JP3773056B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that improves the viewing angle dependency of a display screen by combining an optical retardation plate with a liquid crystal display element.

  Conventionally, liquid crystal display devices using nematic liquid crystal display elements have been widely used in numerical segment type display devices such as watches and calculators. Recently, however, they have been used in word processors, notebook personal computers, in-vehicle liquid crystal televisions, and the like. It has come to be used.

  The liquid crystal display element generally has a light-transmitting substrate, and electrode lines and the like are formed on the substrate for turning on / off pixels. For example, in an active matrix liquid crystal display device, an active element such as a thin film transistor is formed on the substrate together with the electrode line as switching means for selectively driving a pixel electrode that applies a voltage to the liquid crystal. Further, in a liquid crystal display device that performs color display, color filter layers such as red, green, and blue are provided on a substrate.

  As a liquid crystal display method used for the liquid crystal display element as described above, a different method is appropriately selected according to the twist angle of the liquid crystal. For example, an active drive type twisted nematic liquid crystal display system (hereinafter referred to as TN system) and a multiplex drive type super twisted nematic liquid crystal display system (hereinafter referred to as STN system) are well known.

  In the TN system, nematic liquid crystal molecules are aligned in a 90 ° twisted state, and display is performed by guiding light along the twisted direction. The STN method utilizes the fact that the transmittance near the threshold value of the liquid crystal applied voltage changes sharply by expanding the twist angle of nematic liquid crystal molecules to 90 ° or more.

  Since the STN method uses the birefringence effect of liquid crystal, a specific color is added to the background of the display screen due to color interference. In order to eliminate such inconvenience and perform monochrome display by the STN method, it is considered effective to use an optical compensator. As a display method using an optical compensator, a double super twist nematic phase compensation method (hereinafter referred to as a DSTN method) and a film type phase compensation method (hereinafter referred to as a film addition type) in which a film having optical anisotropy is arranged. (Referred to as a method).

  The DSTN system uses a two-layer structure having a display liquid crystal cell and a liquid crystal cell that is twisted and aligned with a twist angle opposite to that of the display liquid crystal cell. The film addition type system uses a structure in which a film having optical anisotropy is arranged. From the viewpoints of light weight and low cost, the film addition type is considered to be promising. Since the monochrome display characteristics are improved by adopting such a phase compensation method, a color STN liquid crystal display device in which a color filter layer is provided in an STN display device to enable color display is realized.

  On the other hand, the TN system is roughly classified into a normally black system and a normally white system. In the normally black method, a pair of polarizing plates are arranged so that their polarization directions are parallel to each other, and black is displayed in a state where no on-voltage is applied to the liquid crystal layer (off state). In the normally white system, a pair of polarizing plates are arranged so that their polarization directions are orthogonal to each other, and white is displayed in an off state. From the viewpoint of display contrast, color reproducibility, display viewing angle dependency, and the like, the normally white method is effective.

  In the above TN liquid crystal display device, the liquid crystal molecules have a refractive index anisotropy Δn, and the liquid crystal molecules are inclined with respect to the upper and lower substrates. There is a problem in that the contrast of the display image changes depending on the viewing direction and angle of the viewer, and the viewing angle dependency increases.

  FIG. 11 schematically shows a cross-sectional structure of the TN liquid crystal display element 31. This state shows a case where a voltage for displaying an intermediate color tone (hereinafter referred to as an intermediate tone) is applied and the liquid crystal molecules 32 are slightly raised. In this TN liquid crystal display element 31, the linearly polarized light 35 that passes through the normal direction of the surfaces of the pair of substrates 33 and 34, and the linearly polarized light 36 and 37 that passes through the normal direction with an inclination are liquid crystal molecules 32. The angle at which they intersect is different. Since the liquid crystal molecules 32 have a refractive index anisotropy Δn, normal light and extraordinary light are generated when the linearly polarized light 35, 36, and 37 in each direction passes through the liquid crystal molecules 32. It is converted into elliptically polarized light, which becomes a source of viewing angle dependency.

  Further, inside the actual liquid crystal layer, the liquid crystal molecules 32 have different tilt angles between the vicinity of the intermediate portion between the substrate 33 and the substrate 34 and the vicinity of the substrate 33 or the substrate 34, and the liquid crystal molecules 32 have the normal direction as an axis. The molecule 32 is twisted by 90 °.

  As described above, the linearly polarized light 35, 36, and 37 passing through the liquid crystal layer is subjected to various birefringence effects depending on the direction and angle thereof, and exhibits complicated viewing angle dependency.

  As the above viewing angle dependency, specifically, when the viewing angle is tilted from the normal direction of the display screen to the normal viewing angle direction which is the downward direction of the display surface, the display image is colored at a certain angle or more (hereinafter referred to as the viewing angle dependency). A phenomenon called “coloring phenomenon” and a phenomenon in which black and white are reversed (hereinafter referred to as “inversion phenomenon”). Further, when the viewing angle is tilted in the anti-viewing angle direction, which is the upper direction of the display screen, the contrast rapidly decreases.

  In addition, the liquid crystal display device has a problem that the viewing angle becomes narrower as the display screen becomes larger. When a large liquid crystal display screen is viewed from the front direction at a short distance, the colors displayed on the upper and lower portions of the display screen may differ due to the effect of viewing angle dependency. This is because the prospective angle for viewing the entire display screen is large, which is the same as viewing the display screen from a more oblique direction.

  In order to improve such viewing angle dependency, it has been proposed to insert an optical retardation plate (retardation film) as an optical element having optical anisotropy between the liquid crystal display element and one polarizing plate. (See, for example, Japanese Patent Laid-Open Nos. 55-600 and 56-97318).

  This method is an optical retardation plate in which light that has been converted from linearly polarized light to elliptically polarized light because it has passed through liquid crystal molecules having refractive index anisotropy is interposed on one or both sides of a liquid crystal layer having refractive index anisotropy. By passing the light, the phase difference change between normal light and abnormal light generated at the viewing angle is compensated and re-converted into linearly polarized light, and the viewing angle dependency can be improved.

  As such an optical phase difference plate, one in which one main refractive index direction of the refractive index ellipsoid is parallel to the normal direction of the surface of the optical phase difference plate is described in, for example, JP-A-5-313159. ing. However, even if this optical retardation plate is used, there is a limit in improving the reversal phenomenon in the normal viewing angle direction.

  In order to eliminate the inversion phenomenon, for example, in Japanese Patent Application Laid-Open No. 57-186735, each display pattern (pixel) is divided into a plurality of parts so that each divided part has independent viewing angle characteristics. A so-called pixel division method for performing orientation control is disclosed. According to this method, since the liquid crystal molecules rise in different directions in each section, the viewing angle dependency can be eliminated. However, the problem that the contrast is lowered when the viewing angle is tilted in the vertical direction cannot be solved.

  Japanese Patent Application Laid-Open Nos. 6-118406 and 6-194645 disclose a technique for combining an optical phase difference plate with the above pixel division method.

  In the liquid crystal display device disclosed in Japanese Patent Laid-Open No. 6-118406, an optical anisotropic film (optical retardation plate) is inserted between the liquid crystal panel and the polarizing plate, thereby improving the contrast. It has been. The compensation plate (optical retardation plate) disclosed in JP-A-6-194645 has almost no in-plane refractive index in a direction parallel to the compensation plate surface, and a refractive index in a direction perpendicular to the compensation plate surface. Is set to be smaller than the in-plane refractive index, thereby having a negative refractive index. For this reason, when a voltage is applied, the positive refractive index generated in the liquid crystal display element can be compensated, and the viewing angle dependency can be reduced.

  However, even when this optical phase difference plate is used for the pixel division method, it is difficult to cause a coloring phenomenon in an oblique 45 ° direction when the viewing angle is tilted or to uniformly suppress a decrease in contrast in the vertical direction.

  Therefore, one main refractive index direction of the refractive index ellipsoid is generated depending on the viewing angle by using an optical phase difference plate in which the refractive index ellipsoid parallel to the normal direction of the phase difference plate surface is not inclined. There is a limit to improving contrast change, coloring phenomenon, and inversion phenomenon.

  Japanese Patent Laid-Open No. 6-75116 discloses a method using an optical phase difference plate in which the main refractive index direction of the refractive index ellipsoid is inclined with respect to the normal direction of the surface of the optical phase difference plate. Proposed. In this method, the following two types of optical retardation plates are used.

  One of the three main refractive indexes of the refractive index ellipsoid is that the direction of the minimum main refractive index is parallel to the surface, and one of the remaining two main refractive indexes is the optical retardation plate. It is inclined at an angle of θ with respect to the surface, and the other direction is similarly inclined at an angle of θ with respect to the normal direction of the surface of the optical phase difference plate. The value of θ is 20 ° ≦ θ ≦ 70 °. Is an optical retardation plate satisfying the above.

The other is that the three main refractive indexes n _a , n _b and n _c of the refractive index ellipsoid have a relationship of n _a = n _c > n _b , and the main refractive index n _a or n _{c in} the surface is as the axial direction, and a direction parallel principal refractive index n _b in the direction normal to the surface, the direction of the principal refractive index n _a or n _c in the surface is inclined clockwise or counterclockwise, It is an optical phase difference plate with an inclined refractive index ellipsoid.

As for the above-described two types of optical retardation plates, the former can be uniaxial and biaxial. Moreover, those latter to use not only only one optical phase difference plate, a combination of two sheets of light degree retardation plate, each of the inclination direction of the principal refractive index n _b is set at an angle of 90 ° to each other Can be used.

  In a liquid crystal display device configured by interposing at least one optical retardation plate between a liquid crystal display element and a polarizing plate, contrast change, coloring phenomenon, and inversion that occur depending on the viewing angle of a display image The phenomenon can be improved to some extent.

  However, under the circumstances where today's liquid crystal display device with a wider viewing angle and higher display quality is desired, further improvement in viewing angle dependency is demanded, and the optical position disclosed in the above-mentioned JP-A-6-75116 is required. The use of a phase difference plate is not always sufficient, and there is still room for improvement.

  The present invention has been made in view of the above-described problems, and an object thereof is to further improve the viewing angle dependency in addition to the compensation effect by the optical retardation plate, and particularly to effectively improve the coloring phenomenon. There is.

In order to achieve the object of the present invention, the liquid crystal display device according to the present invention is twisted and aligned by approximately 90 ° between a pair of translucent substrates each having a transparent electrode layer and an alignment film formed on opposite surfaces. A liquid crystal display element in which a liquid crystal layer is enclosed, a pair of polarizers disposed on both sides of the liquid crystal display element, and an optical retardation plate interposed between at least one liquid crystal display element and the polarizer a is, three principal refractive index n _a of the refractive index ellipsoid, n _b, has a n _c, the direction of the principal refractive index n _a or n _c in the surface as an axis, parallel to the direction normal to the surface the direction of a principal refractive index n _b, by the direction of the principal refractive index n _c or n _a in the surface is inclined clockwise or counterclockwise, the optical position of the refractive index ellipsoid is inclined retardation plate, or a three principal refractive index n _a of the refractive index ellipsoid, n _b, and n _c, the surface The direction of the principal refractive index n _a or n _c of the inner as an axis and a direction parallel principal refractive index n _b in the direction normal to the surface, the direction of the principal refractive index n _c or n _a watch in the surface around or by tilting counterclockwise, and the refractive index ellipsoid is inclined, the thickness of the optical retardation plate as d, a first retardation value (n _c -n _a) × d approximately 0nm And the second retardation value (n _c −n _b ) × d includes an optical phase difference plate set within a range of 80 nm to 250 nm, and is characterized by the following points.

In the first liquid crystal display device, the liquid crystal material in the liquid crystal layer has a refractive index anisotropy Δn _L (450) for light having a wavelength of 450 nm and a refractive index anisotropy Δn _L (550) for light having a wavelength of 550 nm. there _{Δn L (450) / Δn L} (550), the refractive index anisotropy [Delta] n _F (550 with respect to light having a wavelength of 450nm of the optical retardation plate anisotropy [Delta] n _F and (450) of wavelength 550nm to light ) Δn _F (450) / Δn _F (550)

It is set to satisfy the relationship.

In the second liquid crystal display device, the ratio of the refractive index anisotropy Δn _L (650) with respect to light having a wavelength of 650 nm and the refractive index anisotropy Δn _L (550) with respect to light having a wavelength of 550 nm of the liquid crystal material in the liquid crystal layer. there _{Δn L (650) / Δn L} (550), the refractive index anisotropy [Delta] n _F (550 with respect to light having a wavelength of 650nm of the optical retardation plate anisotropy [Delta] n _F and (650) of wavelength 550nm to light ) Δn _F (650) / Δn _F (550)

It is set to satisfy the relationship.

According to the above configuration, the three principal refractive index n _a of the refractive index ellipsoid, n _b, has a n _c, the direction of the principal refractive index n _a or n _c in the surfaces as the axis, the normal direction of the surface the direction of the principal refractive index n _b parallel to the direction of the principal refractive index n _c or n _a in surface by inclined clockwise or counterclockwise, the refractive index ellipsoid is inclined optical retardation plate, or three principal refractive index n _a of the refractive index ellipsoid, n _b, has a n _c, the direction of the principal refractive index n _a or n _c in the surface as an axis normal to the surface the direction of the principal refractive index n _b parallel to the direction, by which the direction of the principal refractive index n _c or n _a in the surface is inclined clockwise or counter-clockwise, and the refractive index ellipsoid is inclined cage, the thickness of the optical retardation plate as d, a first retardation value (n _c -n _a) a × d is approximately 0 nm, the second Rita Since Shon value (n _c -n _b) × d is an optical retardation plate is set within a range of 80nm~250nm is interposed between the polarizer and the liquid crystal layer, the linearly polarized light having birefringence When normal light and extraordinary light are generated through the liquid crystal layer and are converted into elliptically polarized light according to their phase difference, the phase difference change between normal light and extraordinary light that occurs according to the viewing angle is caused by this optical Compensated by the phase difference plate.

  However, even with such a compensation function, it cannot always be said that further improvement in viewing angle dependency is required. As a result of further research, the inventors of the present application have found that the liquid crystal material in the liquid crystal layer The degree of change between the change in refractive index anisotropy Δn with respect to the wavelength of light and the change in refractive index anisotropy Δn of the optical phase difference plate with respect to the wavelength of light affects the coloring of the liquid crystal screen depending on the viewing angle. As a result, the present invention has been completed.

  The change in the refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer with respect to the wavelength of the light is set in any of the ranges described in the first and second liquid crystal display devices, so that it is required in a normal liquid crystal display device. At a viewing angle of 50 °, although there is some coloration, it can be sufficiently used from any direction, and the coloration of the screen can be further prevented. In contrast, the contrast change and the reversal phenomenon can be improved as compared with the case of only the compensation function of the retardation plate.

  In a liquid crystal display device having a wider viewing angle such as a viewing angle of 70 °, the range of change of the refractive index anisotropy Δn of the liquid crystal material with respect to the wavelength of light is preferably set to the following range.

  That is,

Set to satisfy the relationship.

  Or

Set to satisfy the relationship.

  By setting to any one of these ranges, even when viewed from all directions at a viewing angle of 70 ° required for a liquid crystal display device with a wide viewing angle, there can be no coloring phenomenon at all.

  In each liquid crystal display device of the present invention described above, the refractive index anisotropy Δn (550) of the liquid crystal material in the liquid crystal layer with respect to light having a wavelength of 550 nm is set in a range larger than 0.060 and smaller than 0.120. It is preferable to do.

  This is because, when the refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm, which is the central region of the visible light region, is 0.060 or less or 0.120 or more, depending on the viewing angle direction, the inversion phenomenon or contrast ratio This is because it has been confirmed that a decrease in the occurrence of this occurs. Therefore, by setting the refractive index anisotropy Δn (550) for light having a wavelength of 550 nm of the liquid crystal material in a range larger than 0.060 and smaller than 0.120, a phase difference corresponding to a viewing angle generated in the liquid crystal display element is obtained. Since it can be eliminated, not only the coloring phenomenon that occurs depending on the viewing angle, but also the contrast change, the left-right reversal phenomenon, etc. can be further improved in the liquid crystal screen.

  In this case, the viewing angle generated in the liquid crystal display element is further set by setting the refractive index anisotropy Δn (550) of the liquid crystal material in the liquid crystal layer to light having a wavelength of 550 nm in the range of 0.070 to 0.095. Since the phase difference corresponding to the above can be more effectively eliminated, it is possible to surely improve the contrast change and the left-right reversal phenomenon in the liquid crystal display image.

  In each liquid crystal display device of the present invention described above, it is preferable that the inclination angle of the refractive index ellipsoid is set between 15 ° and 75 ° in all the optical retardation plates.

  Thus, in all the optical phase difference plates interposed in the liquid crystal display device, the inclination angle of the refractive index ellipsoid is set between 15 ° and 75 °, so that the optical phase difference provided by the present invention described above is provided. The compensation function of the phase difference by the plate can be obtained with certainty.

In order to achieve the object of the present invention, the liquid crystal display device according to the present invention is twisted and aligned by approximately 90 ° between a pair of translucent substrates each having a transparent electrode layer and an alignment film formed on opposite surfaces. A liquid crystal display element in which a liquid crystal layer is enclosed, a pair of polarizers disposed on both sides of the liquid crystal display element, and an optical retardation plate interposed between at least one liquid crystal display element and the polarizer a is, three principal refractive index n _a of the refractive index ellipsoid, n _b, has a n _c, the direction of the principal refractive index n _a or n _c in the surface as an axis, parallel to the direction normal to the surface the direction of a principal refractive index n _b, by the direction of the principal refractive index n _c or n _a in the surface is inclined clockwise or counterclockwise, the optical position of the refractive index ellipsoid is inclined retardation plate, or a three principal refractive index n _a of the refractive index ellipsoid, n _b, and n _c, the surface The direction of the principal refractive index n _a or n _c of the inner as an axis and a direction parallel principal refractive index n _b in the direction normal to the surface, the direction of the principal refractive index n _c or n _a watch in the surface around or by tilting counterclockwise, and the refractive index ellipsoid is inclined, the thickness of the optical retardation plate as d, a first retardation value (n _c -n _a) × d approximately 0nm And the second retardation value (n _c −n _b ) × d includes an optical phase difference plate set within a range of 80 nm to 250 nm, and is characterized by the following points.

In the first liquid crystal display device, the liquid crystal material in the liquid crystal layer has a refractive index anisotropy Δn _L (450) for light having a wavelength of 450 nm and a refractive index anisotropy Δn _L (550) for light having a wavelength of 550 nm. there _{Δn L (450) / Δn L} (550), the refractive index anisotropy [Delta] n _F (550 with respect to light having a wavelength of 450nm of the optical retardation plate anisotropy [Delta] n _F and (450) of wavelength 550nm to light ) Δn _F (450) / Δn _F (550)

It is set to satisfy the relationship.

In the second liquid crystal display device, the ratio of the refractive index anisotropy Δn _L (650) with respect to light having a wavelength of 650 nm and the refractive index anisotropy Δn _L (550) with respect to light having a wavelength of 550 nm of the liquid crystal material in the liquid crystal layer. there _{Δn L (650) / Δn L} (550), the refractive index anisotropy [Delta] n _F (550 with respect to light having a wavelength of 650nm of the optical retardation plate anisotropy [Delta] n _F and (650) of wavelength 550nm to light ) Δn _F (650) / Δn _F (550)

It is set to satisfy the relationship.

  As a result, in the first and second liquid crystal display devices according to the present invention, the change in the phase difference of the liquid crystal display element is further improved as compared with the case of only the compensation function by the phase difference plate, and the coloration of the liquid crystal screen particularly depending on the viewing angle. Since the phenomenon can be further prevented, a liquid crystal display device including such a retardation plate and a liquid crystal display element can prevent a reversal phenomenon, a decrease in contrast ratio in the counter viewing angle direction, and a coloring phenomenon.

  Therefore, the above configuration has an effect that the quality of the display image of the liquid crystal display device is remarkably improved because the contrast ratio in the monochrome display is not influenced by the viewing angle direction of the viewer.

  An embodiment of the present invention will be described below with reference to FIGS.

  First, before describing an embodiment of the present invention, a liquid crystal display device of a reference example will be described. As shown in FIG. 1, the liquid crystal display device includes a liquid crystal display element 1, a pair of optical retardation plates 2 and 3, and a pair of polarizing plates (polarizers) 4 and 5.

  The liquid crystal display element 1 has a structure in which a liquid crystal layer 8 is sandwiched between electrode substrates 6 and 7 arranged to face each other. In the electrode substrate 6, a transparent electrode 10 made of ITO (indium tin oxide) is formed on the surface of the glass substrate 9 (translucent substrate) 9 on the liquid crystal layer 8 side, and an alignment film 11 is formed thereon. ing. In the electrode substrate 7, a transparent electrode 13 made of ITO is formed on the surface of the glass substrate (translucent substrate) 12 serving as a base on the liquid crystal layer 8 side, and an alignment film 14 is formed thereon.

  For simplification, FIG. 1 shows a configuration for two pixels. In the entire liquid crystal display element 1, the strip-shaped transparent electrodes 10 and 13 having a predetermined width are spaced apart from each other by a predetermined interval on the glass substrates 9 and 12. The glass substrates 9 and 12 are formed so as to be orthogonal to each other when viewed from the direction perpendicular to the substrate surface. A portion where the transparent electrodes 10 and 13 intersect corresponds to a pixel for display, and these pixels are arranged in a matrix in the entire liquid crystal display device.

  The electrode substrates 6 and 7 are bonded together with a seal resin 15, and a liquid crystal layer 8 is sealed in a space formed by the electrode substrates 6 and 7 and the seal resin 15. A voltage based on display data is applied to the liquid crystal layer 8 from the drive circuit (voltage applying means) 17 through the transparent electrodes 10 and 13.

  Although the details will be described later, in the present liquid crystal display device, the pretilt angle of the liquid crystal layer 8 is set so as to achieve a combination having a phase difference compensation function by the optical phase difference plates 2 and 3 and the best characteristics. Has been.

  In the liquid crystal display device, the liquid crystal cell 16 is a unit in which the optical phase difference plates 2 and 3 and the polarizing plates 4 and 5 are formed on the liquid crystal display element 1.

  The alignment films 11 and 14 are preliminarily rubbed so that the intervening liquid crystal molecules are twisted by about 90 °. As shown in FIG. 2, the rubbing direction R1 of the alignment film 11 and the rubbing direction R2 of the alignment film 14 are set in directions orthogonal to each other.

  The optical phase difference plates 2 and 3 are respectively interposed between the liquid crystal display element 1 and polarizing plates 4 and 5 disposed on both sides thereof. The optical phase difference plates 2 and 3 are formed by tilting or hybridly aligning and crosslinking a discotic liquid crystal on a support made of a transparent organic polymer. Thereby, a later-described refractive index ellipsoid in the optical phase difference plates 2 and 3 is formed to be inclined with respect to the optical phase difference plates 2 and 3.

  As a support for the optical retardation plates 2 and 3, triacetyl cellulose (TAC), which is generally used for polarizing plates, is suitable because of its high reliability. Other than that, a colorless and transparent organic polymer film excellent in environmental resistance and chemical resistance such as polycarbonate (PC) and polyethylene terephthalate (PET) is suitable.

As shown in FIG. 3, the optical phase difference plates 2 and 3, has a main refractive index n _a · n _b · n _c of three different directions. Direction of the principal refractive index n _a is, y coordinate and direction of each coordinate axis in the orthogonal coordinates xyz is coincident with each other. Direction of the principal refractive index n _b is inclined θ in the direction of arrow A with respect to the vertical z axis on a surface corresponding to the screen in the optical phase difference plates 2 and 3 (direction normal to the surface).

The optical phase difference plates 2 and 3 satisfy the relationship that the main refractive indexes are n _a = n _c > n _b . Thereby, since there is only one optical axis, the optical phase difference plates 2 and 3 are uniaxial and the refractive index anisotropy is negative. The first retardation value (n _c −n _a ) × d of the optical phase difference plates 2 and 3 is approximately 0 nm because n _a = n _c . The second retardation value (n _c −n _b ) × d is set to an arbitrary value within the range of 80 nm to 250 nm. By setting the second retardation value (n _c −n _b ) × d within such a range, the phase difference compensation function by the optical phase difference plates 2 and 3 can be reliably obtained. The above n _c -n _a and n _c -n _b represents refractive index anisotropy [Delta] n, d represents the thickness of the optical phase difference plates 2, 3.

The angle theta of principal refractive index n _b of the optical phase difference plates 2 and 3 is inclined, i.e., the inclination angle theta of the refractive index ellipsoid, set to any value within the range of 15 ° ≦ θ ≦ 75 ° Is done. By setting the inclination angle θ within such a range, the compensation function of the phase difference by the optical phase difference plates 2 and 3 can be reliably obtained regardless of the direction of inclination of the refractive index ellipsoid in the counterclockwise direction. be able to.

  As for the arrangement of the optical retardation plates 2 and 3, even if only one of the optical retardation plates 2 and 3 is arranged on one side, the optical retardation plates 2 and 3 are stacked on one side. It can also be arranged. Further, three or more optical phase difference plates can be used.

As shown in FIG. 4, in the liquid crystal display device of the reference example, the polarizing plates 4 and 5 in the liquid crystal display element 1 have the absorption axes AX ₁ and AX ₂ of the alignment films 11 and 14 (see FIG. 1). ) In the rubbing directions R ₁ and R ₂ . In the present liquid crystal display device, since the rubbing directions R ₁ and R ₂ are orthogonal to each other, the absorption axes AX ₁ and AX ₂ are also orthogonal to each other.

Here, as shown in FIG. 3, a direction in which the direction of the principal refractive index n _b is projected on the surface of the optical phase difference plates 2 and 3 which is inclined in a direction to give anisotropy to the optical phase difference plates 2 and 3 Define D. As shown in FIG. 4, the optical phase difference plate 2 is arranged so that the direction D (direction D ₁ ) is parallel to the rubbing direction R _1, and the optical phase difference plate 3 has the direction D (direction D ₂ ) in the rubbing direction. Arranged so as to be parallel to R ₂ .

  With the arrangement of the optical retardation plates 2 and 3 and the polarizing plates 4 and 5 as described above, the present liquid crystal display device performs a so-called normally white display that transmits light and displays a white color when off.

Generally, in the optically anisotropic member such as a liquid crystal and an optical phase difference plate (phase difference film), the three-dimensional directions of the anisotropy of the principal refractive index n _a · n _c · n _b as described above with the refractive index ellipsoid expressed. The refractive index anisotropy Δn varies depending on the direction from which this refractive index ellipsoid is observed.

  Next, the setting of the pretilt angle in the liquid crystal layer 8 will be described in detail.

  As shown in FIG. 5, the pretilt angle is an angle ψ formed by the long axis of the liquid crystal molecules 20 and the alignment film 14 (11). The pretilt angle depends on the combination of the rubbing with respect to the alignment films 11 and 14 and the liquid crystal material. It is to be decided.

  As described above, in the liquid crystal display device of the reference example, the pretilt angle of the liquid crystal layer 8 is set so as to achieve a combination having a phase difference compensation function by the optical phase difference plates 2 and 3 and the best characteristics. More specifically, this pretilt angle is a halftone display state in which a voltage close to the threshold voltage of the liquid crystal is applied to the liquid crystal, here a normally white display, so in a halftone display state close to white, The range is set so that gradation inversion does not occur. Hereinafter, a halftone close to white is called a white gradation.

  On the other hand, it has been experimentally confirmed that as the pretilt angle increases, gradation inversion in the anti-viewing angle direction during white gradation does not occur, but on the other hand, if the pretilt angle is too large, It was also confirmed that there was a sharp drop in brightness at the time of white gradation. That is, for setting the pretilt angle, it is necessary to set the pretilt angle within a range in which a sharp luminance decrease in the normal viewing angle direction does not occur during white gradation.

  Specifically, as the alignment films 11 and 14 and the liquid crystal material, a combination of an alignment film and a liquid crystal material having a pretilt angle in the range of more than 2 ° and less than 12 ° is used. In this case, it is more preferable to use a combination of an alignment film and a liquid crystal material so that the pretilt angle is in the range of 4 ° to 10 °.

  In this way, by setting the pretilt angle within the range of more than 2 ° and less than 12 °, the anti-viewing angle direction at the time of white gradation which becomes a problem at a viewing angle of 50 ° required in a normal liquid crystal display device. Therefore, it can be used sufficiently from any direction without gradation inversion.

  In particular, by setting the pretilt angle within the range of 4 ° or more and 10 ° or less, there can be no gradation reversal in the counter-viewing angle direction during white gradation at a viewing angle of 70 °.

  Furthermore, in the liquid crystal display device of the reference example, the liquid crystal material in the liquid crystal layer 8 is designed such that the refractive index anisotropy Δn (550) for light with a wavelength of 550 nm is greater than 0.060 and less than 0.120. Is selected. In this case, it is more preferable to use a liquid crystal material designed so that Δn (550) is in a range of 0.070 to 0.095.

  As a result, in addition to the compensation function for the phase difference by the optical retardation plates 2 and 3 and the compensation function for setting the pretilt angle within the above range, the contrast ratio in the anti-viewing angle direction is reduced, and the inversion phenomenon in the left-right direction is reduced. Further improvement is possible.

As described above, in the liquid crystal display device of the reference example, the three main refractive indexes n _a , n _b , and n _c of the refractive index ellipsoid are n _a = n between the liquid crystal display element 1 and the polarizing plates 4 and 5. have the relationship of _c> n _b, a direction of the principal refractive index n _a or n _c in the surface as an axis, the direction of the principal refractive index n _b parallel to the direction normal to the surface, the main refractive index in the surface by the direction of n _c or n _a is inclined around clockwise or counterclockwise, in the liquid crystal display device configured to include an optical phase difference plates 2 and 3 in which the refractive index ellipsoid is inclined, the liquid crystal In this configuration, the pretilt angle in the layer 8 is set in a range in which gradation inversion in the counter viewing angle direction does not occur in a halftone display state in which a voltage close to the threshold voltage of the liquid crystal is applied to the liquid crystal.

  As a result, the compensation function by the optical retardation plates 2 and 3 for the phase difference corresponding to the viewing angle generated in the liquid crystal display element 1 and the compensation function by setting the pretilt angle in the above range can be used. It is possible to particularly effectively improve the reversal phenomenon that occurs during the white gradation in the viewing angle direction (because of normally white display), and at the same time, the contrast change is also improved and a high-quality image can be displayed. .

  Moreover, in this liquid crystal display device, the liquid crystal material in the liquid crystal layer 8 is designed so that the refractive index anisotropy Δn (550) with respect to light having a wavelength of 550 nm is larger than 0.060 and smaller than 0.120. Therefore, in addition to the compensation function for the phase difference by the optical retardation plates 2 and 3 and the compensation function for setting the pretilt angle in the above range, the contrast ratio in the anti-viewing angle direction is reduced, and the reversal phenomenon in the left-right direction is performed. Can be further improved.

  Here, the liquid crystal display device for normally white display has been described as an example. However, in the liquid crystal display device for normally black display, the pretilt angle is adjusted to the liquid crystal display according to the compensation effect by the optical phase difference plates 2 and 3. By setting a range in which gradation inversion in the anti-viewing angle direction does not occur in halftone display (black gradation) when a voltage close to the threshold voltage is applied to the liquid crystal, and obtaining a compensation effect by this, the same effect as described above can be obtained. Obtainable.

  Although a simple matrix liquid crystal display device has been described here, the present invention can also be applied to an active matrix liquid crystal display device using an active switching element such as a TFT.

  Next, a liquid crystal display device of another reference example will be described with reference to FIG. For convenience of explanation, members having the same functions as those shown in the liquid crystal display device of the reference example described above (hereinafter referred to as the first reference example) are denoted by the same reference numerals and description thereof is omitted. .

  The liquid crystal display device of the second reference example described here has substantially the same configuration as the liquid crystal display device of FIG. 1 which is the first reference example described above. The difference is that in the liquid crystal display device of the first reference example, the pretilt angle of the liquid crystal layer 8 is a liquid crystal so that the combination of the retardation compensation function by the optical retardation plates 2 and 3 and the best characteristic is obtained. In the halftone display state in which a voltage close to the threshold voltage of the liquid crystal is applied to the layer 8, the range is set in a range where gradation inversion in the anti-viewing angle direction does not occur, whereas in the liquid crystal display device of the second reference example, the optical Application for displaying a halftone obtained by applying a voltage close to the threshold voltage of the liquid crystal to the liquid crystal layer 8 so as to obtain a combination having a phase difference compensation function by the phase difference plates 2 and 3 and the best characteristics. The voltage value is set in a range in which gradation inversion in the counter-viewing angle direction does not occur in the halftone display state.

  Hereinafter, this point will be described in detail. Since the liquid crystal display device of the second reference example is normally white display, the halftone display state in which a voltage close to the threshold voltage of the liquid crystal is applied to the liquid crystal, that is, the applied voltage value for white gradation is It is set in a range where gradation inversion in the direction opposite to the viewing angle does not occur when the voltage is applied.

  On the other hand, it has been experimentally confirmed that as the transmittance at the white gradation is lowered, gradation inversion in the anti-viewing angle direction at the white gradation does not occur, but on the other hand, if the transmittance is set too low, Luminance decreases sharply in the normal viewing angle direction and the left-right direction. In other words, the liquid crystal application voltage that determines the transmissivity at the time of white gradation needs to be set within a range in which a sharp luminance decrease in the normal viewing angle direction and the horizontal direction does not occur at the time of white gradation.

  Specifically, the liquid crystal applied voltage at the time of white gradation is set so as to obtain a transmittance greater than 85% with respect to the transmittance of 100% in the off state where the liquid crystal applied voltage is zero. In this case, more preferably, the liquid crystal applied voltage at the time of white gradation is set so as to obtain a transmittance that falls within the range of 90% to 97% with respect to the transmittance of 100% in the off state.

  Thus, by setting the liquid crystal applied voltage at the time of white gradation so as to obtain a transmittance greater than 85% with respect to the transmittance of 100% in the off state, a viewing angle of 50 ° required for a normal liquid crystal display device is obtained. However, there is no gradation reversal in the anti-viewing angle direction at the time of white gradation, which can be a problem.

  In particular, by setting the voltage applied to the liquid crystal at the time of white gradation to a range of 90% to 97% with respect to the transmittance of 100% in the off state, at the viewing angle of 70 °, There can be no gradation inversion.

That is, in the liquid crystal display device of the second reference example, the three main refractive indexes n _a , n _b and n _c of the refractive index ellipsoid are n _a = n between the liquid crystal display element 1 and the polarizing plates 4 and 5. have the relationship of _c> n _b, a direction of the principal refractive index n _a or n _c in the surface as an axis, the direction of the principal refractive index n _b parallel to the direction normal to the surface, the main refractive index in the surface by the direction of n _c or n _a is inclined around clockwise or counterclockwise, in the liquid crystal display device configured to include an optical phase difference plates 2 and 3 in which the refractive index ellipsoid is inclined, the liquid crystal The applied voltage value for performing a halftone display state in which a voltage close to the threshold voltage is applied to the liquid crystal is set in a range in which gradation inversion in the counter-viewing angle direction does not occur in the state where the voltage is applied.

  Thus, the compensation function by setting the liquid crystal application voltage at the time of white gradation within the above range as well as the compensation function by the optical retardation plates 2 and 3 for the phase difference corresponding to the viewing angle generated in the liquid crystal display element 1. It is possible to particularly effectively improve the reversal phenomenon that occurs during white gradation in the anti-viewing angle direction depending on the viewing angle (because of normally white display), and at the same time, the contrast change is also improved and high Can display quality images.

  Further, the liquid crystal display device of the second reference example is also designed so that the refractive index anisotropy Δn (550) with respect to light having a wavelength of 550 nm is larger than 0.060 and smaller than 0.120 as the liquid crystal material in the liquid crystal layer 8. More preferably, by using a liquid crystal material designed so that Δn (550) is in a range of 0.070 or more and 0.095 or less, a retardation compensation function by the optical retardation plates 2 and 3 is used. In addition to the compensation function by setting the voltage applied to the liquid crystal at the time of white gradation within the above range, it is possible to further improve the reduction in contrast ratio in the anti-viewing angle direction and the inversion phenomenon in the left-right direction.

  Here, the liquid crystal display device for normally white display has been described as an example. However, in the liquid crystal display device for normally black display, the threshold voltage of the liquid crystal is adjusted in accordance with the compensation effect by the optical phase difference plates 2 and 3. The liquid crystal application voltage for displaying the halftone (black gradation) obtained by applying a voltage close to the liquid crystal to the liquid crystal is set in a range in which the gradation inversion in the anti-viewing angle direction does not occur in the halftone, and compensation is thereby performed. By obtaining the effect, the same effect as described above can be obtained.

  In addition to the liquid crystal display device of the first reference example, the present invention can be applied to an active matrix liquid crystal display device using active switching elements such as TFTs in addition to the simple matrix liquid crystal display device. .

  Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described. For convenience of explanation, members having the same functions as the members shown in the first and second reference examples described above are denoted by the same reference numerals and description thereof is omitted.

  The liquid crystal display device according to the present embodiment (hereinafter referred to as the present liquid crystal display device) has substantially the same configuration as the liquid crystal display device of the first reference example shown in FIG. The difference is that in the liquid crystal display device of the first reference example, the pretilt angle of the liquid crystal layer 8 is a liquid crystal so that the combination of the retardation compensation function by the optical retardation plates 2 and 3 and the best characteristic is obtained. In the halftone display state in which a voltage close to the threshold voltage of the liquid crystal is applied to the layer 8, the range is set so that gradation inversion in the anti-viewing angle direction does not occur. In the liquid crystal display device of the present embodiment, the optical position is The change of the refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer 8 with respect to the wavelength of the light in the liquid crystal layer 8 and the optical retardation plate of the optical retardation plate so as to obtain a combination having the best characteristic and the retardation compensation function by the retardation plates 2 and 3 This is that the degree of change of the refractive index anisotropy Δn with respect to the light wavelength is set in a range in which coloring of the liquid crystal screen depending on the viewing angle does not occur.

  Hereinafter, this point will be described in detail. The degree of change between the change in refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer 8 with respect to the wavelength of light and the change in the refractive index anisotropy Δn of the optical retardation plate with respect to the wavelength of light depends on the viewing angle. Specifically, the setting of the optical retardation films 2 and 3 and the liquid crystal material in such a combination that satisfies the conditions of at least one setting range of (i) and (b) below is set to a range where coloring of the screen does not occur. Use it.

(B) The ratio of refractive index anisotropy Δn _L (450) with respect to light having a wavelength of 450 nm and refractive index anisotropy Δn _L (550) with respect to light having a wavelength of 550 nm in the liquid crystal layer 8 is Δn _L (450) / Δn _L (550) is the ratio of refractive index anisotropy Δn _F (450) for light of wavelength 450 nm of the optical retardation plate 2, 3 and refractive index anisotropy Δn _F (550) for light of wavelength 550 nm. Δn _F (450) / Δn _F (550)

It may be set so as to satisfy the relationship. And more preferably,

More preferably,

It is set to satisfy the relationship.

B The ratio of refractive index anisotropy Δn _L (650) of the liquid crystal material in the liquid crystal layer 8 to light having a wavelength of 650 nm and refractive index anisotropy Δn _L (550) of light having a wavelength of 550 nm is Δn _L (650) / Δn _L (550) is the ratio of refractive index anisotropy Δn _F (650) for light of wavelength 650 nm of the optical phase difference plate 2, 3 and refractive index anisotropy Δn _F (550) for light of wavelength 550 nm. Δn _F (650) / Δn _F (550)

It may be set so as to satisfy the relationship. And more preferably,

More preferably,

It is set to satisfy the relationship.

  By using a liquid crystal material and an optical retardation plate designed to satisfy at least one of the above-mentioned conditions, the viewing angle of the display screen can be increased by the phase difference compensation function of the optical retardation plates 2 and 3. In addition to improving the contrast change, reversal phenomenon, and coloring phenomenon that occur depending on this, the coloring phenomenon of the display screen can be particularly effectively improved.

  More specifically, by satisfying at least one of the wide range of Lo and Lo, there is a slight coloration at a viewing angle of 50 ° required for a normal liquid crystal display device, but it can be used from any direction. Can withstand. Further, by satisfying at least one of the more preferable ranges in the above (ii), although there is a slight coloration at a viewing angle of 60 °, it can be sufficiently used from any direction. In particular, by satisfying at least one of the more preferable ranges in the above-mentioned (1) and (2), it is possible to achieve no coloring from any direction.

  Further, by satisfying at least one of (i) and (b), the contrast change and the inversion phenomenon can be improved as compared with the case of only the compensation function of the optical phase difference plates 2 and 3.

  FIG. 10 shows Δn for each wavelength (λ) in one combination of a liquid crystal material that can be used for the liquid crystal layer 8 in the present liquid crystal display device and an optical retardation plate that can be used for the optical retardation plates 2 and 3. (Λ) / Δn (550) is shown. A curve a indicated by a solid line is Δn (λ) / Δn (550) with respect to the wavelength (λ) of one liquid crystal material, and a curve b indicated by a one-dot chain line is Δn with respect to the wavelength (λ) of one optical retardation plate. (Λ) / Δn (550).

As described above, the liquid crystal display device of this embodiment, between the liquid crystal display element 1 and the polarizing plate 4 and 5, three principal refractive index n _a of the refractive index ellipsoid, n _b, n _c is n _a = N _c > n _b, the direction of the main refractive index n _b parallel to the normal direction of the surface with the direction of the main refractive index n _a or n _{c in} the surface as the axis, and the main in the surface by the direction of the refractive index n _c or n _a is inclined clockwise or counter-clockwise, the liquid crystal display device configured to include an optical phase difference plates 2 and 3 in which the refractive index ellipsoid is inclined The degree of change between the change of the refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer 8 with respect to the wavelength of light and the change of the refractive index anisotropy Δn of the optical retardation plate with respect to the wavelength of light depended on the viewing angle. In this configuration, the liquid crystal screen is set in a range where coloring does not occur.

  As a result, the phase difference corresponding to the viewing angle generated in the liquid crystal display element 1 is compensated by the optical phase difference plates 2 and 3, and the refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer 8 is changed with respect to the wavelength of light. The compensation function by setting the degree of change of the refractive index anisotropy Δn of the optical phase difference plate with respect to the wavelength of the light within the above range particularly effectively improves the coloring of the display screen depending on the viewing angle. At the same time, the contrast change and gradation inversion can be improved, and a high-quality image can be displayed.

  Further, in the liquid crystal display device of the present embodiment, the liquid crystal material in the liquid crystal layer 8 is designed such that the refractive index anisotropy Δn (550) for light having a wavelength of 550 nm is greater than 0.060 and less than 0.120. More preferably, by using a liquid crystal material designed so that Δn (550) is in a range of 0.070 or more and 0.095 or less, a retardation compensation function by the optical retardation plates 2 and 3; Further, in addition to the compensation function by setting the above degree of change in the above range, it is possible to further improve the reduction in contrast ratio in the counter viewing angle direction and the inversion phenomenon in the left-right direction.

  Here, the liquid crystal display device of normally white display has been described as an example, but the same effect as described above can be obtained also in the liquid crystal display device of normally black display.

  Further, similarly to the liquid crystal display device of Reference Example 1 described above, the present invention can be applied to an active matrix liquid crystal display device using active switching elements such as TFTs in addition to the simple matrix liquid crystal display device.

  Next, examples that support the effects of the liquid crystal display device according to the embodiment of the present invention will be described.

(Reference Example 1)
This reference example is for supporting the effects of the liquid crystal display devices according to the first reference example and the second reference example, and here, the alignment film 11 of the liquid crystal cell 16 in the liquid crystal display device of FIG. 14 is made of Nippon Synthetic Rubber's Optomer AL (trade name), and the pretilt angles are 2.0 °, 3.0 °, 4.0 °, 5.0 with respect to the alignment films 11 and 14. Five sample cells # 1 to # 7 were prepared using a liquid crystal material of °, 10.0 °, 11.0 °, 12.0 ° and a cell thickness (the thickness of the liquid crystal layer 8) of 5 μm.

  The pretilt angles of these sample cells # 1 to # 7 were measured by preparing homogeneous cells into which the materials of the sample cells # 1 to # 7 were injected and measuring with a pretilt angle measuring device NSMAP-3000LCD (manufactured by Sigma Koki Co., Ltd.). .

Further, as the optical phase difference plates 2 and 3 in the sample cells # 1 to # 7, a discotic liquid crystal is applied to a transparent support (for example, triacetyl cellulose (TAC)), and the discotic liquid crystal is tilted and aligned. made by forming crosslinked Te, a first retardation value of the above 0 nm, a second retardation value of the above 100 nm, the direction of the principal refractive index n _b is an arrow with respect to the z-axis direction in the xyz-axis coordinate Inclined so as to be approximately 20 ° in the direction indicated by A, and similarly, the direction of the main refractive index nc _forms an angle of approximately 20 ° in the direction indicated by arrow B with respect to the x axis (ie, A refractive index ellipsoid having an inclination angle θ = 20 ° was used.

  Tables 1 to 7 show the results of visual tests performed on white light with respect to these sample cells # 1 to # 7 with various applied voltages during white gradation.

  Table 1 shows 100% transmittance as the liquid crystal applied voltage for obtaining the white gradation, assuming that the transmittance in the normal direction of the surface of the liquid crystal cell 16 is 100% in the off state where the applied voltage to the liquid crystal is zero. The value obtained in the normal direction is set for each sample cell, and the display state at the time of white gradation is examined.

  From Table 1, when the transmittance is set to 100% and the voltage at the time of white gradation is set, the sample cells # 4 and # 5 having the pretilt angles of 5.0 ° and 10.0 ° have the viewing angle of 70 ° and the opposite angle. Even when viewed from the viewing angle direction, gradation inversion was not confirmed and the image quality was good.

  In addition, in sample cell # 2 with a pretilt angle of 3.0 ° and sample cell # 3 with a pretilt angle of 4.0 °, the gradation inversion is confirmed even when viewed from the opposite viewing angle direction up to a viewing angle of 60 °. However, if the viewing angle is 70 °, the sample cell # 2 confirms gradation inversion that can be used, and the sample cell # 3 has no gradation inversion, but the gradation is It was crushed. However, all of them were able to withstand use at a viewing angle of 70 °.

  In sample cell # 6 with a pretilt angle of 11.0 °, the image quality was good up to a viewing angle of 60 °, but the luminance was lowered to the extent that it could not be used when viewed from the normal viewing angle direction at a viewing angle of 70 °. Was confirmed.

  On the other hand, in sample cell # 1 with a pretilt angle of 2.0 °, gradation inversion is confirmed when viewed from the opposite viewing angle direction even at a viewing angle of 50 °, and the pretilt angle is 12.0 °. In sample cell # 7, it was confirmed that the luminance was lowered to such an extent that it could not be used when viewed from the normal viewing angle direction even at a viewing angle of 50 °.

  Table 2 shows the results obtained by checking the transmittance for the off-state transmittance at 97% and setting the voltage during white gradation for each sample cell.

  From Table 2, sample cells # 3, # 4, and # 5 with pretilt angles of 4.0 °, 5.0 °, and 10.0 ° when the white gradation voltage is set with a transmittance of 97% are shown. Then, even when viewed from the opposite viewing angle direction with a viewing angle of 70 °, tone inversion was not confirmed and the image quality was good.

  In sample cell # 2 with a pretilt angle of 3.0 °, tone inversion was not confirmed up to a viewing angle of 50 ° even when viewed from the counter-viewing angle direction, but the tone was lost at a viewing angle of 60 °. It was. However, since gradation inversion was not confirmed, it could withstand use even at a viewing angle of 60 °. In sample cell # 6 with a pretilt angle of 11.0 °, the image quality was good up to a viewing angle of 50 °, but when viewed from the normal viewing angle direction at a viewing angle of 60 °, the luminance was lowered to the extent that it could not be used. It was confirmed.

  On the other hand, in sample cell # 1 with a pretilt angle of 2.0 °, gradation inversion was confirmed when viewed from the opposite viewing angle direction even at a viewing angle of 50 °. Further, in sample cell # 7 in which the pretilt angle was 12.0 °, it was confirmed that the luminance was lowered enough to be unusable when viewed from the normal viewing angle direction even at a viewing angle of 50 °.

  Table 3 shows the results obtained by setting the transmissivity with respect to the off-state transmissivity to 95% and setting the voltage during white gradation for each sample cell. This was the same result as in Table 2 in which the voltage was set with a transmittance of 95%.

  Table 4 shows the results obtained by checking the transmittance for the off-state transmittance at 92% and setting the voltage during white gradation for each sample cell.

  From Table 4, sample cells # 3, # 4, and # 5 with pretilt angles of 4.0 °, 5.0 °, and 10.0 ° when the voltage at white gradation is set at a transmittance of 92%. Then, even when viewed from the opposite viewing angle direction with a viewing angle of 70 °, tone inversion was not confirmed and the image quality was good.

  In sample cell # 2 with a pretilt angle of 3.0 °, gradation inversion was not confirmed even when viewed from the opposite viewing angle direction up to a viewing angle of 60 °, but the gradation was reversed at a viewing angle of 70 °. did. However, it was enough to withstand use. In sample cell # 6 with a pretilt angle of 11.0 °, the image quality was good up to a viewing angle of 50 °, but the luminance was lowered to the extent that it could not be used when viewed from the normal viewing angle direction at a viewing angle of 60 °. Was confirmed. In sample cell # 1 with a pretilt angle of 2.0 °, the gradation was inverted at a viewing angle of 50 °, but it was of a level that could withstand use.

  On the other hand, in sample cell # 7 having a pretilt angle of 12.0 °, a luminance drop that could not be used when viewed from the normal viewing angle direction was confirmed even at a viewing angle of 50 °.

  Table 5 shows the results obtained by checking the transmittance for the off-state transmittance at 90% and setting the voltage during white gradation for each sample cell.

  From Table 5, when the white gradation voltage is set with a transmittance of 90%, sample cells # 3 and # 4 with pretilt angles of 4.0 ° and 5.0 ° are set to a viewing angle of 70 °. Even when viewed from the viewing angle direction, gradation inversion was not confirmed and the image quality was good.

  In sample cell # 5 with a pretilt angle of 10.0 °, the image quality was good up to a viewing angle of 50 °, but it was confirmed that the luminance decreased when viewed from the normal viewing angle direction at a viewing angle of 60 °. However, this decrease in luminance was enough to withstand use. In sample cell # 2 with a pretilt angle of 3.0 °, tone inversion was not confirmed even when viewed from the opposite viewing angle direction up to a viewing angle of 60 °, but the gradation was lost at a viewing angle of 70 °. It was. However, there was no gradation inversion, and it was enough to withstand use. In sample cell # 6 with a pretilt angle of 11.0 °, it was confirmed that the luminance decreased when viewed from the normal viewing angle direction at a viewing angle of 50 °. there were. In sample cell # 1 with a pretilt angle of 2.0 °, the gray level collapsed at a viewing angle of 50 ° and the gray level was inverted at a viewing angle of 60.

  On the other hand, in sample cell # 7 having a pretilt angle of 12.0 °, a luminance drop that could not be used when viewed from the normal viewing angle direction was confirmed even at a viewing angle of 50 °.

  Table 6 shows the results obtained by setting the white gradation voltage for each sample cell with the transmittance with respect to the transmittance in the off state being 87%.

  From Table 6, sample cells # 2, # 3, and # 4 with pretilt angles of 3.0 °, 4.0 °, and 5.0 ° when the transmissivity is 87% and the white gradation voltage is set. Thus, although the image quality was good up to a viewing angle of 50 °, it was confirmed that the luminance decreased when viewed from the normal viewing angle direction at a viewing angle of 60 °. However, this decrease in luminance was enough to withstand use. In addition, at a viewing angle of 70 °, it was confirmed that the luminance was lowered to an extent that could not be used when viewed from the normal viewing angle direction.

  In sample cell # 5 with a pretilt angle of 10.0 °, it was confirmed that the luminance decreased when viewed from the normal viewing angle direction at a viewing angle of 50 ° and a viewing angle of 60 °. there were. In addition, at a viewing angle of 70 °, it was confirmed that the luminance was lowered to an extent that could not be used when viewed from the normal viewing angle direction.

  In sample cells # 6 and # 7 with pretilt angles of 11.0 ° and 12.0 °, a luminance drop that could not be used when viewed from the normal viewing angle direction was confirmed even at a viewing angle of 50 °. .

  In sample cell # 1 with a pretilt angle of 2.0, tone reversal was not confirmed even when viewed from the opposite viewing angle direction until a viewing angle of 50 °, but the image quality was good, but when viewed from the normal viewing angle direction at a viewing angle of 60 °. In this case, a decrease in luminance was confirmed. However, it was enough to withstand use. In addition, at a viewing angle of 70 °, it was confirmed that the luminance was lowered to such an extent that it could not be used when viewed from the normal viewing angle direction.

  Table 7 shows the results obtained by setting the white gradation voltage for each sample cell with the transmittance with respect to the transmittance in the off state being 85%.

  From Table 7, when the transmittance is 85% and the white gradation voltage is set, the pretilt angles are 3.0 °, 4.0 °, 5.0 °, 10.0 °, 11.0 °, 12 The sample cells # 2, # 3, # 4, # 5, # 6, and # 7 set at .0 ° are not suitable for use when viewed from the normal viewing angle direction and the left-right direction even at a viewing angle of 50 °. A decrease in brightness was confirmed.

  On the other hand, in sample cell # 1 with a pretilt angle of 2.0, a decrease in luminance was confirmed when viewed from the normal viewing angle direction at a viewing angle of 50 °, but it could withstand use. In addition, at a viewing angle of 60 °, it was confirmed that the luminance was lowered to such an extent that it could not be used when viewed from the normal viewing angle direction.

  That is, from Tables 1 to 7, it can be said that the gradation inversion in the counter viewing angle direction can be improved by adjusting the pretilt angle or adjusting the transmittance at the time of white gradation. In that case, when the white gradation transmittance is normally set to about 95 to 97%, the pretilt angle is set in the range of more than 2 ° and less than 12 °, so that the gradation inversion in the counter viewing angle direction is performed at the viewing angle of 50 °. It can be said that the display can be improved with no improvement in luminance in the normal viewing angle direction. Further, by setting the range to 4 ° or more and 10 ° or less, the gray level inversion in the anti-viewing angle direction is improved even at a viewing angle of 70 ° with a wide viewing angle, and the luminance is not reduced in the normal viewing angle direction. It can be said that.

  In addition, at a pretilt angle of 2 ° to 10 ° that is normally set, a transmissivity greater than 85% is obtained as a transmissivity at the time of white gradation, so that gradation inversion in the counter viewing angle direction is achieved at a viewing angle of 50 °. It can be said that the display can be improved with no improvement in luminance in the normal viewing angle direction. Furthermore, by adjusting the pretilt angle by obtaining a transmittance that falls within the range of 90% or more and 97% or less, gradation inversion in the counter viewing angle direction is improved even at a viewing angle of 70 ° with a wide viewing angle. In addition, it can be said that the display can be performed satisfactorily without luminance reduction in the normal viewing angle direction.

  Further, it can be said that an improvement effect can be obtained by combining the adjustment of the pretilt angle and the adjustment of the transmittance at the time of white gradation.

  Next, with respect to the same sample cell # 1 and sample cell # 4 as described above, as shown in FIG. 6, the viewing angle of the liquid crystal display device is measured using a measurement system including a light receiving element 21, an amplifier 22 and a recording device 23. Dependency was examined.

  In this measurement system, the liquid crystal cell 16 of the liquid crystal display device is installed so that the surface 16a on the glass substrate 9 side is positioned on the reference plane XY of the orthogonal coordinates XYZ. The light receiving element 21 is an element that can receive light at a constant three-dimensional light receiving angle, and is disposed at a position that is a predetermined distance from the coordinate origin in a direction that forms an angle φ (viewing angle) with respect to the Z direction perpendicular to the surface 16a. ing.

  At the time of measurement, the liquid crystal cell 16 installed in the measurement system is irradiated with monochromatic light having a wavelength of 550 nm from the surface opposite to the surface 16a. Part of the monochromatic light transmitted through the liquid crystal cell 16 enters the light receiving element 21. The output of the light receiving element 21 is amplified to a predetermined level by the amplifier 22 and then recorded by a recording device 23 such as a waveform memory or a recorder.

  Here, the output level of the light receiving element 21 with respect to the voltage applied to the sample cells # 1 and # 4 when the light receiving element 21 is fixed at a constant angle φ was measured.

  In the measurement, the light receiving element 21 is arranged so as to have an angle φ of 50 °, and it is assumed that the Y direction is the left side of the screen and the X direction is the lower side (normal viewing angle direction) of the screen. This was performed by changing the arrangement position in the upward direction (anti-viewing angle direction), downward direction (normal viewing angle direction), and left-right direction.

  The result is shown to Fig.7 (a)-(c). FIGS. 7A to 7C show the light transmittance (transmission) with respect to the voltage applied to the sample cell # 4 having a pretilt angle of 5.0 ° and the sample cell # 1 having a pretilt angle of 2.0 °. It is a graph showing a ratio-liquid crystal applied voltage characteristic).

  FIG. 7A shows the result of measurement from the upper direction of FIG. 2, FIG. 7B shows the result of measurement from the lower direction of FIG. 2, and FIG. 7C shows the result of measurement from the left and right direction.

  In FIG. 7A, a curve L1 indicated by a one-dot chain line is a result measured from the front, that is, from the normal direction of the surface, and the sample cells # 1 and # 4 have the same transmittance-liquid crystal applied voltage characteristics.

  In FIGS. 7A to 7C, L2, L4, and L6 indicated by solid lines are for sample cell # 4, and curves L3, L5, and L7 indicated by broken lines are for sample cell # 1.

  When comparing the upward transmittance-liquid crystal applied voltage characteristics of sample cell # 4 and sample cell # 1, from FIG. 7A, the curve L3 of sample cell # 1 is missing from around 1V to around 2V. While the transmittance once increases and then decreases and has a hump, the curve L2 of the sample cell # 4 lacks near 1V to 2V, the transmittance is almost constant, the hump disappears, and the inversion phenomenon It was confirmed that there was no.

  7B and 7C, when the transmittance and the liquid crystal applied voltage characteristics in the downward direction and the horizontal direction are compared, the curves L4 and L6 of the sample cell # 4 are respectively the curves L5 and L7 of the sample cell # 1. However, the transmittance of the sample cell # 4 is about 2.5 V in FIG. 7B and about 3 V in FIG. It can be confirmed that there is no adverse effect caused by increasing the pretilt angle to 5.0 °.

  Further, as the optical retardation plates 2 and 3, the same sample cells as the above sample cells # 1 to # 7 except that the discotic liquid crystal is hybrid-aligned on a transparent support. Results were obtained.

Example 1
This example is for supporting the effects of the first and second reference examples and the liquid crystal display device according to the embodiment. Here, the liquid crystal cell 16 in the liquid crystal display device of FIG. Optomer AL (trade name) manufactured by Nippon Synthetic Rubber Co. is used for the alignment films 11 and 14, and the refractive index anisotropy Δn (550) at a wavelength of 550 nm with a pretilt angle of 3 ° with respect to the alignment films 11 and 14. ) Are used for the liquid crystal layer 8 with liquid crystal materials set to 0.070, 0.080, and 0.095, respectively, and the cell thickness (the thickness of the liquid crystal layer 8) is 5 μm. 18 were prepared.

  Here, the pretilt angle was measured with a pretilt angle measuring device NSMAP-3000 by preparing homogeneous cells into which the materials of sample cells # 16 to # 18 were injected.

  Further, as the optical phase difference plates 2 and 3 in these sample cells # 16 to # 18, the same optical phase difference plates 2 and 3 in the above-described Comparative Example 1 in which the discotic liquid crystal is tilted are used.

  Then, using the measurement system shown in FIG. 6 similar to that described in Reference Example 1, the voltage applied to the sample cells # 16 to # 18 when the light receiving element 21 is fixed at a constant angle φ is used. The output level of the light receiving element 21 was measured.

  In the measurement, as in Reference Example 1, the light receiving element 21 is arranged so as to have an angle φ of 50 °, the Y direction is the left side of the screen, and the X direction is the lower side of the screen (normal viewing angle direction). Assuming that the arrangement position of the light receiving element 21 is changed in the upward direction (counter viewing angle direction), the downward direction (normal viewing angle direction), and the left and right direction, respectively.

  The result is shown to Fig.8 (a)-(c). 8A to 8C are graphs showing the light transmittance (transmittance-liquid crystal applied voltage characteristics) with respect to the voltage applied to the sample cells # 16 to # 18.

  FIG. 8A shows the result of measurement from the upper direction of FIG. 2, FIG. 8B shows the result of measurement from the right direction of FIG. 2, and FIG. 8C shows the result of measurement from the left direction.

  8A to 8C, curves L8, L11, and L4 indicated by alternate long and short dash lines are for the sample cell # 16 using a liquid crystal material of Δn (550) = 0.070 for the liquid crystal layer 8, Curves L9, L12, and L15 indicated by solid lines are for sample cell # 17 using the liquid crystal material of Δn (550) = 0.080 for the liquid crystal layer 8, and curves L10, L13, and L16 indicated by broken lines are the liquid crystal layers. 8 is a sample cell # 18 using a liquid crystal material of Δn (550) = 0.095.

  As a comparative example for the present embodiment, a liquid crystal material in which the refractive index anisotropy Δn (550) at a wavelength of 550 nm is set to 0.060 and 0.120, respectively, in the liquid crystal layer 8 in the liquid crystal cell 16 of FIG. Two sample cells for comparison # 103 and # 104 are prepared in the same manner as in this embodiment except that they are used, and they are installed in the measurement system shown in FIG. 6, and the light receiving element 21 is fixed in the same manner as in this embodiment. The output level of the light receiving element 21 with respect to the voltage applied to the comparative sample cells # 103 and # 104 when fixed at the angle φ was also measured.

  In the measurement, the light receiving element 21 is arranged so as to have an angle φ of 50 ° as in the present embodiment, the Y direction is the left side of the screen, and the X direction is the lower side of the screen (normal viewing angle direction). Assuming that the arrangement position of the light receiving element 21 is changed in the upward direction (counterview angle direction), the right direction, and the left direction, respectively.

  The results are shown in FIGS. 9 (a) to (c). FIGS. 9A to 9C are graphs showing the light transmittance (transmittance-liquid crystal applied voltage characteristics) with respect to the voltage applied to the comparative example samples # 103 and # 104.

  FIG. 9A shows the result of measurement from the upper direction of FIG. 2, FIG. 9B shows the result of measurement from the right direction of FIG. 2, and FIG. 9C shows the result of measurement from the left direction. .

  9A to 9C, curves L17, L19, and L21 indicated by solid lines are for the comparative sample cell # 103 using the liquid crystal material of Δn (550) = 0.060 for the liquid crystal layer 8, Curves L18, L20, and L22 indicated by broken lines are for the comparative sample cell # 104 in which the liquid crystal layer 8 is made of a liquid crystal material having Δn (550) of 0.120.

  When comparing the upward transmittance-liquid crystal applied voltage characteristics of the sample cells # 16 to # 18 and the comparative sample cells # 103 and # 104, in FIG. 8A, curves L9, L8, and L10 are shown. It was confirmed that the transmittance was sufficiently lowered as the voltage was increased. On the other hand, in FIG. 9A, the curve L18 does not sufficiently reduce the transmittance even when the voltage is increased as compared with the curves L8, L9, and L10 in FIG. Further, it was confirmed that the curve L17 has an inversion phenomenon in which the transmittance decreases once and then increases again as the voltage is increased.

  Similarly, when the right-direction transmittance-liquid crystal applied voltage characteristics of the sample cells # 16 to # 18 and the comparative sample cells # 103 and # 104 are compared, the curves L11, L12,. It was confirmed that the transmittance decreased to almost zero when the voltage was increased for both L13. Also in FIG. 9B, when the voltage of the curve L19 is increased, the transmittance decreases until the transmittance becomes almost zero as in FIG. 8B, but the above inversion phenomenon is observed for the curve L20. confirmed.

  Similarly, it was confirmed that the sample cells # 16 to # 18 and the comparative sample cells # 103 and # 104 are similar to the right direction even in the left direction.

  Further, the sample cells # 16 to # 18 and the comparative sample cells # 103 and # 104 were visually confirmed under white light.

  The sample cells # 16 to # 18 and the comparative sample cell # 103 had good image quality with no coloration seen from any direction with a viewing angle of 50 °. On the other hand, it was confirmed that the sample cell for comparison # 104 was colored from yellow to orange when viewed from the left and right directions with a viewing angle of 50 °.

  From the above results, as shown in FIGS. 8A to 8C, the liquid crystal layer 8 has refractive index anisotropy Δn (550) at a wavelength of 550 nm of 0.070, 0.080, 0.095, respectively. When using a liquid crystal material set to, the transmittance decreases sufficiently when a voltage is applied, and the inversion phenomenon is not observed, so the viewing angle is expanded, and there is no coloring phenomenon. It can be seen that the display quality of the apparatus has been greatly improved.

  On the other hand, as shown in FIGS. 9A to 9C, the liquid crystal layer 8 has a refractive index anisotropy Δn (550) at a wavelength of 550 nm set to 0.060 and 0.120, respectively. It can be seen that the viewing angle dependency is not sufficiently improved when the material is used.

  Further, as the optical retardation plates 2 and 3, the same as the sample cells # 16 to # 18 and the comparative sample cells # 103 and # 104 except that the discotic liquid crystal is hybrid-aligned on a transparent support. Similar results were obtained for the sample cell and the comparative sample cell.

  Further, the inclination angle θ of the refractive index ellipsoid of the optical phase difference plates 2 and 3 was changed, and the dependence of the transmittance-liquid crystal applied voltage characteristics on the inclination angle θ was examined. As a result, 15 ° ≦ θ ≦ 75 ° As long as it is within the range, basically no change was made regardless of the orientation state of the discotic liquid crystal in the optical phase difference plates 2 and 3. It was confirmed that the viewing angle in the opposite viewing angle direction did not widen when the above range was exceeded.

  Furthermore, as a result of changing the second retardation value of the optical retardation plates 2 and 3 and investigating the dependency of the transmittance-liquid crystal applied voltage characteristics on the second retardation value, the second retardation value was 80 nm to If it was in the range of 250 nm, it did not change fundamentally irrespective of the orientation state of the discotic liquid crystal in the phase difference plates 2 and 3. It was confirmed that the viewing angle in the left-right direction did not widen when the above range was exceeded.

  Further, based on the result of the visual test of the comparative sample cells # 103 and # 104, the refractive index anisotropy Δn (550) at the wavelength of 550 nm of the liquid crystal layer 8 in the liquid crystal cell 16 of FIG. , 0.100, and 0.115 except that liquid crystal materials are used, three sample cells # 19 to # 21 are prepared in the same manner as in this example, and the measurement system shown in FIG. In the same manner, the output level of the light receiving element 21 with respect to the voltage applied to the sample cells # 19 to # 21 when the light receiving element 21 is fixed at a constant angle φ was measured. Further, visual confirmation was performed under white light.

  As a result, in sample cell # 20 in which the refractive index anisotropy Δn (550) is 0.100 and in sample cell # 21 in which the refractive index anisotropy Δn (550) is 0.115, the angle φ50 °. In this case, a slight increase in transmittance was confirmed when the voltage was increased in the left-right direction. However, the reversal phenomenon did not occur visually, and such an increase in transmittance could withstand use. There was no problem in the upward results. On the other hand, in the sample cell # 19 in which the refractive index anisotropy Δn (550) is 0.065, like the above-described comparative sample cell # 103, when the voltage is increased in the upward direction, the transmittance once sinks and floats. However, the degree of increase in transmittance was smaller than that of the comparative sample cell # 103 shown in FIG. 9A, and it was able to withstand use. There was no problem in the horizontal results.

  Further, in the visual inspection, in the sample cells # 20 and # 21, a slight coloration from yellow to orange was confirmed, but this was not a problem. It was confirmed that sample cell # 19 was slightly bluish. However, this level of bluish color was not a problem.

  As a supplement, a voltage of about 1 V was applied to the sample cell # 19 and the comparative sample cell # 103, and the transmittance during white display in the normal direction of the surface of the liquid crystal cell 16 was measured. As a result, in the comparative sample cell # 103, a decrease in transmittance was observed to such an extent that it could not be used. On the other hand, in sample cell # 19, although a slight decrease in transmittance was confirmed, it was of a level that could withstand use.

  Further, an optomer AL (trade name) manufactured by Nippon Synthetic Rubber Co., Ltd. is used for the alignment films 11 and 14 of the liquid crystal cell 16 in the liquid crystal display device of FIG. 1, and the pretilt angle is 4 °, 5 with respect to the alignment films 11 and 14. Similar results were obtained when the liquid crystal materials having the angles of °, 10 °, and 11 ° were used for the liquid crystal layer 8, respectively.

(Example 2)
This example is intended to support the effect of the liquid crystal display device according to the above-described embodiment. Here, the liquid crystal layer 8 of the liquid crystal cell 16 in the liquid crystal display device of FIG. Isotropic Δn _L (450), refractive index anisotropy Δn _L (550) at a wavelength of 550 nm, refractive index anisotropy Δn _F (450) at a wavelength of 450 nm, and refractive index at a wavelength of 550 nm. The liquid crystal material and the optical position in which the relationship represented by the expression (1) with the anisotropy Δn _F (550) is set to 0, 0.15, 0.25, 0.30, and 0.33, respectively. Five sample cells # 31 to # 35 were prepared using a phase difference plate and having a cell thickness (the thickness of the liquid crystal layer 8) of 5 μm.

As the optical phase difference plates 2 and 3 in the sample cells # 31 to # 35, a discotic liquid crystal is applied to a transparent support (for example, triacetyl cellulose (TAC)), and the discotic liquid crystal is inclined and cross-linked. in and formed by forming a first retardation value of the above 0 nm, a second retardation value of the above 100 nm, the arrow a direction of the principal refractive index n _b is the z-axis direction in the xyz-axis coordinate are inclined to be about 20 ° in the direction shown, likewise what direction of the principal refractive index n _c is at an angle of approximately 20 ° in the direction indicated by the arrow B with respect to the x-axis (i.e., the refractive index An ellipsoid having an inclination angle θ = 20 ° was used.

  As a comparative example for this embodiment, the relationship represented by the above formula (1) is 0.35, 1.0, 1.... In the liquid crystal layer 8 of the liquid crystal cell 16 in the liquid crystal display device of FIG. Comparative sample cells # 301 to # 303 were prepared in the same manner as in this example except that one liquid crystal material and an optical phase difference plate were used.

  Table 8 shows the results of a visual test under white light on the sample cells # 31 to # 35 and the comparative sample cells # 301 to # 303.

  Sample cells # 31 to # 33 had good image quality with no coloration seen from any direction with a viewing angle of 70 °. In sample cell # 24, coloring was not confirmed from any direction up to a viewing angle of 50 °, and the image quality was good. However, at viewing angle 60 °, slight coloring was confirmed when viewed from the left and right directions. The coloration was such that it could be used. In the sample cell # 25, coloring was not observed from any direction up to a viewing angle of 50 °, and the image quality was good. However, at a viewing angle of 60 °, coloring was unusable when viewed from the left-right direction. confirmed.

  On the other hand, in the comparative sample cells # 301 to # 303, even when viewed from the left and right directions even at a viewing angle of 50 °, coloring from yellow to orange that could not be used was confirmed.

  Further, as the optical phase difference plates 2 and 3, the same as the sample cells # 31 to # 35 and the comparative sample cells # 301 to # 303 of this embodiment, except that a discotic liquid crystal is hybrid-aligned on a transparent support. The same results as above were obtained for the sample cell and comparative sample cell.

(Example 3)
This example is for supporting the effect of the liquid crystal display device according to the third embodiment, and here, the refractive index at a wavelength of 550 nm is provided on the liquid crystal layer 8 of the liquid crystal cell 16 in the liquid crystal display device of FIG. Anisotropy Δn _L (550), refractive index anisotropy Δn _L (650) at a wavelength of 650 nm, refractive index anisotropy Δn _F (550) at a wavelength of 550 nm and refraction at a wavelength of 650 nm. Liquid crystal materials and optical systems in which the relationship represented by the equation (2) with the rate anisotropy Δn _F (650) is set to 0, 0.10, 0.20, 0.23, 0.25, respectively. Five sample cells # 41 to # 45 with a retardation plate and a cell thickness (thickness of the liquid crystal layer 8) of 5 μm were prepared.

As the optical phase difference plates 2 and 3 in the sample cells # 41 to # 45, a discotic liquid crystal is coated on a transparent support (for example, triacetyl cellulose (TAC)), and the discotic liquid crystal is tilted and crosslinked. in and formed by forming a first retardation value of the above 0 nm, a second retardation value of the above 100 nm, the arrow a direction of the principal refractive index n _b is the z-axis direction in the xyz-axis coordinate are inclined to be about 20 ° in the direction shown, likewise what direction of the principal refractive index n _c is at an angle of approximately 20 ° in the direction indicated by the arrow B with respect to the x-axis (i.e., the refractive index An ellipsoid having an inclination angle θ = 20 ° was used.

  In addition, as a comparative example with respect to the present embodiment, the relationship expressed by the above formula (2) is 0.27, 1.0, 1.V in the liquid crystal layer 8 of the liquid crystal cell 16 in the liquid crystal display device of FIG. Comparative sample cells # 401 to # 403 were prepared in the same manner as in this example except that one liquid crystal material and an optical retardation plate were used.

  Table 9 shows the results of a visual test under white light on the sample cells # 41 to # 45 and the comparative sample cells # 401 to # 403.

  Sample cells # 41 to # 43 had good image quality with no coloration seen from any direction with a viewing angle of 70 °. In sample cell # 44, coloring was not observed from any direction up to a viewing angle of 50 °, and the image quality was good. However, at viewing angle 60 °, slight coloring was observed when viewed from the left-right direction. The coloration was such that it could be used. In sample cell # 45, a slight coloration was observed when viewed from the left-right direction at a viewing angle of 50 °, but the color was enough to withstand use.

  On the other hand, in the comparative sample cells # 401 to # 403, yellow to orange coloring that could not be used was confirmed even when viewed from the left-right direction even at a viewing angle of 50 °.

  Further, as the optical phase difference plates 2 and 3, the same as the sample cells # 41 to # 45 and the comparative sample cells # 401 to # 403 of the present embodiment, except that a discotic liquid crystal is hybrid-aligned on a transparent support. The same results as above were obtained for the sample cell and the comparative sample cell.

It is sectional drawing which decomposes | disassembles and shows the structure of the liquid crystal display device which concerns on one Embodiment of this invention. It is explanatory drawing which shows the relationship between the rubbing direction and normal viewing angle direction of the alignment film in the said liquid crystal display device. It is a perspective view which shows the main refractive index in the optical phase difference plate of the said liquid crystal display device. It is a perspective view which decomposes | disassembles each part of a liquid crystal display device, and shows optical arrangement | positioning of the polarizing plate and optical phase difference plate in the said liquid crystal display device. It is explanatory drawing which shows the pretilt angle which is an angle | corner which the long axis of a liquid crystal molecule and alignment film make. It is a perspective view which shows the measuring system which measures the viewing angle dependence of the said liquid crystal display device. 6 is a graph showing transmittance-liquid crystal applied voltage characteristics of a liquid crystal display device of Comparative Example 1 and Comparative Example of Comparative Example 1; 6 is a graph showing transmittance-liquid crystal applied voltage characteristics of the liquid crystal display device in Example 1. 6 is a graph showing transmittance-liquid crystal applied voltage characteristics of a liquid crystal display device of a comparative example with respect to Example 1. FIG. It is a graph which shows (DELTA) n ((lambda)) / (DELTA) n (550) with respect to the wavelength of one liquid crystal material used for the liquid crystal layer of the said liquid crystal display device, and one optical phase difference plate. It is a schematic diagram which shows the twist orientation of the liquid crystal molecule in a TN liquid crystal display element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2.3 Optical phase difference plate 4.5 Polarizer (polarizer)
8 Liquid crystal layer 9/12 Glass substrate (Translucent substrate)
10.13 Transparent electrode (transparent electrode layer)
11.14 Alignment film

Claims (7)

A liquid crystal display element in which a liquid crystal layer twisted and aligned by approximately 90 ° is sealed between a pair of translucent substrates each having a transparent electrode layer and an alignment film formed on opposite surfaces;
A pair of polarizers disposed on both sides of the liquid crystal display element;
An optical retardation plate interposed at least one between the liquid crystal display element and the polarizer has three principal refractive index n _a of the refractive index ellipsoid, n _b, and n _c, the surface as the axial direction of the principal refractive index n _a or n _c, the direction of the principal refractive index n _b parallel to the direction normal to the surface, the main refractive index n _c or n _a direction and is clockwise in the surface, or by tilting counterclockwise, and the refractive index ellipsoid is inclined, the thickness of the optical retardation plate as d, a first retardation value (n _c -n _a) × d approximately 0nm And the second retardation value (n _c −n _b ) × d is set within the range of 80 nm to 250 nm, and an optical retardation plate,
In addition, the liquid crystal material in the liquid crystal layer has a refractive index anisotropy Δn _L (450) with respect to light having a wavelength of 450 nm and a refractive index anisotropy Δn _L (550) with respect to light having a wavelength of 550 nm, Δn _L (450). / Δn _L (550) and the ratio of refractive index anisotropy Δn _F (450) for light with a wavelength of 450 nm and refractive index anisotropy Δn _F (550) for light with a wavelength of 550 nm of the optical retardation plate _F (450) / Δn _F (550) is

A liquid crystal display device set to satisfy the above relationship. Δn _L (450) / Δn which is the ratio of the refractive index anisotropy Δn _L (450) for light with a wavelength of 450 nm and the refractive index anisotropy Δn _L (550) for light with a wavelength of 550 nm of the liquid crystal material in the liquid crystal layer. _L (550) and the ratio of refractive index anisotropy Δn _F (450) for light with a wavelength of 450 nm and refractive index anisotropy Δn _F (550) for light with a wavelength of 550 nm of the optical retardation plate Δn _F ( 450) / Δn _F (550)

The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set so as to satisfy the relationship. A liquid crystal display element in which a liquid crystal layer twisted and aligned by approximately 90 ° is sealed between a pair of translucent substrates each having a transparent electrode layer and an alignment film formed on opposite surfaces;
A pair of polarizers disposed on both sides of the liquid crystal display element;
An optical retardation plate interposed at least one between the liquid crystal display element and the polarizer has three principal refractive index n _a of the refractive index ellipsoid, n _b, and n _c, the surface as the axial direction of the principal refractive index n _a or n _c, the direction of the principal refractive index n _b parallel to the direction normal to the surface, the main refractive index n _c or n _a direction and is clockwise in the surface, or by tilting counterclockwise, and the refractive index ellipsoid is inclined, the thickness of the optical retardation plate as d, a first retardation value (n _c -n _a) × d approximately 0nm And the second retardation value (n _c −n _b ) × d is set within the range of 80 nm to 250 nm, and an optical retardation plate,
In addition, the liquid crystal material in the liquid crystal layer has a ratio of refractive index anisotropy Δn _L (650) for light having a wavelength of 650 nm and refractive index anisotropy Δn _L (550) for light having a wavelength of 550 nm, Δn _L (650). / Δn _L (550) and the ratio of refractive index anisotropy Δn _F (650) for light of wavelength 650 nm and refractive index anisotropy Δn _F (550) for light of wavelength 550 nm of the optical retardation plate _F (650) / Δn _F (550) is

A liquid crystal display device set to satisfy the above relationship. In the liquid crystal layer, Δn _L (650) / Δn _L, which is a ratio of refractive index anisotropy Δn _L (650) with respect to light having a wavelength of 650 nm and refractive index anisotropy Δn _L (550) with respect to light having a wavelength of 550 nm. and (550), Δn _F (650 is the ratio of the refractive index anisotropy [Delta] n _F (550) to the refractive index anisotropy [Delta] n _F (650) and a wavelength of 550nm light with respect to light having a wavelength of 650nm of the optical retardation plate ) / Δn _F (550)

The liquid crystal display device according to claim 3, wherein the liquid crystal display device is set so as to satisfy the relationship. Of the liquid crystal material in the liquid crystal layer, according to claim 1 to 4, the refractive index anisotropy Δn for light having a wavelength of 550 nm (550), characterized in that it is set to 0.120 smaller ranges greater than 0.060 A liquid crystal display device according to any one of the above . Of the liquid crystal material in the liquid crystal layer, the wavelength of 550nm refractive index anisotropy Δn for light (550), according to claim 5, characterized in that it is set to a range of 0.070 or more 0.095 or less Liquid crystal display device. The liquid crystal display device according to claim 1, wherein an inclination angle of the refractive index ellipsoid is set between 15 ° and 75 ° in all of the optical retardation plates.

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