JP5042139B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a multi-domain vertical alignment (MVA) liquid crystal device.

  In general liquid crystal display devices, liquid crystal is displayed by sandwiching liquid crystal between two substrates, at least one of which has electrodes, and applying a voltage from the electrodes to the liquid crystal. Liquid crystal display devices are used in a wide range of applications due to their features such as low power consumption, thinness, and light weight. Among them, a thin film transistor (TFT) is used as a switching device that applies a voltage to liquid crystal in different regions in a screen. Since the active type liquid crystal display device used can have high definition, it is used in televisions, monitors, small portable devices, and the like.

  The display quality of the liquid crystal display device greatly depends on the alignment state of the liquid crystal. A TN (Twisted Nematic: TN) liquid crystal display device in which the liquid crystal is aligned substantially parallel to the substrate surface and the difference (twisting angle) of the alignment direction of the liquid crystal on the substrate surface sandwiching the liquid crystal is 90 ° is from the front of the display screen. It has been widely used because of its high contrast ratio (Contrast Ratio: CR) and high manufacturing stability. However, when the line of sight is shifted from the front, the CR is remarkably reduced, that is, the viewing angle is narrowed, and the gradation is inverted when viewed from a specific direction (the actual display luminance does not increase or decrease monotonously with respect to the gradation signal). There is a problem that a color abnormality accompanying the phenomenon occurs.

  As a countermeasure against such a problem, a liquid crystal display device using a liquid crystal alignment different from TN has been developed and put into practical use. As one type, when no voltage is applied, the liquid crystal is aligned substantially perpendicular to the substrate surface. There is a vertical alignment (VA) liquid crystal display device.

  Among the VA liquid crystal devices, an MVA (Multi) that is divided into a plurality of regions in which the liquid crystal tilt direction is different by forming a structure that controls the liquid crystal tilt direction when a voltage is applied, such as by resinous protrusions or electrode punching. -Domain vertical alignment (MVA), and by dividing into four regions so that the liquid crystal tilt direction is different by 90 ° and having 90 ° rotational symmetry, the viewing angle characteristics can be made symmetric vertically and horizontally And the viewing angle can be widened (see, for example, Patent Document 1). In display devices, display characteristics in the vertical and horizontal directions are generally regarded as important. However, liquid crystal display devices are more dependent on viewing angle than self-luminous display devices such as CRT (Cathode Ray Tube) and PDP (Plasma Display Panel). Therefore, the improvement was demanded. It is considered that the high symmetry of the viewing angle characteristic of the four-divided MVA liquid crystal display device is very good.

  In the MVA liquid crystal display device of Patent Document 1, since the light incident on the liquid crystal is linearly polarized light, the brightness of the light when viewed from the front of the display device unless the liquid crystal is inclined by 45 ° with respect to the transmission axis of the polarizing plate. There is a problem that the transmittance of the liquid crystal decreases. However, by making the light incident on the liquid crystal circularly polarized using a ¼ wavelength plate, if the applied voltage is equal, the same transmittance can be obtained when viewed from the front regardless of the direction in which the liquid crystal is tilted (for example, , See Patent Document 2).

  In addition, by adopting an axially symmetric orientation in which the liquid crystal tilt direction changes continuously with a specific point as the center of symmetry, the liquid crystal orientation becomes very symmetric without a decrease in transmittance, and a highly symmetric field of view. Angular characteristics can be realized (see, for example, Patent Document 3). Axisymmetric alignment does not apply to the MVA definition of “dividing into regions” with different liquid crystal tilt directions, but it can be taken as the limit of extrapolation of the number of divisions to infinity, and is therefore included in MVA in this specification. .

  In this specification, an MVA liquid crystal display device in which light incident on the liquid crystal from the normal direction of the substrate is circularly polarized light is described as a circularly polarized MVA liquid crystal display device in this specification. An MVA liquid crystal display device in which light incident on the liquid crystal is linearly polarized light is described as a linearly polarized MVA liquid crystal display device.

  Furthermore, by adding a half-wave plate between the polarizing plate and the quarter-wave plate, the light incident on the liquid crystal in a wide wavelength region is made circularly polarized, thereby reducing the luminance of black display when viewed from the front. The CR when viewed from the front can be increased. At this time, on the backlight side and the observer side, the retardations of the quarter-wave plates are equal to each other, the retardations of the half-wave plates are equal, the transmission axes of the polarizing plates, the slow axes of the quarter-wave plates, The slow axis of the wave plate is configured to be orthogonal to each other, and black display when no voltage is applied to the liquid crystal is a condition for increasing the CR (see, for example, Patent Document 4).

  In addition, the advantage of using circularly polarized light incident on the liquid crystal is that, in order to improve outdoor visibility, the reflective mode for display using external light and the normal transmission for display using backlight light. It is possible to realize a VA liquid crystal display device called a transflective type or a transflective type that can display in both modes (see, for example, Patent Document 5).

Japanese Patent No. 2947350 JP 2002-303869 A Japanese Patent No. 3875125 Japanese Patent No. 3767419 Japanese Patent No. 3410663

  The above circularly polarized MVA liquid crystal display device is characterized in that it can utilize highly symmetrical liquid crystal alignment (axial symmetry alignment) without causing a decrease in transmittance. However, in white display, when the liquid crystal layer is thickened, the birefringence of the liquid crystal material is increased, the applied voltage to the liquid crystal is increased, the retardation of the liquid crystal layer is increased, and the transmittance is increased. There is a problem that gradation inversion occurs in the horizontal direction and the vertical direction.

  In conventional liquid crystal display devices, high symmetry with high CR and a wide viewing angle is required, so it is necessary to align liquid crystals with high symmetry. Further, in order to eliminate the gradation inversion as described above, it is necessary to reduce the transmittance. Recently, however, liquid crystal display devices are used for applications that do not necessarily require isotropic viewing angle characteristics, such as in-vehicle and ticket vending machines, as the durability of members and the expansion of the operating temperature range. became. For example, in a vehicle, a high display quality is required in the left-right direction, but the positional relationship between the user's head and the panel is substantially fixed in the up-down direction, so the demand in the up-down direction is higher than in the left-right direction. Absent. Also, in ticket vending machines and ATMs, display quality in the left-right direction is not so much required, and it is required to cope with changes in the viewing angle in the vertical direction that changes depending on the height and standing position of the user.

  The present invention has been made in order to solve these problems, and has a high transmittance in applications where high display quality is required in a specific direction without necessarily requiring isotropic viewing angle characteristics. Another object of the present invention is to provide a liquid crystal display device having high display quality that does not cause gradation inversion.

  In order to solve the above problems, a liquid crystal display device according to the present invention includes a first substrate having electrodes periodically arranged to apply a voltage to the liquid crystal, and a first substrate having an electrode for applying a voltage to the liquid crystal. A liquid crystal layer having negative liquid crystal sandwiched between the second substrate, the first substrate and the second substrate and oriented substantially perpendicular to the substrate surface; and on a side different from the liquid crystal side of the first substrate A first polarizing plate that is disposed, a second polarizing plate that is disposed on a side different from the liquid crystal side of the second substrate, and that has a transmission axis perpendicular to the transmission axis of the first polarizing plate; A first retardation plate disposed between the substrate and the first polarizing plate and having a slow axis which is not parallel to the transmission axis of the first polarizing plate and which is not orthogonal to the first polarizing plate; A second retardation plate disposed between the first retardation plate and a second retardation plate disposed between the second substrate and the second polarizing plate. A third retardation plate having a slow axis orthogonal to the slow axis, and disposed between the second substrate and the third retardation plate, and orthogonal to the slow axis of the second retardation plate. A fourth retardation plate having a slow axis, a control structure disposed on the liquid crystal side of the first substrate and / or the second substrate, and controlling the inclination of the liquid crystal when a voltage is applied to the liquid crystal layer; Liquid crystal display device comprising: a first region in which the liquid crystal is tilted in one direction when a voltage is applied to the liquid crystal; and a second region in which the liquid crystal is tilted in a direction that is approximately 180 ° different from the direction in which the liquid crystal in the first region is tilted. The angle between the direction in which the liquid crystal inclines in the first region and the horizontal direction of the screen of the liquid crystal display device is 22 ° to 39 ° or 51 ° to 68 °.

  In order to solve the above problems, a liquid crystal display device according to the present invention includes a first substrate having electrodes periodically arranged to apply a voltage to the liquid crystal, and an electrode for applying a voltage to the liquid crystal. A second substrate having a liquid crystal layer sandwiched between the first substrate and the second substrate and having a negative type liquid crystal aligned substantially perpendicular to the substrate surface, and the liquid crystal side of the first substrate is different A first polarizing plate disposed on the side, a second polarizing plate disposed on a side different from the liquid crystal side of the second substrate, and having a transmission axis perpendicular to the transmission axis of the first polarizing plate, A first retardation plate disposed between one substrate and the first polarizing plate, having a slow axis that is not parallel to the transmission axis of the first polarizing plate and is not orthogonal, and a second substrate; A second retardation plate disposed between the second polarizing plate and having a slow axis perpendicular to the slow axis of the first retardation plate; A control structure that is disposed on the liquid crystal side of the plate and / or the second substrate and controls the tilt of the liquid crystal when a voltage is applied to the liquid crystal layer; and a first region in which the liquid crystal tilts in one direction when a voltage is applied to the liquid crystal layer; A liquid crystal display device including a second region in which the liquid crystal is tilted in a direction approximately 180 ° different from a direction in which the liquid crystal is tilted in the first region, and the liquid crystal display device in which the liquid crystal is tilted in the first region The angle between the left and right direction of the screen is 25 ° to 39 ° or 51 ° to 65 °.

  According to the present invention, the angle formed between the direction in which the liquid crystal inclines in the first region and the horizontal direction of the screen of the liquid crystal display device is 22 ° to 39 ° or 51 ° to 68 °. In applications where high display quality is required in a specific direction without requiring characteristics, a liquid crystal display device having high display quality that does not cause gradation inversion even with high transmittance can be provided.

  In addition, since the angle formed between the liquid crystal tilt direction and the left-right direction of the liquid crystal display device in the first region is 25 ° to 39 ° or 51 ° to 65 °, isotropic viewing angle characteristics are always required. In applications where high display quality is required in a specific direction, a liquid crystal display device having high display quality that does not cause gradation inversion even with high transmittance can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1>
FIG. 1 is a schematic configuration diagram of a circularly polarized MVA liquid crystal display device according to an embodiment of the present invention. A liquid crystal layer 9 made of negative liquid crystal is sandwiched between the substrate 1 and the substrate 2. Although not shown here, electrodes and auxiliary capacitance electrodes for applying voltage to the liquid crystal, switching elements such as TFTs for controlling the application of voltage, and wiring are periodically arranged on the liquid crystal side of the substrate 1. An electrode for applying a voltage to the liquid crystal is disposed on the liquid crystal side 2. On the liquid crystal side of the substrate 1 and the substrate 2, a process such as formation of a vertical alignment film is performed so that the liquid crystal layer 9 is aligned substantially perpendicular to the substrate surface when no voltage is applied. The alignment direction of the liquid crystal layer 9 may be substantially perpendicular to the substrate and may have an inclination of 10 degrees or less from the vertical direction. For example, the alignment direction of the liquid crystal layer 9 can be slightly inclined from the vertical by a method such as forming a slight inclination in the vertical alignment film. However, in order to obtain a larger contrast ratio, the inclination is preferably within 5 degrees.

  Since the liquid crystal display device according to the embodiment of the present invention enables display in a transmission mode, an opening is formed in a part of a region where the electrode of the substrate 1 is disposed and a part of the substrate 2 opposite to the region so as to transmit light. Forming part. At least in the opening, a transparent substrate material such as glass or amorphous plastic is used for the substrate, and the electrode has a high transmittance such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). A transparent electrode material is used.

  In the embodiment of the present invention, a transmissive mode circularly polarized MVA liquid crystal display device will be described as a transmissive liquid crystal display device. However, the circularly polarized MVA liquid crystal display device can also be used as a transflective liquid crystal display device. A region for displaying in the reflection mode may be formed separately from the portion.

  The polarizing plate 3 is disposed on a side different from the liquid crystal side of the substrate 1, the polarizing plate 4 is disposed on a side different from the liquid crystal side of the substrate 2, and the transmission axis 3 a of the polarizing plate 3 and the transmission axis of the polarizing plate 4. It arrange | positions so that 4a may be orthogonally crossed. Therefore, the polarizing plate 3 and the polarizing plate 4 are also orthogonal to the absorption axis orthogonal to the transmission axis. The retardation plate 7 is disposed between the substrate 1 and the polarizing plate 3, and the slow axis 7 a indicating the direction of the highest refractive index of the retardation plate 7 is not parallel to the transmission axis 3 a of the polarizing plate 3, And it arrange | positions so that it may not orthogonally cross. The phase difference plate 5 is disposed between the substrate 1 and the phase difference plate 7. The retardation film 8 is disposed between the substrate 2 and the polarizing plate 4, and the slow axis 8 a of the retardation film 8 is disposed so as to be orthogonal to the slow axis 7 a of the retardation film 7. The retardation film 6 is disposed between the substrate 2 and the retardation film 8, and the slow axis 6 a of the retardation film 6 is disposed so as to be orthogonal to the slow axis 5 a of the retardation film 5.

  Although there is a method that does not use the retardation plate 7 and the retardation plate 8 in the circularly polarized MVA liquid crystal display device, this embodiment will be described using the above configuration.

  When the liquid crystal display device is viewed from the front, that is, from the normal direction (z-axis direction) of the substrate 1, if no voltage is applied to the liquid crystal layer 9, the retardation of the liquid crystal layer 9 is 0, so that the liquid crystal layer 9 passes through the liquid crystal layer 9. The polarization state of light does not change. As shown in FIG. 1, the transmission axis 3a and the transmission axis 4a, the slow axis 5a and the slow axis 6a, and the slow axis 7a and the slow axis 8a are orthogonal to each other. If the retardation and retardation of the phase difference plate 7 and the phase difference plate 8 are equal to each other, the respective retardations cancel each other, so that the darkest display state can be realized in principle as black display. Although it is difficult to accurately cross the polarizing plate and the retardation plate, according to Patent Document 4, a deviation of ± 10 ° is an allowable range. Although depending on manufacturing conditions, the normal deviation is about ± 2 ° to ± 3 ° at the maximum, and such a deviation is not a problem in practice.

  The retardation of the retardation plate 7 and retardation plate 8 is half of the predetermined wavelength λ (half-wave plate), and the retardation of the retardation plate 5 and retardation plate 6 is 1/4 of the predetermined wavelength λ (¼ wavelength plate). ), The combination of the phase difference plate 5 and the phase difference plate 7 and the combination of the phase difference plate 6 and the phase difference plate 8 have a function as a broadband circularly polarizing plate centered on a predetermined wavelength λ. .

  For example, if the predetermined wavelength λ is 550 nm, which has the highest human visibility, the retardation of the phase difference plate 7 and the phase difference plate 8 which are half-wave plates is 550 nm / 2 = 275 nm, which is about a quarter wavelength plate. Retardation of the phase difference plate 5 and the phase difference plate 6 is 550 nm / 4 = 137.5 nm. Under such conditions, the light incident on the liquid crystal layer 9 becomes completely circularly polarized light at a predetermined wavelength λ (550 nm). Therefore, a voltage is applied to the liquid crystal layer 9 to reduce the effective retardation of the liquid crystal layer 9 to a half wavelength ( 275 nm), the transmittance is maximum in principle, and white display with the highest transmittance can be realized. However, since light with a wavelength of 550 nm is yellowish green, white display tends to be biased to yellowish green in the above setting. Therefore, by setting the predetermined wavelength λ on the shorter wavelength side than 550 nm, the maximum transmittance and the color characteristics are balanced. Further, even if the retardation of half and ¼ of the predetermined wavelength λ is not strict, the transmittance and the color are only slightly changed, and the strict predetermined is required except when the maximum transmittance in principle is required. It is not necessary to set the retardation to half of the wavelength λ and 1/4. Instead of adjusting the retardation of the half-wave plate and the quarter-wave plate, the voltage applied to the liquid crystal layer 9 can be lowered to balance the transmittance and the color. Strictly speaking, if the retardation of the half-wave plate is not λ / 2 and the retardation of the quarter-wave plate is not λ / 4, the circular wave is not completely circularly polarized but becomes elliptically polarized. A circularly polarized MVA liquid crystal display device is obtained when 4 times the retardation and 2 times the retardation of the half-wave plate are in the visible region (380 nm to 780 nm). However, the retardation of the phase difference plate 5 and the phase difference plate 6 and the retardation of the phase difference plate 7 and the phase difference plate 8 must be equal.

  As described above, it is one of the conditions for realizing the darkest black display in principle that the retardation of the retardation plate 5 and the retardation plate 6 and the retardation of the retardation plate 7 and the retardation plate 8 are equal. . If the retardation is different, a certain amount of light is transmitted even when no voltage is applied to the liquid crystal layer 9, and the CR cannot be increased. Although the tolerance of each retardation is about ± 30 nm (see Patent Document 4), the deviation of the retardation of the stretched resin film that is a generally used retardation film is about ± 10 nm at the maximum. There is no problem in practical use. Like a phase difference plate cut from the same original fabric, it may deviate from the target retardation value, but if the amount of deviation is equal, the transmittance for black display is very small. However, since the transmittance of white display changes slightly, CR changes slightly.

  The retardation plate used in the MVA liquid crystal display device has a main axis of refractive index parallel to the substrate normal direction and the substrate surface, and main values n1 and n2 of the refractive index in the substrate surface and the refractive index in the normal direction. Are classified into the following three types based on the magnitude relationship of the main value n3 of First, as a first classification, a retardation plate satisfying n1> n2 = n3 is referred to as (positive) a-plate. Next, as a second classification, a retardation plate satisfying n1> n2, n1> n3, and n2 ≠ n3 is called a biaxial retardation plate. These two types of retardation plates have retardation which is not 0 because the refractive indexes n1 and n2 in the substrate surface are different. Such retardation plates can be used for the retardation plates 5 to 8 described above. As a third classification, a retardation plate satisfying n1 = n2> n3 is referred to as a (negative) c-plate. Since this retardation plate has n1 = n2, the retardation is 0, but it is used to widen the viewing angle. Since this c-plate has the same in-plane refractive index and is maximum, the direction of the slow axis cannot be defined. However, in the present invention, c-plate may be used as an addition of the phase difference plates 5 to 8.

  In order to express the above classification as a numerical value, a value of Nz = (n1-n3) / (n1-n2) is used.

  The retardation of the retardation plate in the above is (n1-n2) · t, and t is the thickness of the retardation plate. This corresponds to the optical phase difference given to the polarized light when the polarized light is incident on the retardation plate from the front, expressed in wavelength units. The phase difference is 360 ° at one wavelength. The effective retardation of the liquid crystal layer 9 represents an optical phase difference given to polarized light that has passed through the liquid crystal layer 9 in wavelength units.

  Although not shown in FIG. 1, when color display is performed using a color filter, a color filter is disposed. When the color filter is disposed on the liquid crystal layer 9 side of the substrate 1 or the substrate 2, color mixing and blurring due to parallax can be prevented. Further, a backlight unit (not shown) is disposed on the opposite side of the polarizing plate 3 or the polarizing plate 4 from the substrate. The observer will see the display from the opposite side where the backlight unit is installed. In addition, a driving circuit that generates a voltage signal applied from the image signal to the liquid crystal layer 9 and a control signal to a switching element such as a TFT for controlling application of a voltage to the liquid crystal layer 9 in a different region in the display screen; Wirings for supplying various signals to wirings arranged on the substrate 1 are arranged (none of them are shown).

  A liquid crystal display device is such that a substrate, a retardation plate, a polarizing plate, a backlight unit, a drive circuit, wiring, etc. are stored in a housing and an image is displayed only by supplying an image signal and power. Although it often refers to a device, it may also refer to a device that displays an image by inputting a voltage signal, a control signal, and light from the outside without providing a backlight or a drive circuit. In the present invention, all of the above are collectively referred to as a liquid crystal display device.

  Up to this point, a circularly polarized MVA liquid crystal display device using a quarter-wave plate and a half-wave plate has been described. Next, the characteristic of the present invention, the direction of the liquid crystal when the voltage is applied to the liquid crystal layer 9, the direction control structure for controlling the direction of inclination, and the positional relationship with the user of the liquid crystal display device will be described. To do.

  FIG. 2 is a diagram showing a positional relationship between the liquid crystal display device 14 and the observer 18 according to the embodiment of the present invention. The observer's line of sight 15 is a vector from the evaluation area of the liquid crystal display device 14 evaluated by the observer 18 toward the measuring instrument 17. At this time, a vector connecting the center of the evaluation region to the center of the light receiving unit of the measuring instrument 17 is used. It is a definition that assumes evaluation by a measuring instrument, but it is generally used as a vector that connects a user's attention area and the user.

  Next, the xyz orthogonal coordinate system is defined. As shown in FIG. 2, the z-axis is parallel to the substrate normal direction, and the direction from the surface of the liquid crystal display device 14 toward the viewer is the positive direction of the z-axis. The x-axis and y-axis are parallel to the substrate surface (if the substrate is curved, the tangent plane of the evaluation area is the substrate surface). When displaying an image, the x-axis is approximately perpendicular to the vertical direction 16 and the xyz coordinate system is a right-handed system. The direction toward the right of the observer 18 (the left direction in FIG. 2) is taken as the positive direction of the x axis. The x-axis direction is the screen horizontal direction of the liquid crystal display device 14, and the y-axis direction is the screen vertical direction of the liquid crystal display device 14. By adopting such an xyz coordinate system, when the projection of the observer's line of sight 15 onto the x-axis is the positive direction of the x-axis, from the right direction in the figure, and when the projection is the negative direction of the x-axis, the figure is shown. You are looking from the left. Similarly, when the projection of the observer's line of sight 15 to the y-axis is the positive direction of the y-axis, the projection is seen from the upper direction in the figure, and when the projection is the negative direction of the y-axis, the observation is from the lower direction in the figure. Become.

  The direction of the line of sight refers to the projection of the line of sight 15 of the observer onto the xy plane. When there is no possibility of confusion, the angle (azimuth angle) between the above projection and the positive direction of the x-axis is also described as the line-of-sight direction (line-of-sight direction). If the line-of-sight direction is 0 °, the liquid crystal display device 14 is viewed from the right side. The line-of-sight angle is the angle (polar angle) formed by the observer's line of sight 15 and the z-axis. If the line-of-sight angle is 0 °, the z-axis and the observer's line of sight 15 are parallel, and the liquid crystal display device is viewed from the front.

  The liquid crystal used in the MVA liquid crystal display device is a negative type, and the dielectric constant in the major axis direction of the liquid crystal is smaller than the dielectric constant in the direction orthogonal to the major axis. Torque is generated in the direction in which the axial direction is orthogonal to the lines of electric force. When the plate electrodes are disposed on the parallel opposing substrates, the electric lines of force are parallel to the z-axis, so that the liquid crystal is tilted from the z-axis direction by applying a voltage. At this time, the projection of the vector parallel to the major axis of the liquid crystal onto the substrate surface (xy plane) is the direction in which the liquid crystal is inclined. Further, the angle (azimuth angle) formed by the projection and the positive direction of the x-axis is also described as the direction in which the liquid crystal is tilted unless there is a possibility of confusion. If the direction in which the liquid crystal is tilted is 0 °, the liquid crystal is tilted rightward as viewed from the observer.

  When applying a voltage to a negative type liquid crystal that is aligned perpendicular to a sufficiently wide parallel electrode, if the major axis direction of the liquid crystal is completely parallel to the lines of electric force, the torque will be The liquid crystal does not move evenly in all directions. However, in reality, if the liquid crystal falls down at a location where the electric lines of force are distorted at the end of the electrode, etc., torque due to elasticity will propagate, and the torque will act in an appropriate direction depending on the location in the liquid crystal screen. Incline in an appropriate direction. In the case of a linearly polarized MVA liquid crystal display device, the transmittance decreases unless the tilt direction of the liquid crystal is 45 ° with respect to the transmission axis of the polarizing plate. Therefore, a technique for controlling the tilt direction of the liquid crystal has been developed and published. (For example, refer to Patent Document 1). As described above, the linearly polarized MVA liquid crystal display device is an MVA liquid crystal display device in which light incident on the liquid crystal is linearly polarized light.

  FIG. 3 is a schematic view and a cross-sectional view of the liquid crystal display device 14 according to Embodiment 1 of the present invention when viewed from the front. As shown in FIG. 3A, electrodes 10 for applying a voltage to the liquid crystal are periodically arranged on the liquid crystal side of the substrate 1. Two structures are shown here, but such a structure is periodically arranged on the entire display screen. In the drawing, the electrode 13 on the substrate 2 side is shown as a rectangle, but the electrode 13 covers the entire display screen of the liquid crystal display device 14. As will be described later, a part of the electrode 13 may be removed to control the direction in which the liquid crystal is tilted. FIG. 3B is a cross-sectional view taken along the line A-A ′ in FIG. Here, switching elements such as auxiliary capacitance electrodes and TFTs, wirings, and the like are omitted.

  As shown in FIG. 3, resin protrusions 12a and 12b are formed in order to control the direction in which the liquid crystal is tilted (the direction in which the liquid crystal is tilted by voltage application, hereinafter also simply referred to as the tilt direction). Although not shown, vertical alignment processing is performed so as to cover the electrodes 10 and 13 and the resin protrusions 12a and 12b. Therefore, since the liquid crystal is aligned perpendicularly to the inclined surface of the resin protrusions 12a and 12b when no voltage is applied, the liquid crystal on the inclined surface is slightly inclined from the z axis. When a voltage is applied in this state, the liquid crystal on the slope portion is tilted in a direction parallel to the projection of the normal line of the slope onto the xy plane, so that liquid crystals other than the slope portion are also shown in FIG. Tilt in the same direction. With the structure shown in FIG. 3, a region 11a and a region 11b in which the liquid crystal tilt direction is approximately 180 ° different are formed.

  In FIG. 3, the cross sections of the resin protrusions 12 a and 12 b are triangular. However, they may be inclined surfaces, and may be depressions instead of hooks or protrusions.

  Further, even if the alignment of the liquid crystal when the voltage is not applied by rubbing or photo-alignment processing is inclined from the vertical direction, the liquid crystal is inclined in the inclined direction like the above-described inclined portion. However, in order to achieve MVA, it is necessary to partially change the direction of the initial inclination within the substrate surface (patterning the initial inclination direction), which complicates the manufacturing process, and extremely high patterning alignment accuracy. Is disadvantageous in production.

  FIG. 4 is a schematic view and a cross-sectional view of the liquid crystal display device 14 according to Embodiment 1 of the present invention when viewed from the front. As shown in FIG. 4, as a structure for controlling the direction in which the liquid crystal is tilted, a slit is formed by removing the portion of the electrode having the protrusion in FIG. 3 instead of the resin protrusion. As shown in FIG. 4A, electrodes 10 for applying a voltage to the liquid crystal are periodically arranged on the liquid crystal side of the substrate 1. FIG. 4B is a cross-sectional view taken along line B-B ′ in FIG. Here, switching elements such as auxiliary capacitance electrodes and TFTs, wirings, and the like are omitted. The electric lines of force 20 tend to be perpendicular to the surface of the electrode 10, and are thus distorted near the ends of the slit 19 and the ends of the electrode 10. Accordingly, the liquid crystal in the vicinity is inclined because the major axis direction of the liquid crystal tends to be perpendicular to the distorted electric lines of force. Then, similarly to the structure shown in FIG. 3, the region 11a and the region 11b are formed in which the direction in which the liquid crystal is inclined is approximately 180 ° different.

  In the embodiment of the present invention, the slit is formed by intentionally removing the electrode in order to control the tilting direction of the liquid crystal, but the edge of the electrode is also a boundary portion between the portion where the electrode is present and the portion where the electrode is not present. In addition, since the direction in which the liquid crystal is tilted is controlled by using the distortion of the electric lines of force, both are simply referred to as slits since they can be regarded as the same as the slits. Also, a combination of protrusions and slits may be used, such as forming protrusions on the substrate 1 and slits on the substrate 2. Although not shown in FIGS. 3A and 4A, the opening is set so that the overlap when viewed from the front with the regions 11a and 11b is approximately equal.

  A structure (control structure) that controls the direction in which the liquid crystal is tilted, such as protrusions, slits, and electrode edges (control structure), can change the direction in which the liquid crystal is tilted by changing the direction in which the structure is formed. It becomes. In Embodiment 1 of the present invention, in order to control the direction in which one liquid crystal inclines in two regions 11a and 11b in which the direction in which the liquid crystal inclines differs by 180 °, the direction in which the inclined surface is extended (control structure extending direction) ) To be 22 ° to 39 ° or 51 ° to 68 ° with respect to the x-axis. The reason for determining the angle range in the direction in which the liquid crystal is tilted will be described below.

  FIG. 5 is a diagram showing parameters of each component of the liquid crystal display device 14 according to Embodiment 1 of the present invention. Under the conditions shown in FIG. 5, the line-of-sight angle dependency of the transmittance of the liquid crystal display device 14 when the line-of-sight angle was changed to the left and right in the liquid crystal display device 14 shown in FIGS. The calculation results are shown in FIG. FIG. 6 is a diagram showing a simulation result of the line-of-sight angle dependency of the transmittance in the liquid crystal display device 14 according to Embodiment 1 of the present invention. As shown in FIG. 6, the horizontal axis is the viewing angle, and the positive side is observed from the right side of the liquid crystal display device 14. In FIG. 5, Δn · d is the product of the birefringence Δn and the thickness d of the liquid crystal layer 9, and the larger the value, the lower the applied voltage, the same transmittance can be obtained. Therefore, the white display voltage is set in the range of about 300 nm to 450 nm so that the voltage during white display is about 4 V to 5 V. Simulation software (LCD Master, manufactured by Symantec) was used for the calculation. The liquid crystal tilt directions are 0 ° and 180 °, that is, tilt in the left-right direction. Further, the area ratio of the regions 11a and 11b is set to 1: 1 in order to increase the symmetry of the optical characteristics when the line of sight is changed to the left and right. As shown in FIG. 6, the gray level (Level) is divided into seven equal parts between the white display (Level 8) and the CR 100 gray level (the gray level whose luminance is 1/100 of white display, that is, Level 1). It was made to become. Level 0 is black display. For the above-mentioned literature 1 (J.Hirata, "Viewing-Angle Evaluation Method for LCDs with Gray-Scale Image", 1993 Society for Information Display International Symposium Digest of Technical Papers, Society for Information Display, 1993, p.561-564) checking ...

  Next, it is determined whether or not gradation reversal has occurred depending on the line-of-sight angle, based on the index Q (Θ) obtained by the following equation (1).

  Here, Vm and Vn are applied voltages of two gradations for evaluating whether inversion occurs, and θi and θj are two consecutive line-of-sight angles in calculation (in the embodiment of the present invention, calculation is performed at intervals of 10 °). , Θj = θi + 10 °), T (V, θ) is the transmittance at the voltage V and the line-of-sight angle θ, and Θ is the maximum value of the line-of-sight angle for confirming the presence or absence of gradation inversion. min indicates that the set of (i, j) and the set of (m, n) are scanned to obtain the minimum value. However, Vn> Vm.

  Since the circularly polarized MVA liquid crystal display device according to the embodiment of the present invention is normally black, T (Vn, θi)> T (Vm, θi) and T (Vn, θj)> T (Vm, θj), and the values in parentheses in the expression (1) are positive values. Therefore, if there is no gradation inversion at all gradations or at all viewing angles, Q (Θ)> 0. When gradation reversal occurs, when the line-of-sight angle is gradually increased from the front where gradation reversal does not occur, the product of the two parentheses in equation (1) is negative at the line-of-sight angle where gradation reversal occurs. In other words, Q (Θ) <0 because the magnitude relation of the transmittance is reversed between θi and θj sandwiching the line-of-sight angle where gradation inversion occurs.

As shown in FIG. 6, attention is paid to white display (Level 8 having the highest transmittance at a viewing angle of 0 °). When the line-of-sight direction is directed to the right from the line-of-sight angle of 0 °, the transmittance of the lower gradation (Level 7 or the like) becomes higher than the transmittance of white display when the line-of-sight angle exceeds 40 °, resulting in gradation inversion. ing. The gradation inversion immediately before the viewing angle _{40 °, T (V Level8,} 40 °)> T is a (V _Level7, 40 °), the gradation reversal immediately after the viewing angle _{50 ° T (V Level8, 50} °) <since the _{T (V Level7, 50 °)} , (T (V Level8, 40 °) / T (V Level7, 40 °) -1) (T (V Level8, 50 °) / T (V Level7, 50 °) -1) <0. Therefore, Q (Θ) is always negative when Θ> 50 °.

  As described above, when gradation inversion occurs, Q (Θ) <0. FIG. 7 is a diagram showing a simulation result of the index Q (60 °) in the liquid crystal display device 14 according to Embodiment 1 of the present invention. The horizontal axis is the direction in which the liquid crystal inclines in the region 11a or 11b, and is at 5 ° intervals. The parameters used for the calculation are the same as those in FIG. 5 except for the direction in which the liquid crystal is tilted. Further, scaling is performed by multiplying the vertical axis by an appropriate positive value so that Q (60 °) becomes a numerical value of 1 to 2 digits. When the line-of-sight angle range in which Q (60 °)> 0 is obtained by interpolating between the points in FIG. 7 with a straight line, it is 21.3 ° to 39.7 °. Accordingly, the liquid crystal tilt direction in one of the regions 11a and 11b where the liquid crystal tilt direction is 180 ° different is set within the range of 21.3 ° to 39.7 °, so that the visual line angle is within the range of 60 °. Tone inversion no longer occurs. In addition, since 10 degrees or less and 50 degrees or more were negative and the absolute value became very large, it is not illustrated. FIG. 8 is a diagram showing a simulation result of the index Q (80 °) in the liquid crystal display device 14 according to Embodiment 1 of the present invention. The horizontal axis is the direction in which the liquid crystal inclines in the region 11a or 11b, and is at 5 ° intervals. The range of the tilting direction of the liquid crystal where Q (80 °)> 0 is 22.5 ° to 34.8 °. By setting within this range, gradation inversion does not occur in a larger viewing angle range. It is more preferable than the range of the tilt direction of the liquid crystal where (60 °)> 0. 7 and 8, the maximum value of Q is most preferably 30 ° ± 4 ° because the direction in which the liquid crystal is tilted is within the range of less than 30 ° ± 5 °.

  In the circularly polarized MVA liquid crystal display device, when the applied voltage is equal, the transmittance when viewed from the front with respect to the direction in which the liquid crystal is tilted hardly changes. Therefore, it can be used without gradation reversal by controlling the tilting direction of the liquid crystal to an appropriate range while maintaining the maximum transmittance substantially equal to that of white display (Level 8).

  FIG. 10 is a diagram showing a simulation result of the index Q (60 °) in the liquid crystal display device according to Embodiment 1 of the present invention when the parameters of FIG. 9 are used, and FIG. 11 is a diagram when the parameters of FIG. 9 are used. It is a figure which shows the simulation result of the parameter | index Q (80 degrees) in the liquid crystal display device by Embodiment 1 of this invention. From both figures, the range of the tilt direction where Q (60 °)> 0 is 21.2 ° to 41.1 °, and the range of the tilt direction where Q (80 °)> 0 is 22.3 ° to 34. It was 4 °. Therefore, the maximum value of Q is in the range where the liquid crystal tilt direction is less than 30 ° ± 5 °. That is, it can be seen that the range of the liquid crystal tilt direction does not significantly affect the details of the retardation plate and the polarizing plate.

  This is because the display characteristic in the left-right direction is important, and a wide viewing angle in the left-right direction is required. Since the circularly polarized MVA liquid crystal display device is normally black, the liquid crystal is not tilted in black display and is aligned perpendicular to the substrate. Accordingly, the retardation plates 5 to 8 are set so that the transmittance is low when the vertically aligned liquid crystal layer 9 is viewed from the left and right. Regardless of the specific settings of the phase difference plates 5 to 8, the required optical characteristics are determined by one parameter of Δn · d of the liquid crystal layer 9. Since Δn · d is actually a narrow range of 300 nm to 450 nm in consideration of the maximum applied voltage (lower as Δn · d increases and power consumption decreases) and response time (where d becomes shorter), The range of the direction in which the liquid crystal is tilted has little influence on the details of the retardation plate and the polarizing plate.

  From the above, in the circularly polarized MVA liquid crystal display device having the two regions 11a and 11b whose liquid crystal tilt directions are 180 ° different from each other, the liquid crystal in one region can be used regardless of the details of the retardation plate and the polarizing plate. The viewing angle was changed to the left and right by setting the direction of tilting to within the range of 22 ° to 39 °, more preferably 23 ° to 34 °, and even more preferably 30 ° ± 4 ° with respect to the x-axis. The gradation inversion at the time does not occur.

  On the other hand, when the entire liquid crystal display device 14 is rotated 90 ° about the z axis, the horizontal direction of the screen before the rotation becomes the vertical direction of the screen after the rotation. Therefore, by setting the tilt direction of the liquid crystal within the range of 51 ° to 68 °, more preferably 56 ° to 67 °, and even more preferably 60 ° ± 4 ° with respect to the x axis, Gradation inversion does not occur when changed.

  Note that in the liquid crystal display device 14 having the characteristics shown in FIG. 6, gradation inversion does not occur if only Level 7 or less is used without using Level 8, but the maximum transmittance per area of the opening is reduced. End up.

  In an actual MVA liquid crystal display device, not all liquid crystals are inclined in two directions, and the inclination near the top of the protrusion is inclined in a direction parallel to the direction in which the protrusion is formed. As described above, the region that does not incline in a desired direction may be removed from the opening due to light shielding or the like. However, since the area of the opening is smaller than that included in the opening, the luminance of the backlight must be increased. The maximum brightness of the liquid crystal display device is reduced. In the case of inclusion in the opening, the influence of a portion that does not tilt in a desired direction appears, so it is preferable to set the most preferable direction in which the liquid crystal tilts.

  In the present invention, a periodic structure for applying a voltage to a liquid crystal and a minimum unit of a region driven by the structure are described as a pixel, and an image composed of one or a plurality of pixels is displayed. The minimum display unit for this is described as an image unit. If one pixel has regions 11a and 11b whose liquid crystal tilt directions are 180 ° different from each other, even if only one pixel or only one image unit is turned on, a highly symmetrical display is obtained. If the device is small and high definition, the pixels may be too small to form the regions 11a and 11b in one pixel. However, if the regions 11a and 11b are created separately for each adjacent pixel, the display is almost symmetric if the display is performed in units of a plurality of images such as natural images.

  Liquid crystal display devices are required to have optical characteristics with a wide viewing angle and high symmetry (see Patent Document 1, Patent Document 3, and Patent Document 4). In particular, the symmetry in the horizontal direction and the vertical direction is regarded as important. FIG. 12 is a diagram for explaining a concept often used for general explanation showing that optical characteristics are symmetric by dividing two regions whose liquid crystal tilt directions are 180 ° different from each other. As shown in FIG. 12, with the division of two regions whose liquid crystal tilt directions differ by 180 ° as a basic unit, the transmittance 19c when viewed from an oblique direction along the liquid crystal tilt direction of the region 11a in the region 11a, The asymmetry of the transmittance 19a when viewed from a direction different from that direction by 180 °, the transmittance 19b when viewed from an oblique direction along the direction in which the liquid crystal in the region 11b inclines in the region 11b, and 180 ° from the direction. By offsetting by the asymmetry of the transmittance 19d when viewed from different directions, when the light transmitted through the two regions is viewed at the same time, the line of sight along the direction in which the liquid crystal in the region 11a is inclined has the same viewing angle. By utilizing the fact that the transmittance 19f in the direction and the transmittance 19e in the line-of-sight direction along the direction in which the liquid crystal in the region 11b is tilted are equal, optical properties with high symmetry are realized. Are (Patent Document 1, see Patent Document 2).

  In order to improve the viewing angle of the liquid crystal display device, the means of dividing the liquid crystal alignment into different regions has been widely applied to TN liquid crystal display devices and later applied to VA liquid crystal display devices ( Reference 2 (Japanese Patent Laid-Open No. 10-301113). Also in the TN liquid crystal display device, when viewed from the direction in which the liquid crystal is tilted, it looks black because the transmittance is low, and when viewed from the opposite side, it looks white because the transmittance is high, so two regions whose tilt directions are opposite to each other are formed. Then, the transmittance is averaged even when viewed from the direction in which the liquid crystal is tilted (refer to Document 3 (Japanese Patent Laid-Open No. 8-129180)). The description of the MVA liquid crystal display device also follows the description of the TN liquid crystal display device. In the TN liquid crystal display device, the viewing angle is narrow in the direction in which it looks black (CR decreases at a small viewing angle), but when divided, it becomes brighter, so the viewing angle is wider than before dividing, and the wide field of view is rather than improved symmetry. The effect of keratinization is often emphasized.

  The symmetry of the optical characteristics in the left-right direction and the up-down direction in the liquid crystal display device is important, as compared with the MVA liquid crystal display device that divides the liquid crystal into two regions in which the tilt direction of the liquid crystal has only 180 ° rotational symmetry about the z axis. The MVA liquid crystal display device that divides the liquid crystal into four regions with higher symmetry of 90 ° rotational symmetry and the liquid crystal tilting direction of the more symmetrical axisymmetric orientation is continuously centered on a specific point as the symmetry center. A changing MVA liquid crystal display is preferred. In the case of an MVA liquid crystal display device that divides the liquid crystal layer into two regions, the liquid crystal is controlled so that the liquid crystal is tilted in the horizontal direction or the vertical direction, where display symmetry is strongly required, or the horizontal direction and the vertical direction are symmetric. In order to achieve this, an example in which the liquid crystal is tilted in 45 ° and 225 ° directions (or 135 ° and 315 ° directions) is disclosed (see Patent Document 1). In addition, in the case of an MVA liquid crystal display device that divides a liquid crystal layer into four regions, an example is disclosed in which the liquid crystal is controlled to tilt in each direction of 45 °, 135 °, 225 °, and 315 ° ( Patent Document 1, Patent Document 2, and Document 4 (see Japanese Patent Application Laid-Open No. 2005-195753). On the other hand, in the present invention, the tilt direction of the liquid crystal is shifted from the disclosed directions such as left and right, up and down, and 45 degrees.

  In the linearly polarized MVA liquid crystal display device, even when the line of sight is tilted in the absorption axis direction of the polarizing plate during black display, light does not leak, so the viewing angle in the absorption axis direction is wide. Therefore, in general, the absorption axis of one polarizing plate is directed in the left-right direction and the other is directed in the up-down direction. However, in the circularly polarized MVA liquid crystal display device, the direction of the wide viewing angle and the direction of the absorption axis of the polarizing plate do not match, so the direction of the absorption axis of the polarizing plate and the direction of the slow axis of the retardation plate must be adjusted. Thus, the wide viewing angle direction is directed to the left and right and up and down directions (refer to Patent Documents 2 and 4 (Japanese Patent Laid-Open No. 2005-195753)). However, if the wide viewing angle is only directed in the left-right direction and the up-down direction, it is only necessary to rotate the polarizing plate, the phase difference plate, and the direction in which the liquid crystal is tilted about the z-axis. Not reported. This is because the direction in which the liquid crystal is tilted deviates from the left-right direction and the up-down direction and the 45 ° direction.

  The symmetry of the liquid crystal tilt direction and the symmetry of the optical characteristics will be examined in detail. FIG. 13 is a diagram illustrating that the optical characteristics are symmetric by dividing two regions whose liquid crystal tilt directions are different by 180 ° according to the embodiment of the present invention. The tilt angle of the liquid crystal in the region 11a is θ, and the tilt direction is φ. As shown in FIG. 13A, when the applied voltages in the two regions 11a and 11b are equal, the tilt angle of the liquid crystal in the region 11b is equal to θ as in the region 11a, and the tilt direction is φ + 180 °. If the area ratio between the region 11a and the region 11b is 1: 1, the alignment state of the liquid crystal has a 180 ° rotational symmetry about an axis parallel to the z axis passing through the center between the region 11a and the region 11b. Become. To be precise, the shapes of the regions 11a and 11b also need to be 180 ° rotationally symmetric, but the measuring instrument 17, which is the basic principle of color display by orientation division and color filters, is located far away, and the regions 11a and 11b The shape is not discussed in particular because it is assumed that it cannot be distinguished from each other. In FIG. 13, the measuring instrument 17 is drawn nearby for convenience.

  Next, as shown in FIG. 13B, when the direction of the line of sight is rotated by 180 ° with the line-of-sight angle maintained, the tilt angle of the liquid crystal in the region 11a and the region 11b remains the same, but is tilted. The direction is φ + 180 ° in the region 11a, φ + 180 ° + 180 ° = φ in the region 11b, and the alignment state of the liquid crystal is switched between the region 11a and the region 11b. Since the polarizing plate and the phase difference plate have 180 ° rotational symmetry about an axis parallel to the z axis and the line-of-sight angle does not change, the liquid crystal in the region 11a and the region 11 before and after rotation in the line-of-sight direction. Only the orientation state and the optical properties are interchanged. When viewing the transmitted light from the region 11a and the region 11b at the same time, the observer can recognize only the sum of the transmitted light from the region 11a and the region 11b, so that the optical characteristics look exactly the same before and after the rotation. Therefore, if the alignment state of the liquid crystal is 180 ° rotationally symmetric about the z axis, the left-right direction is symmetric. For the same reason, the vertical direction is also symmetric. More generally speaking, since the above consideration is established regardless of the value of φ, the line-of-sight directions different by 180 ° are symmetric. This is not related to the details of the relationship between the viewing direction of the observer and the direction in which the liquid crystal is tilted. If such an understanding is not sufficient, as seen in Japanese Patent Laid-Open No. 2004-228688, an erroneous interpretation is made that the optical characteristics are not symmetric in the direction orthogonal to the direction of the liquid crystal tilt.

  From the above, it can be seen that the description that optical properties with high symmetry are realized by liquid crystal alignment with high symmetry, as seen in many documents, requires attention in interpretation. If interpreted straightforwardly, in the black display of the MVA liquid crystal display device, the liquid crystal stands perpendicular to the substrate surface, and a very symmetric alignment state is realized, so the transmittance of the black display is very high. Although it seems to have symmetry, in reality, when a black display is viewed by changing the viewing direction while maintaining the viewing angle, a black screen and a slightly bright screen are alternately viewed at 90 ° intervals. That is, the transmittance of black display is 90 ° rotationally symmetric, and CR also changes with a 90 ° period (refer to Document 5 (Japanese Patent Laid-Open No. 2005-257809, FIG. 9)). This is because the polarizing plate and retardation plate system is 90 ° rotationally symmetric. The polarizing plate and the retardation plate are only 180 ° rotationally symmetric. However, in the circularly polarized MVA liquid crystal display device, the polarizing plate has a transmission axis orthogonal, the retardation plate has a slow axis orthogonal, and retardation is equal to 90 °. It is rotationally symmetric. Therefore, the optical properties of the circularly polarized MVA liquid crystal display device can have only 90 ° rotational symmetry at the maximum. Up to 90 ° rotational symmetry, highly symmetrical optical properties can be realized by highly symmetric liquid crystal alignment, but even if the optical properties have 90 ° rotational symmetry or higher, the optical property symmetry is 90 °. ° No more than rotational symmetry.

  If we extrapolate the fact that the symmetry increases from 90 ° rotational symmetry or lower to 90 ° rotational symmetry, the wrong conclusion that the liquid crystal alignment is highly symmetric and the optical properties are also highly symmetric. Will be led. Axisymmetrically oriented liquid crystal gives the impression that it looks the same from any point of view, and if you are actually looking at only the liquid crystal layer, this is true, and this is a factor that encourages extrapolation as described above. ing. Reference 1 shows the result of viewing angle-contrast characteristics in transmissive display for an MVA liquid crystal display device using an axially symmetric orientation. The viewing angle characteristics in transmissive display are almost omnidirectional. Although it shows a symmetrical characteristic, ... ", FIG. 9 clearly shows an approximately 90 [deg.] Rotational symmetry, not omnidirectional.

  The transmittance of white display of the circularly polarized MVA liquid crystal display device using the axially symmetric orientation shows the dependence on the viewing direction which is nearly omnidirectional, but it is a story of white display, and the circularly polarized MVA liquid crystal display using the axially symmetric orientation. The overall optical properties of the device do not show omnidirectional gaze direction dependence.

  As described above, it is difficult to discuss the symmetry of the optical characteristics unless the symmetry of the entire system such as the polarizing plate, the retardation plate, and the liquid crystal tilt direction is sufficiently considered. It is difficult to say that a viewpoint such as a conclusion obtained from a more accurate and general consideration about symmetry of direction and symmetry of optical properties is generally widely recognized.

  From the above, in the present invention, attention is paid to the fact that the tilt direction of the liquid crystal can be changed while maintaining the symmetry of the optical characteristics in the left-right direction. By quantitatively obtaining the range in the direction of inclination, high transmittance and suppression of gradation inversion in the left-right direction are performed.

  FIG. 14 is a diagram showing simulation results of the line-of-sight angle and direction with the same CR in the parameters of FIGS. 5 and 9 according to the first embodiment of the present invention. FIG. 14A shows the result of simulating the angle and direction of the line of sight with the same CR using the parameters of FIG. 5 and FIG. 14B using the parameters of FIG. Here, the direction in which the liquid crystal is tilted is 30 ° in the region 11a in both figures. When a point in the circle is indicated by polar coordinates (r, φ), the radius r is proportional to the line-of-sight angle, r = 0 corresponds to the line-of-sight angle of 0 °, and the maximum value of r corresponds to the line-of-sight angle of 80 °. Further, the azimuth angle φ corresponds to the line-of-sight direction, and φ = 0 ° corresponds to the right direction (the right direction also in the drawing). In the figure, a line connecting points designated by a viewing angle and a direction having the same CR is shown. The direction in which the liquid crystal is tilted is deviated by 30 ° from the left-right direction, but the viewing angle characteristics are symmetric in the left-right direction and also symmetric in the up-down direction.

  Since the horizontal direction does not change with respect to the 180 ° rotation around the x-axis, the polarizing plate, retardation plate, and liquid crystal layer of the circularly polarized MVA liquid crystal display device that does not cause gradation inversion in the horizontal direction as shown in FIGS. Even if the screen is turned over, gradation inversion does not occur in the left-right direction. When the liquid crystal layer is rotated 180 ° around the x axis, the sign of the liquid crystal tilt direction is reversed. That is, the liquid crystal tilt direction in one of the regions 11a and 11b where the liquid crystal tilt direction is 180 ° different is in the range of −22 ° to −39 °, more preferably −23 ° to −34 °, and still more preferably −. If it is within the range of 30 ° ± 4 °, gradation inversion does not occur in the left-right direction. Although the optical characteristics are switched in the vertical direction, the circularly polarized MVA liquid crystal display device divided into two regions whose liquid crystal tilt directions are 180 ° different from each other has a symmetrical optical characteristic in the line-of-sight directions different by 180 °. In the case of a circularly polarized MVA liquid crystal display device in which inversion does not occur, gradation inversion does not occur in the vertical direction even if it is turned upside down as described above. That is, by setting the direction in which the liquid crystal is tilted within the range of −51 ° to −68 °, more preferably −56 ° to −67 °, and still more preferably −60 ° ± 4 ° with respect to the x axis, No gradation inversion occurs in the direction.

  As described above, the liquid crystal tilt direction can be controlled by a control structure such as a protrusion or a slit. Basically, the liquid crystal in the region sandwiched by the extending direction of the control structure is tilted in a direction perpendicular to the extending direction of the control structure of the control structure (in this description, the structure is formed on different substrates). Even if it is arranged, it is described as adjacent if it appears to be adjacent from the front). However, as described in Patent Document 2, the distance between the control structure extending directions is reduced to extend the control structure. It can also be controlled in a direction parallel to the direction. In any case, it is desirable to uniformly control the tilt direction of the liquid crystal in the widest possible region of the opening. For this purpose, the slope extending direction of the control structure may be long. However, the angle between the slope extending direction of the control structure and the x axis is within the above range. Further, as described in Patent Document 2, when the control structure extending direction adjacent to the region of interest adjacent to the region of interest is not parallel to the front, the liquid crystal in the region has a structure that is approximately adjacent. The direction perpendicular to the average of the angle between the control structure extending direction and the x-axis (when the liquid crystal tilt direction is controlled to the direction perpendicular to the control structure extending direction), or the parallel direction (the liquid crystal (When the direction of inclination is controlled in a direction parallel to the extending direction of the control structure). Therefore, when the control structure extending direction of the structure adjacent to the region of interest and viewed from the front is not parallel, the average of the angles formed by the control structure extending direction of the structure and the x axis is If it is in the range.

  From the above, in the circularly polarized MVA liquid crystal display device divided into two regions where the liquid crystal tilt direction is 180 ° different, the liquid crystal tilt direction of one region is 22 ° to 39 ° with respect to the x-axis. More preferably, by controlling within the range of 23 ° to 34 °, and more preferably 30 ° ± 4 °, gradation inversion does not occur in the left-right direction of the liquid crystal display device. In addition, gradation control is caused in the vertical direction of the liquid crystal display device by controlling within the range of 51 ° to 68 °, more preferably 56 ° to 67 °, and even more preferably 60 ° ± 4 ° with respect to the x-axis. Disappear.

<Embodiment 2>
In the first embodiment, the circularly polarized MVA liquid crystal display device divided into two regions whose liquid crystal tilt directions are different by 180 ° has been described. In the second embodiment, the circularly polarized light divided into four regions whose liquid crystal tilt directions are different from each other. The MVA liquid crystal display device will be described. The polarizing plate and the retardation plate are the same as those in the first embodiment.

  FIG. 15 is a schematic view of a liquid crystal display device according to Embodiment 2 of the present invention when viewed from the front. 15, electrodes 10 for applying a voltage to the liquid crystal are periodically arranged on the liquid crystal side of the substrate 1, and the structure shown in FIG. 15 is periodically arranged on the entire display screen. In FIG. 15, the electrode 13 on the substrate 2 side is rectangular, but covers the entire display screen. Further, auxiliary capacitance electrodes, switching elements, wirings, etc. are not shown.

  As shown in FIG. 15, the regions 11A and 11B in which the liquid crystal tilts when the voltage is applied to the liquid crystal are different from each other by about 180 °, and the directions in which the liquid crystal tilts when the voltage is applied to the liquid crystal are different from the region 11A. A region 11C and a region 11D in which the direction in which the liquid crystal is tilted when a voltage is applied to the liquid crystal differ from the region 11C by approximately 180 ° are formed. When the angle formed between the direction in which the liquid crystal is tilted in the region 11A and the positive direction of the x axis is φ, the angle between the direction in which the liquid crystal is tilted in the region 11C and the positive direction of the x axis is 180 ° −φ. The liquid crystal tilt direction in the region 11B is 180 ° + φ = −180 ° + φ, and in the region 11D, 180 ° + 180 ° −φ = −φ. In FIG. 15, the resin protrusion 12 is used as a structure for controlling the direction in which the liquid crystal is tilted. However, any structure may be used as long as it is a structure for controlling the direction in which the liquid crystal is tilted, such as the slit 19. Further, when these are formed on the substrate 1 and the substrate 2, a combination of the resin protrusion 12 and the slit 19 may be used. Although not shown, the opening of the display screen is set so that the overlap with the regions 11A, 11B, 11C, and 11D is substantially equal when viewed from the front.

  In Embodiment 2 of the present invention, the liquid crystal tilt direction is divided into four different regions (11A, 11B, 11C, 11D), and the liquid crystal tilt direction in the region 11A and the positive direction of the x-axis The angle formed between the direction in which the liquid crystal inclines in the region 11C and the positive direction of the x-axis in the region 11C is 180 ° −φ, and φ is 26 ° to 42 ° or 48 ° to 64 °. The reason why the direction in which the liquid crystal inclines is set to the above-described angle range in the polarized MVA liquid crystal display device will be described.

  FIG. 16 is a diagram showing a simulation result of the index Q (60 °) in the liquid crystal display device according to Embodiment 2 of the present invention. The parameters shown in FIG. 5 are used except for the direction in which the liquid crystal is tilted. As shown in FIG. 16, the horizontal axis is the direction φ in which the liquid crystal inclines in the region 11A and is calculated at 5 ° intervals. The areas 11A, 11B, 11C, and 11D have the same area. Further, the vertical axis is scaled by multiplying an appropriate positive value so that Q (60 °) becomes a numerical value of 1 to 2 digits. The calculated point was interpolated with a straight line, and the range of the tilting direction of the liquid crystal so that Q (60 °)> 0 was obtained, which was 25.3 ° to 42.4 °.

  FIG. 17 is a diagram showing a simulation result of the index Q (60 °) in the liquid crystal display device according to Embodiment 2 of the present invention. The parameters shown in FIG. 9 are used except for the direction in which the liquid crystal is tilted. As shown in FIG. 17, the horizontal axis is the direction φ of the liquid crystal in the region 11A, and is calculated at 5 ° intervals. The areas 11A, 11B, 11C, and 11D have the same area. Further, the vertical axis is scaled by multiplying an appropriate numerical value so that Q (60 °) becomes a positive value of 1 to 2 digits. The calculated point was interpolated with a straight line, and the range of the tilting direction of the liquid crystal so that Q (60 °)> 0 was obtained, which was 25.2 ° to 42.4 °.

  Accordingly, the regions 11A and 11B in which the direction in which the liquid crystal tilts when the voltage is applied to the liquid crystal is approximately 180 ° different from each other, the region 11C in which the direction in which the liquid crystal tilts when the voltage is applied to the liquid crystal is different from the region 11A, The direction in which the liquid crystal tilts when a voltage is applied to is divided into a region 11D that is approximately 180 ° different from the region 11C, and the angle between the direction in which the liquid crystal tilts in the region 11A and the positive direction of the x axis is φ In the circularly polarized MVA liquid crystal display device in which the angle formed by the liquid crystal tilt direction in the region 11C and the positive x-axis direction is 180 ° −φ, the liquid crystal tilt direction in the region 11A is 26 ° to 42 °. By setting the value within the range, gradation inversion does not occur in the range where the viewing angle in the horizontal direction is within 60 °.

  FIG. 18 is a diagram showing a simulation result of the index Q (80 °) in the liquid crystal display device according to Embodiment 2 of the present invention. The parameters shown in FIG. 5 are used except for the direction in which the liquid crystal is tilted. As shown in FIG. 18, the horizontal axis represents the direction φ in which the liquid crystal inclines in the region 11A, and is calculated at 5 ° intervals. The areas 11A, 11B, 11C, and 11D have the same area. Further, the vertical axis is scaled by multiplying an appropriate positive value so that Q (80 °) becomes a numerical value of 1 to 2 digits. When the calculated points were interpolated with a straight line, and the range of the liquid crystal tilt direction such that Q (80 °)> 0 was obtained, it was 26.2 ° to 34.9 °.

  FIG. 19 is a diagram showing a simulation result of the index Q (80 °) in the liquid crystal display device according to Embodiment 2 of the present invention. The parameters shown in FIG. 9 are used except for the direction in which the liquid crystal is tilted. As shown in FIG. 19, the horizontal axis is the direction φ of the liquid crystal in the region 11A, and is calculated at 5 ° intervals. The areas 11A, 11B, 11C, and 11D have the same area. Further, the vertical axis is scaled by multiplying an appropriate positive value so that Q (80 °) becomes a numerical value of 1 to 2 digits. The calculated points were interpolated with a straight line, and the range of the tilting direction of the liquid crystal so that Q (80 °)> 0 was obtained, which was 25.9 ° to 35.0 °.

  Accordingly, the regions 11A and 11B in which the direction in which the liquid crystal tilts when the voltage is applied to the liquid crystal is approximately 180 ° different from each other, the region 11C in which the direction in which the liquid crystal tilts when the voltage is applied to the liquid crystal is different from the region 11A, The direction in which the liquid crystal tilts when a voltage is applied to is divided into a region 11D that is approximately 180 ° different from the region 11C, and the angle between the direction in which the liquid crystal tilts in the region 11A and the positive direction of the x axis is φ In the circularly polarized MVA liquid crystal display device in which the angle formed by the liquid crystal tilt direction in the region 11C and the positive x-axis direction is 180 ° −φ, the liquid crystal tilt direction in the region 11A is 27 ° to 34 °. By setting the value within the range, gradation inversion does not occur in the range where the viewing angle in the horizontal direction is within 80 °.

  FIG. 20 is a diagram showing a simulation result of the line-of-sight angle dependency of the transmittance in the liquid crystal display device according to Embodiment 2 of the present invention. The parameters shown in FIG. 5 are used for the calculation. The tilt direction of the liquid crystal in the region 11A is 45 °. This is the setting of the conventional general liquid crystal tilt direction, but gradation inversion occurs as shown in the figure. In Embodiment 2 of the present invention, by appropriately setting the direction in which the liquid crystal is tilted as shown in FIGS. 16 to 19, it is possible to eliminate gradation inversion and use high transmittance.

  On the other hand, when the entire liquid crystal display device 14 is rotated by 90 ° about the z-axis, the left-right direction before rotation becomes the up-down direction after rotation. Therefore, by setting the direction in which the liquid crystal is inclined in the region 11A within the range of 48 ° to 64 °, more preferably 56 ° to 63 ° with respect to the x-axis, the floor when the line-of-sight angle is changed up and down is set. Tone inversion does not occur.

  Note that even if the liquid crystal display device has the characteristics as shown in FIG. 20, gradation inversion can be prevented by using only Level 7 or lower without using Level 8. However, as described above, the maximum transmittance per opening area decreases.

  In an actual MVA liquid crystal display device, not all liquid crystals are inclined in the assumed direction, and the inclination near the top of the protrusion is inclined in a direction parallel to the direction in which the protrusion is formed. As described above, the region that does not incline in a desired direction may be removed from the opening due to light shielding or the like. However, since the area of the opening is smaller than that included in the opening, the luminance of the backlight must be increased. The maximum brightness of the liquid crystal display device is reduced. In the case of inclusion in the opening, the influence of a portion that does not tilt in a desired direction appears, so it is preferable to set the most preferable direction in which the liquid crystal tilts.

  The liquid crystal tilt direction is divided into four different regions (11A, 11B, 11C, 11D), and the angle between the liquid crystal tilt direction in the region 11A and the positive x-axis direction is φ. In the circularly polarized MVA liquid crystal display device in which the angle between the liquid crystal tilt direction in the region 11C and the positive direction of the x axis is 180 ° −φ, four regions (11A, 11B, 11C, and 11D) are combined into one pixel. Even if only one pixel or only one image unit is lit, the display is highly symmetric, but if the liquid crystal display device is small and high definition, the pixel is too small and there are four There is a possibility that the regions (11A, 11B, 11C, 11D) cannot be formed in one pixel. However, if four regions (11A, 11B, 11C, and 11D) are created separately for each adjacent pixel, the display becomes almost symmetrical when displaying in units of a plurality of images such as natural images. Don't be. In addition, when only one pixel is lit, when the ratio of the lit areas 11A, 11B, 11C, and 11D is extremely biased, the display is not symmetric.

  From the above, in the present invention, attention is paid to the fact that the tilt direction of the liquid crystal can be changed while maintaining the symmetry of the optical characteristics in the left-right direction. By quantitatively obtaining the range in the direction of inclination, high transmittance and suppression of gradation inversion in the left-right direction are performed.

  FIG. 21 is a diagram showing simulation results of the line-of-sight angle and direction with the same CR in the parameters of FIGS. 5 and 9 according to the second embodiment of the present invention. FIG. 21A shows the result of simulating the angle and direction of the line of sight with the same CR using the parameters of FIG. 5 and FIG. 21B using the parameters of FIG. Here, the direction in which the liquid crystal is tilted is 30 ° in the region 11A in both figures. In the figure, a line connecting points designated by a viewing angle and a direction having the same CR is shown. The direction in which the liquid crystal is tilted is deviated by 30 ° from the left-right direction, but the viewing angle characteristics are symmetric in the left-right direction and also symmetric in the up-down direction. Although it looks like 90 ° rotational symmetry, it can be seen from FIG. 21 (b) that the viewing angle is wider in the horizontal direction than in the vertical direction, and is not exactly 90 ° rotationally symmetric. That is, there is no 90 ° rotational symmetry as in the case of the generally known quadrant MVA liquid crystal display device in which the liquid crystal tilt direction is 45 °.

  Since the horizontal direction does not change with respect to the 180 ° rotation around the x-axis, the polarizing plate, retardation plate, and liquid crystal layer of the circularly polarized MVA liquid crystal display device that does not cause gradation inversion in the horizontal direction as shown in FIGS. Even if the screen is turned over, gradation inversion does not occur in the left-right direction. When the liquid crystal layer is rotated 180 ° around the x axis, the sign of the liquid crystal tilt direction is reversed. That is, if the direction in which the liquid crystal inclines in the region 11A is in the range of −26 ° to −42 °, more preferably in the range of −27 ° to −34 °, gradation inversion does not occur in the left-right direction. Although the optical characteristics are switched in the vertical direction, the circularly polarized MVA liquid crystal display device divided into two regions whose liquid crystal tilt directions are 180 ° different from each other has a symmetrical optical characteristic in the line-of-sight directions different by 180 °. In the case of a circularly polarized MVA liquid crystal display device in which inversion does not occur, gradation inversion does not occur in the vertical direction even if it is turned upside down as described above. That is, gradation inversion occurs in the vertical direction by setting the direction in which the liquid crystal is inclined in the region 11A within the range of −48 ° to −64 °, more preferably −56 ° to −63 ° with respect to the x-axis. Absent.

  As described above, the liquid crystal tilt direction can be controlled by a control structure such as a protrusion or a slit. Basically, the liquid crystal in the region sandwiched by the extending direction of the control structure is tilted in a direction perpendicular to the extending direction of the control structure of the control structure (in this description, the structure is formed on different substrates). Even if it is arranged, it is described as adjacent if it appears to be adjacent from the front). However, as described in Patent Document 2, the distance between the control structure extending directions is reduced to extend the control structure. It can also be controlled in a direction parallel to the direction. In any case, it is desirable to uniformly control the tilt direction of the liquid crystal in the widest possible region of the opening. For this purpose, the control structure extending direction of the control structure may be long. However, the angle formed by the control structure extending direction of the control structure and the x axis is within the above range. Further, as described in Patent Document 2, when the control structure extending direction adjacent to the region of interest adjacent to the region of interest is not parallel to the front, the liquid crystal in the region has a structure that is approximately adjacent. The direction perpendicular to the average of the angle between the control structure extending direction and the x-axis (when the liquid crystal tilt direction is controlled to the direction perpendicular to the control structure extending direction), or the parallel direction (the liquid crystal (When the direction of inclination is controlled in a direction parallel to the extending direction of the control structure). Therefore, when the control structure extending direction of the structure adjacent to the region of interest and viewed from the front is not parallel, the average of the angles formed by the control structure extending direction of the structure and the x axis is If it is in the range.

  From the above, the regions 11A and 11B in which the liquid crystal tilts when the voltage is applied to the liquid crystal are different from each other by about 180 °, and the regions 11C where the liquid crystal tilts when the voltage is applied to the liquid crystal are different from the region 11A. And a direction in which the liquid crystal tilts when a voltage is applied to the liquid crystal is divided into a region 11D that is approximately 180 ° different from the region 11C, and an angle formed between the direction in which the liquid crystal tilts in the region 11A and the positive direction of the x axis. In the circularly polarized MVA liquid crystal display device in which the angle between the direction in which the liquid crystal inclines in the region 11C and the positive direction of the x-axis is 180 ° −φ when φ is φ, the direction in which the liquid crystal inclines in the region 11A is x By controlling the angle within the range of 26 ° to 42 °, more preferably 27 ° to 34 ° with respect to the axis, gradation inversion does not occur in the left-right direction of the liquid crystal display device. Further, by controlling the direction in which the liquid crystal is tilted in the region 11A within a range of 48 ° to 64 °, more preferably 56 ° to 63 ° with respect to the x-axis, gradation inversion is performed in the vertical direction of the liquid crystal display device. No longer occurs.

<Embodiment 3>
In the first and second embodiments, four retardation plates having a slow axis are used (FIG. 1). When the phase difference plate 5 and the phase difference plate 6 are orthogonal to each other and the phase difference plate 7 and the phase difference plate 8 are respectively orthogonal to each other, the high CR is obtained when viewed from the front. It is a condition to obtain. It is also a condition that the retardation of the phase difference plate 5 and the phase difference plate 6 is equal, and that of the phase difference plate 7 and the phase difference plate 8 is equal. However, it is difficult to meet these conditions strictly.

  Practically, ± 10 ° in the axial direction and ± 30 nm in the retardation are allowed, but a liquid crystal display device capable of obtaining a higher CR is more preferable. The circularly polarized MVA liquid crystal display device has a method that does not use the phase difference plate 7 and the phase difference plate 8, and since the number of the phase difference plates is small, the number of factors that lower the CR decreases, and the liquid crystal display that can obtain a higher CR It is advantageous for the production of equipment. Since the number of retardation plates is small, there is an advantage that the apparatus can be made thin.

  Each component of the liquid crystal display device according to Embodiment 3 of the present invention is obtained by removing the retardation plate 7 and the retardation plate 8 from FIG. In other words, the first and second retardation plates 5 and 6 are provided in place of the first to fourth retardation plates 7, 5, 8 and 6 in FIG. 1. As in the first embodiment according to the present invention, the liquid crystal layer has two regions 11a and 11b whose inclination directions differ by 180 °. FIG. 22 is a diagram showing parameters of each component of the liquid crystal display device according to Embodiment 3 of the present invention. FIG. 23 is a diagram showing a simulation result of the index Q (80 °) in the liquid crystal display device according to Embodiment 3 of the present invention, and uses the parameters of FIG. In the third embodiment according to the present invention, since the phase difference plate 7 and the phase difference plate 8 are not used in order to show a higher CR, the most demanded 80 ° is considered for the line-of-sight angle range in which gradation inversion does not occur. . The horizontal axis of FIG. 23 is the direction φ in which the liquid crystal inclines in the region 11a and is calculated at intervals of 5 °. The region 11a and the region 11b have the same area. Further, the vertical axis is scaled by multiplying an appropriate positive value so that Q (80 °) becomes a numerical value of 1 to 2 digits. The calculated point was interpolated with a straight line, and the range of the tilt direction of the liquid crystal so that Q (80 °)> 0 was obtained, which was 24.9 ° to 39.5 °.

  Therefore, by setting the liquid crystal tilt direction in one of the region 11a and the region 11b where the liquid crystal tilt direction is 180 ° different to be in the range of 25 ° to 39 °, the horizontal floor is within the range of the line-of-sight angle of 80 °. Tone inversion no longer occurs. From FIG. 23, the maximum value of Q (80 °) is most preferably 30 ° ± 4 ° because the direction in which the liquid crystal is tilted is within the range of less than 30 ° ± 5 °.

  Similar to the first embodiment of the present invention, if the direction in which the liquid crystal is tilted is a complementary angle of 90 °, that is, 51 ° to 65 °, gradation inversion in the vertical direction does not occur. Similar to the first embodiment of the present invention, the same effect can be obtained even if the angle value is negative.

  FIG. 24 is a diagram showing simulation results of the line-of-sight angle and direction with the same CR in the parameters of FIG. 22 according to Embodiment 3 of the present invention. Here, the direction in which the liquid crystal is tilted is 30 ° in the region 11a. When a point in the circle is indicated by polar coordinates (r, φ), the radius r is proportional to the line-of-sight angle, r = 0 corresponds to the line-of-sight angle of 0 °, and the maximum value of r corresponds to the line-of-sight angle of 80 °. Further, the azimuth angle φ corresponds to the line-of-sight direction, and φ = 0 ° corresponds to the right direction (the right direction also in the drawing). In the figure, a line connecting points designated by a viewing angle and a direction having the same CR is shown. The direction in which the liquid crystal is tilted is deviated by 30 ° from the left-right direction, but the viewing angle characteristics are symmetric in the left-right direction and also symmetric in the up-down direction.

  Compared with Embodiment 1 (FIG. 14) of the present invention, the viewing angles in the 45 °, 135 °, 225 °, and 315 ° directions are narrower in the viewing direction. Although it is not preferable for an application such as a monitoring monitor that is supposed to be viewed from various directions, it is not important in a liquid crystal display device for which priority is given to display characteristics in a specific direction such as left and right or up and down, which are the subject of the present invention.

  Although a biaxial retardation plate is used in FIG. 22, a-plate or a-plate may be used in combination with c-plate.

<Embodiment 4>
Each component part of the liquid crystal display device in Embodiment 4 by this invention removes the phase difference plate 7 and the phase difference plate 8 from FIG. Similarly to the second embodiment according to the present invention, the liquid crystal has a region 11A and a region 11B in which the directions in which the liquid crystal is tilted are different from each other by 180 ° when a voltage is applied, and a region in which the liquid crystal is tilted when a voltage is applied to the liquid crystal. It is assumed that a region 11C different from 11A and a region 11D where the direction in which the liquid crystal inclines when the voltage is applied to the liquid crystal is different from the region 11C by approximately 180 ° are formed. When the angle formed between the direction in which the liquid crystal is tilted in the region 11A and the positive direction of the x axis is φ, the angle between the direction in which the liquid crystal is tilted in the region 11C and the positive direction of the x axis is 180 ° −φ. FIG. 25 is a diagram showing a simulation result of the index Q (80 °) in the liquid crystal display device according to Embodiment 4 of the present invention, and uses the parameters shown in FIG. In Embodiment 4 according to the present invention, since the phase difference plate 7 and the phase difference plate 8 are not used in order to show a higher CR, the most demanded 80 ° is considered for the line-of-sight angle range in which gradation inversion does not occur. . The horizontal axis of FIG. 25 is the direction φ in which the liquid crystal inclines in the region 11a, and is calculated at 5 ° intervals. The areas 11A, 11B, 11C, and 11D have the same area. Further, the horizontal axis is scaled by multiplying an appropriate positive value so that Q (80 °) becomes a numerical value of 1 to 2 digits. The calculated points were interpolated with a straight line, and the range of the tilting direction of the liquid crystal so that Q (80 °)> 0 was obtained, which was 28.1 ° -35.2 °.

  Therefore, the liquid crystal tilt direction in one of the region 11a and the region 11b where the liquid crystal tilt direction is 180 ° different is within the range of 29 ° to 35 °, so that the horizontal scale is within the range of the line-of-sight angle of 80 °. Tone inversion no longer occurs.

  Similarly to the second embodiment of the present invention, if the direction in which the liquid crystal is tilted is a complementary angle of 90 °, that is, 55 ° to 61 °, the gradation inversion in the vertical direction does not occur. Similar to the second embodiment of the present invention, the same effect can be obtained even if the angle value is negative.

  FIG. 26 is a diagram illustrating a simulation result of the line-of-sight angle and direction with the same CR in the parameters of FIG. 22 according to the fourth embodiment of the present invention. Here, the direction in which the liquid crystal is inclined is 30 ° in the region 11A. When a point in the circle is indicated by polar coordinates (r, φ), the radius r is proportional to the line-of-sight angle, r = 0 corresponds to the line-of-sight angle of 0 °, and the maximum value of r corresponds to the line-of-sight angle of 80 °. Further, the azimuth angle φ corresponds to the line-of-sight direction, and φ = 0 ° corresponds to the right direction (the right direction also in the drawing). In the figure, a line connecting points designated by a viewing angle and a direction having the same CR is shown. The direction in which the liquid crystal is tilted is deviated by 30 ° from the left-right direction, but the viewing angle characteristics are symmetric in the left-right direction and also symmetric in the up-down direction.

  Compared with Embodiment 2 (FIG. 21) of the present invention, the viewing angles in the 45 °, 135 °, 225 °, and 315 ° directions are narrower in the viewing direction. Although it is not preferable for an application such as a monitoring monitor that is supposed to be viewed from various directions, it is not important in a liquid crystal display device for which priority is given to display characteristics in a specific direction such as left and right or up and down, which are the subject of the present invention.

  Although a biaxial retardation plate is used in FIG. 22, a-plate or a-plate may be used in combination with c-plate.

1 is a schematic configuration diagram of a circularly polarized MVA liquid crystal display device according to an embodiment of the present invention. It is the figure which showed the positional relationship of the liquid crystal display device by an embodiment of this invention, and an observer. It is the schematic diagram and sectional drawing when the liquid crystal display device by Embodiment 1 of this invention is seen from the front. It is the schematic diagram and sectional drawing when the liquid crystal display device by Embodiment 1 of this invention is seen from the front. It is a figure which shows the parameter of each structure part of the liquid crystal display device by Embodiment 1 of this invention. It is a figure which shows the simulation result of the viewing angle dependency of the transmittance | permeability in the liquid crystal display device by Embodiment 1 of this invention. It is a figure which shows the simulation result of the parameter | index Q (60 degrees) in the liquid crystal display device by Embodiment 1 of this invention. It is a figure which shows the simulation result of the parameter | index Q (80 degrees) in the liquid crystal display device by Embodiment 1 of this invention. It is a figure which shows the parameter of each structure part of the liquid crystal display device by Embodiment 1 of this invention. It is a figure which shows the simulation result of the parameter | index Q (60 degrees) in the liquid crystal display device by Embodiment 1 of this invention. It is a figure which shows the simulation result of the parameter | index Q (80 degrees) in the liquid crystal display device by Embodiment 1 of this invention. It is a general explanatory view of the principle that optical characteristics are symmetric by dividing two regions whose liquid crystal tilt directions are different by 180 °. It is a figure which shows that an optical characteristic becomes symmetrical by the division | segmentation of two area | regions in which the inclination direction of the liquid crystal differs by 180 degrees by embodiment of this invention. It is a figure which shows the simulation result of the angle | corner of the gaze and direction where CR is equal in the parameter of FIG. 5 and FIG. 9 by Embodiment 1 of this invention. It is a schematic diagram when the liquid crystal display device by Embodiment 2 of this invention is seen from the front. It is a figure which shows the simulation result of the parameter | index Q (60 degrees) in the liquid crystal display device by Embodiment 2 of this invention. It is a figure which shows the simulation result of the parameter | index Q (60 degrees) in the liquid crystal display device by Embodiment 2 of this invention. It is a figure which shows the simulation result of the parameter | index Q (80 degrees) in the liquid crystal display device by Embodiment 2 of this invention. It is a figure which shows the simulation result of the parameter | index Q (80 degrees) in the liquid crystal display device by Embodiment 2 of this invention. It is a figure which shows the simulation result of the gaze angle dependence of the transmittance | permeability in the liquid crystal display device by Embodiment 2 of this invention. It is a figure which shows the simulation result of the angle and the direction of a gaze which have CR equal in the parameter of FIG. 5 and FIG. 9 by Embodiment 2 of this invention. It is a figure which shows the parameter of each structure part of the liquid crystal display device by Embodiment 3 of this invention. It is a figure which shows the simulation result of the parameter | index Q (80 degrees) in the liquid crystal display device by Embodiment 3 of this invention. It is a figure which shows the simulation result of the angle and the direction of the line of sight with which CR is equal in the parameter of FIG. 22 by Embodiment 3 of this invention. It is a figure which shows the simulation result of the parameter | index Q (80 degrees) in the liquid crystal display device by Embodiment 4 of this invention. It is a figure which shows the simulation result of the angle and the direction of a gaze which CR is equal in the parameter of FIG. 22 by Embodiment 4 of this invention.

Explanation of symbols

  1 substrate, 2 substrate, 3 polarizing plate, 3a transmission axis, 4 polarizing plate, 4a transmission axis, 5 phase difference plate, 5a slow phase axis, 6 phase difference plate, 6a slow phase axis, 7 phase difference plate, 7a slow phase Axis, 8 Retardation plate, 8a Slow axis, 9 Liquid crystal layer, 10 Electrode, 11a Region where the tilt direction of the liquid crystal is approximately uniform when a voltage is applied, 11b The tilt direction of the liquid crystal when a voltage is applied is 11a 12a resin protrusion, 12b resin protrusion 13 electrode, 14 liquid crystal display device, 15 observer's line of sight, 16 vertical direction, 17 measuring instrument, 18 observer, 20 lines of electric force.

Claims (12)

A first substrate having electrodes arranged periodically to apply a voltage to the liquid crystal;
A second substrate having an electrode for applying a voltage to the liquid crystal;
A liquid crystal layer having a negative liquid crystal sandwiched between the first substrate and the second substrate and oriented substantially perpendicular to the substrate surface;
A first polarizing plate disposed on a side different from the liquid crystal side of the first substrate;
A second polarizing plate disposed on a side different from the liquid crystal side of the second substrate and having a transmission axis perpendicular to the transmission axis of the first polarizing plate;
A first retardation plate disposed between the first substrate and the first polarizing plate, having a slow axis that is not parallel to the transmission axis of the first polarizing plate and is not orthogonal;
A second retardation plate disposed between the first substrate and the first retardation plate;
A third retardation plate disposed between the second substrate and the second polarizing plate and having a slow axis perpendicular to the slow axis of the first retardation plate;
A fourth retardation plate disposed between the second substrate and the third retardation plate and having a slow axis perpendicular to the slow axis of the second retardation plate;
A control structure that is disposed on the liquid crystal side of the first substrate and / or the second substrate and controls the direction in which the liquid crystal tilts when a voltage is applied to the liquid crystal layer;
A first region in which the liquid crystal tilts in one direction when a voltage is applied to the liquid crystal layer;
A second region in which the liquid crystal tilts in a direction that is approximately 180 ° different from the direction in which the liquid crystal in the first region tilts;
In a liquid crystal display device comprising:
The liquid crystal display device, wherein an angle formed between a direction in which the liquid crystal is inclined in the first region and a horizontal direction of the screen of the liquid crystal display device is 22 ° to 39 ° or 51 ° to 68 °.   The liquid crystal display device according to claim 1, wherein an angle formed between a horizontal direction of the screen of the liquid crystal display device and a control structure extending direction of the control structure is 22 ° to 39 °.   2. The liquid crystal display device according to claim 1, wherein an angle between a horizontal direction of the screen of the liquid crystal display device and a control structure extending direction of the control structure is 51 ° to 68 °. A third region in which the liquid crystal is inclined in a direction different from the first region;
A fourth region in which the liquid crystal is inclined in a direction different by about 180 ° with respect to the direction in which the third region is inclined;
In a liquid crystal display device further comprising:
The direction in which the liquid crystal inclines in the third region and the screen of the liquid crystal display device when the angle formed between the direction in which the liquid crystal inclines in the first region and the horizontal direction of the screen of the liquid crystal display device are φ The angle formed with the left-right direction is 180-φ, and φ is 26 ° -42 ° instead of 22 ° -39 ° or 48 ° -64 ° instead of 51 ° -68 °. Item 2. A liquid crystal display device according to item 1.   When the angle formed between the horizontal direction of the screen of the liquid crystal display device and the control structure extending direction of the control structure in the first region is φ, the direction in which the liquid crystal in the third region is tilted and the liquid crystal 5. The liquid crystal display device according to claim 4, wherein an angle between the display device and the left-right direction of the screen is 180 ° −φ, and φ is 26 ° to 42 °.   When the angle formed between the horizontal direction of the screen of the liquid crystal display device and the control structure extending direction of the control structure in the first region is φ, the direction in which the liquid crystal in the third region is tilted and the liquid crystal The liquid crystal display device according to claim 4, wherein an angle between the display device and the left-right direction of the screen is 180 ° −φ, and φ is 48 ° to 64 °. A first substrate having electrodes arranged periodically to apply a voltage to the liquid crystal;
A second substrate having an electrode for applying a voltage to the liquid crystal;
A liquid crystal layer having a negative liquid crystal sandwiched between the first substrate and the second substrate and oriented substantially perpendicular to the substrate surface;
A first polarizing plate disposed on a side different from the liquid crystal side of the first substrate;
A second polarizing plate disposed on a side different from the liquid crystal side of the second substrate and having a transmission axis perpendicular to the transmission axis of the first polarizing plate;
A first retardation plate disposed between the first substrate and the first polarizing plate, having a slow axis that is not parallel to the transmission axis of the first polarizing plate and is not orthogonal;
A second retardation plate disposed between the second substrate and the second polarizing plate and having a slow axis perpendicular to the slow axis of the first retardation plate;
A control structure that is disposed on the liquid crystal side of the first substrate and / or the second substrate and controls the direction in which the liquid crystal tilts when a voltage is applied to the liquid crystal layer;
A first region in which the liquid crystal tilts in one direction when a voltage is applied to the liquid crystal layer;
A second region in which the liquid crystal tilts in a direction that is approximately 180 ° different from the direction in which the liquid crystal in the first region tilts;
In a liquid crystal display device comprising:
The liquid crystal display device, wherein an angle formed between a direction in which the liquid crystal inclines in the first region and a horizontal direction of the screen of the liquid crystal display device is 25 ° to 39 ° or 51 ° to 65 °.   The liquid crystal display device according to claim 7, wherein an angle formed between a horizontal direction of the screen of the liquid crystal display device and a control structure extending direction of the control structure is 25 ° to 39 °.   The liquid crystal display device according to claim 7, wherein an angle formed between a horizontal direction of the screen of the liquid crystal display device and a control structure extending direction of the control structure is 51 ° to 65 °. A third region in which the liquid crystal is inclined in a direction different from the first region;
A fourth region in which the liquid crystal is inclined in a direction different by about 180 ° with respect to the direction in which the third region is inclined;
In a liquid crystal display device further comprising:
The direction in which the liquid crystal inclines in the third region and the screen of the liquid crystal display device when the angle formed between the direction in which the liquid crystal inclines in the first region and the horizontal direction of the screen of the liquid crystal display device are φ The angle formed with the left-right direction is 180-φ, and φ is 29 ° to 35 ° instead of 25 ° to 39 ° or 55 ° to 61 ° instead of 51 ° to 65 °. Item 8. A liquid crystal display device according to item 7.   When the angle formed between the horizontal direction of the screen of the liquid crystal display device and the control structure extending direction of the control structure in the first region is φ, the direction in which the liquid crystal in the third region is tilted and the liquid crystal 11. The liquid crystal display device according to claim 10, wherein an angle formed between the left and right direction of the screen of the display device is 180 ° −φ, and φ is 29 ° to 35 °.   When the angle formed between the horizontal direction of the screen of the liquid crystal display device and the control structure extending direction of the control structure in the first region is φ, the direction in which the liquid crystal in the third region is tilted and the liquid crystal 11. The liquid crystal display device according to claim 10, wherein an angle between the display device and the left-right direction of the screen is 180 ° −φ, and φ is 55 ° to 61 °.

Images