JP3770400B2 - Liquid crystal display - Google Patents

Description

The present invention relates to a liquid crystal display device in which the viewing angle of a display screen is improved by combining a liquid crystal display element and a phase difference element having optical anisotropy.

Conventionally, liquid crystal display devices using nematic liquid crystals have been widely used in numerical segment type display devices such as watches and calculators, but recently they are also used in word processors, notebook personal computers, in-vehicle liquid crystal televisions and the like. It has become.

In general, this liquid crystal display device has a pair of translucent substrates disposed opposite to each other with a liquid crystal layer interposed therebetween, and electrode wirings for turning pixels on and off are formed on the substrate. Yes. For example, in an active matrix liquid crystal display device, pixel electrodes for applying a voltage to liquid crystal are provided in a matrix, and active elements such as field effect transistors are used as switching means for selectively applying a potential to each pixel electrode. Is provided on the substrate together with the electrode wiring. Further, in a liquid crystal display device that performs color display, color filter layers such as red, green, and blue are provided on a substrate.

In such a liquid crystal display device, a different display method is appropriately selected and used depending on the twist angle of the liquid crystal. Among them, for example, an active drive type twisted nematic liquid crystal display system (hereinafter referred to as TN system) and a multiplex drive type super twisted nematic liquid crystal display system (hereinafter referred to as STN system) are well known.

In the former TN system, nematic liquid crystal molecules are aligned in a state twisted by 90 ° between a pair of substrates, and display is performed by guiding light along the twisted direction.
In the latter STN method, the twist angle of nematic liquid crystal molecules is set to 90 between a pair of substrates.
This is based on the fact that the light transmittance in the vicinity of the threshold value of the applied voltage of the liquid crystal changes abruptly when the angle is larger than °.

Among these display methods, the STN method uses the birefringence effect of the liquid crystal, so that a color unique to the background of the display screen occurs due to color interference. Conventionally, it has been considered effective to use an optical compensator in order to prevent such coloring and perform monochrome display by the STN method. Display systems using this optical compensator are roughly classified into a double super twist nematic phase compensation system (hereinafter referred to as a DSTN system) and a film type phase compensation system (hereinafter referred to as a film addition type system).

The DSTN system has a structure having a liquid crystal cell having two layers of a display liquid crystal cell and a liquid crystal cell twisted and oriented at a twist angle opposite to that of the display liquid crystal cell. And a structure in which a film having optical anisotropy is arranged. From the viewpoint of light weight and low cost, the film addition type is considered to be effective.

In the STN method, the monochrome display characteristics are improved by adopting these phase compensation methods, and therefore, a color STN liquid crystal display device in which a color display is possible by providing a color filter layer is realized.

On the other hand, the TN system is roughly divided into a normally black system and a normally white system.

In the former normally black method, a pair of polarizing plates are arranged so that their polarization directions are parallel to each other across both sides of the liquid crystal display element, and black is applied in the state where no on-voltage is applied to the liquid crystal layer (off state). Is a method for displaying. The latter normally white system is a system in which a pair of polarizing plates are arranged with their polarization directions orthogonal to each other across both sides of the liquid crystal display element, and white is displayed in an off state on the liquid crystal layer. Among these, the normally white method is effective from the viewpoint of display contrast, color reproducibility, display angle dependency of display, and the like.

By the way, in the TN liquid crystal display device, the refractive index anisotropy Δn exists in the liquid crystal molecules, and the liquid crystal molecules are inclined with respect to the upper and lower substrates. There is a problem that the contrast of the display image changes depending on the viewing direction and viewing angle of the display screen, and the viewing angle dependency increases. This problem will be described below.

FIG. 8 schematically shows a cross-sectional structure of a TN liquid crystal display element 31.
A voltage of halftone display is applied to the liquid crystal layer, and the liquid crystal molecules 32 are slightly raised.

In this liquid crystal display element 31, linearly polarized light 35 that passes in the normal direction of the surfaces of the pair of substrates 33 and 34, and linearly polarized light 36 that passes with an inclination with respect to the normal direction.
, 37 have different angles at which the liquid crystal molecules 32 intersect. Here, the liquid crystal molecules 32
Since there is a refractive index anisotropy Δn, normal light and extraordinary light are generated when each linearly polarized light 35, 36, 37 passes through the liquid crystal molecules 32, and is converted into elliptically polarized light according to their phase difference. Therefore, this causes the generation of viewing angle dependency.

Furthermore, in the actual liquid crystal layer, the tilt angle of the liquid crystal molecules 32 is different between the vicinity of the intermediate portion between the substrates 33 and 34 and the vicinity of the substrates 33 and 34, and the normal direction of the substrate surface is taken as the axis. Since the liquid crystal molecules 32 are in a state of being twisted by 90 °, these also cause viewing angle dependency.

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

For example, when the viewing angle is tilted from the normal direction of the screen to the normal viewing angle direction (downward direction of the screen), a phenomenon in which the display screen is colored at a certain angle or more (hereinafter referred to as a coloring phenomenon) or a phenomenon in which black and white is reversed (hereinafter referred to as a coloring phenomenon) , Referred to as a reversal phenomenon). Further, when the viewing angle is tilted from the screen normal direction to the counter viewing angle direction (upward direction of the screen), the contrast rapidly decreases.

Further, the above-described liquid crystal display device has a problem that the viewing angle becomes narrower as the display screen becomes larger. For example, when a large liquid crystal display screen is viewed from the front direction at a short distance, the displayed colors may be different between the upper part and the lower part of the screen due to viewing angle dependency. This is because, when the display screen is enlarged, the prospective angle for viewing the entire screen is increased, which is the same as viewing the display screen from an oblique direction.

In order to improve the viewing angle dependency in such a TN system, a retardation plate (or retardation film) as an optical element (retardation element) having optical anisotropy is provided between the liquid crystal display element and the polarizing plate. A method of arranging in is proposed.

In this method, light that has been converted from linearly polarized light to elliptically polarized light through liquid crystal molecules having refractive index anisotropy passes through a retardation plate provided on one or both sides of a liquid crystal layer having refractive index anisotropy. Let As a result, a change in phase difference between normal light and extraordinary light generated according to the viewing angle can be compensated and reconverted into linearly polarized light, so that viewing angle dependency can be improved.

For example, JP-A-5-313159 discloses a refractive index ellipsoid 1 as a retardation plate.
A method has been proposed in which two main refractive index directions are made parallel to the normal direction of the surface of the retardation plate. However, even if this retardation plate is used, there is a limit to improving the reversal phenomenon in the normal viewing angle direction.

Japanese Patent Laid-Open No. 6-75116 proposes a method using a retardation plate in which the main refractive index direction of the refractive index ellipsoid is inclined with respect to the normal direction of the surface of the retardation plate. . Here, the following two types of retardation plates are listed.

One of the three main refractive indexes of the refractive index ellipsoid of the retardation plate is such that the direction of the minimum main refractive index is parallel to the surface of the retardation plate, and the remaining two main refractive indexes are One direction is inclined at an angle θ with respect to the surface of the phase difference plate, and the other direction is inclined at an angle θ with respect to the normal direction of the surface of the phase difference plate, so that the value of θ is 20 ° ≦ θ ≦ 70 °.

The other is that the three main refractive indexes na, nb and nc of the refractive index ellipsoid of the retardation plate are na = nc> nb, and the direction of the main refractive index na or nc parallel to the surface of the retardation plate is set. As the axis, the direction of the main refractive index nb is inclined clockwise or counterclockwise from the normal direction of the surface, and the direction of the main refractive index nc or na is inclined clockwise or counterclockwise from the direction parallel to the surface. It is a phase difference plate in which the refractive index ellipsoid is inclined.

Of these two types of retardation plates, the former can be uniaxial and biaxial. The latter may use only one such retardation plate,
Further, two retardation plates can be used in combination such that the inclination directions of the respective main refractive indexes nb make an angle of 90 ° with each other.

By disposing at least one retardation plate between the liquid crystal display element and the polarizing plate, the contrast change, coloring phenomenon, and inversion phenomenon that occur depending on the viewing angle of the display image are improved to some extent. be able to.

Furthermore, in Japanese Patent Laid-Open No. 8-101381, among the above two types of retardation plates,
In a liquid crystal display device using the latter, a method for improving the viewing angle characteristics of the display color by reducing the wavelength dispersion of the refractive index anisotropy of the phase difference plate compared to the wavelength dispersion of the refractive index anisotropy of the liquid crystal is proposed. Has been. Japanese Patent Laid-Open No. 5-215912 discloses a liquid crystal display device using a conventional retardation plate that does not tilt the refractive index ellipsoid, and the wavelength dispersion of the refractive index anisotropy of the retardation plate is different from that of the liquid crystal. There has been proposed a method for improving the viewing angle characteristics by reducing the chromatic dispersion compared to the isotropic wavelength dispersion.

Here, as a method of adjusting the wavelength dispersion of the retardation plate, there are a method of changing the material of the retardation plate and a method of adjusting the thickness of the retardation plate.

Under the circumstances where a liquid crystal display device having a wide viewing angle and a high display quality is desired as in the present day, further improvement in viewing angle dependency is required.
It is not always sufficient to use only the phase difference plate disclosed in Japanese Patent No. 116.

On the other hand, in the methods disclosed in JP-A-8-101381 and JP-A-5-215912, there is a limit to the materials that can be used as the phase difference plate. Therefore, a phase difference made of a material having an appropriate wavelength dispersion is used. The board is not realistic. Further, if the thickness of the retardation plate is increased, the phase difference changes due to the change in the optical path length and the change in the refractive index ellipsoid when the viewing angle is tilted. Furthermore, this method has not yet improved the coloring phenomenon of the display screen when the viewing angle is tilted, and there is still room for improvement.

The present invention has been made to solve the above-described problems of the prior art, and further improves contrast change, coloring phenomenon, inversion phenomenon, etc. that occur depending on the viewing angle. An object of the present invention is to provide a liquid crystal display device capable of effectively improving the coloring phenomenon.

The liquid crystal display device of the present invention includes at least one of a liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film, a pair of polarizers sandwiching both sides of the liquid crystal display element Liquid crystal display device and at least one phase difference element provided between the liquid crystal display elements, the three main refractive indexes na, nb, and nc of the refractive index ellipsoid of the phase difference element are na = nc> nb, and the direction of the main refractive index nb is from the normal direction of the surface with one direction of the main refractive index na and nc approximately parallel to the surface of the retardation element as an axis. Inclining clockwise or counterclockwise, the other direction of the main refractive indexes na and nc is inclined clockwise or counterclockwise from a direction substantially parallel to the surface, and screen coloring depending on the viewing angle In the liquid crystal layer, The combination conditions of the average alkyl chain length of the liquid crystal material, the degree of change of the liquid crystal material with respect to the wavelength of the normal light refractive index no, and the degree of change of the liquid crystal material with respect to the wavelength of the extraordinary light refractive index ne are set. This achieves the above object.

The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is set in a range of m <3.40, and the extraordinary refractive index ne (4) of the liquid crystal material with respect to light having a wavelength of 450 nm.
50), extraordinary refractive index ne (550) and wavelength 65 for light having a wavelength of 550 nm.
The degree of change of the extraordinary refractive index ne (650) with respect to 0 nm light and the wavelength 450 nm
Normal light refractive index no (450) for light of 550 nm, normal light refractive index no (550) for light of wavelength 550 nm, and normal light refractive index no (65) for light of wavelength 650 nm.
The degree of change of 0)
1 ≦ ((((no (450) −no (550)) / (no (550) −no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.422 m + 2.55
It may be set in the range.

The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; Normal light refractive index no (450) for light having a wavelength of 450 nm, normal light refractive index no for light having a wavelength of 550 nm
(550) and the degree of change of the normal light refractive index no (650) with respect to light having a wavelength of 650 nm,
1 ≦ ((((no (450) −no (550)) / (no (550) −no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.343m + 2.26
It is preferable that the range is set.

The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is 3.40 ≦ m ≦ 3.
. The extraordinary refractive index ne (450) for light having a wavelength of 450 nm, the extraordinary refractive index ne (550) for light having a wavelength of 550 nm, and the extraordinary refractive index ne for light having a wavelength of 650 nm. 650), normal light refractive index no (450) for light with a wavelength of 450 nm, normal light refractive index no (550) for light with a wavelength of 550 nm, and changes in normal light refractive index no (650) for light with a wavelength of 650 nm. The degree is
0.80 ≦ (((no (450) −no (550)) / (no (550) −n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) ≤ 1.20
It may be set in the range.

The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; Normal light refractive index no (450) for light having a wavelength of 450 nm, normal light refractive index no for light having a wavelength of 550 nm
(550) and the degree of change of the normal light refractive index no (650) with respect to light having a wavelength of 650 nm,
0.85 <((((no (450) -no (550)) / (no (550) -n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) <1.15
It is preferable that the range is set.

The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is set in a range of m> 3.90, and the extraordinary refractive index ne (4) of the liquid crystal material with respect to light having a wavelength of 450 nm.
50), extraordinary refractive index ne (550) and wavelength 65 for light having a wavelength of 550 nm.
The degree of change of the extraordinary refractive index ne (650) with respect to 0 nm light and the wavelength 450 nm
Normal light refractive index no (450) for light of 550 nm, normal light refractive index no (550) for light of wavelength 550 nm, and normal light refractive index no (65) for light of wavelength 650 nm.
The degree of change of 0)
−0.422 m + 2.55 ≦ (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
It may be set in the range.

The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; Normal light refractive index no (450) for light having a wavelength of 450 nm, normal light refractive index no for light having a wavelength of 550 nm
(550) and the degree of change of the normal light refractive index no (650) with respect to light having a wavelength of 650 nm,
−0.343m + 2.26 ≦ (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
It is preferable that the range is set.

The refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm is 0.
. It is preferably set in a range larger than 060 and smaller than 0.120.

The refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm is 0.
. It is preferably set in the range of 070 or more and 0.095 or less.

The inclination angle of the refractive index ellipsoid in the retardation element is preferably set in the range of 15 ° to 75 °.

The product (na−nb) × d of the difference between the main refractive indexes na and nb of the retardation element and the thickness d of the retardation element is preferably set in the range of 80 nm to 250 nm.

  Hereinafter, the background to the completion of the present invention and the operation of the present invention will be described.

In the present invention, the three main refractive indexes na, nb, and nc of the refractive index ellipsoid of the retardation element have a relationship of na = nc> nb, and the main refractive index is substantially parallel to the surface of the retardation element. The direction of the main refractive index nb is inclined clockwise or counterclockwise from the normal direction of the surface with one direction of na and nc as an axis, and the other direction of the main refractive indexes na and nc is on the surface. The refractive index ellipsoid of the phase difference element is tilted by tilting clockwise or counterclockwise from a substantially parallel direction. When linearly polarized light passes through a liquid crystal layer having birefringence and normal light and extraordinary light are generated, the passing light is changed to elliptically polarized light with the phase difference. The phase difference from the extraordinary light is compensated.

However, only the compensation function of such a retardation plate cannot sufficiently satisfy the demand for further improvement in viewing angle dependency.

Therefore, as a result of repeated research, the inventors of the present application have found that in the liquid crystal layer sealed in the liquid crystal display element, the average alkyl chain length of the liquid crystal material, the degree of change of the normal light refractive index no of the liquid crystal material with respect to the wavelength, and the liquid crystal material It was found that the combination condition of the extraordinary refractive index ne with the degree of change with respect to the wavelength particularly affects the coloring of the liquid crystal display screen, and the present invention has been completed.

In the liquid crystal display device of the present invention, the average alkyl chain length of the liquid crystal material, the degree of change of the liquid crystal material with respect to the wavelength of the normal light refractive index no, and the degree of change of the liquid crystal material with respect to the wavelength of the extraordinary light refractive index ne. The combination condition is set in a range where screen coloring depending on the viewing angle does not occur. As a result, it becomes possible to further prevent coloring of the screen, and as shown in the embodiments described later, contrast change and inversion phenomenon can be further improved compared to the case of only the compensation function of the retardation plate. did it.

The relationship between the average alkyl chain length of the liquid crystal material, the degree of change of the normal light refractive index no of the liquid crystal material with respect to the wavelength, and the degree of change of the abnormal light refractive index ne of the liquid crystal material with respect to the wavelength is
Specifically, the following range is set.

(1) When the length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is m <3.40, the extraordinary refractive index ne (450) for the light of the wavelength 450 nm of the liquid crystal material, the wavelength of 550 nm Change degree of extraordinary refractive index ne (550) for light of 650 nm and extraordinary refractive index ne (650) for light of wavelength 650 nm, normal refractive index no (450) for light of wavelength 450 nm, normal for light of wavelength 550 nm Photorefractive index no
(550) and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm,
1 ≦ ((((no (450) −no (550)) / (no (550) −no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.422 m + 2.55
Set to the range.

In this case, as shown in Embodiment 1 to be described later, although a slight coloration occurs at a viewing angle of 50 ° required for a normal liquid crystal display device, a display that can sufficiently withstand use from any direction is obtained. It is done.

More preferably,
1 ≦ ((((no (450) −no (550)) / (no (550) −no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.343m + 2.26
Set to the range.

In this case, as shown in Embodiment 1 described later, in a liquid crystal display device having a wider viewing angle of 70 °, a display having no coloring phenomenon can be obtained from any direction.

(2) The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is 3.40 ≦ m ≦
In the case of 3.90, the extraordinary refractive index ne (4 for the light of wavelength 450 nm of the liquid crystal material.
50), extraordinary refractive index ne (550) and wavelength 65 for light having a wavelength of 550 nm.
The degree of change of the extraordinary refractive index ne (650) with respect to 0 nm light and the wavelength 450 nm
Normal light refractive index no (450) for light of 550 nm, normal light refractive index no (550) for light of wavelength 550 nm, and normal light refractive index no (65) for light of wavelength 650 nm.
0)
0.80 ≦ (((no (450) −no (550)) / (no (550) −n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) ≤ 1.20
Set to the range.

In this case, as shown in Embodiment 2 to be described later, although a slight coloration occurs at a viewing angle of 50 ° required for a normal liquid crystal display device, a display that can sufficiently withstand use from any direction is obtained. It is done.

More preferably,
0.85 <((((no (450) -no (550)) / (no (550) -n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) <1.15
Set to the range.

In this case, as shown in Embodiment 2 described later, in a liquid crystal display device with a wider viewing angle of 70 °, a display without any coloring phenomenon can be obtained from any direction.

(3) When the length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is m> 3.90, the extraordinary refractive index ne (450) for the light with a wavelength of 450 nm of the liquid crystal material, the wavelength of 550 nm Change degree of extraordinary refractive index ne (550) for light of 650 nm and extraordinary refractive index ne (650) for light of wavelength 650 nm, normal refractive index no (450) for light of wavelength 450 nm, normal for light of wavelength 550 nm Photorefractive index no
(550) and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm,
−0.422 m + 2.55 ≦ (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
Set to the range.

In this case, as shown in Embodiment 3 to be described later, although a slight coloration occurs at a viewing angle of 50 ° required for a normal liquid crystal display device, a display that can sufficiently withstand use from any direction is obtained. It is done.

More preferably,
−0.343m + 2.26 ≦ (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
Set to the range.

In this case, as shown in Embodiment 3 described later, in a liquid crystal display device having a wider viewing angle of 70 °, a display without any coloring phenomenon can be obtained from any direction.

In the liquid crystal display device of the present invention, it is preferable that the refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm is set in a range larger than 0.060 and smaller than 0.120. When the refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm, which is in the visible light region, is 0.060 or less or 0.120 or more, it is inverted depending on the viewing angle direction as shown in a fourth embodiment described later. This is because it has been confirmed that a phenomenon and a decrease in contrast ratio occur. The refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm is greater than 0.060 and 0.120.
By setting a smaller range, the phase difference corresponding to the viewing angle can be eliminated, so the coloring phenomenon that occurs depending on the viewing angle on the liquid crystal display screen is naturally improved, as is the contrast change and the horizontal reversal phenomenon. can do.

Here, the refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm.
Is set in the range of 0.070 or more and 0.095 or less, the phase difference corresponding to the viewing angle can be more effectively eliminated as shown in the fourth embodiment described later.
Therefore, it is possible to reliably improve the coloring phenomenon depending on the viewing angle on the liquid crystal display screen, the contrast change, the horizontal reversal phenomenon, and the like.

In the liquid crystal display device of the present invention, the inclination angle of the refractive index ellipsoid in the retardation element is preferably set in the range of 15 ° to 75 °. By setting the inclination angle of the refractive index ellipsoid of the phase difference element in this way, as shown in Embodiment 4 described later, the phase difference change between the normal light and the abnormal light generated according to the viewing angle is changed. Compensation can be ensured by the phase difference element.

In the liquid crystal display device of the present invention, the product (na−nb) × d of the difference between the main refractive indexes na and nb of the retardation element and the thickness d of the retardation element is in the range of 80 nm to 250 nm. It is preferable to set. Thus, the main refractive indexes na and nb of the phase difference element
By setting the product of the difference between the above and the thickness d of the phase difference element, the change in the phase difference between the normal light and the abnormal light generated according to the above-described viewing angle can be expressed as the phase difference as shown in the fourth embodiment described later. Compensation can be ensured by the element.

As described in detail above, in the case of the present invention, the three main refractive indexes n of the refractive index ellipsoid are shown.
a, nb, and nc have a relationship of na = nc> nb, and the direction of the main refractive index nb is the normal direction of the surface with the direction of one of the main refractive indexes na and nc approximately parallel to the surface as an axis By using a phase difference plate that is inclined clockwise or counterclockwise from the other and whose other direction of the main refractive indexes na and nc is inclined clockwise or counterclockwise from a direction substantially parallel to the surface. A change in phase difference of the display element can be compensated. In addition, the viewing angle of the combination condition of the average alkyl chain length of the liquid crystal material of the liquid crystal layer, the degree of change of the normal light refractive index no of the liquid crystal material with respect to the wavelength, and the degree of change of the abnormal light refractive index ne of the liquid crystal material with respect to the wavelength It is possible to further prevent the coloration of the liquid crystal display screen depending on the viewing angle by setting it in a range in which the screen coloring depending on the display does not occur. This can be further improved as compared with the case of only the compensation function of the retardation plate.

In particular, at a viewing angle of 50 ° required for a normal liquid crystal display device, it is possible to suppress coloration of the liquid crystal display screen to such an extent that it can be sufficiently used when viewed from all directions.

Furthermore, according to the present invention , in a liquid crystal display device having a wider viewing angle of 70 °, it is possible to realize a state where the liquid crystal display screen has no coloring phenomenon when viewed from any direction.

Therefore, according to the present invention, since the contrast ratio in black and white display is not influenced by the viewing angle direction of the observer, the quality of the display image of the liquid crystal display device can be significantly improved.

Further, in the case of the present invention , the refractive index anisotropy Δn (550) with respect to light having a wavelength of 550 nm is set in a range larger than 0.060 and smaller than 0.120, so that the liquid crystal display element is generated according to the viewing angle. The phase difference can be eliminated. Therefore, the coloring phenomenon that occurs depending on the viewing angle on the liquid crystal display screen can naturally be further improved with respect to contrast change, left-right inversion phenomenon, and the like.

Furthermore, in the case of the present invention, by setting the refractive index anisotropy Δn with a wavelength of 550nm to light a (550) in the range of 0.070 or more 0.095 or less, even more, the phase difference caused depending on the viewing angle Can be effectively eliminated. Therefore, it is possible to more reliably improve the coloring phenomenon that occurs depending on the viewing angle on the liquid crystal display screen, the contrast change, the horizontal reversal phenomenon, and the like.

Further, in the case of the present invention, by setting the inclination angle of the refractive index ellipsoid within the range of 15 ° or more and 75 ° or less, the phase difference compensation function by the phase difference element can be surely obtained. Can be improved with certainty.

Further, according to the present invention, the product (na−nb) × d of the difference between the main refractive indexes na and nb of the phase difference element and the thickness d of the phase difference element is set in the range of 80 nm to 250 nm. As a result, the compensation function of the phase difference by the phase difference element can be obtained with certainty, and the visibility can be improved with certainty.

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

FIG. 1 is a cross-sectional view showing the structure of a liquid crystal display device according to an embodiment of the present invention.
The liquid crystal display device includes a liquid crystal display element 1, a pair of retardation plates 2 and 3, and a pair of polarizing plates 4.
5 and a driving circuit 17 are provided.

In the liquid crystal display element 1, a liquid crystal layer 8 is sandwiched between a pair of electrode substrates 6, 7 arranged to face each other. One 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 on the liquid crystal layer 8 side, and an alignment film 11 is formed thereon. In the other electrode substrate 7, a transparent electrode 13 made of ITO is formed on the surface of the glass substrate (translucent substrate) 12 serving as a base on the liquid crystal layer 8 side, and an alignment film 14 is formed thereon.

Both transparent electrodes 10 and 11 are connected to a drive circuit 17. In FIG. 1, for simplification, a configuration corresponding to two pixels is shown. However, in almost the entire display portion of the liquid crystal display element 1, strip-like transparent electrodes 10 and 13 having a predetermined width are formed on the glass substrates 9 and 12. The transparent electrode 10 on one glass substrate 9 and the transparent electrode 13 on the other glass substrate 10 are formed so as to cross each other (here, orthogonal) when viewed from a direction perpendicular to the substrate surface. ing.

The alignment films 11 and 14 are rubbed in advance so that the liquid crystal molecules in the liquid crystal layer 8 are twisted by about 90 °. The rubbing direction R1 of the alignment film 11 and the rubbing direction R2 of the alignment film 14 are set in directions orthogonal to each other as shown in FIG.

Both electrode substrates 6 and 7 are bonded together by a sealing resin 15, and the electrode substrate 6
, 7 and the sealing resin 15 are enclosed in a liquid crystal layer 8. In addition,
Although details of the liquid crystal layer 8 will be described later, an alkyl chain of the liquid crystal material in the liquid crystal layer 8 and a normal light refractive index so that the best characteristics can be obtained in combination with the retardation compensation function by the retardation plates 2 and 3. The relationship between the change degree with respect to the wavelength of no and the change degree with respect to the wavelength of the extraordinary light refractive index ne is set within a predetermined range.

The retardation plates 2 and 3 are each 1 between the liquid crystal display element 1 and the polarizing plates 4 and 5 on both sides thereof.
It is arranged one by one. The retardation plates 2 and 3 are obtained by cross-linking a discotic liquid crystal with a tilt alignment or a hybrid alignment on a support made of a transparent organic polymer. Thereby, as will be described later, the phase difference plate 2 in which the refractive index ellipsoid is inclined,
3 is obtained.

As a support material for the retardation plates 2 and 3, triacetyl cellulose (TAC) generally used for a polarizing plate is suitable, and a highly reliable retardation plate can be obtained. As other materials, colorless and transparent organic polymer films excellent in environmental resistance and chemical resistance such as polycarbonate (PC) and polyethylene terephthalate (PET) are suitable.

As shown in FIG. 3, the phase difference plates 2 and 3 have different main refractive indexes na, nb,
nc.

The three main refractive indexes na, nb, and nc have a relationship of na = nc> nb.
In this case, since there is only one optical axis, the phase difference plates 2 and 3 are uniaxial, and the refractive index anisotropy is negative.

The direction of the main refractive index na coincides with the y-axis direction parallel to the surfaces of the phase difference plates 2 and 3 (parallel to the screen) of the orthogonal coordinate axes xyz. The direction of the main refractive index nb is from the z-axis direction perpendicular to the surface of the phase difference plates 2 and 3 (normal direction of the surface, perpendicular to the screen) from the direction of the main refractive index na to the direction of the arrow A. θ is inclined. The direction of the main refractive index nc is parallel to the surface of the phase difference plates 2 and 3 with the direction of the main refractive index na as the axis (parallel to the screen).
Inclined θ from the x-axis direction to the arrow B direction. The tilt angle θ of this refractive index ellipsoid
Is preferably 15 ° ≦ θ ≦ 75 °. By setting within this range, the phase difference compensation function by the phase difference plates 2 and 3 can be reliably obtained regardless of whether the refractive index ellipsoid is inclined clockwise or counterclockwise. Here, D is a direction in which the direction of the main refractive index nb that is inclined in the direction in which the phase difference plates 2 and 3 are given anisotropy is projected onto the surface of the phase difference plates 2 and 3.

The first retardation value of the phase difference plates 2 and 3 is expressed by the product (nc−na) × d of the difference between the main refractive indexes na and nc (refractive index anisotropy Δn) and the thickness d of the phase difference element. However, since na = nc, it becomes almost 0 nm. The second retardation value is the product (na−) of the difference between the main refractive indexes na and nb (refractive index anisotropy Δn) and the thickness d of the retardation element.
nb) × d, but is preferably set in the range of 80 nm to 250 nm. By setting within this range, the phase difference compensation function by the phase difference plates 2 and 3 can be reliably obtained.

In an optical anisotropic body such as a liquid crystal or a retardation plate (retardation film), 3
The anisotropy of the main refractive indexes na, nb, and nc in the dimensional direction is represented by a refractive index ellipsoid. The refractive index anisotropy Δn varies depending on the direction from which the refractive index anisotropic body is observed.

In the liquid crystal display device of this embodiment, the liquid crystal display element 1, the phase difference plates 2, 3 and the polarizing plates 4, 5 are arranged as shown in FIG.

The polarizing plate 4 is disposed so that the absorption axis AX1 thereof is parallel to the rubbing direction R1 of the alignment film 11, and the polarizing plate 5 is configured such that the absorption axis AX2 is parallel to the rubbing direction R2 of the alignment film 14. It is arranged to become. In this liquid crystal display device,
Since the rubbing directions R1 and R2 are orthogonal to each other, the absorption axes AX1 and AX2 are also orthogonal to each other.

The phase difference plate 2 has a direction D (D1) shown in FIG.
The retardation film 3 is arranged so that the direction D (D2) shown in FIG. 3 is parallel to the rubbing direction R2 of the alignment film 14.

With the arrangement of the liquid crystal display element 1, the retardation plates 2, 3 and the polarizing plates 4, 5,
A so-called normally white mode liquid crystal display device that transmits white light and displays white when the on voltage is not applied to the liquid crystal layer 8 is obtained.

In addition, about arrangement | positioning of the phase difference plates 2 and 3, only either one of the phase difference plates 2 and 3 may be arrange | positioned on the one side of the liquid crystal display element 1, or both of the phase difference plates 2 and 3 may be arranged. The liquid crystal display element 2 may be arranged so as to overlap one side. Further, it is possible to use three or more retardation plates.

  Next, the liquid crystal layer 8 will be described in detail.

As described above, the alkyl chain of the liquid crystal material in the liquid crystal layer 8 and the normal light refractive index no so that the best characteristics can be obtained in combination with the retardation compensation function by the retardation plates 2 and 3.
The relationship between the degree of change with respect to the wavelength and the degree of change with respect to the wavelength of the extraordinary light refractive index ne is set in a range where coloring depending on the viewing angle does not occur on the display screen.

Specifically, the relationship between the average alkyl chain length of the liquid crystal material, the degree of change of the liquid crystal material with respect to the wavelength of the normal light refractive index no, and the degree of change of the liquid crystal material with respect to the wavelength of the extraordinary light refractive index ne is as follows: It sets so that the conditions of the setting range of at least any one of 1)-(3) may be satisfy | filled.

(1) When the length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is m <3.40, the extraordinary refractive index ne (450) for the light of the wavelength 450 nm of the liquid crystal material, the wavelength of 550 nm Change degree of extraordinary refractive index ne (550) for light of 650 nm and extraordinary refractive index ne (650) for light of wavelength 650 nm, normal refractive index no (450) for light of wavelength 450 nm, normal for light of wavelength 550 nm Photorefractive index no
(550) and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm,
1 ≦ ((((no (450) −no (550)) / (no (550) −no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.422 m + 2.55
Set to the range.

More preferably,
1 ≦ ((((no (450) −no (550)) / (no (550) −no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.343m + 2.26
Set to the range.

(2) The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is 3.40 ≦ m ≦
In the case of 3.90, the extraordinary refractive index ne (4 for the light of wavelength 450 nm of the liquid crystal material.
50), extraordinary refractive index ne (550) and wavelength 65 for light having a wavelength of 550 nm.
The degree of change of the extraordinary refractive index ne (650) with respect to 0 nm light and the wavelength 450 nm
Normal light refractive index no (450) for light of 550 nm, normal light refractive index no (550) for light of wavelength 550 nm, and normal light refractive index no (65) for light of wavelength 650 nm.
0)
0.80 ≦ (((no (450) −no (550)) / (no (550) −n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) ≤ 1.20
Set to the range.

More preferably,
0.85 <((((no (450) -no (550)) / (no (550) -n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) <1.15
Set to the range.

(3) When the length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is m> 3.90, the extraordinary refractive index ne (450) for the light with a wavelength of 450 nm of the liquid crystal material, the wavelength of 550 nm Change degree of extraordinary refractive index ne (550) for light of 650 nm and extraordinary refractive index ne (650) for light of wavelength 650 nm, normal refractive index no (450) for light of wavelength 450 nm, normal for light of wavelength 550 nm Photorefractive index no
(550) and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm,
−0.422 m + 2.55 ≦ (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
Set to the range.

More preferably,
−0.343m + 2.26 ≦ (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
Set to the range.

With this configuration, the liquid crystal display device according to the present embodiment compensates for a phase difference change between normal light and abnormal light generated in the liquid crystal display element 1 according to the viewing angle by using the phase difference plates 2 and 3 and also occurs on the liquid crystal display screen. Coloring depending on the viewing angle can be compensated particularly effectively by the liquid crystal material of the liquid crystal layer 8. Accordingly, the coloring of the display screen depending on the viewing angle is effectively improved, and at the same time, the contrast change and the inversion phenomenon are also improved, so that a high-quality image can be obtained.

The liquid crystal display device of the present invention will be described below with further specific embodiments.

(Embodiment 1)
In the first embodiment, in the liquid crystal display device shown in FIG. 1, a material system represented by the following structural formula is blended as the liquid crystal material of the liquid crystal layer 8, and an average alkyl chain (C _m H _{2m + 1} − ) Where m <3.40 and the wavelength of the liquid crystal material is 450 nm.
Extraordinary refractive index ne (450) for light of 550 nm, extraordinary refractive index ne (550) for light of wavelength 550 nm, and extraordinary refractive index ne (65 of light of wavelength 650 nm).
0) and normal light refractive index no (450) for light having a wavelength of 450 nm,
The degree of change of the normal light refractive index no (550) with respect to light having a wavelength of 550 nm and the degree of change of the normal light refractive index no (650) with respect to light having a wavelength of 650 nm is expressed as 1 ≦ ((((no (450) −no (550))) / (no (550) -no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.422 m + 2.55
The one set in the range was used.

The cell thickness of the liquid crystal cell 16 (thickness of the liquid crystal layer 8) was 5 μm, and five liquid crystal display devices (samples # 11 to # 15) shown in Table 1 below were produced.

As the phase difference plates 2 and 3, a transparent support (for example, triacetyl cellulose (T
AC) etc.) is applied with a discotic liquid crystal, the discotic liquid crystal is tilted and cross-linked, and the first retardation value (nc-na) × d is 0 nm, and the second retardation value (na-nb). ) × d is 100 nm, and the direction of the main refractive index nb shown in FIG. 3 is about 20 from the z-axis direction in the xyz coordinate axis to the direction of the arrow A.
A refractive index ellipsoid having an inclination angle θ of 20 ° and a main refractive index nc of about 20 ° from the x-axis direction in the direction of arrow B was produced.

Further, for comparison, in the liquid crystal display device shown in the liquid crystal display device of FIG.
1> ((((no (450) -no (550))) / (no (550) -no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650))))
Or (((no (450) -no (550)) / (no (550) -no (650
))) / ((Ne (450) -ne (550)) / (ne (550) -ne (6
50))))>-0.422m + 2.55
Two liquid crystal display devices (Comparative Samples # 100 and # 101) shown in Table 1 below were produced in the same manner as in the present embodiment except that the one set in the range was used.

For the above samples # 11 to # 15 and comparative samples # 100 and # 101,
The results of a visual test under white light are shown in Table 1 below. In Table 1 below and Tables 2 and 3 in Embodiments 2 and 3 described later,
F (no (λ), ne (λ) = (((no (450) −no (550)) / (
no (550) -no (650))) / ((ne (450) -ne (550))
/ (Ne (550) -ne (650)))),
○ indicates no coloration, Δ indicates coloration that can withstand use, and x indicates coloration that does not withstand use.

As shown in Table 1, the samples # 13 to # 15 of this embodiment were not colored when viewed from any direction at a viewing angle of 70 °, and good image quality was obtained. Therefore,
1 ≦ ((((no (450) −no (550)) / (no (550) −no (6
50))) / ((ne (450) -ne (550)) / (ne (550) -ne
(650)))) ≦ −0.343m + 2.26
It can be seen that particularly excellent characteristics can be obtained in the range of.

In addition, with respect to Samples # 11 and # 12 of this embodiment, coloring was not confirmed from any direction up to a viewing angle of 50 °, and good image quality was obtained. At a viewing angle of 60 °, slight coloration was observed when viewed from the left and right directions, but the coloration was such that it could be used.

On the other hand, the comparative samples # 100 and # 101 were confirmed to have a yellow to orange color that could not be used when viewed from the left-right direction even at a viewing angle of 50 °.

Further, Sample # 11 to Sample # 15 of this embodiment except that a discotic liquid crystal is applied to a transparent support as the retardation plates 2 and 3 and hybrid alignment is performed.
Similar results were obtained for the liquid crystal display devices manufactured in the same manner as Comparative Samples # 100 and # 101.

(Embodiment 2)
In the second embodiment, in the liquid crystal display device shown in FIG. 1, a material system represented by the following structural formula is blended as the liquid crystal material of the liquid crystal layer 8, and an average alkyl chain (C _m H _{2m + 1} − ) Is 3.40 ≦ m ≦ 3.90, the extraordinary refractive index ne (450) for the light of wavelength 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for the light of wavelength 550 nm, and the wavelength 650 nm. Of the extraordinary light refractive index ne (650) for the light of the normal light and the normal light refractive index no (
450), normal light refractive index no (550) and wavelength 6 for light having a wavelength of 550 nm.
The degree of change in the normal light refractive index no (650) with respect to 50 nm light is 0.80 ≦ (((no (450) −no (550)) / (no (550) −n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) ≤ 1.20
The one set in the range was used.

The cell thickness of the liquid crystal cell 16 was 5 μm, and five liquid crystal display devices (samples # 21 to # 25) shown in Table 2 below were produced.

As the phase difference plates 2 and 3, a transparent support (for example, triacetyl cellulose (T
AC) etc.) is applied with a discotic liquid crystal, the discotic liquid crystal is tilted and cross-linked, and the first retardation value (nc-na) × d is 0 nm, and the second retardation value (na-nb). ) × d is 100 nm, and the direction of the main refractive index nb shown in FIG. 3 is about 20 from the z-axis direction in the xyz coordinate axis to the direction of the arrow A.
A refractive index ellipsoid having an inclination angle θ of 20 ° and a main refractive index nc of about 20 ° from the x-axis direction in the direction of arrow B was produced.

Further, for comparison, in the liquid crystal display device shown in the liquid crystal display device of FIG.
0.80> (((no (450) -no (550)) / (no (550) -n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))
Or (((no (450) -no (550)) / (no (550) -no (650
))) / ((Ne (450) -ne (550)) / (ne (550) -ne (6
50))))> 1.20
Two liquid crystal display devices (Comparative Samples # 200 and # 201) shown in Table 2 below were produced in the same manner as in the present embodiment except that the one set in this range was used.

For the above samples # 21 to # 25 and comparative samples # 200 and # 201,
The results of a visual test under white light are shown in Table 2 below.

As shown in Table 2, the samples # 22 to # 24 of the present embodiment were not colored when viewed from any direction at a viewing angle of 70 °, and good image quality was obtained. Therefore,
0.85 <((((no (450) -no (550)) / (no (550) -n
o (650))) / ((ne (450) -ne (550)) / (ne (550)
-Ne (650))))) <1.15
It can be seen that particularly excellent characteristics can be obtained in the range of.

In addition, for samples # 21 and # 25 of this embodiment, no coloration was observed from any direction up to a viewing angle of 50 °, and good image quality was obtained. At a viewing angle of 60 °, slight coloration was observed when viewed from the left and right directions, but the coloration was such that it could be used.

On the other hand, Comparative Samples # 200 and # 201 were colored yellow to orange so that they could not be used when viewed from the left-right direction even at a viewing angle of 50 °.

Further, Sample # 21 to Sample # 25 of the present embodiment, except that a discotic liquid crystal is applied to a transparent support as the retardation plates 2 and 3 and hybrid alignment is performed.
Similar results were obtained for the liquid crystal display devices manufactured in the same manner as Comparative Samples # 200 and # 201.

(Embodiment 3)
In the third embodiment, in the liquid crystal display device shown in FIG. 1, a material system represented by the following structural formula is blended as the liquid crystal material of the liquid crystal layer 8, and an average alkyl chain (C _m H _{2m + 1} − ) M = 3.90, and the wavelength of the liquid crystal material is 450 nm.
Extraordinary refractive index ne (450) for light of 550 nm, extraordinary refractive index ne (550) for light of wavelength 550 nm, and extraordinary refractive index ne (65 of light of wavelength 650 nm).
0) and normal light refractive index no (450) for light having a wavelength of 450 nm,
The change rate of the normal light refractive index no (550) for light having a wavelength of 550 nm and the normal light refractive index no (650) for light having a wavelength of 650 nm is −0.422 m + 2.55 ≦ ((((no (450) −no (550 )) / (N
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
The one set in the range was used.

The cell thickness of the liquid crystal cell 16 was 5 μm, and five liquid crystal display devices (samples # 31 to # 35) shown in Table 3 below were manufactured.

As the phase difference plates 2 and 3, a transparent support (for example, triacetyl cellulose (T
AC) etc.) is applied with a discotic liquid crystal, the discotic liquid crystal is tilted and cross-linked, and the first retardation value (nc-na) × d is 0 nm, and the second retardation value (na-nb). ) × d is 100 nm, and the direction of the main refractive index nb shown in FIG. 3 is about 20 from the z-axis direction in the xyz coordinate axis to the direction of the arrow A.
A refractive index ellipsoid having an inclination angle θ of 20 ° and a main refractive index nc of about 20 ° from the x-axis direction in the direction of arrow B was produced.

Further, for comparison, in the liquid crystal display device shown in the liquid crystal display device of FIG.
As the liquid crystal material of the liquid crystal layer 8, −0.422 m + 2.55> (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))))
Or (((no (450) -no (550)) / (no (550) -no (650
))) / ((Ne (450) -ne (550)) / (ne (550) -ne (6
50))))> 1
Two liquid crystal display devices (Comparative Samples # 300 and # 301) shown in Table 3 below were produced in the same manner as in the present embodiment except that the one set in this range was used.

For the above samples # 31 to # 35 and comparative samples # 300 and # 301,
The results of a visual test under white light are shown in Table 3 below.

As shown in Table 3 above, the samples # 33 to # 35 of this embodiment were not colored when viewed from any direction at a viewing angle of 70 °, and good image quality was obtained. Therefore,
−0.343m + 2.26 ≦ (((no (450) −no (550)) / (n
o (550) -no (650))) / ((ne (450) -ne (550)) /
(Ne (550) -ne (650)))) ≦ 1
It can be seen that particularly excellent characteristics can be obtained in the range of.

For sample # 31 of this embodiment, no coloration was observed from any direction up to a viewing angle of 50 °, and good image quality was obtained. At a viewing angle of 60 °, there was coloring that could not be used when viewed from the left-right direction.

For sample # 32 of this embodiment, no coloration was observed from any direction up to a viewing angle of 50 °, and good image quality was obtained. At a viewing angle of 60 °, slight coloration was observed when viewed from the left and right directions, but the coloration was such that it could be used.

On the other hand, Comparative Samples # 300 and # 301 were confirmed to have a yellow to orange color that could not be used when viewed from the left and right directions even at a viewing angle of 50 °.

Further, Sample # 31 to Sample # 35 of this embodiment except that a discotic liquid crystal is applied to a transparent support as the retardation plates 2 and 3 and hybrid alignment is performed.
The same results were obtained for the liquid crystal display devices manufactured in the same manner as Comparative Samples # 300 and # 301.

(Embodiment 4)
In the fourth embodiment, in the liquid crystal display device shown in FIG. 1, the refractive index anisotropy Δn (550) with respect to light having a wavelength of 550 nm is set to 0.070 as the liquid crystal material of the liquid crystal layer 8.
Using a material set to 0.080 and 0.095, the cell thickness of the liquid crystal cell 16 is 5 μm.
Three liquid crystal display devices (samples # 41 to # 43) were produced. The average alkyl chain length m and the degree of change of the normal light refractive index no and the degree of change F (no (λ), ne (λ) of the extraordinary light refractive index ne of each sample are as shown in Table 4 below.

As the phase difference plates 2 and 3, the same ones as those in the first embodiment in which discotic liquid crystal is tilted and aligned are used.

Further, for comparison, in the liquid crystal display device shown in the liquid crystal display device of FIG.
Refractive index anisotropy Δn (55 for light having a wavelength of 550 nm as the liquid crystal material of the liquid crystal layer 8
Two liquid crystal display devices (Comparative Samples # 401 and # 402) were produced in the same manner as in the present embodiment, except that a device in which 0) was set to 0.060 and 0.120 was used.

For the above samples # 41 to # 43 and comparative samples # 401 and # 402,
The viewing angle dependency of the liquid crystal display device was measured using a measurement system including the light receiving element 21, the amplifier 22, and the recording device 23 as shown in FIG.

In this measurement system, the liquid crystal cell 16 of the liquid crystal display device has a surface 1 on the glass substrate 9 side.
6a is installed so as to be at the position of the reference plane xy of the orthogonal coordinate axis xyz.

The light receiving element 21 is an element that can receive light with a certain three-dimensional light receiving angle, and is located at a predetermined distance from the coordinate origin in a direction that forms an angle φ (viewing angle) with respect to the z direction perpendicular to the surface 16a of the liquid crystal cell 16. Is arranged.

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

In this measurement system, samples # 41 to # 43 and comparative sample # 401 of this embodiment are used.
, # 402, and the relationship between the voltage applied to each liquid crystal display device and the output level of the light receiving element 21 when the light receiving element 21 is fixed at a certain angle φ was measured.

Here, assuming that the x direction is the lower side of the screen and the y direction is the left side of the screen, the arrangement position of the light receiving element 21 is upward, rightward and leftward so that the angle φ is 50 °. The measurement was carried out by changing each of the above.

The measurement results for the samples # 41 to # 43 of this embodiment are shown in FIGS.
), The measurement results for the comparative samples # 401 and # 402 are shown in FIGS.
c). FIGS. 6A to 6C and FIGS. 7A to 7C are graphs showing the light transmittance (transmittance-liquid crystal applied voltage characteristics) with respect to the voltage applied to each liquid crystal display device. 6 (a) and 7 (a) are the results of measurement from the top of FIG. 2, and FIGS. 6 (b) and 7 (b) are the results of measurement from the right of FIG. Yes, Fig. 6
(C) and FIG.7 (c) are the results of having measured from the left direction of FIG.

6A to 6C, curves L1, L4, and L7 indicated by alternate long and short dash lines indicate Sample # 41 in which the liquid crystal layer 8 uses a liquid crystal material of Δn (550) = 0.070, and is indicated by a solid line. Curves L2, L5, and L8 shown in the liquid crystal layer 8 are Δn (550) = 0.08.
Sample # 42 using a liquid crystal material of 0 is shown, and curves L3, L6, L shown by dotted lines
9 is a sample # 43 using a liquid crystal material of Δn (550) = 0.095 for the liquid crystal layer 8.
Indicates. In FIGS. 7A to 7C, curves L10, L12, and L1 indicated by solid lines
4 is a comparative sample # using a liquid crystal material of Δn (550) = 0.060 for the liquid crystal layer 8
Curves L11, L13, and L15 indicated by 401 are indicated by dotted lines in the liquid crystal layer 8 as Δn (5
50) = 0.120 Comparative sample # 402 using a liquid crystal material is shown.

For the upward transmittance-liquid crystal applied voltage characteristics, sample # 41 of this embodiment is used.
In # 43, as indicated by L1 to L3 in FIG. 6A, it was confirmed that the transmittance was sufficiently lowered as the voltage increased. On the other hand, as shown by L11 in FIG. 7A in the comparative sample # 402, even if the voltage is increased, the transmittance is not sufficiently lowered, and in the comparative sample # 401, it is indicated by L10 in FIG. 7A. Thus, a reversal phenomenon was observed in which the transmittance once decreased after the transmittance once decreased as the voltage increased.

Similarly, with respect to the transmittance in the right direction and the liquid crystal applied voltage characteristics, in samples # 41 to # 43 of this embodiment, as shown by L4 to L6 in FIG. It was confirmed that the rate dropped to almost zero. On the other hand, in the comparative sample # 401, as indicated by L12 in FIG. 7B, the transmittance decreases to almost 0 as the voltage increases, but in the comparative sample # 402, L1 in FIG. 7B.
As shown in FIG. 3, a reversal phenomenon was observed in which the transmittance once decreased and then increased again as the voltage increased.

Similarly, with respect to the transmittance in the left direction-liquid crystal applied voltage characteristics, in samples # 41 to # 43 of this embodiment, as shown by L7 to L9 in FIG. It was confirmed that the rate dropped to almost zero. On the other hand, as shown by L14 in FIG. 7C, in the comparative sample # 401, the transmittance decreases to almost 0 as the voltage increases, but in the comparative sample # 402, L1 in FIG. 7C.
As shown in FIG. 5, a reversal phenomenon was observed in which the transmittance once decreased and then increased again as the voltage increased.

Further, when a visual test was performed under white light on the samples # 41 to # 43 and the comparative samples # 401 and # 402, the samples # 41 to # 43 of the present embodiment were obtained.
For # 43 and comparative sample # 401, no coloration was observed from any direction up to a viewing angle of 50 °, and good image quality was obtained.

On the other hand, in comparison sample # 402, yellow to orange coloring was confirmed when viewed from the left and right directions at a viewing angle of 50 °.

From the above results, the liquid crystal display device of this embodiment (sample) in which the refractive index anisotropy Δn (550) with respect to light having a wavelength of 550 nm is set to 0.070, 0.080, and 0.095 as the liquid crystal material of the liquid crystal layer 8. In # 41 to # 43), FIG. 6 (a) to FIG. 6 (c)
As shown in Fig. 4), when the voltage is applied, the transmittance is sufficiently lowered and the inversion phenomenon is not observed, so the viewing angle is widened, and the coloring phenomenon is not seen, so the display of the liquid crystal display device It can be seen that the quality has improved dramatically.

In contrast, in the liquid crystal display device (comparative samples # 401 and # 402) in which the refractive index anisotropy Δn (550) with respect to light having a wavelength of 550 nm is set to 0.060 and 0.120 as the liquid crystal material of the liquid crystal layer 8. As shown in FIGS. 7A to 7C, it is understood that the viewing angle dependency is not sufficiently improved.

Further, Sample # 41 to Sample # 43 of the present embodiment except that the phase difference plates 2 and 3 are subjected to hybrid alignment by applying a discotic liquid crystal to a transparent support.
The same results were obtained for the liquid crystal display devices manufactured in the same manner as Comparative Samples # 401 and # 402.

As a result of investigating the dependence of the transmittance-liquid crystal applied voltage characteristic on the tilt angle θ by changing the tilt angle θ of the refractive index ellipsoid of the phase difference plates 2 and 3, the range is 15 ° ≦ θ ≦ 75 °. If there were, the same results as described above were obtained basically regardless of the orientation state of the discotic liquid crystal in the phase difference plates 2 and 3. On the other hand, it was confirmed that when the tilt angle is less than 15 ° or exceeds 75 °, the viewing angle in the anti-viewing angle direction is not enlarged.

The second retardation value (na−nb) × d of the retardation plates 2 and 3 was changed, and the dependence of the transmittance-liquid crystal applied voltage characteristic on the second retardation value was examined. If the retardation value is in the range of 80 nm or more and 250 nm or less, regardless of the orientation state of the discotic liquid crystal in the phase difference plates 2 and 3,
Basically the same results as described above were obtained. On the other hand, when the 2nd retardation value was less than 80 nm or exceeded 250 nm, it was confirmed that the viewing angle in a horizontal direction (left-right direction) is not expanded.

Furthermore, based on the result of the visual test of the comparative samples # 401 and # 402, in the liquid crystal display device shown in the liquid crystal display device of FIG. 1, the refractive index anisotropic with respect to light having a wavelength of 550 nm as the liquid crystal material of the liquid crystal layer 8 Property Δn (550) of 0.065, 0.
Three liquid crystal display devices (samples # 44 to # 46) were produced in the same manner as in the present embodiment except that those set to 100 and 0.115 were used.

When these samples # 44 to # 46 are installed in the measurement system shown in FIG. 5 and the light receiving element 21 is fixed at a certain angle φ, the voltage applied to each liquid crystal display device and the light receiving element 2
The relationship with the output level of 1 was measured, and a visual test was performed under white light.

As a result, the refractive index anisotropy Δn (550) for light having a wavelength of 550 nm is 0.1.
In samples # 45 and # 46 of this embodiment set to 00 and 0.115, a slight increase in transmittance was confirmed when the voltage was increased in the left-right direction when the angle φ was 50 °. However, the reversal phenomenon did not occur visually, and such an increase in transmittance could withstand use. In the upward direction, no problem was obtained. On the other hand, refractive index anisotropy Δn for light having a wavelength of 550 nm
In the sample # 44 of the present embodiment in which (550) is set to 0.065, as with the comparative sample # 401 described above, the transmittance once increases after the transmittance decreases once as the voltage is increased in the upward direction. Although there was such a reversal phenomenon, the degree of increase in transmittance was small compared to the comparative sample # 401 (L10) shown in FIG. In the left-right direction, no problem was obtained.

Further, in the visual test, although slight coloring from yellow to orange was confirmed for samples # 45 and # 46 of the present embodiment, the coloring was not problematic. On the other hand, although it was confirmed that sample # 44 of the present embodiment had a slight bluish color, the bluish color was not problematic.

Further, for sample # 44 and comparative sample # 401, a voltage of about 1 V was applied, and the transmittance during white display in the normal direction of the surface of the liquid crystal cell 16 was measured.
As a result, the comparative sample # 401 showed a decrease in transmittance that could not be used. On the other hand, in Sample # 44 of this embodiment, although a slight decrease in transmittance was confirmed, it was enough to withstand use.

It is sectional drawing which shows the structure of the liquid crystal display device which is one Embodiment of this invention. It is a figure which shows the relationship between the rubbing direction and viewing angle direction of the alignment film in the liquid crystal display device of FIG. FIG. 2 is a perspective view showing a direction of a main refractive index of a retardation plate in the liquid crystal display device of FIG. 1. FIG. 2 is a perspective view illustrating an optical arrangement of a liquid crystal display element, a polarizing plate, and a retardation plate in the liquid crystal display device of FIG. 1. 10 is a perspective view showing a measurement system for measuring the viewing angle dependency of the liquid crystal display device of Embodiment 4. FIG. 6 is a graph showing transmittance-liquid crystal applied voltage characteristics of the liquid crystal display device of Embodiment 4. It is a graph which shows the transmittance | permeability-liquid crystal applied voltage characteristic of the liquid crystal display device of a comparative example. It is a schematic diagram which shows the twist orientation of the liquid crystal molecule in a TN liquid crystal display element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display element 2, 3 Phase difference plate 4, 5 Polarizing plate 6, 7 Electrode substrate 8 Liquid crystal layer 9, 12 Translucent substrate 10, 13 Transparent electrode 11, 14 Orientation film 15 Sealing resin 16 Liquid crystal cell 17 Drive circuit

Claims (10)

A liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film;
A pair of polarizers sandwiching both sides of the liquid crystal display element;
In a liquid crystal display device having at least one polarizer and at least one phase difference element provided between the liquid crystal display elements,
Three principal refractive index na of the refractive index ellipsoid of the retardation element, nb and nc are as one axis direction of the retardation generally parallel principal refractive index na and nc on the surface of the device, the main refraction The direction of the refractive index nb is inclined clockwise or counterclockwise from the normal direction of the surface, and the other direction of the main refractive indexes na and nc is inclined clockwise or counterclockwise from the direction substantially parallel to the surface. And
The first retardation value (nc−na) × d is approximately 0 nm, and the second retardation value (nc−nb) × d is in the range of 80 nm to 250 nm, where d is the thickness of the retardation element . And set to
The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is set in a range of m <3.40;
The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; The normal light refractive index no (450) for light having a wavelength of 450 nm, the normal light refractive index no (550) for light having a wavelength of 550 nm, and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm are:
1 ≦ ((no (450) −no (550)) / (no (550) −no (650))) / ((ne (450) −ne (550)) / (ne (550) −ne (650) ))) ≦ −0.422m + 2.55
Liquid crystal display device set in the range. The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; The normal light refractive index no (450) for light having a wavelength of 450 nm, the normal light refractive index no (550) for light having a wavelength of 550 nm, and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm are:
1 ≦ ((no (450) −no (550)) / (no (550) −no (650))) / ((ne (450) −ne (550)) / (ne (550) −ne (650) ))) ≤ -0.343m + 2.26
The liquid crystal display device according to claim 1 , which is set in a range of A liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film;
A pair of polarizers sandwiching both sides of the liquid crystal display element;
In a liquid crystal display device having at least one polarizer and at least one phase difference element provided between the liquid crystal display elements,
Three principal refractive index na of the refractive index ellipsoid of the retardation element, nb and nc are as one axis direction of the retardation generally parallel principal refractive index na and nc on the surface of the device, the main refraction The direction of the refractive index nb is inclined clockwise or counterclockwise from the normal direction of the surface, and the other direction of the main refractive indexes na and nc is inclined clockwise or counterclockwise from the direction substantially parallel to the surface. And
The first retardation value (nc−na) × d is approximately 0 nm, and the second retardation value (nc−nb) × d is in the range of 80 nm to 250 nm, where d is the thickness of the retardation element . And set to
The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is set in the range of 3.40 ≦ m ≦ 3.90,
The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; The normal light refractive index no (450) for light having a wavelength of 450 nm, the normal light refractive index no (550) for light having a wavelength of 550 nm, and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm are:
0.80 ≦ ((no (450) −no (550)) / (no (550) −no (650))) / ((ne (450) −ne (550)) / (ne (550) −ne (650))) ≦ 1.20
Liquid crystal display device set in the range. The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; The normal light refractive index no (450) for light having a wavelength of 450 nm, the normal light refractive index no (550) for light having a wavelength of 550 nm, and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm are:
0.85 <(((no (450) -no (550)) / (no (550) -no (650))) / ((ne (450) -ne (550)) / (ne (550) -ne (650))) <1.15
The liquid crystal display device according to claim 3 , wherein the liquid crystal display device is set in a range of 5. A liquid crystal display element in which a liquid crystal layer is sandwiched between a pair of substrates each having an electrode layer and an alignment film;
A pair of polarizers sandwiching both sides of the liquid crystal display element;
In a liquid crystal display device having at least one polarizer and at least one phase difference element provided between the liquid crystal display elements,
Three principal refractive index na of the refractive index ellipsoid of the retardation element, nb and nc are as one axis direction of the retardation generally parallel principal refractive index na and nc on the surface of the device, the main refraction The direction of the refractive index nb is inclined clockwise or counterclockwise from the normal direction of the surface, and the other direction of the main refractive indexes na and nc is inclined clockwise or counterclockwise from the direction substantially parallel to the surface. And
The first retardation value (nc−na) × d is approximately 0 nm, and the second retardation value (nc−nb) × d is in the range of 80 nm to 250 nm, where d is the thickness of the retardation element . And set to
The length _m of the average alkyl chain (C _m H _{2m + 1} −) of the liquid crystal material is set in a range of m>3.90;
The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; The normal light refractive index no (450) for light having a wavelength of 450 nm, the normal light refractive index no (550) for light having a wavelength of 550 nm, and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm are:
−0.422m + 2.55 ≦ ((no (450) −no (550)) / (no (550) −no (650))) / ((ne (450) −ne (550)) / (ne (550 ) -Ne (650))) ≦ 1
Liquid crystal display device set in the range. The degree of change of the extraordinary refractive index ne (450) for light with a wavelength of 450 nm of the liquid crystal material, the extraordinary refractive index ne (550) for light with a wavelength of 550 nm, and the extraordinary refractive index ne (650) for light with a wavelength of 650 nm; The normal light refractive index no (450) for light having a wavelength of 450 nm, the normal light refractive index no (550) for light having a wavelength of 550 nm, and the degree of change of the normal light refractive index no (650) for light having a wavelength of 650 nm are:
−0.343m + 2.26 ≦ ((no (450) −no (550)) / (no (550) −no (650))) / ((ne (450) −ne (550)) / (ne (550 ) -Ne (650))) ≦ 1
The liquid crystal display device according to claim 5 , which is set in a range of The liquid crystal display according to any one of claims 1 to 6 , wherein a refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm is set in a range larger than 0.060 and smaller than 0.120. apparatus. The liquid crystal display device according to claim 7 , wherein a refractive index anisotropy Δn (550) of the liquid crystal material with respect to light having a wavelength of 550 nm is set in a range of 0.070 or more and 0.095 or less. 9. The liquid crystal display device according to claim 1, wherein an inclination angle of the refractive index ellipsoid in the retardation element is set in a range of 15 ° to 75 °. The liquid crystal layer, the liquid crystal display device according to any one of claims 1 to 9, characterized in that oriented twisted approximately 90 °.

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