JP5316270B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device including a viewing angle improving element having a discotic liquid crystal layer.

  In the liquid crystal display device, electrodes that form a plurality of pixels are provided on the mutually facing inner surfaces of a pair of substrates arranged opposite to each other, and liquid crystal molecules are substantially interposed between the substrates between the pair of substrates. In particular, a TN (twisted nematic) type composed of a liquid crystal element provided with a liquid crystal layer twist-aligned at a twist angle of 90 ° and a pair of polarizing plates arranged with the liquid crystal element sandwiched therebetween. Widely used.

  However, this TN type liquid crystal display device has a problem that the viewing angle of display (observation angle range in which display can be observed with good contrast) is narrow.

  Therefore, conventionally, a discotic liquid crystal molecule is aligned between the liquid crystal element and the pair of polarizing plates, the tilt direction is aligned in one direction, and the surface facing the polarizing plate and the surface facing the liquid crystal element A liquid crystal display device having a wide viewing angle has been proposed by disposing a viewing angle improving element having a discotic liquid crystal layer oriented with different tilt angles sequentially from one to the other (Patent Document 1). reference).

JP 2000-338489 A

  However, in the liquid crystal display device including 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 are wavelength-dependent, and the optical action is the viewing angle (display). Therefore, the hue of the display changes according to the change in the viewing angle.

  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.

  In a color liquid crystal display device in which a liquid crystal element is provided with three color filters of red, green, and blue corresponding to the plurality of pixels, the transmission intensity of light of each color depending on the viewing angle varies depending on the viewing angle. Therefore, the hue of the color image observed according to the viewing angle changes, and the contrast also decreases.

  An object of the present invention is to provide a liquid crystal display device which has a wide viewing angle and hardly changes the display color depending on the viewing angle, and allows a color image having substantially the same contrast and hue to be observed over a wide viewing angle. It is what.

In order to achieve the above object, an embodiment of the liquid crystal display element of the present invention includes a liquid crystal element in which a liquid crystal layer in which liquid crystal molecules are twist-aligned at a twist angle of 90 ° between the substrates is provided between a pair of substrates; A pair of viewing angle improving elements arranged across the liquid crystal element and having a base material and a discotic liquid crystal layer including discotic liquid crystal molecules formed on the base material, and the pair of viewing angle improvements A pair of polarizing plates having transmission axes in directions orthogonal to each other and sandwiching the element , and the discotic liquid crystal layer is formed on a facing surface of the base facing the liquid crystal element, The discotic liquid crystal molecules are aligned so that a tilt angle in a tilt direction with respect to the facing surface sequentially increases from the facing surface of the substrate toward the liquid crystal element, and an azimuth angle in the tilt direction The discotic depends azimuth and 180 ° of the liquid crystal molecular alignment direction in the plane of the liquid crystal layer side of the substrate adjacent to the liquid crystal layer, an average tilt angle α of the tilt angle of the discotic liquid crystal molecules, the liquid crystal molecules the when the average tilt angle of the liquid crystal molecules when a voltage is rising oriented from the substrate is applied between the electrodes of the liquid crystal element theta, is set to a value satisfying the relationship of α = 90-θ, it It is characterized by.

The liquid crystal display device of the present invention has a wide viewing angle, and there is almost no change in display color depending on the viewing angle, and a color image having substantially the same contrast and hue can be observed over a wide viewing angle.

1 is a cross-sectional view of a part of a liquid crystal display device showing a first embodiment of the present invention; FIG. 3 is a schematic cross-sectional view of a discotic liquid crystal layer of a viewing angle improving element. Shows the liquid crystal molecular alignment direction in the vicinity of the pair of substrates of the liquid crystal element of the liquid crystal display device, the direction of the transmission axis of the pair of polarizing plates, the direction of the substrate projection optical axes of the pair of viewing angle improvement element. Sectional drawing of the part of liquid crystal display device which shows 2nd Example of this invention. Sectional drawing of the part of liquid crystal display device which shows 2nd Example of this invention. The figure which shows the value of the color shift with respect to each (DELTA) nd of the liquid-crystal layer in the liquid crystal display element using each liquid crystal whose value of (DELTA) n (450nm) / (DELTA) n (650nm) is 1.06-1.13. The figure which shows the relationship between (DELTA) nd of a liquid crystal layer of a liquid crystal element, a horizontal contrast, and an upper contrast. FIG. 4 is a diagram showing a relationship between a voltage applied to a liquid crystal element and an average tilt angle of liquid crystal molecules. The figure which shows the horizontal contrast of the said liquid crystal display device. FIG. 3 is a diagram showing a color shift of the liquid crystal display device. The figure which shows the upward contrast of the said liquid crystal display device. The figure which shows the horizontal color shift when the halftone of the said liquid crystal display device is displayed. The figure which shows the upward color shift when displaying the black of the said liquid crystal display device. The figure which shows the viewing angle dependence of the color shift when the white of the comparative examples 1 and 2 and Examples 1 and 2 is displayed. The figure which shows the viewing angle dependence of the color shift when the black of the comparative examples 1 and 2 and Examples 1 and 2 is displayed. The figure which shows the viewing angle dependence of the color shift when the halftone of 50% of the comparative examples 1 and 2 and Examples 1 and 2 is displayed. The figure which shows the viewing angle dependence of the color shift when the halftone of 20% of the comparative examples 1 and 2 and Examples 1 and 2 is displayed. FIG. 6 is a diagram showing the liquid crystal layer thickness dependence of the upward relative transmittance with respect to the applied voltage in Example 2. The figure which shows the liquid crystal layer thickness dependence of the upper direction relative transmittance of the comparative example 2.

  1 to 3 show a first embodiment of the present invention, and FIG. 1 is a sectional view of a part of a liquid crystal display device.

  The liquid crystal display device of this embodiment is an aircraft liquid crystal display device equipped in an aircraft cockpit. As shown in FIG. 1, the liquid crystal element 1 and the front and rear sides of the liquid crystal element 1 A pair of polarizing plates 12 and 13, 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.

  The liquid crystal element 1 includes a plurality of pixels that are arranged opposite to each other on mutually facing inner surfaces of a pair of front and rear transparent substrates (for example, glass substrates) 2 and 3 that are arranged to face each other and are bonded via a frame-shaped sealing material (not shown). Are formed on the inner surface of one substrate, for example, a front substrate (hereinafter referred to as a front substrate) 1 that is a display observation side (upper side in FIG. 1). Corresponding three color filters 6R, 6G and 6B of red, green and blue are provided, and a liquid crystal layer 10 is provided between the pair of substrates 2 and 3.

  The liquid crystal element 1 is an active matrix liquid crystal display element having, for example, 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 is arranged in the row direction and 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.

  Although omitted 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 each of the plurality of pixel electrodes 5 is connected to a TFT corresponding to the pixel electrode 5.

  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 the color filters 6R, 6G, and 6B. Has been.

  Further, horizontal alignment films 8 and 9 are formed on the inner surfaces of the pair of substrates 2 and 3 so as to cover the electrodes 4 and 5 and to be aligned in directions substantially orthogonal to each other.

  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 nematic liquid crystal having 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 the solid line in FIG. Twist orientation.

  The liquid crystal layer 10 of the liquid crystal element 1 has a refractive index anisotropy of Δn (450 nm) for light having a wavelength of 450 nm, that is, light in the blue wavelength band, and for light having a wavelength of 650 nm, that is, light in the red wavelength band. When the refractive index anisotropy is Δn (650 nm), a value of Δn (450 nm) / Δn (650 nm) is 1.07 or less and the liquid crystal material is larger than 1.

  FIG. 6 shows the color shift value for each Δnd of the 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. In this case, the upper limit of the color shift is 0.05 to 0.06.

From FIG. 6, the liquid crystal layer 10 of the liquid crystal element 1 has a liquid crystal material having a value of Δn (450 nm) / Δn (650 nm) of 1.07 or less and greater than 1, that is,
1 <Δn (450 nm) / Δn (650 nm) ≦ 1.07
It is preferable to form the liquid crystal material satisfying

Further, the liquid crystal layer thickness d of the liquid crystal element 1 is formed 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 layer 10 of the liquid crystal element 1 has a maximum lateral contrast and upper contrast when the product Δnd of the refractive index anisotropy Δn and the liquid crystal layer thickness d is 340 to 430 nm. For the sake of illustration, the value of Δnd is set to 340 to 430 nm.

  Further, this liquid crystal display device is of a normally white mode, and the pair of polarizing plates 12 and 13 are arranged with their transmission axes 12a and 13a (see FIG. 3) substantially orthogonal to each other. .

  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 the transparent film substrate 16. 17 and the discotic liquid crystal molecules 19 are aligned with the tilt direction being aligned in one direction and the tilt angle being sequentially changed from the surface adjacent to the film substrate 16 toward the other surface. The discotic liquid crystal layer 18 is provided.

  That is, the discotic liquid crystal layer 18 is obtained by applying a discotic liquid crystal on the alignment treatment film 17 of the film substrate 16, and applying the discotic liquid crystal 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 on the surface opposite to the film substrate 16 while being arranged with a large tilt angle with respect to the film substrate 16. It is made of discotic film.

  As described above, the viewing angle improving elements 14 and 15 are arranged so that the discotic liquid crystal molecules 19 have the tilt direction aligned in one direction and gradually from one surface (the surface on the film substrate 16 side) toward the other surface. The discotic liquid crystal layer 18 is aligned so that the tilt angle is increased.

  The discotic liquid crystal layer 18 is arranged such that each molecular axis 19a perpendicular to the disc-like 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 taken as the optical axis 20 of the discotic liquid crystal layer 18 having the minimum refractive index, and has negative optical anisotropy.

Tilt indicated by the pair of each discotic average tilt angle of the tilt angle against the film substrate 16 of the liquid crystal molecules 19 were averaged across the layer thickness (one-dot chain line in FIGS. 1 and 2 of the view angle improving elements 14 and 15 The angle α is a voltage for displaying black between the electrodes 4 and 5 of the liquid crystal element 1 (the liquid crystal molecules 11 are rising almost perpendicular to the substrates 2 and 3 as shown by the two-dot chain line in FIG. When the average tilt angle of the liquid crystal molecules 11 when a voltage for aligning at an angle is applied is θ,
α = 90−θ
It is set to a value that satisfies the relationship.

  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 that behave according to the electric field. FIG. 9 shows 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 the normal line of the display screen in the u′v ′ chromaticity coordinate system (CIE1976UCS chromaticity coordinate). A value of color shift which is a change in display color when observed is shown, and FIG. 11 shows an upward contrast which is a contrast in a direction inclined by 30 ° with respect to the normal line of the display screen.

  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.

  On the other hand, the discotic liquid crystal layer 18 of the viewing angle improving elements 14 and 15 has a higher lateral contrast when the average tilt angle α of the discotic liquid crystal molecules 19 is larger as shown in FIG.

  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 the average tilt angle is as shown in FIG. A sufficiently high contrast is obtained in the range of 17 ° to 19 °.

  As shown in these figures, the range of the average tilt angle of the discotic liquid crystal molecules for obtaining sufficient contrast and sufficiently small color shift is 17 ° to 19 °, particularly 18 °. It is desirable that

  The average tilt angle θ of the liquid crystal molecules 11 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 is about 72 °, and therefore the pair of viewing angle improving elements 14 and 15. The discotic liquid crystal molecules 19 are aligned so that the average tilt angle α is about 18 ° (α = 90−72 = 18).

  Further, as shown in FIGS. 9, 10, and 11, the discotic liquid crystal layer has a in-plane retardation value of 150 nm which is a difference in refractive index between ordinary light and extraordinary light with respect to light incident in the normal direction. When the tick liquid crystal layer 18 is used, characteristics excellent in both contrast and color shift can be obtained.

  Therefore, in this liquid crystal display device, viewing angle improving elements 14 and 15 having an in-plane phase difference of 150 nm are used.

The pair of viewing angle improving elements 14, 15 make the tilt angle change directions of the discotic liquid crystal molecules 19 opposite to each other, and the optical axis 20 that minimizes the refractive index of the discotic liquid crystal layer 18. Is disposed between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13 with a direction 20a projected on the surface of the discotic liquid crystal layer 18 (hereinafter referred to as a substrate projection optical axis) directed in a predetermined direction. Has been.

  In this embodiment, as shown in FIG. 1, the pair of viewing angle improving elements 14 and 15 are arranged with the surface side of each discotic liquid crystal molecule 19 having a large tilt angle facing the liquid crystal element 1, The adhesive layer 21 is attached to the liquid crystal element 1.

  3 shows liquid crystal molecule alignment directions 2a and 3a in the vicinity of 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 a pair of viewing angle improving elements. 14 and 15 show the directions of the substrate projection optical axes 20a.

  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 in the counterclockwise direction when viewed from the front side which is the display viewing side with respect to the horizontal axis x of the screen of the liquid crystal display device. The liquid crystal molecule alignment direction 3a in the direction shifted by 0 ° and in the vicinity of the rear substrate 3 is in the direction shifted by 45 ° clockwise as viewed from the front side with respect to the horizontal axis x, and the liquid crystal of the liquid crystal layer 10 of the liquid crystal element 1 The molecules 11 are twist-oriented with a twist angle of substantially 90 ° from the rear substrate 3 toward the front substrate 2 and clockwise when viewed from the front side, as indicated by broken line arrows in the figure.

  Further, 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 in the vicinity of the front substrate 2 of the liquid crystal element 1 as shown in FIG. Alternatively, the rear polarizing plate 13 is arranged substantially in parallel, and the transmission axis 13 a is arranged so as to be substantially orthogonal to the transmission axis 12 a of the front polarizing plate 12.

  Further, of the pair of viewing angle improving elements 14, 15, the front viewing angle improving element 14 is disposed between the liquid crystal element 1 and the front polarizing plate 12 and the substrate projection optical axis (of the discotic liquid crystal layer 18). (A direction in which an optical axis 20 having a minimum refractive index is projected onto the surface of the discotic liquid crystal layer 18) 20a is disposed substantially parallel to the liquid crystal molecule alignment direction 2a in the vicinity of the front substrate 2 of the liquid crystal element 1. The rear viewing angle improving element 15 includes the substrate projection optical axis 20a between the liquid crystal element 1 and the rear polarizing plate 13, and the liquid crystal molecule alignment direction 3a in the vicinity of the rear substrate 3 of the liquid crystal element 1. They are arranged substantially in parallel.

  This liquid crystal display device displays using illumination light from a surface light source disposed on the rear side thereof, and is incident on the rear side polarizing plate 13 as linearly polarized light parallel to the transmission axis 13a. The polarization state can be 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 polarizing plate 12 is absorbed by the front polarizing plate 12, and a linearly polarized light component parallel to the transmission axis 12a of the front polarizing plate 12 is absorbed by the front polarizing plate 12. Is transmitted to the observation side.

  The liquid crystal display device is driven by controlling the voltage value applied between the electrodes 4 and 5 of the plurality of pixels of the liquid crystal element 1 according to a predetermined number of display gradations, and displays corresponding to the plurality of pixels. The image is displayed by changing the brightness of the.

  The liquid crystal display device is of a normally white mode in which the front and rear polarizing plates 12 and 13 are arranged with their transmission axes 12a and 13a substantially orthogonal to each other. Among them, it corresponds to a pixel to which a black display voltage is applied between the electrodes 4 and 5 so that the liquid crystal molecules 11 are aligned at a rising angle close to perpendicular to the surfaces of the substrates 2 and 3 as shown by a two-dot chain line in FIG. The display to be displayed is black.

  The display corresponding to the 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. When the applied voltage is substantially 0 V, that is, the liquid crystal molecules 11 are When aligned in the initial twist alignment state, the display corresponding to the pixel becomes the brightest bright display.

  Further, since this liquid crystal display device is provided with the color filters 6R, 6G, and 6B of red, green, and blue corresponding to a plurality of pixels in the liquid crystal element 1, the bright display is red, green, and green. , Blue display, and a color image is expressed by the bright display gradation of the red, green, and blue and the black display.

  In this liquid crystal display device, viewing angle improving elements 14 and 15 each having a discotic liquid crystal layer 18 are disposed between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13, respectively, so that the display viewing angle is wide.

  That is, the liquid crystal molecules 11 of the liquid crystal layer 10 of the liquid crystal element 1 change the alignment state so as to rise with respect to 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 that are strongly subjected to the alignment regulating force remain in a collapsed state at or near the initial pretilt angle even when a voltage is applied. Even when a voltage for aligning the molecules 11 with a rising angle (approximately 72 °) that is nearly perpendicular to the planes of the substrates 2 and 3 is applied, the liquid crystal layer 10 has almost no liquid crystal molecules 11 in the vicinity of the substrate from the initial alignment state. Has residual retardation due to not changing.

  Further, the liquid crystal layer 10 of the liquid crystal element 1 exhibits different retardation for light transmitted through the liquid crystal layer 10 in the vertical direction and light transmitted through the oblique direction (direction inclined with respect to the vertical direction). In the liquid crystal display device of the Marie White mode, when observing from the front direction of the screen (near the direction perpendicular to the screen), it is possible to observe a display with good contrast with sufficient darkness of the black display. When observed, the darkness of the black display rises and the contrast is greatly reduced.

On the other hand, the pair of viewing angle improving elements 14 and 15 have a discotic liquid crystal layer 18, and the discotic liquid crystal molecules 19 are aligned on the same tilt direction and face the polarizing plates 12 and 13. And a pair of viewing angle improving elements 14, 15 are arranged in order from one of the surfaces facing the liquid crystal element 1 toward the other, and the pair of viewing angle improving elements 14, 15 are arranged in the respective discotic liquid crystal molecules 19. Since the tilt angle change directions are opposite to each other and disposed between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13, the optical axis of the discotic liquid crystal molecules 19 of these viewing angle improving elements 14 and 15. 20 is parallel to the liquid crystal molecule alignment state on the 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 the voltage of the liquid crystal element 1 is applied.

  Moreover, since the liquid crystal layer 18 of the viewing angle improving elements 14 and 15 is a discotic liquid crystal layer, the retardation thereof has no directionality.

In this liquid crystal display device, the viewing angle improving element 14 between the liquid crystal element 1 and the front polarizing plate 12 is provided with the substrate projection optical axis (the optical axis 20 at which the refractive index of the discotic liquid crystal layer 18 is minimized). The direction 20a projected onto the surface of the discotic liquid crystal layer 18 is disposed substantially parallel to the liquid crystal molecule alignment 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 the viewing angle improving elements 1 5 between 13 are arranged in the liquid crystal molecular alignment direction 3a substantially parallel in the vicinity of the substrate 3 after the substrate projection optical axis 20a of the liquid crystal device 1.

  Therefore, the residual retardation caused by the liquid crystal molecules 11 in the vicinity of the substrate when the voltage is applied to the liquid crystal element 1 hardly changes from the initial alignment state is canceled by the pair of viewing angle improving elements 14 and 15, and the viewing angle of display, that is, It is possible to widen an observation angle range in which a display with good contrast with sufficient darkness of black display can be observed.

  In addition, this liquid crystal display device is of a normally white mode in which the front and rear polarizing plates 12 and 13 are arranged with their transmission axes 12a and 13a substantially orthogonal to each other. The average tilt angle α of the discotic liquid crystal molecules 19 of 14 and 15, respectively, with respect to the average tilt angle θ of the liquid crystal molecules 11 when a voltage for displaying black between the electrodes 4 and 5 of the liquid crystal element 1 is applied. Since the value satisfying the relationship of α = 90−θ is set, the black display when viewed from the front direction and the black display when viewed from the oblique direction are almost the same color display.

  Therefore, this liquid crystal display device has almost no change in display color depending on the viewing angle. Therefore, a color image having substantially the same contrast and hue can be observed over a wide viewing angle.

  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) with respect to light having a wavelength of 450 nm (light in the blue wavelength band) and a wavelength of 650 nm. The ratio of the refractive index anisotropy Δn (650 nm) to the light (light in the red wavelength band) is 1 <Δn (450 nm) / Δn (650 nm) ≦ 1.07. Therefore, the change in the transmittance balance of light in the red, green, and blue wavelength bands depending on the viewing angle can be reduced, and the viewing angle dependency of the hue of the combined 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.

  Furthermore, in this embodiment, as described above, the in-plane retardation 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 Δnd value of the liquid crystal element 1 is set to 340. Since the thickness is set to ˜430 nm, the residual retardation due to the fact that the liquid crystal molecules 11 in the vicinity of the substrate at the time of voltage application of the liquid crystal element 1 hardly change from the initial alignment state is used as the pair of viewing angle improving elements 14, 15. Thus, the color image can be effectively canceled to the extent that the display is hardly affected, and a color image with almost the same hue and almost no change in contrast and hue can be observed over a wide viewing angle.

  Therefore, this liquid crystal display device has all the functions required for the aircraft display device.

  That is, the display device installed in the cockpit of an aircraft is required to be severe in that the display contrast does not change and the contrast and hue are not visible regardless of the viewing angle.

  As described above, the liquid crystal display device has a wide viewing angle, and there is almost no color change in display depending on the viewing angle, and a color image having substantially the same contrast and hue can be observed over a wide viewing angle. It is suitable for a display device equipped in an aircraft cockpit.

  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 of this embodiment is disposed between the liquid crystal element 1 and the front and rear polarizing plates 12 and 13, respectively. The in-plane retardation of the discotic liquid crystal layer 18 of the paired viewing angle improving elements 14 and 15 is set to 150 nm as described above, and the Δnd value of the liquid crystal element 1 is set to a red color filter (hereinafter referred to as “red color filter”). Δnd of pixels corresponding to 6R and green color filter (hereinafter referred to as green filter) 6G is set to 340 to 430 nm and blue color filter (hereinafter referred to as blue filter) 6B, respectively. Δnd of the corresponding pixel is set to a color shift in the horizontal direction with respect to Δnd of the pixels corresponding to the red and green filters 6R and 6G (a color shift caused by a change in 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.

  That is, FIG. 12 and FIG. 13 show Δnd (comprising 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 the region (pixel) through which the wavelength light is transmitted. The ratio Δnd of the Δnd (650 nm) value formed by the product Δnd of the refractive index anisotropy Δn (650 nm) of the liquid crystal with respect to the light having a wavelength of 650 nm and the liquid crystal layer thickness d of the region through which the wavelength light is transmitted FIG. 12 shows the relationship between the value of (450 nm) / Δnd (650 nm) and the color shift due to the change in viewing angle. FIG. 12 shows the lateral color shift when displaying halftone (gray), and FIG. The upward color shift when black is displayed is shown.

  As shown in FIG. 12, when the upper limit of the color shift is set to 0.05, the value of Δnd (450 nm) / Δnd (650 nm) is 1.1, and as shown in FIG. When 0.1, the value of Δnd (450 nm) / Δnd (650 nm) is 0.94.

  Therefore, the value of Δnd (450 nm) / Δnd (650 nm) is desirably 0.94 or more and 1.10 or less, preferably 1.07 or less, and more preferably 1.02.

  Therefore, in this embodiment, Δnd of the pixel corresponding to the blue filter 6B is set to a value of a ratio of 0.94 to 1.10 with respect to Δnd of the pixels corresponding to the red and green filters 6R and 6G. ing.

  In the liquid crystal display device of this embodiment, Δnd of pixels corresponding to the blue filter 6B of the liquid crystal element 1 is set larger than Δnd of pixels corresponding to the red and green filters 6R and 6G. The configuration is the same as in the first embodiment.

  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. It is desirable to form the liquid crystal material satisfying a ratio of 1 <Δn (450 nm) / Δn (650 nm) ≦ 1.07.

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, it is transparent on the blue filter 6B (below the counter electrode 4). by providing the liquid crystal layer thickness adjusting films 7, it made different from the liquid crystal layer thickness d ₂ of the pixels corresponding to the liquid crystal layer thickness d ₁ and the blue filter 6B of the pixels corresponding to the red filter 6R and green filter 6G, the red The value of Δnd (hereinafter referred to as Δnd ₁ ) of the pixels corresponding to the filter 6R and the green filter 6G and the value of Δnd (hereinafter referred to as Δnd ₂ ) of the pixels corresponding to the blue filter 6B are 0.94 <Δnd. ₂ / Δnd ₁ <1.10 is set.

As described above, Δnd ₁ of the pixels corresponding to the red filter 6R and the green filter 6G of the liquid crystal element 1 is 340 to 430 nm, respectively. Therefore, Δnd ₂ of the pixels corresponding to the blue filter 6B is 374 to 473 nm.

In the liquid crystal display device of this embodiment, the in-plane retardation 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 applied. Δnd _{1 of the} corresponding pixel is 340 to 430 nm, and Δnd ₂ of the pixel corresponding to the blue filter 6B is 0.94 to 1.10 with respect to the value of Δnd ₁ of the pixels corresponding to the red and green filters 6R and 6G. Therefore, the black display can be made closer to black, and a color image with high contrast and color reproducibility can be observed over a wide viewing angle.

  That is, since the 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 is increased.

  However, since the voltage-transmittance characteristics of the liquid crystal display device are wavelength-dependent, 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 in light transmittance in the red, green, and blue wavelength bands on the low voltage side is small, but on the high voltage side, that is, on the black display side, the light transmittance in the blue wavelength band However, the degree of decrease in the transmittance of light in the red and green wavelength bands increases, and the display becomes bluish.

On the other hand, in this embodiment, Δnd ₂ of the pixel corresponding to the blue filter 6B of the liquid crystal element 1 is set larger than Δnd _{1 of} the pixels corresponding to the red and green filters 6R and 6G, and the blue filter 6B Since the ratio of Δnd ₂ of the corresponding pixel to Δnd ₁ of the pixels corresponding to the red and green filters 6R and 6G is 0.94 to 1.10, transmission of light in each wavelength band of blue on the high voltage side The rate can be made substantially the same as the transmittance of light in the red and green wavelength bands, and the band color of the display on the high voltage side, that is, the black display side can be almost eliminated.

  Therefore, according to the liquid crystal display device of this embodiment, the black display can be made closer to black and the band of the low gradation side display close to the black display can be eliminated. A color image with high color reproducibility can be observed.

However, in this embodiment, the transmittance of light in each wavelength band of blue is lower than the transmittance of light in the wavelength bands of red and green on the low voltage side, but Δnd _{2 of} the pixel corresponding to the blue filter 6B. Since the ratio of the pixels corresponding to the red and green filters 6R and 6G to Δnd ₁ is 0.94 to 1.10, the transmittance of light in each wavelength band of blue on the low voltage side and the wavelengths of red and green The difference from the light transmittance in the band hardly affects the contrast and hue of the display.

  Therefore, according to this liquid crystal display device, a color image having high contrast and 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. .

The ratio of Δnd ₂ of the pixel corresponding to the blue filter 6B of the liquid crystal element 1 to Δnd ₁ of the pixels corresponding to the red and green filters 6R and 6G is 1.02 (Δnd ₂ / Δnd ₁ = 1.02). Preferably, a color image with higher contrast and color reproducibility can be displayed from the low voltage side to the high voltage side.

Further, in the second embodiment, in order to differ from the liquid crystal layer thickness d ₂ of the pixels corresponding to the liquid crystal layer thickness d ₁ and a blue filter 6B of the pixels corresponding to the red filter 6R and green filter 6G of the liquid crystal device 1 Further, a liquid crystal layer thickness adjusting film 7 is provided on the blue filter 6B. However, as in the third embodiment shown in FIG. 5, the blue filter 6B is formed by the thicknesses of the red filter 6R and the green filter 6G. by also thick, it may be different from the said red filter 6R and the liquid crystal layer thickness d ₂ of the pixels corresponding to the liquid crystal layer thickness d ₁ and the blue filter 6B of the pixels corresponding to green filter 6G.

  Regarding the second and third embodiments described above, liquid crystal display devices (hereinafter referred to as embodiments) 1 and 2 having the following specifications, and a liquid crystal display device for comparison (hereinafter referred to as a comparative example) 1 , 2 for each, when white is displayed (all pixels of red, green, and blue are displayed), when black is displayed, when 50% halftone (gray) is displayed, and when 20% is intermediate The results of measuring the viewing angle dependency of the color shift when displaying the tone are shown in FIGS. 14, 15, 16, and 17, respectively.

[Example 1]
Liquid crystal layer thickness of the pixel corresponding to the red filter = 4.0 μm
Liquid crystal layer thickness of the pixel corresponding to the green filter = 4.0 μm
Liquid crystal layer thickness of the pixel corresponding to the blue filter = 3.8 μm
Δn = 0.099 with respect to light having a wavelength of 650 nm of liquid crystal
Δn = 0.102 for light having a wavelength of 550 nm of liquid crystal
Δn = 0.107 for light having a wavelength of 475 nm of liquid crystal
Value of Δε 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 the pixel corresponding to the red filter = 4.8 μm
Liquid crystal layer thickness of the pixel corresponding to the green filter = 4.8 μm
Liquid crystal layer thickness of the pixel corresponding to the blue filter = 4.6 μm
Δn = 0.081 for light of wavelength of 650 nm of liquid crystal
Δn = 0.083 for light having a wavelength of 550 nm of liquid crystal
Δn = 0.086 with respect to 450 nm wavelength light of liquid crystal
Value of Δε 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) = 1.018
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 the pixel corresponding to the red filter = 4.1 μm
Liquid crystal layer thickness of the pixel corresponding to the green filter = 4.3 μm
Liquid crystal layer thickness of the pixel corresponding to the blue filter = 4.3 μm
Δn = 0.077 with respect to light having a wavelength of 650 nm of liquid crystal
Δn = 0.079 for 550 nm wavelength light of liquid crystal
Δn = 0.083 with respect to 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 the pixel corresponding to the red filter = 4.3 μm
Liquid crystal layer thickness of the pixel corresponding to the green filter = 4.3 μm
Liquid crystal layer thickness of the pixel corresponding to the blue filter = 4.1 μm
Δn = 0.081 for light of wavelength of 650 nm of liquid crystal
Δn = 0.083 for light having a wavelength of 550 nm of liquid crystal
Δn = 0.086 for the 475 nm wavelength light of the liquid crystal
Value of Δε 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) = 1.014
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, 16 , and 17, the above [Example 1] and [Example 2] have a small color shift with respect to a change in viewing angle and a wide viewing angle.

Further, FIG. 18, the above Example 2 of a liquid crystal layer thickness dependence of the upward relative transmittance with respect to the applied voltage, FIG. 19 is the Comparative Example 2] The liquid crystal layer thickness depends on the direction relative transmission of Showing sex.

As is clear from FIGS. 18 and 19, in the above [Example 2], the value of the variation in relative transmittance with respect to the difference in the liquid crystal layer thickness is small with respect to a constant voltage value. In particular, when the applied voltage is 5 V , the variation in relative transmittance is extremely small. This indicates that the color shift is small even if the error in the liquid crystal layer thickness is large, which makes it easy to manufacture and increases the yield in the manufacturing process.

  The liquid crystal display devices of the first to third embodiments described above are installed in an aircraft cockpit. However, the present invention is not limited to an aircraft liquid crystal display device, but is used for other purposes. It can also be applied to.

  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 ... Orientation film, DESCRIPTION OF SYMBOLS 10 ... Liquid crystal layer, 11 ... Liquid crystal molecule, (theta) ... Average tilt angle of a liquid crystal molecule when a black display voltage is applied, 12, 13 ... Polarizing plate, 12a, 13a ... Transmission axis, 14, 15 ... Viewing angle improvement element, DESCRIPTION OF SYMBOLS 16 ... Film substrate, 17 ... Alignment film | membrane, 18 ... Discotic liquid crystal layer, 19 ... Discotic liquid crystal molecule, 20 ... Optical axis where refractive index becomes the minimum, 20a ... Substrate projection optical axis, α ... Average of discotic liquid crystal molecule Tilt angle, 21 ... adhesive.

Claims (11)

A liquid crystal element in which a liquid crystal layer in which liquid crystal molecules are twist-oriented at a twist angle of 90 ° between the substrates is provided between a pair of substrates;
A pair of viewing angle improving elements disposed between the liquid crystal elements and having a base material and a discotic liquid crystal layer including discotic liquid crystal molecules formed on the base material,
A pair of polarizing plates having transmission axes in directions orthogonal to each other and sandwiched between the pair of viewing angle improvement elements ;
With
The discotic liquid crystal layer is formed on a facing surface of the base facing the liquid crystal element,
The discotic liquid crystal molecules are aligned so that a tilt angle in a tilt direction with respect to the facing surface sequentially increases from the facing surface of the substrate toward the liquid crystal element,
The azimuth angle of the tilt direction, unlike azimuth and 180 ° of the liquid crystal molecular alignment direction in the plane of the liquid crystal layer side of the substrate adjacent to the discotic liquid crystal layer,
The average tilt angle α of the tilt angle of the discotic liquid crystal molecules is when the average tilt angle of the liquid crystal molecules when a voltage for rising and aligning the liquid crystal molecules from the substrate is applied between the electrodes of the liquid crystal element is θ. ,
α = 90−θ
Satisfy the relation is set to a value,
A liquid crystal display device characterized by the above. Wherein the liquid crystal of the liquid crystal element, when the wavelength is the refractive index anisotropy with respect to light having a 450nm and [Delta] n (450nm), wavelength is the refractive index anisotropy with respect to light of 650nm and [Delta] n (650nm),
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 above. Wherein the discotic liquid crystal layer of the pair of viewing angle improvement element is each have an in-plane retardation of 150 nm, the value of the product Δnd of refractive index anisotropy Δn and liquid crystal layer thickness d of the liquid crystal of the liquid crystal element The liquid crystal display device according to claim 1, wherein is set to 340 to 430 nm. The liquid crystal layer of said liquid crystal element, for the values of Δnd which wavelength is a product Δnd of the liquid crystal refractive index anisotropy [Delta] n (450 nm) and the thickness d of the liquid crystal layer with respect to light of 450 nm (450 nm), a wavelength of 650nm light the ratio of the value of the liquid crystal refractive index anisotropy [Delta] n (650 nm) and the Δnd consisting product Δnd of the liquid crystal layer thickness d (650 nm) for the,
0.94 ≦ Δnd (450 nm) / Δnd (650 nm) ≦ 1.10.
So as to satisfy the liquid crystal display device according to claim 1, characterized in that the values of the liquid crystal layer thickness of the refractive index anisotropy of the liquid crystal is set. Said pair of said discotic liquid crystal layer of the viewing angle improvement element has an in-plane retardation of each of 150 nm,
The value of the product [Delta] nd of the refractive index anisotropy Δn and liquid crystal layer thickness d of the liquid crystal of the liquid crystal element, [Delta] nd of the pixel corresponding to the pixel and green color filters corresponding to red color filters, respectively 340~430nm The Δnd of the pixel corresponding to the blue color filter is set larger at a ratio of 1.10 times or less than the Δnd of the pixel corresponding to the red and green color filters. A liquid crystal display device according to 1. The liquid crystal display device according to claim 1, wherein the discotic liquid crystal molecules are aligned in a thickness direction of the discotic liquid crystal layer. The liquid crystal display device according to claim 1, wherein the liquid crystal molecules are aligned in a rising direction in a thickness direction of the liquid crystal layer when the voltage is applied between the electrodes of the liquid crystal element. 2. The liquid crystal display according to claim 1, wherein the average tilt angle α of the discotic liquid crystal layer is an angle obtained by averaging the tilt angles of the discotic liquid crystal molecules in the thickness direction of the discotic liquid crystal layer. apparatus. 2. The liquid crystal display device according to claim 1, wherein the average tilt angle θ of the liquid crystal layer is an angle obtained by averaging the tilt angles of the liquid crystal molecules in the layer thickness direction of the liquid crystal layer. The discotic liquid crystal layer has a negative optical anisotropy with a direction in which molecular axes perpendicular to the disc-shaped surface of the discotic liquid crystal molecules are averaged as an optical axis of the discotic liquid crystal layer having a minimum refractive index. The liquid crystal display device according to claim 1, wherein the liquid crystal display device has characteristics. The liquid crystal display device according to claim 1, wherein the liquid crystal layer includes nematic liquid crystal and has positive dielectric anisotropy.

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