JP2003202572A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of effectively improving a coloring phenomenon depending on a visual angle and displaying image of high quality. <P>SOLUTION: At least one of phase difference plates 2, 3 having negative refractive index anisotropy (n<SB>a</SB>=n<SB>c</SB>>n<SB>b</SB>) and inclining a main refractive index n<SB>b</SB>direction parallel to the normal direction of a surface and the direction of the main refractive index n<SB>c</SB>or n<SB>a</SB>in the surface around the direction of the main refractive index n<SB>a</SB>or n<SB>c</SB>in the surface in the clockwise direction or the counterclockwise direction is arranged between a liquid crystal display element 1 constituted by sealing a liquid crystal layer 8 between a pair of electrode substrates 6, 7 and each of a pair of polarizers 4, 5 arranged on both the sides of the element 1, and the degree of change in the refractive index anisotropy Δn of a liquid crystal material of the layer 8 and the degree of change in the refractive index anisotropy Δn of the plates 6, 7 are set in such a range that coloring depending on the visual angle is not caused on a liquid crystal screen or in such a range that coloring is caused to an available extent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device which improves the viewing angle dependence of a display screen by combining a liquid crystal display element with an optical retardation plate.

[0002]

2. Description of the Related Art Conventionally, liquid crystal display devices using nematic liquid crystal display elements have been widely used for numerical segment type display devices such as watches and calculators. It is also used in LCD TVs.

A liquid crystal display element generally has a translucent substrate on which electrode lines and the like for turning on and off pixels are formed. For example, in an active matrix type liquid crystal display device, active elements such as thin film transistors are formed on the above substrate together with the above electrode lines as switching means for selectively driving a pixel electrode for applying a voltage to liquid crystal. Furthermore, in a liquid crystal display device that performs color display, color filter layers of red, green, blue, etc. are provided on a substrate.

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

The TN system uses 90 nematic liquid crystal molecules.
Display is performed by orienting in a twisted state and guiding light along the twisting direction. The STN method utilizes the fact that the transmittance near the threshold of the liquid crystal applied voltage changes sharply by enlarging the twist angle of the nematic liquid crystal molecules to 90 ° or more.

Since the STN method utilizes the birefringence effect of liquid crystal, a background color of the display screen is given a color due to color interference. It is considered effective to use an optical compensator in order to eliminate such inconvenience and perform black and white display by the STN method. Display methods using an optical compensator include a double super twisted nematic phase compensation method (hereinafter referred to as DSTN method) and a film type phase compensation method in which a film having optical anisotropy is arranged (hereinafter referred to as film addition type). The method is called).

The DSTN method uses a two-layer structure having a display liquid crystal cell and a liquid crystal cell which is twisted and oriented at 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 viewpoint of light weight and low cost,
The film addition type method is considered to be effective. Since the black-and-white display characteristic is improved by adopting such a phase compensation method, a color STN liquid crystal display device is realized in which a color filter layer is provided in an STN display device to enable color display.

On the other hand, the TN method is roughly classified into a normally black method and a normally white method. In the normally black method, a pair of polarizing plates are arranged such that their polarization directions are parallel to each other, and black is displayed in a state where an on-voltage is not applied to the liquid crystal layer (off state). In the normally white method, a pair of polarizing plates are arranged so that their polarization directions are orthogonal to each other, and white is displayed in the off state. The normally white method is effective in terms of display contrast, color reproducibility, and viewing angle dependence of display.

In the above TN liquid crystal display device, the liquid crystal molecules have the refractive index anisotropy Δn, and the liquid crystal molecules are oriented so as to be inclined with respect to the upper and lower substrates. In addition, 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 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, linearly polarized light 3 passing through the normal direction of the surfaces of the pair of substrates 33 and 34.
5, and the linearly polarized lights 36 and 37 that pass with an inclination with respect to the normal direction have different intersecting angles with the liquid crystal molecules 32. Since the liquid crystal molecule 32 has 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 molecule 32, and the phase difference between them causes It will be converted into elliptically polarized light, and this will be the source of the viewing angle dependence.

Furthermore, inside the actual liquid crystal layer, the liquid crystal molecules 32 are formed near the intermediate portion between the substrate 33 and the substrate 34 and the substrate 3.
3 or the vicinity of the substrate 34 has a different tilt angle, and the liquid crystal molecules 32 are twisted by 90 ° about the normal direction.

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

As the viewing angle dependence, specifically, a phenomenon in which a display image is colored at a certain angle or more when the viewing angle is inclined from the normal direction of the display screen to the normal viewing angle direction which is the lower direction of the display surface. (Hereinafter, referred to as “coloring phenomenon”) and black-and-white inversion phenomenon (hereinafter referred to as “inversion phenomenon”) occur. Further, when the viewing angle is tilted in the anti-viewing angle direction which is the upper direction of the display screen, the contrast sharply decreases.

Further, the above 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 a front direction at a short distance, the colors displayed on the upper part and the lower part of the display screen may be different due to the influence of viewing angle dependence. This is because the viewing angle for viewing the entire display screen becomes large, which is the same as viewing the display screen from a more oblique direction.

In order to improve such viewing angle dependence,
It has been proposed to insert an optical retardation plate (retardation film) as an optical element having optical anisotropy between a liquid crystal display element and one polarizing plate (for example, JP-A-55-55).
See Japanese Patent Application Laid-Open No. 600 and Japanese Patent Application Laid-Open No. 56-97318).

This method is an optical system in which light 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 side or both sides of a liquid crystal layer having refractive index anisotropy. By passing through the retardation plate, the phase difference change between the normal light and the extraordinary light occurring at the viewing angle is compensated and reconverted into linearly polarized light, and the viewing angle dependency can be improved.

As such an optical retardation plate, one in which one main refractive index direction of an index ellipsoid is parallel to the normal line direction of the surface of the optical retardation plate is disclosed in, for example, Japanese Patent Laid-Open No. 5-313.
159. However, even using this optical retardation plate, there is a limit in improving the inversion phenomenon in the normal viewing angle direction.

In order to eliminate the inversion phenomenon, for example, in Japanese Patent Laid-Open No. 186735/1982, each display pattern (pixel) is divided into a plurality of portions, and each divided portion has an independent viewing angle characteristic. Orientation control to have,
A so-called pixel division method is disclosed. According to this method, since the liquid crystal molecules rise in different directions in each section, the viewing angle dependence can be eliminated. However, the problem that the contrast is lowered when the viewing angle is tilted in the vertical direction cannot be solved.

Further, Japanese Unexamined Patent Publication No. 6-118406 and Japanese Unexamined Patent Publication No. 6-194645 disclose techniques of combining an optical retardation plate with the above-mentioned pixel division method.

In the liquid crystal display device disclosed in JP-A-6-118406, the contrast is improved by inserting an optically anisotropic film (optical retardation plate) between the liquid crystal panel and the polarizing plate. And so on. The compensating plate (optical retardation plate) disclosed in JP-A-6-194645 has almost no in-plane refractive index in the direction parallel to the compensating plate surface, and the refractive index in the direction perpendicular to the compensating plate surface. Has a negative refractive index by being set to be smaller than the in-plane refractive index. Therefore, when a voltage is applied, the positive refractive index generated in the liquid crystal display element is compensated for,
The viewing angle dependency can be reduced.

However, even if this optical retardation plate is used for the pixel division method, it is possible to uniformly suppress the coloring phenomenon in the oblique 45 ° direction when the viewing angle is inclined and the deterioration of the vertical contrast. difficult.

Therefore, one main refractive index direction of the refractive index ellipsoid is parallel to the normal direction of the surface of the retardation plate, and an optical retardation plate in which the refractive index ellipsoid is not inclined is used to depend on the viewing angle. There is a limit to improving the contrast change, the coloring phenomenon, and the reversal phenomenon that occur.

In view of this, Japanese Patent Laying-Open No. 6-75116 discloses an optical retardation plate in which the main refractive index direction of the index ellipsoid is inclined with respect to the normal direction of the surface of the optical retardation plate. The method used is proposed. In this method, the following two types of optical retardation plates are used.

One of the three main refractive indices of the index ellipsoid has the direction of the minimum main refractive index parallel to the surface, and the remaining two main refractive indices have one direction of the optical position. The surface of the retardation plate is inclined at an angle of θ, and the other direction is also inclined at an angle of θ with respect to the normal direction of the surface of the optical phase difference plate, and the value of θ is 20 ° ≦ θ. The optical retardation plate satisfies ≦ 70 °.

The other is that the three main refractive indices n _a , n _b and n _c of the index ellipsoid have a relationship of n _a = n _c > n _b , and the main refractive indices n _a or With the direction of n _c as an axis, the direction of the main refractive index n _b parallel to the normal direction of the surface and the direction of the main refractive index n _a or n _c in the surface are clockwise.
Alternatively, it is an optical retardation plate in which the refractive index ellipsoid is inclined counterclockwise.

Of the above-mentioned two types of optical retardation plates, the former can be uniaxial or biaxial. In the latter, not only one optical retardation plate is used, but two optical retardation plates are combined so that the inclination directions of the respective main refractive indices n _b are set at 90 ° to each other. Can be used.

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

[0028]

However, under the circumstances where a liquid crystal display device having a wider viewing angle and a higher display quality is desired today, further improvement of the viewing angle dependency is required, and the above-mentioned JP-A-6- It cannot be said that just using the optical retardation plate disclosed in Japanese Patent No. 75116 is sufficient, and there is still room for improvement.

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

[0030]

In order to achieve the object of the present invention, each liquid crystal display device according to the present invention has a pair of translucent substrates each having a transparent electrode layer and an alignment film formed on opposing surfaces. Between the liquid crystal display element and the polarizer, a liquid crystal display element in which a liquid crystal layer twisted and aligned by about 90 ° is enclosed between the pair of polarizers, and a pair of polarizers disposed on both sides of the liquid crystal display element. At least one intervening optical retardation plate, which has three main refractive indices n _a , n _b , and n of an index ellipsoid.
_c has a relationship of n _a = n _c > n _b , and 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 an axis, Principal refractive index in the surface n _c
Alternatively, the optical retardation plate in which the refractive index ellipsoid is inclined by tilting clockwise or counterclockwise with respect to the direction of n _a is provided, and is characterized by the following points.

In the first liquid crystal display device, the refractive index anisotropy Δn _L (450) for the light of wavelength 450 nm and the refractive index anisotropy Δn _L (550) for the light of wavelength 550 nm of the liquid crystal material in the liquid crystal layer. Δn _L (45
0) / Δn _L (550) and the wavelength of the optical retardation plate 4
Refractive index anisotropy Δn _F (450) for light of 50 nm and refractive index anisotropy Δn _F (55 for light of wavelength 550 nm)
The ratio Δn _F (450) / Δn _F (550) of 0) is

[0032]

[Equation 5]

It is set so as to satisfy the relationship of

In the second liquid crystal display device, the refractive index anisotropy Δn _L (650) of light having a wavelength of 650 nm and the refractive index anisotropy Δn _L (550) of light having a wavelength of 650 nm of the liquid crystal material in the liquid crystal layer. The ratio of Δn _L (65
0) / Δn _L (550) and the wavelength of the optical retardation plate 6
Refractive index anisotropy Δn _F (650) for light of 50 nm and refractive index anisotropy Δn _F (55 for light of wavelength 550 nm)
The ratio Δn _F (650) / Δn _F (550) of 0) is

[0035]

[Equation 6]

It is set so as to satisfy the relationship of

According to the above structure, the main refractive indices n _a , n _b ,
n _c has a relationship of n _a = n _c > n _b , and the main refractive index n
_{Since the} optical retardation plate in which the minor axis of the refractive index ellipsoid containing _b is tilted with respect to the normal direction of the surface of the optical retardation plate is interposed between the liquid crystal layer and the polarizer, the linearly polarized light is When normal light and extraordinary light are generated by passing through a liquid crystal layer having a refractive property and are converted into elliptically polarized light due to the phase difference between them, the phase difference between the normal light and the extraordinary light occurs depending on the viewing angle. The change is compensated by this optical retarder.

However, even with such a compensating function, it cannot be said that it is not sufficient if further improvement of the viewing angle dependence is required, and as a result of further studies, the inventors of the present application have found that the above liquid crystal layer. The degree of change between the change in the refractive index anisotropy Δn of the liquid crystal material 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. The present invention has been completed and the present invention has been completed.

Refractive index anisotropy Δ of the liquid crystal material in the liquid crystal layer
By setting the change of n with respect to the wavelength of light to any one of the ranges described in the first and second liquid crystal display devices, at a viewing angle of 50 ° required in a normal liquid crystal display device,
Although it is slightly colored, it can be used sufficiently from any direction, and it is possible to prevent the screen from being colored further. It should be noted that the contrast change and the reversal phenomenon could be improved as compared with the case where only the compensation function of the retardation plate was used.

In a liquid crystal display device having a wider viewing angle such as a visual 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 as follows.

That is,

[0042]

[Equation 7]

It is set so as to satisfy the relationship of.

Or

[0045]

[Equation 8]

It is set so as to satisfy the relationship of.

By setting the range to any of these, it is possible to obtain no coloring phenomenon when viewed from any direction at a viewing angle of 70 ° required in a liquid crystal display device having a wide viewing angle.

Further, in each of the liquid crystal display devices of the present invention described above, the wavelength of the liquid crystal material in the liquid crystal layer is 550 nm.
Refractive index anisotropy Δn (550) with respect to light is 0.06
It is preferable to set it in a range larger than 0 and smaller than 0.120.

This is the refractive index anisotropy Δn 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.
This is because it was confirmed that when (550) is 0.060 or less or 0.120 or more, an inversion phenomenon and a decrease in contrast ratio occur depending on the viewing angle direction. Therefore, the refractive index anisotropy Δn of the liquid crystal material with respect to light having a wavelength of 550 nm
By setting (550) in the range of more than 0.060 and less than 0.120, the phase difference corresponding to the viewing angle generated in the liquid crystal display element can be eliminated. In addition to the coloring phenomenon that occurs, it is possible to further improve the contrast change, the inversion phenomenon in the left-right direction, and the like.

In this case, further, the refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer with respect to light having a wavelength of 550 nm.
By setting (550) in the range of 0.070 or more and 0.095 or less, the phase difference corresponding to the viewing angle generated in the liquid crystal display element can be more effectively eliminated, so that the contrast change in the liquid crystal display image is reduced. The inversion phenomenon in the left-right direction can be surely improved.

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

As described above, in all the optical retardation plates interposed in the liquid crystal display device, the tilt angle of the index ellipsoid is set to 1.
By setting the angle between 5 ° and 75 °, it is possible to surely obtain the above-described retardation compensation function of the optical retardation plate of the present invention.

In each of the liquid crystal display devices of the present invention described above,
In addition, in all optical retardation plates, the main refractive index n_a
And the main refractive index n_bThe product of the difference between and the thickness d of the optical retardation plate
(N _a-N_b) × d is between 80 nm and 250 nm
It is preferably set.

Thus, in all the optical retardation plates interposed in the liquid crystal display device, the main refractive index n _a and the main refractive index n
and the difference is _b, the product of the thickness d of the optical retardation plate (n _a -
By setting n _b ) × d between 80 nm and 250 nm, it is possible to surely obtain the above-described retardation compensation function of the optical retardation plate provided in the present invention.

[0055]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. 1 to 10.

First, before describing the embodiments of the present invention, a liquid crystal display device of a reference example will be described. As shown in FIG. 1, this 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.
・ It has 5 and.

The liquid crystal display element 1 has a structure in which the liquid crystal layer 8 is sandwiched between the electrode substrates 6 and 7 arranged to face each other. The electrode substrate 6 is a glass substrate (translucent substrate) 9 serving as a base.
A transparent electrode 10 made of ITO (indium tin oxide) is formed on the surface of the liquid crystal layer 8 side, and an alignment film 11 is formed thereon. In the electrode substrate 7, a transparent electrode 13 made of ITO is formed on a surface of a 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, but in the entire liquid crystal display element 1, strip-shaped transparent electrodes 10 and 13 having a predetermined width are provided on the glass substrates 9 and 12, respectively. Glass substrates 9 arranged at a predetermined interval
The areas 12 are formed so as to be orthogonal to each other when viewed from the direction perpendicular to the substrate surface. The intersection of the transparent electrodes 10 and 13 corresponds to a pixel for displaying, and these pixels are arranged in a matrix in the entire liquid crystal display device.

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

Although the details will be described later, in the present liquid crystal display device, the pretilt of the liquid crystal layer 8 is provided so as to form a combination having the function of compensating the phase difference by the optical retardation plates 2 and 3 and the best characteristics. The corners are set.

In the liquid crystal display device, the liquid crystal cell 16 is a unit formed by forming the optical phase difference plates 2 and 3 and the polarizing plates 4.5 on the liquid crystal display element 1.

The alignment films 11 and 14 are preliminarily subjected to rubbing treatment so that the intervening liquid crystal molecules have a twisted alignment of 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 to be orthogonal to each other.

The optical retardation plates 2 and 3 are respectively interposed between the liquid crystal display element 1 and the polarizing plates 4 and 5 arranged on both sides thereof. The optical retardation plates 2 and 3 are formed by discotic liquid crystal being tilt-aligned or hybrid-aligned and cross-linked on a support made of a transparent organic polymer. As a result, the later-described refractive index ellipsoids of the optical retardation plates 2 and 3 are formed so as to be inclined with respect to the optical retardation plates 2 and 3.

As a support for the optical retardation plates 2 and 3, triacetyl cellulose (TAC), which is often used for polarizing plates, is suitable because of its high reliability. Otherwise,
A colorless and transparent organic polymer film having excellent environment resistance and chemical resistance, such as polycarbonate (PC) and polyethylene terephthalate (PET), is suitable.

As shown in FIG. 3, the optical retardation plates 2.3
Is the principal refractive index n in three different directions._a・ N _b・ N_cHave
There is. Principal refractive index n_aAre in the Cartesian coordinates xyz.
The direction is the same as the y-coordinate axis among the coordinate axes in the graph.
Principal refractive index n_bDirection of the image on the optical phase difference plates 2 and 3.
Z coordinate axis perpendicular to the surface corresponding to the face (direction of the surface normal)
In contrast, it is inclined by θ in the direction of arrow A.

The optical retardation plates 2 and 3 each have a main refractive index n _a
= N _c > n _b is satisfied. This allows
Since there is only one optical axis, the optical retardation plates 2 and 3 have uniaxiality, and the refractive index anisotropy is negative. The first retardation value of the optical phase difference plates _{2 · 3 (n c -n a} )
Xd is almost 0 nm because n _a = n _c . The second retardation value (n _c −n _b ) × d is 80 nm.
It is set to an arbitrary value within the range of 250 nm. By setting the second retardation value (n _c −n _b ) × d in such a range, the function of compensating the phase difference by the optical phase difference plates 2 and 3 can be surely obtained. The above n _c
-N _a and n _c -n _b represent the refractive index anisotropy Δn, and d
Represents the thickness of the optical phase difference plates 2 and 3.

Further, the main refractive index n _{b of the} optical phase difference plates 2 and 3
Is the angle θ, that is, the tilt angle θ of the index ellipsoid
Is set to an arbitrary value within the range of 15 ° ≦ θ ≦ 75 °. By setting the tilt angle θ within such a range,
Regardless of whether the tilt direction of the refractive index ellipsoid is clockwise or counterclockwise, the function of compensating for the phase difference by the optical phase difference plates 2 and 3 can be surely obtained.

Regarding the arrangement of the optical retardation plates 2 and 3, it is possible to arrange only one of the optical retardation plates 2 and 3 on one side, or the optical retardation plates 2 and 3 on one side. It can also be placed on top of each other. Furthermore, it is also possible to use three or more optical retardation plates.

Then, as shown in FIG. 4, in the liquid crystal display device of the reference example, the polarizing plate 4 in the liquid crystal display element 1 was used.
5 indicates that the absorption axes AX ₁ and AX ₂ are the alignment film 11 described above.
14 (see FIG. 1) are arranged so as to be parallel to the rubbing directions R ₁ and R ₂ respectively. In this 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, the direction of the main refractive index n _b which is inclined in the direction of giving anisotropy to the optical retardation plate 2.3 is projected on the surface of the optical retardation plate 2.3. Direction D
It is defined as As shown in FIG. 4, the optical retardation plate 2 is arranged so that the direction D (direction D ₁ ) is parallel to the rubbing direction R _1, and the optical retardation plate 3 is arranged so that the direction D (direction D ₂ ) is the rubbing direction. It is arranged so as to be parallel to R ₂ .

Due to 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 so-called normally white display in which light is transmitted and white display is performed.

Generally, in an optically anisotropic body such as a liquid crystal or an optical retardation plate (retardation film), the above-mentioned 3
The anisotropy of the main refractive index n _a · n _c · n _{b in} the dimension direction is represented by a refractive index ellipsoid. The refractive index anisotropy Δn has a different value depending on from which direction the refractive index ellipsoid is observed.

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

The pretilt angle is as shown in FIG.
Angle ψ formed by the long axis of the liquid crystal molecules 20 and the alignment film 14 (11)
And rubbing on the alignment films 11 and 14,
It is determined by the combination with the liquid crystal material.

As described above, in the liquid crystal display device of the reference example, the liquid crystal layer 8 is formed so that the combination of the optical retardation plates 2 and 3 has the phase compensation function and the best characteristics.
The pretilt angle of is set, and in detail, 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. In the display state, it is set to a range in which grayscale inversion in the counter-viewing angle direction does not occur. Less than,
Halftones close to white are called white gradations.

On the other hand, the larger the pretilt angle,
It was experimentally confirmed that the grayscale inversion in the counter-viewing angle direction at the time of white gradation does not occur, but on the other hand, if the pretilt angle is made too large, the brightness at the time of white gradation in the normal viewing angle direction becomes sharp. It was also confirmed that a decrease occurred. In other words, it is necessary to set the pretilt angle within a range in which a sharp decrease in luminance 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 the alignment film and the 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 the alignment film and the liquid crystal material such that the pretilt angle is in the range of 4 ° or more and 10 ° or less.

By setting the pretilt angle within the range of more than 2 ° and less than 12 ° in this way, at a viewing angle of 50 ° required in a normal liquid crystal display device, a problem occurs in a white gradation. There is no gradation reversal in the direction of the counter-viewing angle, and it can be used sufficiently from any direction.

In particular, the pretilt angle is 4 ° or more 1
By setting it within the range of 0 ° or less, at the viewing angle of 70 °, gradation inversion in the direction of the opposite viewing angle at the time of white gradation can be completely eliminated.

Further, in the liquid crystal display device of the reference example, 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. The selected one is selected. In this case, more preferably, Δn (5
50) is to use a liquid crystal material designed in the range of 0.070 to 0.095.

As a result, in addition to the function of compensating for the phase difference by the optical retardation plates 2 and 3 and the function of compensating for setting the pretilt angle within the above range, the contrast ratio in the anti-viewing angle direction decreases, and It is possible to further improve the inversion phenomenon.

As described above, the liquid crystal display device of the reference example is
Between the liquid crystal display element 1 and the polarizing plates 4 and 5, the three main refractive indices n _a , n _b and n _c of the index ellipsoid have a relationship of n _a = n _c > n _b , The direction of the principal refractive index n _b parallel to the normal direction of the surface with the direction of the principal refractive index n _a or n _c as the axis and the direction of the principal refractive index n _c or n _a in the surface are clockwise, or By tilting counterclockwise,
In the liquid crystal display device having the optical retardation plates 2 and 3 having the tilted refractive index ellipsoids, the pre-tilt angle in the liquid crystal layer 8 is a halftone display in which a voltage close to the threshold voltage of the liquid crystal is applied to the liquid crystal. In this state, the configuration is set to a range in which grayscale inversion in the counter-viewing angle direction does not occur.

As a result, in addition to the function of compensating the phase difference corresponding to the viewing angle generated in the liquid crystal display element 1 by the optical retardation plates 2 and 3, the compensating function by setting the pretilt angle in the above range allows the viewing angle to be changed. It is possible to particularly effectively improve the reversal phenomenon that occurs during the dependent grayscale in the direction of the counter-viewing angle (because it is normally white display), and at the same time, improve the contrast change to obtain a high-quality image. Can be displayed.

Moreover, in this liquid crystal display device, the liquid crystal layer 8
Since the liquid crystal material used in (1) is designed to have a refractive index anisotropy Δn (550) with respect to light having a wavelength of 550 nm in a range larger than 0.060 and smaller than 0.120, the optical retardation plates 2.3 Phase difference compensation function,
Also, in addition to the compensation function by setting the pretilt angle in the above range, it is possible to further improve the reduction of the 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 is described as an example, but also in the liquid crystal display device of normally black display, the pretilt is adjusted in accordance with the compensation effect of the optical phase difference plates 2 and 3. Halftone display (black gradation) with a voltage applied to the liquid crystal whose angle is close to the liquid crystal threshold voltage
By setting a range in which gray scale inversion in the counter-viewing angle direction does not occur and obtaining a compensation effect by this, the same effect as described above can be obtained.

Although a simple matrix type liquid crystal display device has been described here, the present invention is not limited to this.
It is also applicable to an active matrix type 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 the members shown in the liquid crystal display device of the above-mentioned reference example (hereinafter referred to as the first reference example) are designated by the same reference numerals, and the description thereof will be 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 set to the liquid crystal layer 8 so that the optical retardation plates 2 and 3 have a function of compensating for the phase difference and the best characteristics. In the halftone display state in which a voltage close to the threshold voltage of the liquid crystal is applied to the layer 8, it is set to a range in which grayscale inversion in the counter-viewing angle direction does not occur, whereas in the liquid crystal display device of the second reference example, 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 that a combination having the phase difference compensation function by the phase difference plates 2 and 3 and the best characteristics is obtained. The point is that the voltage value is set in a range in which grayscale 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 a normally white display, a 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 performing white gradation is It is set in a range in which grayscale inversion in the counter-viewing angle direction does not occur with the voltage applied.

On the other hand, it was experimentally confirmed that the lower the transmittance at the white gradation, the less the gradation reversal in the counter-viewing angle direction at the white gradation occurred. However, on the other hand, the transmittance was set low. After that, the luminance sharply decreases in the normal viewing angle direction and the left-right direction. That is, in order to set the liquid crystal applied voltage that determines the transmittance at the time of the white gradation, it is also necessary to set the voltage within a range in which a sharp decrease in the luminance in the normal viewing angle direction and the horizontal direction does not occur at the white gradation.

Specifically, the liquid crystal applied voltage at the time of white gradation is 100% in the off state where the liquid crystal applied voltage is zero.
Is set to obtain a transmittance of greater than 85%. In this case, more preferably, the liquid crystal applied voltage at the time of white gradation is 9 with respect to the transmittance of 100% in the off state.
The setting is to obtain a transmittance within the range of 0% to 97%.

Thus, by setting the liquid crystal applied voltage at the time of white gradation so as to obtain a transmissivity of more than 85% with respect to the transmissivity of 100% in the off state, it is required in a normal liquid crystal display device. At a viewing angle of 50 °, there is no gradation reversal in the direction of the opposite viewing angle at the time of white gradation, which is a problem, and it can be sufficiently used from any direction.

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

That is, in the liquid crystal display device of the second reference example, between the liquid crystal display element 1 and the polarizing plates 4 and 5, the refractive index ellipsoid 3 is formed.
The two main refractive indices n _a , n _b , and n _c have a relationship of n _a = n _c > n _b , and the direction of the main refractive index n _a or n _{c in} the surface is an axis in the normal direction of the surface. Optics in which the refractive index ellipsoid is tilted by tilting the parallel main refractive index n _b direction and the in-surface main refractive index n _c or n _a direction clockwise or counterclockwise. In the liquid crystal display device having the phase difference plates 2 and 3, the applied voltage value for performing a halftone display state in which a voltage close to the threshold voltage of the liquid crystal is applied to the liquid crystal The configuration is set in a range in which directional grayscale inversion does not occur.

As a result, the liquid crystal applied voltage at the time of white gradation is set within the above range, as well as the function of compensating the phase difference corresponding to the viewing angle generated in the liquid crystal display element 1 by the above optical phase difference plates 2 and 3. With the compensation function, 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, improve the contrast change. Therefore, a high quality image can be displayed.

Further, also in the liquid crystal display device of the second reference example, the liquid crystal material in the liquid crystal layer 8 has a wavelength of 550 nm.
Refractive index anisotropy Δn (550) with respect to light is 0.06
It is preferable that the Δn (550) is designed to be in the range of more than 0 and less than 0.120.
By using a liquid crystal material designed in the range of 70 or more and 0.095 or less, the function of compensating the phase difference by the optical phase difference plates 2 and 3 and the liquid crystal applied voltage at the time of white gradation are set within the above range. In addition to the compensation function by, it is possible to further reduce the contrast ratio in the counter-viewing angle direction and the reversal phenomenon in the left-right direction.

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

Further, similar to the liquid crystal display device of the first reference example described above, in addition to the simple matrix liquid crystal display device,
It is also applicable to an active matrix type liquid crystal display device using an active switching element such as a TFT.

Liquid crystal display devices according to embodiments of the present invention will be described below. For convenience of description, members having the same functions as the members shown in the first and second reference examples described above will be designated by the same reference numerals, and the description thereof will be omitted.

The liquid crystal display device according to the present embodiment (hereinafter,
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 set to the liquid crystal layer 8 so that the optical retardation plates 2 and 3 have a function of compensating for the phase difference and the best characteristics. 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 layer 8 is set to a range in which grayscale inversion in the counter-viewing angle direction does not occur, whereas in the liquid crystal display device of the present embodiment, The liquid crystal layer 8 has a phase difference compensating function by the phase difference plates 2 and 3 and a combination having the best characteristics.
The degree of change between the change of the refractive index anisotropy Δn of the liquid crystal material 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 in the liquid crystal screen depending on the viewing angle. The point is that it is set within the range where

Hereinafter, this point will be described in detail. Liquid crystal layer 8
The degree of change between the change of the refractive index anisotropy Δn of the liquid crystal material 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 in the liquid crystal screen depending on the viewing angle. The setting of the range in which the optical phase difference plate 2 or 3 does not occur is specifically a combination that satisfies the condition of at least one of the following setting ranges.
Alternatively, a liquid crystal material may be used.

Refractive index anisotropy Δn _L (450) of the liquid crystal material in the liquid crystal layer 8 with respect to light having a wavelength of 450 nm
And refractive index anisotropy Δn _L (5
50) ratio Δn _L (450) / Δn _L (550)
When the ratio of the optical retardation plate refractive index anisotropy of the 2/3 wavelength 450nm for light Δn _F (450) the refractive index anisotropy and a wavelength 550nm for light Δn _F (550) Δn _F
(450) / Δn _F (550)

[0103]

[Equation 9]

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

[0105]

[Equation 10]

More preferably,

[0107]

[Equation 11]

The setting is to satisfy the relationship of.

Refractive index anisotropy Δn _L (650) of the liquid crystal material in the liquid crystal layer 8 with respect to light having a wavelength of 650 nm
And refractive index anisotropy Δn _L (5
50) ratio Δn _L (650) / Δn _L (550)
When the ratio of the optical retardation plate refractive index anisotropy of the 2/3 wavelength 650nm for light Δn _F (650) the refractive index anisotropy and a wavelength 550nm for light Δn _F (550) Δn _F
(650) / Δn _F (550)

[0110]

[Equation 12]

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

[0112]

[Equation 13]

More preferably,

[0114]

[Equation 14]

The setting is to satisfy the relationship of.

By using the liquid crystal material and the optical retardation plate designed to satisfy at least one of the above, the viewing angle of the display screen by the phase difference compensating function of the optical retardation plates 2 and 3 is used. In addition to the improvement of the contrast change, the reversal phenomenon, and the coloring phenomenon that occur depending on, the coloring phenomenon of the display screen can be improved particularly effectively.

To be more specific, by satisfying at least one of the broader ranges of ·, there is some coloring at a viewing angle of 50 ° required in a normal liquid crystal display device, but it is sufficiently visible from any direction. It can be used. Further, by satisfying at least one of the more preferable ranges in the above-mentioned items, it is possible to sufficiently use it from any direction, although there is some coloring at a viewing angle of 60 °. In particular, by satisfying at least one of the more preferable ranges in the above-mentioned items, it is possible to obtain no coloring from any direction.

By satisfying at least one of the following, it is possible to improve the contrast change and the inversion phenomenon as compared with the case where only the compensation function of the optical phase difference plates 2 and 3 is used.

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

As described above, in the liquid crystal display device of the present embodiment, the three main refractive indices n _a , n _b and n _c of the index ellipsoid are provided between the liquid crystal display element 1 and the polarizing plates 4 and 5. Is n _a = n _c >
has a relationship of n _b and has a main refractive index n _a or n in the surface.
The direction of the _c an axis, and a direction parallel principal refractive index n _b in the direction normal to the surface, that the direction of the principal refractive index n _c or n _a in the surface is inclined clockwise or counterclockwise, The optical retardation plate 2 in which the refractive index ellipsoid is inclined by
In the liquid crystal display device having the configuration of 3, the change in 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 in the refractive index anisotropy Δn of the optical retardation plate with respect to the wavelength of light. This is a configuration in which the degree of change with the change is set in a range in which coloring of the liquid crystal screen depending on the viewing angle does not occur.

As a result, the retardation corresponding to the viewing angle generated in the liquid crystal display element 1 is compensated by the optical retardation plates 2 and 3 and the wavelength of light having the refractive index anisotropy Δn of the liquid crystal material in the liquid crystal layer 8 is obtained. And the change in the degree of change of the refractive index anisotropy Δn of the optical retardation plate with respect to the wavelength of light within the above range are compensated by the compensation function, and the display screen coloration depending on the viewing angle is particularly effective. It is possible to improve the image quality, and at the same time, it is possible to improve the contrast change and the gradation inversion and display a high quality image.

Further, also in the liquid crystal display device of this embodiment, the liquid crystal material in the liquid crystal layer 8 has a wavelength of 550 nm.
Refractive index anisotropy Δn (550) with respect to light is 0.06
It is preferable that the Δn (550) is designed to be in the range of more than 0 and less than 0.120.
By using the liquid crystal material designed in the range of 70 or more and 0.095 or less, the phase difference compensation function by the optical retardation plates 2 and 3 and the compensation function by setting the degree of change in the above range can be achieved. In addition, it is possible to further reduce the contrast ratio in the counter-viewing angle direction and the inversion phenomenon in the left-right direction.

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

Further, similar to the liquid crystal display device of the above-mentioned reference example 1, in addition to the simple matrix type liquid crystal display device, TF
It is also applicable to an active matrix type liquid crystal display device using an active switching element such as T.

[0125]

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

Reference Example 1 This reference example is for supporting the effect of the liquid crystal display device according to the first reference example and the second reference example, and here, the liquid crystal display device of FIG. Optomer AL (trade name) manufactured by Japan Synthetic Rubber Co., Ltd. is used for the alignment films 11 and 14 of the liquid crystal cell 16 in FIG.
3.0 °, 4.0 °, 5.0 °, 10.0 °, 11.0
Of five sample cells # 1 to # 1 having a cell thickness (thickness of the liquid crystal layer 8) of 5 μm using a liquid crystal material of 1 ° and 12.0 °
I prepared # 7.

To measure the pretilt angles of these sample cells # 1 to # 7, a homogeneous cell in which the material of the sample cells # 1 to # 7 was injected was prepared, and a pretilt angle measuring device NSMAP-3000LCD (manufactured by Sigma Koki Co., Ltd.) was used. It was measured at.

As the optical retardation 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) or the like) to form a discotic liquid crystal. The first retardation value is 0 nm and the second retardation value is 100 n, which is formed by being inclined and crosslinked.
m, and the main refractive index n _b is inclined such that the direction of the main refractive index n _b is approximately 20 ° in the direction indicated by arrow A with respect to the z-axis direction in the xyz-axis coordinates, and similarly, the direction of the main refractive index n _c is x. An angle of about 20 ° with respect to the axis in the direction indicated by arrow B (that is, a tilt angle θ of the index ellipsoid θ = 20 °)
Was used.

For these sample cells # 1 to # 7,
Tables 1 to 7 show the results of a visual test under white light with various applied voltages during white gradation.

[0130]

[Table 1]

Table 1 shows the liquid crystal applied voltage for obtaining white gradation in the off state in which the applied voltage to the liquid crystal is zero.
As a result of investigating the display state at the time of white gradation, the transmittance obtained in the normal direction of the surface of the liquid crystal cell 16 is set to 100%, and a value for obtaining the transmittance of 100% in the normal direction is set for each sample cell. Is.

From Table 1, when the voltage for white gradation is set with the transmittance of 100%, the pretilt angle is 5.0 °,
In sample cells # 4 and # 5 set to 10.0 °, even when the viewing angle was set to 70 ° and no gradation inversion was observed when viewed from the direction of the opposite viewing angle, good image quality was obtained.

Further, in the sample cell # 2 having a pretilt angle of 3.0 ° and the sample cell # 3 having a pretilt angle of 4.0 °, the gradation is up to 60 ° even when viewed from the opposite viewing angle direction. Although no reversal was confirmed and the image quality was good, when the viewing angle was 70 °, in the sample cell # 2, it was confirmed that the gradation reversal was sufficient to withstand use, and the sample cell # 2
In No. 3, there was no gradation inversion, but the gradation was destroyed. However, all of them could be used sufficiently at a viewing angle of 70 °.

In the sample cell # 6 having the pretilt angle of 11.0 °, the image quality was good up to the viewing angle of 60 °, but the brightness was unusable when viewed from the normal viewing angle direction at the viewing angle of 70 °. It was confirmed to decrease.

On the other hand, in sample cell # 1 having a pretilt angle of 2.0 °, gradation reversal was confirmed even when viewed from the opposite viewing angle direction even at a viewing angle of 50 °, and the pretilt angle was set to 12.0. In sample cell # 7 set to °,
Even at a viewing angle of 50 °, it was confirmed that the brightness was too low to be used when viewed from the normal viewing direction.

[0136]

[Table 2]

Table 2 shows the results of an examination by setting the transmittance for the off-state transmittance to 97% and setting the voltage for white gradation for each individual sample cell.

From Table 2, when the voltage for white gradation is set with the transmittance of 97%, the pretilt angle is 4.0 °,
Sample cells # 3, # 4 set to 5.0 ° and 10.0 °
In # 5, even if the viewing angle was set to 70 ° and no gradation reversal was observed when viewed from the opposite viewing angle direction, the image quality was good.

In sample cell # 2 having 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 50 °, and the image quality was good.
The gradation was lost at °. However, since no gradation inversion was confirmed, it could be used even at a viewing angle of 60 °. In the sample cell # 6 having the pretilt angle of 11.0 °, the image quality was good up to the viewing angle of 50 °.
It was confirmed that when viewed from the normal viewing angle direction at a viewing angle of 60 °, the brightness was lowered so that it could not be used.

On the other hand, in sample cell # 1 having a pretilt angle of 2.0 °, gradation inversion was confirmed even when viewed from the opposite viewing angle direction even at a viewing angle of 50 °. Further, in the sample cell # 7 having the pretilt angle of 12.0 °,
Even at a viewing angle of 50 °, it was confirmed that the brightness was too low to be used when viewed from the normal viewing direction.

[0141]

[Table 3]

Table 3 shows the results of an examination by setting the voltage at the white gradation for each sample cell with the transmittance for the off-state transmittance being 95%. This has a transmittance of 95%
The result was the same as in Table 2 in which the voltage was set as.

[0143]

[Table 4]

Table 4 shows the results of an examination with the transmittance for the off-state transmittance set to 92% and the voltage for white gradation set for each sample cell.

From Table 4, when the transmittance is set to 92% and the voltage for the white gradation is set, the pretilt angle is 4.0 °,
Sample cells # 3, # 4 set to 5.0 ° and 10.0 °
In # 5, even if the viewing angle was set to 70 ° and no gradation reversal was observed when viewed from the opposite viewing angle direction, the image quality was good.

In the sample cell # 2 having a pretilt angle of 3.0 °, no gradation inversion was confirmed even when viewed from the opposite viewing angle direction up to a viewing angle of 60 °, and the image quality was good, but the viewing angle 70
The gradation was reversed at °. However, it was only usable. Sample cell # 6 having a pretilt angle of 11.0 ° had good image quality up to a viewing angle of 50 °, but the brightness was so low as to be unusable when viewed from the normal viewing angle direction at a viewing angle of 60 °. Was confirmed. In the sample cell # 1 having the pretilt angle of 2.0 °, the gradation was reversed at the viewing angle of 50 °, but the gradation was enough to withstand use.

On the other hand, in the sample cell # 7 having the pretilt angle of 12.0 °, it was confirmed that the luminance was too low to be used when viewed from the normal viewing angle direction even at the viewing angle of 50 °.

[0148]

[Table 5]

Table 5 shows the results of an examination by setting the voltage for white gradation for each sample cell with the transmittance for the off-state transmittance being 90%.

From Table 5, when the voltage at white gradation is set with the transmittance of 90%, the pretilt angle is 4.0 °,
In sample cells # 3 and # 4 set to 5.0 °, the viewing angle is 7
Gradient inversion was not confirmed even when viewed from the direction of the counter-viewing angle at 0 °, and the image quality was good.

In the sample cell # 5 having the pretilt angle of 10.0 °, the image quality was good up to the visual angle of 50 °, but it was confirmed that the luminance was lowered when viewed from the normal visual angle direction at the visual angle of 60 °. Was done. However, this decrease in brightness was such that it could be used. In the sample cell # 2 having the pretilt angle of 3.0 °, no gradation reversal was confirmed even from the direction of the opposite viewing angle up to a viewing angle of 60 °, and the image quality was good, but the gradation was degraded at a viewing angle of 70 °. It was However, there was no gradation reversal, and it was a level that could withstand use. In sample cell # 6 having a pretilt angle of 11.0 °, it was confirmed that the luminance was reduced when viewed from the normal viewing angle direction at a viewing angle of 50 °, but this reduction in luminance is not enough to withstand use. there were. Pretilt angle of 2.0
In the sample cell # 1 having a viewing angle of 50 °, the gradation was destroyed at the viewing angle of 50 °, and the gradation was reversed at the viewing angle of 60, but it was acceptable for use.

On the other hand, in the sample cell # 7 having the pretilt angle of 12.0 °, it was confirmed that the luminance was too low to be used when viewed from the normal viewing angle direction even at the viewing angle of 50 °.

[0153]

[Table 6]

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

From Table 6, when the transmittance is 87% and the voltage at the white gradation is set, the pretilt angle is 3.0 °,
Sample cells # 2, # 3, # set to 4.0 ° and 5.0 °
In 4, the image quality was good up to a viewing angle of 50 °, but it was confirmed that the brightness was reduced when viewed from the normal viewing angle direction at a viewing angle of 60 °. However, this decrease in brightness was such that it could be used. At a viewing angle of 70 °, it was confirmed that the brightness was too low to be used when viewed from the normal viewing angle direction.

It has been confirmed that the sample cell # 5 having a pretilt angle of 10.0 ° has a reduced brightness when viewed from the normal viewing angle direction at a viewing angle of 50 ° and a viewing angle of 60 °, but it is usable to a sufficient extent. It was the one. At a viewing angle of 70 °, it was confirmed that the brightness was too low to be used when viewed from the normal viewing angle direction.

Pretilt angles are 11.0 ° and 12.0 °
In sample cells # 6 and # 7, it was confirmed that the brightness was too low to be used when viewed from the normal viewing angle direction even at a viewing angle of 50 °.

In the sample cell # 1 having a pretilt angle of 2.0, gradation reversal was not confirmed even when viewed from the opposite viewing angle direction up to a viewing angle of 50 °, and the image quality was good, but the viewing angle was 60 °.
A decrease in luminance was confirmed when viewed from the normal viewing angle direction. However, it was only usable. At a viewing angle of 70 °, it was confirmed that the brightness was too low to be used when viewed from the normal viewing angle direction.

[0159]

[Table 7]

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

From Table 7, when the voltage at the white gradation is set with the transmittance of 85%, the pretilt angle is 3.0 °,
4.0 °, 5.0 °, 10.0 °, 11.0 °, 12.
Sample cells # 2, # 3, # 4, # 5, # set to 0 °
6 and # 7, even at a viewing angle of 50 °, the normal viewing angle direction,
When viewed from the left and right, it was confirmed that the brightness was too low for use.

On the other hand, in sample cell # 1 having 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 was usable. At a viewing angle of 60 °, it was confirmed that the brightness was too low to be used when viewed from the normal viewing angle direction.

That is, from Tables 1 to 7, it can be said that the gradation reversal 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, 95 to 9 which is usually set as the transmittance of the white gradation
At about 7%, the pretilt angle is greater than 2 ° and 12 °
It can be said that by setting the range to be less than, it is possible to improve the gradation inversion in the counter-viewing angle direction at a viewing angle of 50 ° and to obtain a good display without a decrease in luminance in the normal viewing angle direction. And then 4
It can be said that by setting the range in the range from 10 ° to 10 °, it is possible to improve the gradation reversal in the counter-viewing angle direction even at a viewing angle of 70 ° with a wide viewing angle, and to obtain a good display without a decrease in luminance in the normal viewing angle direction.

Further, at a pretilt angle of 2 ° to 10 ° which is usually set, by obtaining a transmissivity of more than 85% at the time of white gradation, the floor in the anti-view angle direction at the visual angle of 50 ° is obtained. It can be said that a good display can be obtained in which the tone reversal is improved and the luminance in the normal viewing angle direction does not decrease. And
Further, by adjusting the pretilt angle by obtaining the transmittance within the range of 90% or more and 97% or less, it is possible to improve the gradation inversion in the anti-viewing angle direction even at the viewing angle of 70 ° of the wide viewing angle, In addition, it can be said that a good display can be obtained without a decrease in luminance in the normal viewing angle direction.

Further, it can be said that a further 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, for the same sample cell # 1 and sample cell # 4 as described above, as shown in FIG.
1. The viewing angle dependence of the liquid crystal display device was examined by using a measurement system including the amplifier 1, the amplifier 22, and the recording device 23.

In this measuring 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 located on the reference plane XY of the orthogonal coordinates XYZ.
The light receiving element 21 is an element capable of receiving light at a fixed stereoscopic light receiving angle, and has an angle φ (viewing angle) with respect to the Z direction perpendicular to the surface 16a.
It is arranged at a position spaced a predetermined distance from the coordinate origin in the direction of.

At the time of measurement, with respect to the liquid crystal cell 16 installed in this measurement system, the wavelength of 550n was measured from the surface opposite to the surface 16a.
Irradiate m monochromatic light. A 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 the recording device 23 such as a waveform memory or a recorder.

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

In the measurement, it is assumed that the light receiving element 21 is arranged at 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). The arrangement of the light receiving elements 21 was changed to the upward direction (counter-viewing angle direction), the downward direction (normal viewing angle direction), and the left-right direction.

The results are shown in FIGS. 7 (a) to 7 (c).
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 °. 3 is a graph showing the ratio-liquid crystal applied voltage characteristic).

FIG. 7 (a) shows the result of measurement from the upper side of FIG. 2, FIG. 7 (b) shows the lower side of FIG. 2, and FIG. 7 (c).
Is the result of each measurement from the left and right directions.

In FIG. 7A, a curved line L1 indicated by an alternate long and short dash line is the result of measurement from the front, that is, the normal direction of the surface, and the same transmittance-liquid crystal applied voltage characteristic is obtained in both sample cells # 1 and # 4. Becomes

In FIGS. 7A to 7C, L2, L4, and L6 represented by solid lines are those of sample cell # 4, and curves L3, L5, and L7 shown by broken lines are those of sample cell # 1. is there.

When the upward transmittance-liquid crystal applied voltage characteristics of the sample cell # 4 and the sample cell # 1 are compared, the curve L3 of the sample cell # 1 is shown in FIG. 7A.
Has a hump after it has dropped from around 1V to around 2V and then has a hump, while the curve L2 of sample cell # 4 lacks from around 1V to around 2V and has a substantially constant transmittance. It was confirmed that the hump disappeared and there was no inversion phenomenon.

7 (b) and 7 (c), comparing the transmittance and the liquid crystal applied voltage characteristics in the downward and leftward directions, the curves L4 and L6 of the sample cell # 4 are the curves of the sample cell # 1. It is shown that the transmittance starts to drop a little faster than L5 and L7. However, the transmittance of sample cell # 4 is about 2.5V in FIG. 7 (b) and 3V in FIG. 7 (c). Almost matches that of cell # 1,
It can be confirmed that there is no adverse effect of increasing the pretilt angle to 5.0 °.

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

Example 1 This example is intended to support the effects of the above-mentioned first and second reference examples and the liquid crystal display device according to the embodiment. Here, FIG. Alignment films 11 and 14 of liquid crystal cell 16 in a liquid crystal display device
For the alignment film 11 and 14, a pretilt angle of 3 is used for the alignment film 11 and 14 by using Optomer AL (trade name) manufactured by Japan Synthetic Rubber Co.
And refractive index anisotropy Δn at a wavelength of 550 nm
(550) is 0.070, 0.080, 0.
The liquid crystal material set to 095 was used for the liquid crystal layer 8, and three sample cells # 16 to # 18 having a cell thickness (thickness of the liquid crystal layer 8) of 5 μm were prepared.

In this case also, the pretilt angle was measured by preparing a homogeneous cell in which the materials of the sample cells # 16 to # 18 were injected, and measuring the pretilt angle with NSMAP-3000.
It was measured at.

In addition, these sample cells # 16 to # 18
As the optical retardation plates 2 and 3 in, the same ones as the optical retardation plates 2 and 3 in the above-mentioned Comparative Example 1 in which the discotic liquid crystal was inclined and aligned were used.

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

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

The results are shown in FIGS. 8 (a) to 8 (c).
8A to 8C are graphs showing the light transmittance (transmittance-liquid crystal applied voltage characteristic) with respect to the voltage applied to the sample cells # 16 to # 18.

FIG. 8 (a) shows the result of measurement from the upper direction of FIG. 2, FIG. 8 (b) shows the right direction of FIG. 2, and FIG. 8 (c).
Is the result of each measurement from the left.

In FIGS. 8A to 8C, the curved lines L8, L11, and L4, which are respectively indicated by alternate long and short dash lines, are Δ in the liquid crystal layer 8.
A sample cell # 16 made of a liquid crystal material of n (550) = 0.070 and having curved lines L9, L12, L shown by solid lines.
15 is the sample cell # 17 using a liquid crystal material of Δn (550) = 0.080 for the liquid crystal layer 8, and the curves L10, L13, and L16 indicated by broken lines are Δn (55
0) = 0.095 sample cell # 1 using liquid crystal material
8 of them.

As a comparative example to this example, the liquid crystal layer 8 in the liquid crystal cell 16 of FIG. 1 has a refractive index anisotropy Δn (550) of 0.0 at a wavelength of 550 nm.
Two comparative sample cells # 103, which are similar to the present example except that the liquid crystal materials set to 60 and 0.120 are used.
# 104 is prepared and installed in the measurement system shown in FIG. 6, and the sample cells for comparison # 103 and # 104 in the case where the light receiving element 21 is fixed at a constant angle φ by the same method as this embodiment The output level of the light receiving element 21 with respect to the applied voltage was also measured.

In the measurement, similarly to the present embodiment, the light receiving element 21 is arranged so that the angle φ is 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 to the upward direction (counter-viewing angle direction), the right direction, and the left direction.

The results are shown in FIGS. 9 (a) to 9 (c).
9A to 9C show comparative example samples # 103 and # 1.
4 is a graph showing the light transmittance (transmittance-liquid crystal applied voltage characteristic) with respect to the voltage applied to No. 04.

FIG. 9 (a) shows the result of measurement from the upper direction of FIG. 2, FIG. 9 (b) shows the right direction of FIG. 2, and FIG. 9 (c).
Is the result of each measurement from the left direction.

In FIGS. 9A to 9C, the curves L17, L19, and L21 shown by the solid lines are Δn (55) in the liquid crystal layer 8.
0) = 0.060 of the comparative sample cell # 103 using the liquid crystal material, and the curves L18, L20, ...
L22 is a sample cell # 104 for comparison which uses a liquid crystal material having Δn (550) of 0.120 for the liquid crystal layer 8.

When the sample cells # 16 to # 18 and the comparative sample cells # 103 and # 104 are compared in the upward transmittance-liquid crystal applied voltage characteristic, the curves L9 and L8 are shown in FIG. 8A. -It was confirmed that the transmittance of L10 was sufficiently lowered as the voltage was increased. On the other hand, in FIG. 9A, the curve L18 does not have a sufficiently low transmittance even when the voltage is increased, as compared with the curves L8, L9, and L10 of FIG. 8A. Also, the curve L17
It was confirmed that, as the voltage was increased, the transmittance once decreased and then increased again.

Similarly, the sample cells # 16 to # 18 and the sample cells for comparison # 103 and # 104 are compared with each other in the rightward transmittance-liquid crystal applied voltage characteristic, as shown in FIG.
In (b), it was confirmed that the transmittances of the curves L11, L12, and L13 decreased until the voltage was increased to almost 0 when the voltage was increased. Also in FIG. 9B, the curve L1
For 9, as the voltage was increased, the transmittance decreased until it became almost 0 as in FIG. 8B, but the above-mentioned inversion phenomenon was confirmed for the curve L20.

Similarly, with respect to the sample cells # 16 to # 18 and the comparison sample cells # 103 and # 104, the same thing as in the right direction was confirmed even in the left direction.

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

With respect to the sample cells # 16 to # 18 and the comparative sample cell # 103, no coloring was observed and the image quality was good no matter which direction the viewing angle was 50 °. On the other hand, it was confirmed that the comparative sample cell # 104 was colored from yellow to orange when viewed from the left and right 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) of 0.070 and 0.0 at a wavelength of 550 nm, respectively.
When a liquid crystal material set to 80 or 0.095 is used, the transmittance is sufficiently reduced when a voltage is applied, and no reversal phenomenon is observed, so that the viewing angle is widened and the coloring phenomenon is increased. Nonetheless, it can be seen that the display quality of the liquid crystal display device has been remarkably improved.

On the other hand, as shown in FIGS. 9A to 9C, the liquid crystal layer 8 has a refractive index anisotropy Δn (550) of 0.060 and 0.12 at a wavelength of 550 nm, respectively.
It can be seen that the viewing angle dependence is not sufficiently improved when the liquid crystal material set to 0 is used.

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

Further, as a result of examining the dependency of the transmittance-liquid crystal applied voltage characteristic on the inclination angle θ by changing the inclination angle θ of the refractive index ellipsoid of the optical phase difference plates 2 and 3, it was found that it was 15 °.
Within the range of ≦ θ ≦ 75 °, regardless of the alignment state of the discotic liquid crystal in the optical retardation plates 2 and 3,
It didn't change basically. It was confirmed that the viewing angle in the opposite viewing angle direction did not widen when the value exceeded the above range.

Further, by changing the second retardation value of the optical phase difference plates 2 and 3 and examining the dependency of the transmittance-liquid crystal applied voltage characteristic on the second retardation value, the second retardation value was obtained. Is 80 nm to 250 nm
Within the range of 1, the change did not basically occur regardless of the alignment state of the discotic liquid crystal in the retardation films 2 and 3. It was confirmed that the viewing angle in the left-right direction was not widened when the range was exceeded.

Further, the comparison sample cell # 103,
Based on the result of the visual test of # 104, the liquid crystal cell 16 of FIG.
In the liquid crystal layer 8 in FIG.
Three sample cells # 19 to # 21 similar to the present example except that the liquid crystal materials of 0 and 0.115 were used were prepared.
The output level of the light receiving element 21 with respect to the applied voltage to the sample cells # 19 to # 21 when the light receiving element 21 is fixed at a constant angle φ by the same method as in the present embodiment using the measurement system shown in FIG. It was measured. In addition, visual confirmation was performed under white light.

As a result, sample cell # 20 having a refractive index anisotropy Δn (550) of 0.100 and sample cell # 2 having a refractive index anisotropy Δn (550) of 0.115.
In No. 1, when the angle was φ50 °, a slight increase in transmittance was confirmed when the voltage was increased in the left-right direction. However, inversion did not occur visually,
This increase in transmittance was acceptable for use. There was no problem in the upward result. on the other hand,
In the sample cell # 19 in which the refractive index anisotropy Δn (550) is 0.065, the comparison sample cell # 10 described above is used.
Similar to 3, when the voltage is increased in the upward direction, the transmittance becomes a curve that sinks and rises once.
Compared with the sample cell # 103 for comparison shown in (a), the degree of increase in transmittance was small, and it was usable. There were no problems with the results in the left-right direction.

Further, in the visual inspection, in the sample cells # 20 and # 21, slight coloring 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 blueness 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 of the surface of the liquid crystal cell 16 in the normal direction during white display was measured. As a result, the comparison sample cell #
In 103, a decrease in transmittance was observed to the 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 to a degree that it could be used.

Further, 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 with respect to the alignment films 11 and 14. Similar results were obtained when liquid crystal materials having an angle of 5 °, 5 °, 10 °, and 11 ° were used for the liquid crystal layer 8, respectively.

(Embodiment 2) This embodiment is a modification of the above embodiment.
For supporting the effect of the liquid crystal display device according to
Here, here, the liquid crystal cell 1 in the liquid crystal display device of FIG.
No. 6 liquid crystal layer 8 has a refractive index anisotropy at a wavelength of 450 nm.
Δn_LAnisotropy of refractive index at (450) and wavelength of 550 nm
Sex Δn_L(550) and the wavelength 45 of the optical phase difference plates 2 and 3
Refractive index anisotropy Δn at 0 nm_F(450) and wavelength 5
Refractive index anisotropy Δn at 50 nm _FExpression with (550)
The relationship represented by (1) is 0, 0.15, respectively.
Liquid crystal material set to 0.25, 0.30, 0.33
Cell thickness (thickness of liquid crystal layer 8) is 5μ using an optical retardation plate.
Prepare 5 sample cells # 31 to # 35 with m
It was

[0207]

[Equation 15]

As the optical retardation 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 tilted. The first retardation value is 0 nm and the second retardation value is 100 nm.
And the direction of the principal refractive index n _b is z in the xyz axis coordinates.
It is inclined with respect to the axial direction in the direction indicated by arrow A to be about 20 °, and similarly the direction of the main refractive index n _c forms an angle of about 20 ° in the direction indicated by arrow B with respect to the x-axis. (That is, the one having an inclination angle of the index ellipsoid θ = 20 °) was used.

As a comparative example to this embodiment, the liquid crystal layer 8 of the liquid crystal cell 16 in the liquid crystal display device of FIG.
The relationship represented by the above formula (1) is 0.35, 1.
Comparative sample cells # 301 to # 303 similar to the present example except that the liquid crystal materials of 0 and 1.1 and the optical retardation plate were used.
Prepared.

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

[0211]

[Table 8]

Regarding the sample cells # 31 to # 33,
Coloring was not confirmed from any direction when the viewing angle was 70 °, and the image quality was good. In the sample cell # 24, coloring was not confirmed in any direction up to a viewing angle of 50 ° and the image quality was good, but at a viewing angle of 60 °, slight coloring was confirmed when viewed from the left and right directions. It was colored enough to withstand use. In sample cell # 25, the viewing angle is 50 °
Up to this point, no coloring was observed in any direction, and the image quality was good, but at a viewing angle of 60 °, coloring was found that was unusable when viewed from the left and right directions.

On the other hand, comparison sample cell # 301
In ~ # 303, even when viewed from the left / right direction even at a viewing angle of 50 °, coloring from yellow to orange, which was unbearable for use, was confirmed.

As the optical retardation plates 2 and 3, sample cells # 31 to # 35 of the present example and comparative sample cells # 301 to # 35 are used, except that a discotic liquid crystal is hybrid-aligned on a transparent support. The same results as above were obtained for the sample cell similar to 303 and the comparative sample cell.

(Example 3) This example is for supporting the effect of the liquid crystal display device according to the above-described third embodiment, and here, here, the liquid crystal layer of the liquid crystal cell 16 in the liquid crystal display device of FIG. 8 shows the refractive index anisotropy Δn _L (550) at a wavelength of 550 nm, the refractive index anisotropy Δn _L (650) at a wavelength of 650 nm, and the wavelength 5 of the optical retardation plates 2 and 3.
Relationship represented by formula (2) between the refractive index anisotropy [Delta] n _F (650) in the refractive index anisotropy [Delta] n _F (550) and wavelength 650nm at 50nm, respectively, 0, 0.1
Five sample cells # 41 to # 45 having a cell thickness (thickness of the liquid crystal layer 8) of 5 μm using a liquid crystal material set to 0, 0.20, 0.23 and 0.25 and an optical retardation plate. Prepared.

[0216]

[Equation 16]

As the optical retardation plates 2 and 3 in the sample cells # 41 to # 45, a discotic liquid crystal is applied to a transparent support (eg, triacetyl cellulose (TAC)) and the discotic liquid crystal is tilted. The first retardation value is 0 nm and the second retardation value is 100 nm.
And the direction of the principal refractive index n _b is z in the xyz axis coordinates.
It is inclined with respect to the axial direction in the direction indicated by arrow A to be about 20 °, and similarly the direction of the main refractive index n _c forms an angle of about 20 ° in the direction indicated by arrow B with respect to the x-axis. (That is, the one having an inclination angle of the index ellipsoid θ = 20 °) was used.

As a comparative example to this embodiment, the liquid crystal layer 8 of the liquid crystal cell 16 in the liquid crystal display device of FIG.
The relationship represented by the above equation (2) is 0.27, 1.
Comparative sample cells # 401 to # 403 similar to this example except that the liquid crystal materials of 0 and 1.1 and the optical retardation plate were used.
Prepared.

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

[0220]

[Table 9]

Regarding the sample cells # 41 to # 43,
Coloring was not confirmed from any direction when the viewing angle was 70 °, and the image quality was good. In sample cell # 44, coloring was not confirmed from any direction up to a viewing angle of 50 ° and the image quality was good, but at a viewing angle of 60 °, slight coloring was confirmed when viewed from the left and right directions. It was colored enough to withstand use. In sample cell # 45, the viewing angle is 50 °
As a result, some coloration was confirmed when viewed from the left and right directions, but it was coloration that could be used.

On the other hand, comparison sample cell # 401
In # 403, coloring from yellow to orange, which is unbearable for use, was confirmed even when viewed from the left and right even at a viewing angle of 50 °.

Also, as the optical retardation plates 2 and 3, sample cells # 41 to # 45 of the present example and comparative sample cells # 401 to # 40 are used, except that a discotic liquid crystal is hybrid-aligned on a transparent support. The same results as above were obtained for the sample cell similar to 403 and the sample cell for comparison.

[0224]

As described above, the first liquid crystal display device according to the present invention is twisted by approximately 90 ° between a pair of translucent substrates each having a transparent electrode layer and an alignment film formed on opposing surfaces. And a liquid crystal display element in which a liquid crystal layer oriented is enclosed.
A pair of polarizers arranged on both sides of the liquid crystal display element,
At least one optical retarder interposed between the liquid crystal display device and the polarizer, wherein the three main refractive indices n _a , n _b , and n _{c of the} index ellipsoid are 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 an axis, and the main refractive index n in the surface. an optical retardation plate in which the refractive index ellipsoid is inclined by tilting clockwise or counterclockwise with respect to the direction of _c or n _a , and the wavelength of the liquid crystal material in the liquid crystal layer. Refractive index anisotropy Δn _L (450) and wavelength 550 for light of 450 nm
Δn _L (450) / Δn _L (550), which is the ratio of the refractive index anisotropy Δn _L (550) to the light having a wavelength of 450 nm, and the refractive index anisotropy Δ of the optical retardation plate with respect to the light having a wavelength of 450 nm.
Δn _F (450) / Δ, which is the ratio of n _F (450) and refractive index anisotropy Δn _F (550) for light with a wavelength of 550 nm
n _F (550) is

[0225]

[Equation 17]

It is characterized in that it is set so as to satisfy the relationship of.

As a more preferable structure,

[0228]

[Equation 18]

It is characterized in that it is set so as to satisfy the relationship of.

The second liquid crystal display device according to the present invention is opposed to
A transparent electrode layer and an alignment film were formed on the surface
Liquid crystal in which a pair of translucent substrates are twisted and aligned by about 90 °
A liquid crystal display element in which a layer is enclosed, and the above liquid crystal display element
A pair of polarizers arranged on both sides of the liquid crystal display device,
And at least one optical position interposed between the above-mentioned polarizer and
It is a phase difference plate and has three main refractive indices n of an index ellipsoid._a,
n_b, N_cIs n_a= N _c> N_bHas a relationship with the surface
Principal refractive index n_aOr n_cThe axis of the direction of
Principal refractive index n parallel to the normal direction_bDirection and the main bending in the surface
Folding rate n_cOr n_aIs clockwise or counterclockwise
By tilting around the meter, the index ellipsoid is tilted.
An oblique optical retardation plate, and
Refractive index of liquid crystal material for 650 nm wavelength light
Anisotropy Δn_L(650) and for light with a wavelength of 550 nm
Refractive index anisotropy Δn_LΔn, which is the ratio of (550)_L(65
0) / Δn_L(550) and the wavelength 6 of the optical retardation plate
Refractive index anisotropy Δn for light of 50 nm_F(650) and
Refractive index anisotropy Δn for light with a wavelength of 550 nm_F(55
Δn, which is the ratio of 0)_F(650) / Δn_F(550) and
But,

[0231]

[Formula 19]

It is characterized in that it is set so as to satisfy the relationship of.

As a more preferable structure,

[0234]

[Equation 20]

It is characterized in that it is set so as to satisfy the relationship of.

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

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

Further, in each of the liquid crystal display devices according to the above-mentioned invention, the wavelength of the liquid crystal material in the liquid crystal layer is 550 n.
The refractive index anisotropy Δn (550) for light of m is 0.0
It is preferably set to a range larger than 60 and smaller than 0.120.

As a result, since the phase difference corresponding to the viewing angle generated in the liquid crystal display element can be eliminated, not only the coloring phenomenon that occurs depending on the viewing angle on the display screen, but also the contrast change and the inversion phenomenon in the left and right direction. Etc. can be further improved.

Further, in this case, the refractive index anisotropy Δn (5
50) is preferably set in the range of 0.070 to 0.095.

As a result, it is possible to further improve the contrast change, the inversion phenomenon in the left-right direction, and the like which occur depending on the viewing angle.

Further, in each of the liquid crystal display devices according to the present invention described above, it is preferable that the tilt angle of the refractive index ellipsoid is set between 15 ° and 75 ° in all the retardation plates.

As described above, in all the optical retardation plates interposed in the liquid crystal display device, the tilt angle of the index ellipsoid is set to 1.
By setting the angle between 5 ° and 75 °, it is possible to surely obtain the function of compensating for the phase difference by the above-described optical retardation plate of the present invention and surely improve the visibility.

In each of the liquid crystal display devices according to the present invention described above, the difference between the main refractive index n _a and the main refractive index n _b and the thickness d of the optical phase difference plate in all the optical phase difference plates. product (n _a -n _b) × d and is preferably set between the 250nm from 80 nm.

Thus, in all the optical retardation plates interposed in the liquid crystal display device, the main refractive index n _a and the main refractive index n
and the difference is _b, the product of the thickness d of the optical retardation plate (n _a -
By setting n _b ) × d between 80 nm and 250 nm, it is possible to reliably obtain the function of compensating for the phase difference by the above-described optical retardation plate of the present invention, and surely improve the visibility. obtain.

[Brief description of drawings]

FIG. 1 is an exploded cross-sectional view showing a configuration of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a rubbing direction of an alignment film and a normal viewing angle direction in the liquid crystal display device.

FIG. 3 is a perspective view showing a main refractive index of an optical retardation plate of the liquid crystal display device.

FIG. 4 is a perspective view showing an optical arrangement of a polarizing plate and an optical retardation plate in the liquid crystal display device by disassembling each part of the liquid crystal display device.

FIG. 5 is an explanatory diagram showing a pretilt angle which is an angle formed by a long axis of liquid crystal molecules and an alignment film.

FIG. 6 is a perspective view showing a measuring system for measuring the viewing angle dependence of the liquid crystal display device.

FIG. 7 is a graph showing transmittance-liquid crystal applied voltage characteristics of Comparative Example 1 and a liquid crystal display device of Comparative Example with respect to Comparative Example 1.

FIG. 8 is a graph showing transmittance-liquid crystal applied voltage characteristics of the liquid crystal display device in Example 1.

9 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.

FIG. 10 shows Δn (λ) / with respect to wavelengths of one liquid crystal material and one optical retardation plate used for the liquid crystal layer of the liquid crystal display device.
It is a graph which shows (DELTA) n (550).

FIG. 11 is a schematic diagram showing twisted alignment of liquid crystal molecules in a TN liquid crystal display device.

[Explanation of symbols]

1 Liquid crystal display element 2.3 Optical retarder 4.5 Polarizing plate (polarizer) 8 Liquid crystal layer 9 ・ 12 Glass substrate (translucent substrate) 10 ・ 13 Transparent electrode (transparent electrode layer) 11.14 Alignment film

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H049 BA02 BA06 BA42 BB03 BB49                       BC02 BC05 BC22                 2H088 HA06 HA08 HA15 HA16 HA18                       JA05 JA13 KA05 KA06 KA07                       KA14 KA29 KA30 MA02 MA07                 2H091 FA08X FA08Z FA11X FA11Z                       FA12X FA12Z FB02 FB06                       GA11 GA13 HA07 HA10 KA01                       KA02 KA05 KA10 LA17 LA19                       LA20

Claims (8)

[Claims] 1. A transparent electrode layer and an alignment film are provided on opposite surfaces.
A twist of approximately 90 ° is formed between each pair of translucent substrates formed.
A liquid crystal display element in which a twisted and aligned liquid crystal layer is enclosed, A pair of polarizers arranged on both sides of the liquid crystal display element, At least one sheet between the liquid crystal display element and the polarizer
An optical phase difference plate interposed between the three optical index ellipsoids.
Principal refractive index n of_a, N_b, N_cIs n_a= N_c> N _bSay
Have a relationship and the principal refractive index n in the surface_aOr n_cThe direction of
A principal refractive index n parallel to the surface normal direction as an axis_bDirection
And the main refractive index n in the surface_cOr n_aThe direction of
Or by tilting counterclockwise,
An optical phase difference plate having a tilted index ellipsoid, In addition, the liquid crystal material in the liquid crystal layer has a wavelength of 450 nm.
Refractive index anisotropy Δn of light_L(450) and wavelength 55
Refractive index anisotropy Δn for 0 nm light_LRatio of (550)
Δn_L(450) / Δn_L(550) and the light
Refractive Index Anisotropy of Optical Retardation Plate for 450 nm Wavelength
Δn_F(450) and the refractive index for light with a wavelength of 550 nm
Anisotropy Δn_FΔn, which is the ratio of (550)_F(450) /
Δn_F(550) [Equation 1] Is set to satisfy the relationship of
Liquid crystal display device. 2. The wavelength 450 of the liquid crystal material in the liquid crystal layer.
refractive index anisotropy ΔnL (450) for wavelength of 550 nm and refractive index anisotropy ΔnL (550) for wavelength of 550 nm
ΔnL (450) / ΔnL (550), which is the ratio of ΔnL (450) / ΔnL (550), and the refractive index anisotropy ΔnF (450) of light having a wavelength of 450 nm, and the refractive index anisotropy ΔnF (550) of light having a wavelength of 550 nm. The ratio of ΔnF (45
0) / ΔnF (550) is given by The liquid crystal display device according to claim 1, wherein the liquid crystal display device is set so as to satisfy the relationship of. 3. A transparent electrode layer and an alignment film are provided on opposite surfaces.
A twist of approximately 90 ° is formed between each pair of translucent substrates formed.
A liquid crystal display element in which a twisted and aligned liquid crystal layer is enclosed, A pair of polarizers arranged on both sides of the liquid crystal display element, At least one sheet between the liquid crystal display element and the polarizer
An optical phase difference plate interposed between the three optical index ellipsoids.
Principal refractive index n of_a, N_b, N_cIs n_a= N_c> N _bSay
Have a relationship and the principal refractive index n in the surface_aOr n_cThe direction of
A principal refractive index n parallel to the surface normal direction as an axis_bDirection
And the main refractive index n in the surface_cOr n_aThe direction of
Or by tilting counterclockwise,
An optical phase difference plate having a tilted index ellipsoid, The wavelength of the liquid crystal material in the liquid crystal layer is 650 nm.
Refractive index anisotropy Δn of light_L(650) and wavelength 55
Refractive index anisotropy Δn for 0 nm light_LRatio of (550)
Δn_L(650) / Δn_L(550) and the light
Refractive index anisotropy of retardation plate for light with wavelength of 650 nm
Δn_F(650) and the refractive index for light with a wavelength of 550 nm
Anisotropy Δn_FΔn, which is the ratio of (550)_F(650) /
Δn_F(550) [Equation 3] Is set to satisfy the relationship of
Liquid crystal display device. 4. The wavelength 650 of the liquid crystal material in the liquid crystal layer.
anisotropy Δn _L (650) for light of wavelength nm and anisotropy Δn _L (550) for light of wavelength 550 nm
Δn _L (650) / Δn _L (550), which is the ratio of Δn _L (650) / Δn _L (550), and the refractive index anisotropy Δn _F (650) of the optical retardation plate with respect to light having a wavelength of 650 nm and the refractive index anisotropy Δn of light with wavelength of 550 nm. Δn _F (65 which is the ratio of _F (550)
0) / Δn _F (550) is given by The liquid crystal display device according to claim 3, wherein the liquid crystal display device is set so as to satisfy the relationship of. 5. The wavelength 55 of the liquid crystal material in the liquid crystal layer.
The refractive index anisotropy Δn (550) for 0 nm light is
The liquid crystal display device according to any one of claims 1 to 4, wherein the liquid crystal display device is set in a range larger than 0.060 and smaller than 0.120. 6. The wavelength 55 of the liquid crystal material in the liquid crystal layer.
The refractive index anisotropy Δn (550) for 0 nm light is
The liquid crystal display device according to claim 5, wherein the liquid crystal display device is set in a range of 0.070 to 0.095. 7. The liquid crystal according to claim 1, wherein the tilt angle of the refractive index ellipsoid is set between 15 ° and 75 ° in all the optical retardation plates. Display device. 8. A main refractive index n in all optical retardation plates.
The product (n _a −n _b ) × d of the difference between _a and the main refractive index n _b and the thickness d of the optical retardation plate is set between 80 nm and 250 nm. Item 7. The liquid crystal display device according to any one of items 1 to 6.