystal element and the pair of polarizing plates, and a pair of polarizing plates having transmission axes in directions substantially orthogonal to each other disposed with the liquid crystal element interposed therebetween; The molecules were aligned with their tilt directions aligned in one direction, and the tilt angle was sequentially changed from one of the surface facing the polarizing plate and the surface facing the liquid crystal element to a different tilt angle. A pair of viewing angle improving elements having a discotic liquid crystal layer, wherein the average tilt angle α of the discotic liquid crystal molecules of the pair of viewing angle improving elements was respectively applied with a voltage for displaying black between the electrodes of the liquid crystal element. When the average tilt angle of the liquid crystal molecules at the time is θ, the value is set to a value satisfying the relationship α = 90−θ.
[0011]
In this liquid crystal display device, a viewing angle improving element having the discotic liquid crystal layer is disposed between the liquid crystal element and the pair of polarizing plates, so that a display viewing angle is wide.
[0012]
In addition, this liquid crystal display device is of a normally white mode in which the pair of polarizing plates are arranged with their transmission axes substantially orthogonal to each other. However, the discotic liquid crystal molecules of the pair of viewing angle improving elements are used. Is set to a value satisfying the relationship α = 90−θ with respect to the average tilt angle θ of liquid crystal molecules when a voltage for displaying black is applied between the electrodes of the liquid crystal element. Therefore, there is almost no color change in display due to the viewing angle, and therefore, a color image having substantially the same contrast and hue can be observed over a wide viewing angle.
[0013]
As described above, in the liquid crystal display device of the present invention, the electrodes that form the plurality of pixels are provided on the mutually facing inner surfaces of the pair of substrates by the regions facing each other, and the inner surface of one of the substrates respectively corresponds to the plurality of pixels. A liquid crystal element provided with three color filters of red, green, and blue, and a liquid crystal layer between the pair of substrates, in which liquid crystal molecules are twisted at a twist angle of substantially 90 ° between the substrates; And a pair of polarizing plates having transmission axes in directions substantially orthogonal to each other disposed with the liquid crystal element interposed therebetween, each of which has a discotic liquid crystal molecule, the tilt direction of which is aligned in one direction, and A viewing angle improving element having a discotic liquid crystal layer that is sequentially oriented with a different tilt angle from one of the surface facing the polarizing plate and the surface facing the liquid crystal element to the other is provided. Further, the average tilt angle α of the discotic liquid crystal molecules of the viewing angle improving element, with respect to the average tilt angle θ of the liquid crystal molecules when a voltage for displaying black is applied between the electrodes of the liquid crystal element, By setting a value that satisfies the relationship α = 90−θ, the viewing angle is widened, and the color change of the display due to the viewing angle is almost eliminated, and a color image with substantially the same contrast and hue is observed over a wide viewing angle. It is something that can be done.
[0014]
In the liquid crystal display device of the present invention, the liquid crystal layer of the liquid crystal element has a refractive index anisotropy of Δn (450 nm) for light having a wavelength of 450 nm and a refractive index anisotropy of Δn (650 nm) for light having a wavelength of 650 nm. In this case, it is preferable that the liquid crystal material satisfies 1 <Δn (450 nm) / Δn (650 nm) ≦ 1.07.
[0015]
Further, in the liquid crystal display device of the present invention, the liquid crystal layer of the liquid crystal element has a refractive index anisotropy Δn (450 nm) of the liquid crystal with respect to light having a wavelength of 450 nm and a product Δnd of the liquid crystal layer thickness d, Δnd (450 nm). The ratio of the refractive index anisotropy Δn (650 nm) of the liquid crystal with respect to light having a wavelength of 650 nm to the liquid crystal layer thickness d and the Δnd (650 nm) value is 0.94 ≦ Δnd (450 nm) / Δnd. It is preferable to set the value of the refractive index anisotropy of the liquid crystal and the value of the liquid crystal layer thickness so as to satisfy (650 nm) ≦ 1.10.
[0016]
Further, the discotic liquid crystal layers of the pair of viewing angle improving elements each have an in-plane retardation of 150 nm, and the value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal element and the liquid crystal layer thickness d is: It is desirable to set it to 340 to 430 nm.
[0017]
Further, when the in-plane phase difference of the discotic liquid crystal layer of the pair of viewing angle improving elements is 150 nm, the value of Δnd of the liquid crystal element corresponds to the pixel corresponding to the red color filter and the green color filter. Are set to 340 to 430 nm, respectively, and the Δnd of the pixel corresponding to the blue color filter is set to be 1.10 times or less larger than the Δnd of the pixel corresponding to the red and green color filters. Is more desirable.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show a first embodiment of the present invention. FIG. 1 is a sectional view of a part of a liquid crystal display device.
[0019]
The liquid crystal display device of this embodiment is an aircraft liquid crystal display device installed in a cockpit of an aircraft. As shown in FIG. 1, a liquid crystal element 1 and a front side and a rear side of the liquid crystal element 1 with the liquid crystal element 1 interposed therebetween. And a pair of viewing angle improving elements 14 and 15 disposed between the liquid crystal element 1 and the pair of polarizing plates 12 and 13, respectively.
[0020]
The liquid crystal element 1 has a plurality of pixels formed by opposing regions on opposing inner surfaces of a pair of front and rear transparent substrates (for example, glass substrates) 2 and 3 which are arranged to face each other and are joined via a frame-shaped sealing material (not shown). Are provided on one of the substrates, for example, on an inner surface of a front substrate (hereinafter, referred to as a front substrate) 1 which is a display observation side (an upper side in FIG. 1), and is provided on each of the plurality of pixels. Three corresponding color filters 6R, 6G, 6B of red, green, and blue are provided, and a liquid crystal layer 10 is provided between the pair of substrates 2, 3.
[0021]
The liquid crystal element 1 is, for example, an active matrix liquid crystal display element having a TFT (thin film transistor) as an active element, and an electrode 5 formed on the inner surface of a rear substrate (hereinafter, referred to as a rear substrate) 3 has a row direction and a vertical direction. The plurality of pixel electrodes arranged in a matrix in the column direction and the electrode 4 formed on the inner surface of the front substrate 2 are a single-film counter electrode facing the plurality of pixel electrodes 5.
[0022]
Although not shown in FIG. 1, on the inner surface of the rear substrate 3, a plurality of TFTs respectively corresponding to the plurality of pixel electrodes 5, a plurality of gate wirings for supplying gate signals to the TFTs in each row, A plurality of data lines for supplying data signals to the TFTs in each column are provided, and the plurality of pixel electrodes 5 are connected to the TFTs corresponding to the pixel electrodes 5, respectively.
[0023]
The red, green, and blue color filters 6R, 6G, and 6B are formed on the substrate surface of the front substrate 2, and the counter electrode 4 is formed on these color filters 6R, 6G, and 6B. Have been.
[0024]
Further, on the inner surfaces of the pair of substrates 2 and 3, there are formed horizontal alignment films 8 and 9 which cover the electrodes 4 and 5 and are aligned in directions substantially orthogonal to each other.
[0025]
The liquid crystal layer 10 is formed by filling a region surrounded by the sealing material between the pair of substrates 2 and 3 with a nematic liquid crystal having a positive dielectric anisotropy. Is defined by the horizontal alignment films 8 and 9 in the vicinity of the front and rear substrates 2 and 3, and as shown by a solid line in FIG. And twist-oriented.
[0026]
The liquid crystal layer 10 of the liquid crystal element 1 has a refractive index anisotropy of Δn (450 nm) with respect to light having a wavelength of 450 nm, that is, light in a blue wavelength band, and has light with a wavelength of 650 nm, that is, light in a red wavelength band. When the refractive index anisotropy is Δn (650 nm), the liquid crystal material is formed of a liquid crystal material having a value of Δn (450 nm) / Δn (650 nm) of 1.07 or less and greater than 1.
[0027]
FIG. 6 shows the value of the color shift for each Δnd of the liquid crystal layer in the liquid crystal display element using each liquid crystal having the value of Δn (450 nm) / Δn (650 nm) of 1.06 to 1.13. In this case, the upper limit of the color shift is 0.05 to 0.06.
[0028]
From FIG. 6, the liquid crystal layer 10 of the liquid crystal element 1 has a liquid crystal material in which the value of Δn (450 nm) / Δn (650 nm) is 1.07 or less and larger than 1, that is,
1 <Δn (450 nm) / Δn (650 nm) ≦ 1.07
Of a liquid crystal material satisfying the following.
[0029]
Further, the liquid crystal layer thickness d of the liquid crystal element 1 is substantially equal over all the pixels corresponding to the red, green and blue color filters 6R, 6G and 6B. As shown in FIG. 7, the liquid crystal of this liquid crystal element 1 has a maximum lateral contrast and an upper contrast when the product Δnd of the refractive index anisotropy Δn and the thickness d of the liquid crystal layer is between 340 and 430 nm. , Δnd are set to 340 to 430 nm.
[0030]
Further, this liquid crystal display device is of a normally white mode, and the pair of polarizing plates 12 and 13 are disposed with their transmission axes 12a and 13a (see FIG. 3) substantially orthogonal to each other. .
[0031]
On the other hand, each of the pair of viewing angle improving elements 14 and 15 disposed between the liquid crystal element 1 and the pair of polarizing plates 12 and 13 has an alignment treatment film on one surface of a transparent film substrate 16. 17 are formed thereon, and the discotic liquid crystal molecules 19 are aligned with the tilt direction thereof being aligned in one direction and the tilt angle is sequentially changed from the surface adjacent to the film substrate 16 to the other surface. In this embodiment, a discotic liquid crystal layer 18 is provided.
[0032]
That is, the discotic liquid crystal layer 18 is formed by applying a discotic liquid crystal on the alignment film 17 of the film substrate 16, and applying the discotic liquid crystal 19 to the discotic liquid crystal molecules 19 adjacent to the film substrate 16. The film 17 is arranged substantially parallel to the surface of the film substrate 16, and the discotic liquid crystal molecules 19 are cured in a state where the discotic liquid crystal molecules 19 are arranged at a large tilt angle with respect to the film substrate 16 on the surface opposite to the film substrate 16. Made of discotic film.
[0033]
As described above, the viewing angle improving elements 14 and 15 align the discotic liquid crystal molecules 19 in one direction and gradually tilt the discotic liquid crystal molecules 19 from one surface (the surface on the film substrate 16 side) to the other surface. It has a discotic liquid crystal layer 18 oriented to increase the tilt angle.
[0034]
The discotic liquid crystal layer 18 is arranged so that each molecular axis 19a perpendicular to the disc-shaped surface of the discotic liquid crystal molecules 19 is continuously inclined as shown in FIG. The direction in which these molecular axes 19a are averaged is defined as the optical axis 20 of the discotic liquid crystal layer 18 having the minimum refractive index, and has a negative optical anisotropy.
[0035]
An average tilt angle obtained by averaging the tilt angles of the discotic liquid crystal molecules 19 of the pair of viewing angle improving elements 14 and 15 with respect to the film substrate 16 over the entire layer thickness (the tilt angles indicated by alternate long and short dash lines in FIGS. 1 and 2). A) is a voltage for displaying black between the electrodes 4 and 5 of the liquid crystal element 1 (the rising angle of the liquid crystal molecules 11 close to perpendicular to the surfaces of the substrates 2 and 3 as shown by the two-dot chain line in FIG. 1). When the average tilt angle of the liquid crystal molecules 11 when applying a voltage for applying
α = 90−θ
Is set to a value that satisfies the relationship.
[0036]
FIG. 8 shows the relationship between the voltage applied between the electrodes 4 and 5 of the liquid crystal element 1 and the average tilt angle of the liquid crystal molecules 11 acting by the electric field. FIG. 9 shows the relationship between the normal line of the display screen. FIG. 10 shows a horizontal contrast that is a contrast in a direction inclined by 50 ° with respect to a direction inclined by 50 ° with respect to a normal line of a display screen in a u′v ′ chromaticity coordinate system (chromaticity coordinates of CIE1976 UCS). FIG. 11 shows a value of a color shift which is a change of a display color upon observation, and FIG. 11 shows an upward contrast which is a contrast in a direction inclined by 30 ° with respect to a normal line of the display screen.
[0037]
As shown in FIG. 8, when a voltage of 6 V is applied between the electrodes 4 and 5 of the liquid crystal element 1, the average tilt angle θ of the liquid crystal molecules 11 becomes approximately 72 °, and black with low transmittance is displayed.
[0038]
On the other hand, in the discotic liquid crystal layers 18 of the viewing angle improving elements 14 and 15, as shown in FIG. 9, the larger the average tilt angle α of the discotic liquid crystal molecules 19 is, the higher the lateral contrast is.
[0039]
On the other hand, the color shift by the discotic liquid crystal layer 18 shows a minimum value when the average tilt angle α of the discotic liquid crystal molecules 19 is between 17 ° and 19 °, and as shown in FIG. A sufficiently high contrast is obtained in the range of 17 ° to 19 °.
[0040]
As shown in these figures, the range of the average tilt angle of the discotic liquid crystal molecules is 17 ° to 19 °, particularly 18 °, in order to obtain a sufficient contrast and sufficiently reduce the color shift. It is desirable that
[0041]
When a black display voltage is applied between the electrodes 4 and 5 of the liquid crystal element 1 of the liquid crystal display device, the average tilt angle θ of the liquid crystal molecules 11 is about 72 °, and therefore, the pair of viewing angle improving elements 14 and 15 is used. Are aligned such that the average tilt angle α is about 18 ° (α = 90−72 = 18).
[0042]
Further, as shown in FIGS. 9, 10, and 11, the discotic liquid crystal layer has a discotic liquid crystal layer whose in-plane retardation value, which is the difference between the refractive index of ordinary light and the extraordinary light with respect to light incident in the normal direction, is 150 nm. When the tick liquid crystal layer 18 is used, characteristics excellent in both contrast and color shift are obtained.
[0043]
Therefore, in this liquid crystal display device, the viewing angle improving elements 14 and 15 having an in-plane phase difference of 150 nm are used.
[0044]
The pair of viewing angle improving elements 14 and 15 make the tilt angle changing directions of the discotic liquid crystal molecules 19 opposite to each other, and the optical axis 20 at which the refractive index of the discotic liquid crystal layer 18 is minimized. Is arranged between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13 with a direction (hereinafter, referred to as a substrate projection optical axis) 20a of the liquid crystal element 18 projected on the surface of the discotic liquid crystal layer 18 in a predetermined direction. Have been.
[0045]
In this embodiment, as shown in FIG. 1, the pair of viewing angle improving elements 14 and 15 are arranged such that the surfaces of the discotic liquid crystal molecules 19 where the tilt angle is large face the liquid crystal element 1, It is attached to the liquid crystal element 1 by the adhesive layer 21.
[0046]
FIG. 3 shows the liquid crystal molecule alignment directions 2a and 3a near the pair of substrates 2 and 3 of the liquid crystal element 1, the directions of the transmission axes 12a and 13a of the front and rear polarizing plates 12 and 13, and the pair of viewing angle improving elements. 14 and 15 show the directions of the substrate projection optical axis 20a.
[0047]
As shown in FIG. 3, the liquid crystal molecule alignment direction 2a in the vicinity of the front substrate 2 of the liquid crystal element 1 is 45 degrees counterclockwise with respect to the horizontal axis x of the screen of the liquid crystal display device when viewed from the front side, which is the display observation side. The liquid crystal molecule orientation direction 3a in the vicinity of the rear substrate 3 is shifted by 45 ° clockwise with respect to the horizontal axis x when viewed from the front side. The molecules 11 are twist-oriented from the rear substrate 3 to the front substrate 2 with a twist angle of substantially 90 ° clockwise as viewed from the front side, as indicated by the dashed arrow in the drawing.
[0048]
The polarizing plate 12 on the front side of the liquid crystal element 1 has its transmission axis 12a substantially orthogonal to the liquid crystal molecule alignment direction 2a near the front substrate 2 of the liquid crystal element 1 as shown in FIG. Alternatively, the rear polarizing plate 13 is disposed substantially in parallel, and the transmission axis 13 a of the rear polarizing plate 13 is disposed substantially orthogonal to the transmission axis 12 a of the front polarizing plate 12.
[0049]
Further, of the pair of viewing angle improving elements 14 and 15, the front viewing angle improving element 14 is provided between the liquid crystal element 1 and the front polarizing plate 12, through the substrate projection optical axis (the discotic liquid crystal layer 18). The direction (projection of the optical axis 20 having the minimum refractive index on the surface of the discotic liquid crystal layer 18) 20a is substantially parallel to the liquid crystal molecule orientation direction 2a in the vicinity of the front substrate 2 of the liquid crystal element 1. The rear viewing angle improving element 15 is arranged between the liquid crystal element 1 and the rear polarizing plate 13 so that the substrate projection optical axis 20 a is aligned with the liquid crystal molecule orientation direction 3 a near the rear substrate 3 of the liquid crystal element 1. They are arranged substantially in parallel.
[0050]
This liquid crystal display device uses an illuminating light from a surface light source disposed on the rear side to perform display. The rear polarizing plate 13 converts the light into linearly polarized light parallel to its transmission axis 13a, and the light enters the liquid crystal display. The polarization state is changed by the discotic liquid crystal layer 18 of the viewing angle improving element 15 on the side, the liquid crystal layer of the liquid crystal element 1, and the discotic liquid crystal layer 18 of the viewing angle improving element 14 on the front side. A linearly polarized light component parallel to the absorption axis (not shown) of the front-side polarizing plate 12 is absorbed by the front-side polarizing plate 12, and a linearly-polarized light component parallel to the transmission axis 12 a of the front-side polarizing plate 12 is And exits to the observation side.
[0051]
This liquid crystal display device is driven by controlling a voltage value applied between the electrodes 4 and 5 of a plurality of pixels of the liquid crystal element 1 in accordance with a predetermined number of display gradations, and a display corresponding to the plurality of pixels is performed. The image is displayed by changing the brightness of the image.
[0052]
This liquid crystal display device is of a normally white mode in which front and rear polarizing plates 12 and 13 are arranged with their transmission axes 12a and 13a substantially orthogonal to each other. Of these, the liquid crystal molecules 11 are aligned between the electrodes 4 and 5 at a rising angle nearly perpendicular to the surfaces of the substrates 2 and 3 as shown by a two-dot chain line in FIG. Is displayed in black.
[0053]
A display corresponding to a pixel to which a voltage lower than the black display voltage is applied is a bright display with a gradation corresponding to the applied voltage, and when the applied voltage becomes substantially 0 V, that is, when the liquid crystal molecules 11 When the pixel is aligned in the initial twist alignment state, the display corresponding to the pixel becomes the brightest bright display.
[0054]
Further, in this liquid crystal display device, the liquid crystal element 1 is provided with three color filters 6R, 6G, 6B of red, green, and blue corresponding to a plurality of pixels, respectively. , Or blue, and a color image is expressed by the gradation of bright display of red, green, and blue and the black display.
[0055]
In this liquid crystal display device, the viewing angle improving elements 14 and 15 each having the discotic liquid crystal layer 18 are arranged between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13, so that the display viewing angle is wide.
[0056]
That is, the alignment state of the liquid crystal molecules 11 of the liquid crystal layer 10 of the liquid crystal element 1 is changed so as to rise with respect to the surfaces of the substrates 2 and 3 while maintaining the twist alignment state by applying a voltage. The liquid crystal molecules 11 in the vicinity of the substrate, which are strongly subjected to the alignment control force, remain in a state of falling down at an initial pretilt angle or an angle close thereto even when a voltage is applied. Even when a voltage for aligning the molecules 11 at a rising angle (approximately 72 °) close to the perpendicular to the surfaces of the substrates 2 and 3 is applied, the liquid crystal layer 10 keeps the liquid crystal molecules 11 near the substrate almost out of the initial alignment. Has residual retardation due to no change.
[0057]
In addition, the liquid crystal layer 10 of the liquid crystal element 1 exhibits different retardations with respect to light transmitted through the liquid crystal layer 10 in a vertical direction and light transmitted through an oblique direction (a direction inclined with respect to the vertical direction). In a liquid crystal display device of a mari-white mode, when viewed from the front of the screen (near the direction perpendicular to the screen), a black display with sufficient darkness can be observed with good contrast. When observed, the darkness of the black display rises, and the contrast is greatly reduced.
[0058]
On the other hand, the pair of viewing angle improving elements 14 and 15 have a discotic liquid crystal layer 18, and align the discotic liquid crystal molecules 19 in one tilt direction, and face the polarizing plates 12 and 13. And the liquid crystal element 1 is oriented so that the tilt angle is sequentially changed from one of the surfaces facing the liquid crystal element 1 to the other, and the pair of viewing angle improving elements 14 and 15 form the respective discotic liquid crystal molecules 19. Since the tilt angle change directions are opposite to each other, the liquid crystal element 1 and the front and rear polarizers 12 and 13 are disposed between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13. Is apparently opposite to the liquid crystal molecule alignment state on one substrate side and the liquid crystal molecule alignment state on the other substrate side from the center of the liquid crystal layer thickness when voltage is applied to the liquid crystal element 1.
[0059]
Moreover, since the liquid crystal layers 18 of the viewing angle improving elements 14 and 15 are discotic liquid crystal layers, their retardations have no directivity.
[0060]
In this liquid crystal display device, the viewing angle improving element 14 between the liquid crystal element 1 and the front polarizer 12 is connected to the substrate projection optical axis (the optical axis 20 at which the refractive index of the discotic liquid crystal layer 18 is minimum). The direction (projected onto the surface of the discotic liquid crystal layer 18) 20a is substantially parallel to the liquid crystal molecule orientation direction 2a in the vicinity of the front substrate 2 of the liquid crystal element 1, and the liquid crystal element 1 and the rear polarizing plate are arranged. The viewing angle improving element 14 between the liquid crystal element 13 and the substrate 13 is arranged so that its substrate projection optical axis 20a is substantially parallel to the liquid crystal molecule orientation direction 3a near the rear substrate 3 of the liquid crystal element 1.
[0061]
Therefore, when the voltage of the liquid crystal element 1 is applied, the residual retardation caused by the liquid crystal molecules 11 near the substrate hardly changing from the initial alignment state is canceled out by the pair of viewing angle improving elements 14 and 15, and the display viewing angle, that is, It is possible to widen the observation angle range in which the display of a good contrast with sufficient darkness of the black display can be observed.
[0062]
In addition, this liquid crystal display device is of a normally white mode in which the front and rear polarizing plates 12, 13 are arranged with their transmission axes 12a, 13a substantially orthogonal to each other. The average tilt angles α of the discotic liquid crystal molecules 19 of the liquid crystal elements 14 and 15 with respect to the average tilt angle θ of the liquid crystal molecules 11 when a voltage for displaying black is applied between the electrodes 4 and 5 of the liquid crystal element 1, respectively. Since a value satisfying the relationship α = 90−θ is set, the black display when viewed from the front and the black display when viewed from an oblique direction are almost the same color display.
[0063]
Therefore, in this liquid crystal display device, there is almost no color change in display depending on the viewing angle, and therefore, a color image having substantially the same contrast and hue can be observed over a wide viewing angle.
[0064]
In addition, in this embodiment, as described above, the liquid crystal layer 10 of the liquid crystal element 1 has a refractive index anisotropy Δn (450 nm) for light having a wavelength of 450 nm (light in a blue wavelength band) and a wavelength of 650 nm. Is formed of a liquid crystal material that satisfies 1 <Δn (450 nm) / Δn (650 nm) ≦ 1.07 with respect to the refractive index anisotropy Δn (650 nm) of the light (red wavelength band light). Therefore, the change in the transmittance balance of light in each of the red, green, and blue wavelength bands due to the viewing angle can be reduced, and the viewing angle dependency of the hue of the composite color of the emitted light of red, green, and blue can be extremely reduced. Therefore, a color image having almost the same hue can be observed over a wide viewing angle.
[0065]
Further, in this embodiment, as described above, the in-plane phase difference of the discotic liquid crystal layer 18 of the pair of viewing angle improving elements 14 and 15 is set to 150 nm, and the value of Δnd of the liquid crystal element 1 is set to 340. 430 nm, the residual retardation caused by the fact that the liquid crystal molecules 11 near the substrate hardly change from the initial alignment state when the above-described voltage is applied to the liquid crystal element 1 is reduced by the pair of viewing angle improving elements 14 and 15. Accordingly, it is possible to effectively cancel out the image so as not to substantially affect the display, and to observe a color image having almost the same hue and little change in contrast and hue over a wide viewing angle.
[0066]
Therefore, this liquid crystal display device has all functions required for an aircraft display device.
[0067]
That is, a display device installed in a cockpit of an aircraft is required to have a structure in which the display contrast does not change and the contrast and the hue do not change even when viewed at any viewing angle.
[0068]
As described above, the liquid crystal display device has a wide viewing angle, has almost no change in display color depending on the viewing angle, and can observe a color image having substantially the same contrast and hue over a wide viewing angle. It is suitable for a display device installed in a cockpit of an aircraft.
[0069]
FIG. 4 is a sectional view of a part of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display device according to this embodiment is disposed between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13, respectively. The in-plane phase difference of the discotic liquid crystal layer 18 of the pair of viewing angle improving elements 14 and 15 is set to 150 nm as described above, and the value of Δnd of the liquid crystal element 1 is set to a red color filter (hereinafter, referred to as “color filter”). The Δnd of the pixel corresponding to 6R and the pixel corresponding to 6G of the green color filter (hereinafter referred to as green filter) are set to 340 to 430 nm, respectively, and the blue color filter (hereinafter referred to as blue filter) 6B. The Δnd of the corresponding pixel is shifted with respect to the Δnd of the pixel corresponding to the red and green filters 6R and 6G by a color shift in the horizontal direction (caused by a change in the viewing angle in the horizontal axis direction of the screen). Shifuto) and color shift upward (vertical axis color shift due to change in viewing angle in the direction of the screen) in which was set to be within the upper limit.
[0070]
That is, FIGS. 12 and 13 show Δnd (), which is the product Δnd of the refractive index anisotropy Δn (450 nm) of the liquid crystal with respect to light having a wavelength of 450 nm and the liquid crystal layer thickness d of a region (pixel) where the wavelength light is transmitted. The ratio of the refractive index anisotropy Δn (650 nm) of the liquid crystal to the light having a wavelength of 650 nm to the value of Δnd (650 nm), which is the product of the thickness d of the liquid crystal layer in a region through which the light is transmitted, with respect to the value 450 nm FIG. 12 shows the relationship between the value of (450 nm) / Δnd (650 nm) and the color shift due to the change in the viewing angle. FIG. 12 shows the horizontal color shift when displaying a halftone (gray), and FIG. This shows an upward color shift when black is displayed.
[0071]
When the upper limit of the color shift is set to 0.05 as shown in FIG. 12, the value of Δnd (450 nm) / Δnd (650 nm) is 1.1, and as shown in FIG. When the value is 0.1, the value of Δnd (450 nm) / Δnd (650 nm) is 0.94.
[0072]
Therefore, the value of Δnd (450 nm) / Δnd (650 nm) is desirably in the range of 0.94 or more and 1.10 or less, preferably 1.07 or less, and more preferably 1.02.
[0073]
Therefore, in this embodiment, Δnd of the pixel corresponding to the blue filter 6B is set to a value of 0.94 to 1.10 with respect to Δnd of the pixel corresponding to the red and green filters 6R and 6G. ing.
[0074]
In the liquid crystal display device of this embodiment, Δnd of the pixel corresponding to the blue filter 6B of the liquid crystal element 1 is set to be larger than Δnd of the pixel corresponding to the red and green filters 6R and 6G. The configuration is the same as in the first embodiment.
[0075]
Also in this embodiment, the liquid crystal layer 10 of the liquid crystal element 1 has a refractive index anisotropy Δn (450 nm) for light having a wavelength of 450 nm and a refractive index anisotropy Δn (650 nm) for light having a wavelength of 650 nm. Is desirably formed of a liquid crystal material satisfying a ratio of 1 <Δn (450 nm) / Δn (650 nm) ≦ 1.07.
[0076]
In this embodiment, of the red, green, and blue color filters 6R, 6G, and 6B provided on the inner surface of the front substrate 2 of the liquid crystal element 1, a transparent filter is provided on the blue filter 6B (below the counter electrode 4). By providing the liquid crystal layer thickness adjusting film 7, the liquid crystal layer thickness d of the pixel corresponding to the red filter 6R and the green filter 6G is provided. ₁ And the liquid crystal layer thickness d of the pixel corresponding to the blue filter 6B. ₂ And Δnd (hereinafter, Δnd) of pixels corresponding to the red filter 6R and the green filter 6G. ₁ ) And Δnd (hereinafter, Δnd) of the pixel corresponding to the blue filter 6B. ₂ 0.94 <Δnd) ₂ / Δnd ₁ <1.10.
[0077]
As described above, Δnd of the pixel corresponding to the red filter 6R and the green filter 6G of the liquid crystal element 1 ₁ Are 340 to 430 nm, respectively, so that the Δnd of the pixel corresponding to the blue filter 6B is ₂ Is 374 to 473 nm.
[0078]
In the liquid crystal display device of this embodiment, the in-plane phase difference of the discotic liquid crystal layer 18 of the pair of viewing angle improving elements 14 and 15 is set to 150 nm, respectively, and the red and green filters 6R and 6G of the liquid crystal element 1 are used. Δnd of the corresponding pixel ₁ Are 340 to 430 nm, respectively, and Δnd of the pixel corresponding to the blue filter 6B. ₂ Is the Δnd of the pixel corresponding to the red and green filters 6R and 6G. ₁ Is set at a ratio of 0.94 to 1.10, the black display can be made even closer to black, and a color image with high contrast and color reproducibility can be observed over a wide viewing angle. .
[0079]
That is, since this liquid crystal display device is of a normally white mode, the light transmittance decreases as the voltage applied between the electrodes 3 and 4 of the liquid crystal element 1 increases.
[0080]
However, since the voltage-transmittance characteristic of this liquid crystal display device has wavelength dependence, the Δnd values of the pixels corresponding to the red, green, and blue filters 6R, 6G, and 6B of the liquid crystal element 1 are the same. In some cases, the difference between the transmittance of light in each of the red, green, and blue wavelength bands on the low voltage side is small, but on the high voltage side, that is, the black display side, the difference in the transmittance of light in each of the blue wavelength bands is smaller. Also, the degree of reduction in the transmittance of light in the red and green wavelength bands becomes large, and the display becomes bluish.
[0081]
On the other hand, in this embodiment, Δnd of the pixel corresponding to the blue filter 6B of the liquid crystal element 1 ₂ Is the Δnd of the pixel corresponding to the red and green filters 6R and 6G. ₁ Δnd of the pixel corresponding to the blue filter 6B. ₂ Δnd of pixels corresponding to red and green filters 6R and 6G of ₁ To 0.94 to 1.10, the transmittance of light in each of the blue wavelength bands on the high voltage side is made substantially the same as the transmittance of light in the red and green wavelength bands. That is, it is possible to substantially eliminate the band color of the display on the black display side.
[0082]
Therefore, according to the liquid crystal display device of this embodiment, the black display can be made even closer to black, and the band of the display on the low gradation side close to the black display can be eliminated. A color image with high color reproducibility can be observed.
[0083]
However, in this embodiment, although the transmittance of light in each of the blue wavelength bands is lower than the transmittance of light in the red and green wavelength bands on the low voltage side, Δnd of the pixel corresponding to the blue filter 6B ₂ Δnd of pixels corresponding to red and green filters 6R and 6G of ₁ Is 0.94 to 1.10, the difference between the transmittance of light in each of the blue wavelength bands and the transmittance of light in the red and green wavelength bands on the low voltage side is determined by the contrast and the display of the display. Has little effect on hue.
[0084]
Therefore, according to this liquid crystal display device, a color image with high contrast and high color reproducibility can be displayed from the low voltage side to the high voltage side, and the image can be observed with substantially the same contrast and hue over a wide viewing angle. .
[0085]
The Δnd of the pixel corresponding to the blue filter 6B of the liquid crystal element 1 ₂ Δnd of pixels corresponding to red and green filters 6R and 6G of ₁ Is 1.02 (Δnd ₂ / Δnd ₁ = 1.02), whereby a color image with higher contrast and color reproducibility can be displayed from the low voltage side to the high voltage side.
[0086]
In the second embodiment, the liquid crystal layer thickness d of the pixel corresponding to the red filter 6R and the green filter 6G of the liquid crystal element 1 is set. ₁ And the liquid crystal layer thickness d of the pixel corresponding to the blue filter 6B ₂ The liquid crystal layer thickness adjustment film 7 is provided on the blue filter 6B in order to make the blue filter 6B different from the red filter 6R and the green filter as in the third embodiment shown in FIG. 6G, the liquid crystal layer thickness d of the pixel corresponding to the red filter 6R and the green filter 6G is formed. ₁ And the liquid crystal layer thickness d of the pixel corresponding to the blue filter 6B. ₂ And may be different.
[0087]
Regarding the above-described second and third embodiments, liquid crystal display devices (hereinafter, referred to as examples) 1 and 2 having the following specifications and a liquid crystal display device (hereinafter, referred to as a comparative example) 1 for comparison. , 2 are produced and white is displayed (display of all pixels of red, green, and blue), black is displayed, 50% halftone (gray) is displayed, and 20% halftone is displayed. The results of measuring the viewing angle dependence of the color shift when displaying the tones are shown in FIGS. 14, 15, 16 and 17, respectively.
[0088]
[Example 1]
Liquid crystal layer thickness of pixel corresponding to red filter = 4.0 μm
Liquid crystal layer thickness of pixel corresponding to green filter = 4.0 μm
Liquid crystal layer thickness of pixel corresponding to blue filter = 3.8 μm
Δn = 0.099 with respect to light of 650 nm wavelength of liquid crystal
Δn = 0.102 for a liquid crystal having a wavelength of 550 nm
Δn = 0.107 for 475 nm wavelength light of liquid crystal
Δε value of liquid crystal = 4.6
Δnd (650 nm) = 0.396
Δnd (550 nm) = 0.408
Δnd (450 nm) = 0.407
Δnd (450 nm) / Δnd (650 nm) = 1.028
Average tilt angle of discotic liquid crystal = 18 °
In-plane retardation of discotic liquid crystal = 150 nm
[Example 2]
Liquid crystal layer thickness of pixel corresponding to red filter = 4.8 μm
Liquid crystal layer thickness of pixel corresponding to green filter = 4.8 μm
Liquid crystal layer thickness of pixel corresponding to blue filter = 4.6 μm
Δn = 0.081 for light of 650 nm wavelength of liquid crystal
Δn = 0.083 for 550 nm wavelength light of liquid crystal
Δn = 0.086 for 450 nm wavelength light of liquid crystal
Δε value of liquid crystal = 5.3
Δnd (650 nm) = 0.389
Δnd (550 nm) = 0.398
Δnd (450 nm) = 0.395
Δnd (450 nm) / Δnd (650 nm) = 1.017
Average tilt angle of discotic liquid crystal = 18 °
In-plane retardation of discotic liquid crystal = 150 nm
[Comparative Example 1]
Liquid crystal layer thickness of pixel corresponding to red filter = 4.1 μm
Liquid crystal layer thickness of pixel corresponding to green filter = 4.3 μm
Liquid crystal layer thickness of pixel corresponding to blue filter = 4.3 μm
Δn = 0.077 for the 650 nm wavelength light of the liquid crystal
Δn = 0.079 for 550 nm wavelength light of liquid crystal
Δn = 0.083 for 450 nm wavelength light of liquid crystal
Δε value of liquid crystal = 4.7
Δnd (650 nm) = 0.316
Δnd (550 nm) = 0.340
Δnd (450 nm) = 0.357
Δnd (450 nm) / Δnd (650 nm) = 1.130
Average tilt angle of discotic liquid crystal = 15 °
In-plane retardation of discotic liquid crystal = 130 nm
[Comparative Example 2]
Liquid crystal layer thickness of pixel corresponding to red filter = 4.3 μm
Liquid crystal layer thickness of pixel corresponding to green filter = 4.3 μm
Liquid crystal layer thickness of pixel corresponding to blue filter = 4.1 μm
Δn = 0.081 for light of 650 nm wavelength of liquid crystal
Δn = 0.083 for 550 nm wavelength light of liquid crystal
Δn = 0.086 for 475 nm wavelength light of liquid crystal
Δε value of liquid crystal = 5.3
Δnd (650 nm) = 0.348
Δnd (550 nm) = 0.357
Δnd (450 nm) = 0.353
Δnd (450 nm) / Δnd (650 nm) = 1.013
Average tilt angle of discotic liquid crystal = 15 °
In-plane retardation of discotic liquid crystal = 130 nm
As can be seen from FIGS. 14, 15, 15, and 17, in the above [Example 1] and [Example 2], the color shift with respect to the change in the viewing angle is small and the viewing angle is wide.
[0089]
18 shows the dependency of the upward color shift on the liquid crystal layer thickness with respect to the applied voltage in [Example 2]. FIG. 19 shows the dependency of the upward color shift on the liquid crystal layer thickness in [Comparative Example] 2. Is shown.
[0090]
As apparent from FIGS. 18 and 19, in the above [Example 2], the value of the color shift with respect to the difference in the thickness of the liquid crystal layer is small for a fixed voltage value. In particular, when the applied voltage is 5, the color shift becomes extremely small. This indicates that the color shift is small even if the error in the thickness of the liquid crystal layer is large, so that the manufacturing can be facilitated and the yield in the manufacturing process can be increased.
[0091]
Although the liquid crystal display devices according to the first to third embodiments described above are provided in the cockpit of an aircraft, the present invention is not limited to a liquid crystal display device for an aircraft, but may be used for other purposes. Can also be applied.
[0092]
【The invention's effect】
In the liquid crystal display device of the present invention, electrodes forming a plurality of pixels are provided on regions facing each other on inner surfaces of a pair of substrates, and red, green, and red respectively correspond to the plurality of pixels on an inner surface of one of the substrates. A liquid crystal element provided with a color filter of three colors of blue, a liquid crystal layer provided between the pair of substrates and having liquid crystal molecules twist-oriented at a twist angle of substantially 90 ° between the substrates, Each of the discotic liquid crystal molecules has a tilt direction aligned in one direction between a pair of polarizing plates having transmission axes in directions substantially orthogonal to each other with the element interposed therebetween, and faces the polarizing plate. A viewing angle improving element having a discotic liquid crystal layer oriented with a different tilt angle sequentially from one side of the surface facing the liquid crystal element to the other side, and further, The average tilt angle α of the discotic liquid crystal molecules of the viewing angle improving element is defined as α = 90− with respect to the average tilt angle θ of the liquid crystal molecules when a voltage for displaying black is applied between the electrodes of the liquid crystal element. θ is set to a value that satisfies the relationship of θ, so that the viewing angle is wide, there is almost no change in display color due to the viewing angle, and a color image with substantially the same contrast and hue can be observed over a wide viewing angle. it can.
[0093]
In the liquid crystal display device of the present invention, the liquid crystal layer of the liquid crystal element has a refractive index anisotropy Δn (450 nm) for light having a wavelength of 450 nm and a refractive index anisotropy Δn (650 nm) for light having a wavelength of 650 nm. Desirably, the liquid crystal material satisfies a ratio of 1 <Δn (450 nm) / Δn (650 nm) = ≦ 1.07. In this manner, colors having almost the same hue over a wide viewing angle are obtained. Images can be observed.
[0094]
The discotic liquid crystal layers of the pair of viewing angle improving elements each have an in-plane retardation of 150 nm, and the value of Δnd of the liquid crystal element is desirably set to 340 to 430 nm. By doing so, a color image with almost the same hue and little change in contrast and hue can be observed over a wide viewing angle.
[0095]
Further, in the liquid crystal display device according to the present invention, the liquid crystal layer of the liquid crystal element has a refractive index anisotropy Δn (450 nm) of the liquid crystal with respect to light having a wavelength of 450 nm and a product Δnd of the liquid crystal layer thickness d Δnd (450 nm). The ratio of the refractive index anisotropy Δn (650 nm) of the liquid crystal to light having a wavelength of 650 nm to the liquid crystal layer thickness d and the Δnd (650 nm) value is 0.94 ≦ Δnd (450 nm) / Δnd. It is desirable to set the value of the refractive index anisotropy of the liquid crystal and the value of the liquid crystal layer thickness so as to satisfy (650 nm) ≦ 1.10. A color image with high reproducibility can be observed.
[0096]
Further, when the in-plane phase difference between the discotic liquid crystal layers of the pair of viewing angle improving elements is 150 nm, the value of Δnd of the liquid crystal element is Δnd of the pixel corresponding to the red filter and the Δnd of the pixel corresponding to the green filter. 340 to 430 nm, respectively, and it is more preferable that the Δnd of the pixel corresponding to the blue filter is set to be larger than the Δnd of the pixel corresponding to the red and green filters at a ratio of 1.10 times or less. Thus, the black display can be made even closer to black, and a color image with high contrast and color reproducibility can be observed over a wide viewing angle.
[Brief description of the drawings]
FIG. 1 is a sectional view of a part of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a discotic liquid crystal layer of a viewing angle improving element.
FIG. 3 shows a liquid crystal molecule alignment direction in the vicinity of a pair of substrates of a liquid crystal element of the liquid crystal display device, a direction of a transmission axis of a pair of polarizing plates, and a direction of a substrate projection optical axis of a pair of viewing angle improving elements. FIG.
FIG. 4 is a cross-sectional view of a part of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 5 is a cross-sectional view of a part of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 6 is a diagram showing a color shift value for each Δnd of a liquid crystal layer in a liquid crystal display element using each liquid crystal having a value of Δn (450 nm) / Δn (650 nm) of 1.06 to 1.13.
FIG. 7 is a diagram showing a relationship between Δnd of a liquid crystal of a liquid crystal element, a lateral contrast, and an upper contrast.
FIG. 8 is a diagram showing a relationship between a voltage applied to a liquid crystal element and an average tilt angle of liquid crystal molecules.
FIG. 9 is a view showing a lateral contrast of the liquid crystal display device.
FIG. 10 is a view showing a color shift of the liquid crystal display device.
FIG. 11 is a diagram showing an upward contrast of the liquid crystal display device.
FIG. 12 is a view showing a color shift in a horizontal direction when a halftone of the liquid crystal display device is displayed.
FIG. 13 is a diagram showing an upward color shift when black is displayed on the liquid crystal display device.
FIG. 14 is a diagram showing the viewing angle dependence of the color shift when displaying white in Comparative Examples 1 and 2 and Examples 1 and 2.
FIG. 15 is a view showing the viewing angle dependence of the color shift when displaying black in Comparative Examples 1 and 2 and Examples 1 and 2.
FIG. 16 is a diagram showing the viewing angle dependence of the color shift when displaying 50% halftones of Comparative Examples 1 and 2 and Examples 1 and 2.
FIG. 17 is a diagram showing the viewing angle dependence of the color shift when displaying a halftone of 20% in Comparative Examples 1 and 2 and Examples 1 and 2.
FIG. 18 is a diagram showing the dependence of the upward color shift on the applied voltage in the liquid crystal layer thickness in Example 2.
FIG. 19 is a view showing the dependence of the upward color shift of Comparative Example 2 on the thickness of the liquid crystal layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Liquid crystal element, 2,3 ... Substrate, 2a, 3a ... Liquid crystal molecular orientation direction, 4,5 ... Electrode, 6R, 6G, 6B ... Color filter, 7 ... Liquid crystal layer thickness adjustment film, 8, 9 ... Alignment film, 10: liquid crystal layer, 11: liquid crystal molecules, θ: average tilt angle of liquid crystal molecules when black display voltage is applied, 12, 13: polarizing plate, 12a, 13a: transmission axis, 14, 15: viewing angle improving element, Reference numeral 16: film substrate, 17: alignment film, 18: discotic liquid crystal layer, 19: discotic liquid crystal molecule, 20: optical axis at which the refractive index is minimum, 20a: substrate projection optical axis, α: average of discotic liquid crystal molecules Tilt angle, 21 ... Adhesive.

Claims (5)

Electrodes for forming a plurality of pixels are provided on regions facing each other on inner surfaces of a pair of substrates arranged opposite to each other, and red, green, and blue 3 corresponding to the plurality of pixels are provided on an inner surface of one of the substrates. A liquid crystal element provided with a color filter of a color, and a liquid crystal layer in which liquid crystal molecules are twisted at a twist angle of substantially 90 ° between the substrates, and a liquid crystal layer is provided between the pair of substrates;
A pair of polarizing plates having transmission axes in directions substantially orthogonal to each other disposed with the liquid crystal element interposed therebetween,
The discotic liquid crystal molecules are arranged between the liquid crystal element and the pair of polarizing plates, and the tilt directions of the discotic liquid crystal molecules are aligned in one direction, and one of a surface facing the polarizing plate and a surface facing the liquid crystal element. And a pair of viewing angle improving elements having a discotic liquid crystal layer that is sequentially oriented with different tilt angles toward the other,
When the average tilt angle α of the discotic liquid crystal molecules of the pair of viewing angle improvement elements is θ when the average tilt angle of the liquid crystal molecules when a voltage for displaying black is applied between the electrodes of the liquid crystal element,
α = 90−θ
A liquid crystal display device set to a value satisfying the following relationship: The liquid crystal layer of the liquid crystal element has a refractive index anisotropy of Δn (450 nm) for light having a wavelength of 450 nm and a refractive index anisotropy of Δn (650 nm) for light having a wavelength of 650 nm.
1 <Δn (450 nm) / Δn (650 nm) = ≦ 1.07
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed of a liquid crystal material satisfying the following. The discotic liquid crystal layers of the pair of viewing angle improving elements each have an in-plane retardation of 150 nm, and the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal element and the thickness d of the liquid crystal layer is 340 to 430 nm. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set to: The liquid crystal layer of the liquid crystal element has a liquid crystal layer for the light having a wavelength of 650 nm for a value of Δnd (450 nm) which is a product of the refractive index anisotropy Δn (450 nm) of the liquid crystal for the light having a wavelength of 450 nm and the thickness d of the liquid crystal layer. The ratio of the Δnd (650 nm) value, which is the product of the refractive index anisotropy Δn (650 nm) and the liquid crystal layer thickness d, Δnd, is:
0.94 ≦ Δnd (450 nm) / Δnd (650 nm) ≦ 1.10.
2. The liquid crystal display device according to claim 1, wherein the value of the refractive index anisotropy of the liquid crystal and the value of the liquid crystal layer thickness are set so as to satisfy the following. The discotic liquid crystal layers of the pair of viewing angle improving elements each have an in-plane retardation of 150 nm, and the value of the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal element and the liquid crystal layer thickness d is red. The Δnd of the pixel corresponding to the color filter and the pixel corresponding to the green color filter is 340 to 430 nm, respectively, and the Δnd of the pixel corresponding to the blue color filter is 1 more than the Δnd of the pixel corresponding to the red and green color filters. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set large at a ratio of 10 times or less.

Images