JP3235912B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super-twisted nematic type liquid crystal display device (hereinafter referred to as STN-LCD) which is used for a black-and-white display or a color display of a word processor, a personal computer or the like.

[0002]

2. Description of the Related Art In an STN-LCD, display is performed by utilizing the birefringence of a super twisted nematic liquid crystal.
A so-called coloring phenomenon in which green or blue is colored occurs. In order to compensate for this coloring phenomenon, a color compensating plate is generally provided in the STN-LCD.

As a typical example provided with this color compensator,
A two-layer STN-LCD (DSTN-LCD) may be used. In this method, the coloring generated in the display cell of the first layer is color-corrected by using the optical compensation cell of the second layer having a twisted structure in a direction opposite to the twisted structure of the liquid crystal of the first layer. This realizes a colored display.

Further, instead of a liquid crystal cell for optical compensation,
It has been proposed to perform similar optical compensation using a phase difference plate. For example, JP-A-64-519 discloses that
A phase difference plate type STN-LCD has been disclosed in which an achromatic display is achieved by a phase difference plate formed by uniaxially stretching a polymer film such as polyester or polyvinyl alcohol.

FIG. 17 shows an STN-LCD disclosed in the above-mentioned JP-A-64-519. (A) shows the STN-LCD of Example 20, and (b) shows the STN-LCD of Example 21. In these figures, 1
Is a front polarizing plate, 2 is a front retardation plate made of a uniaxially stretched polymer film, 4 is a translucent substrate of the STN liquid crystal panel 10,
Reference numeral 5 denotes a transparent electrode, 6 denotes an alignment film, 7 denotes a nematic liquid crystal layer (STN liquid crystal layer) to which a chiral dopant is added, 9 denotes a backside retardation plate made of a uniaxially stretched polymer film, and 8 denotes a backside polarizing plate. Also, STN-LC shown in these figures
In D, light is applied to the liquid crystal panel 10 from the rear polarizing plate 8 side.
Incident on. In the STN-LCD of Example 20, one retardation plate made of a uniaxial polymer film is disposed on the front surface of the STN liquid crystal panel.
In an LCD, the retardation plates are arranged one by one on the front and back surfaces of the STN liquid crystal panel.

Further, in Examples 31 to 34 of the above-mentioned Japanese Patent Application Laid-Open No. 64-519, in order to perform optical compensation, a reverse twist structure of 210 to 360 degrees is used instead of a phase difference plate. There is described a configuration in which one liquid crystal polymer film composed of a polypeptide-polymethyl methacrylate mixed film exhibiting a cholesteric phase is disposed on the front surface of an STN liquid crystal panel.

[0007]

However, in the conventional two-layer STN-LCD, two liquid crystal cells, a display cell and a compensation cell, are required.
Compared with D, there is a problem that the entire STN-LCD becomes thicker and the weight increases.

[0008] In addition, as shown in FIG. 17, in a system in which a retardation plate made of a uniaxially stretched polymer film is disposed on the front surface of an STN liquid crystal panel, or on a front surface and a rear surface, one sheet is provided. There is a limit to conversion, and two-layer STN-
There is a problem that the contrast ratio and the black and white tone are inferior to LCD. This is because the wavelength dispersion of the retardation of the liquid crystal panel does not completely match the wavelength dispersion of the retardation of the uniaxially stretched polymer film, so the phase difference must be compensated over the entire visible region. This is because the optical rotation of the liquid crystal panel cannot be compensated for unless a large number of retardation plates are stacked with their optical axes shifted and a pseudo twist structure is provided.

Further, according to a system in which one liquid crystal polymer film exhibiting a cholesteric phase having a reverse twist structure is disposed in front of the STN liquid crystal panel instead of the retardation plate, the two layers are the closest to the STN-LCD. Good display is obtained. However, since it is difficult to match the wavelength dispersion of the retardation of the liquid crystal panel with the wavelength dispersion of the retardation of the liquid crystalline polymer film, there is still a limit to achromatic display. Further, this method has not been put to practical use because there are many problems such as a method of strictly controlling a twist angle of 180 degrees or more, reliability such as environmental resistance, and mass productivity.

The present invention has been made in view of such a situation, and provides a liquid crystal display device which is thin and light, can realize an achromatic color display, and is excellent in mass productivity and reliability. It is an object of the present invention to do so.

[0011]

[0012]

The liquid crystal display device of the present invention comprises a pair of substrates and a super twisted nematic liquid crystal sealed between the pair of substrates and having a twist structure having a twist angle of 180 degrees or more. Equipped liquid crystal panel,
A pair of polarizing plates disposed so as to sandwich the liquid crystal panel, and a torsion structure having a twist angle of 60 degrees or more and 130 degrees or less, wherein one of the pair of polarizing plates and the liquid crystal panel An optically anisotropic member disposed between the two and a uniaxially stretched polymer film, and the other one of the pair of polarizing plates
The above object is achieved by providing a phase difference plate disposed between the liquid crystal panel and the liquid crystal panel, and the phase difference plate is a λ / 4 plate.

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

In the present invention, an optically anisotropic body having a twisted structure and a retardation plate made of a uniaxially stretched polymer film are arranged between one of a pair of polarizing plates and a liquid crystal panel. By doing so, the optical rotation caused by the light passing through the liquid crystal panel is eliminated, and the phase difference between the liquid crystal panel and the phase difference plate is compensated. In this case, the order of disposing the retardation plate and the optically anisotropic body may be on the liquid crystal panel side. Also, it is not necessary to arrange both the optically anisotropic body and the phase difference plate on the front side or the back side of the liquid crystal panel, one of them is arranged on the front side of the liquid crystal panel, and the other is arranged on the back side. Is also good.

In addition, since the wavelength dispersion of the retardation value can be controlled by using an optically anisotropic body having a twisted structure, it is possible to freely use a retardation plate made of different types of polymer films. It becomes possible.

[0023]

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

FIGS. 1, 2 and 3 are schematic sectional views of a liquid crystal display device according to the present invention. The liquid crystal panel 10 includes a translucent substrate 4a, 4b and a nematic liquid crystal (ST) filled with a chiral dopant and sealed between the substrates 4a, 4b.
N liquid crystal layer) 7, transparent electrodes 5 and 5 formed on the sides of the substrates 4a and 4b facing the STN liquid crystal layer 7, and alignment films 6 and 6. The front side of the liquid crystal panel 10 (FIGS. 1 and 2)
The front polarizer 1 is provided on the upper side of the liquid crystal panel 10 and the rear polarizer 8 is provided on the rear side of the liquid crystal panel 10 (the lower side of FIGS. 1, 2 and 3). Further, a retardation plate 2 made of a uniaxially stretched polymer film is disposed on the front side or the back side of the liquid crystal panel, and similarly, the optically anisotropic body 3 having a twisted structure is disposed on the front side or the back side of the liquid crystal panel 10. It is provided in.

FIG. 1 shows a configuration in which both a retardation plate 2 and an optically anisotropic body 3 are provided on the front side of a liquid crystal panel 10. FIG.
Has a configuration in which an optically anisotropic body 3 is provided on the front side of the liquid crystal panel 10 and a retardation plate 2 is provided on the back side. FIG. 3 shows a configuration opposite to the configuration of FIG. The retardation plate 2 has a configuration in which an optically anisotropic body 3 is provided on the back side. In the liquid crystal display device having the configuration shown in FIG. 1, both the phase difference plate 2 and the optically anisotropic body 3 may be arranged on the back side. The body 3 may be arranged on the front polarizing plate 1 side.

FIG. 4 is a diagram showing the relationship between the optical axis of each component and the orientation direction of STN liquid crystal molecules in the liquid crystal display device shown in FIG. FIG. 5 shows the relationship between the optical axis of each component in the liquid crystal display device of FIGS. 2 and 3 and the orientation direction of STN liquid crystal molecules, and FIG. 6 shows the optical axis of each component in the liquid crystal display device of FIG. FIG. 4 is a diagram showing a relationship between an alignment direction of STN liquid crystal molecules and the like.

In FIG. 4, φ denotes the liquid crystal molecule orientation direction 15 on the emission side substrate 4a of the liquid crystal panel 10 and the liquid crystal molecule orientation direction 1 on the incidence side substrate 4b of the liquid crystal panel 10.
6, that is, the torsion angle of the liquid crystal panel 10, and ψ is the angle between the emission-side optical axis (S-axis) 13 of the optically anisotropic body 3 and the incident-side optical axis 14 of the optically anisotropic body 3. Is the torsion angle of the optically anisotropic body 3 expressed as is the intersection angle between the incident optical axis 14 of the optically anisotropic body 3 and the liquid crystal molecule orientation direction 15 on the emission substrate 4a of the liquid crystal panel 10, and α is the front polarizing plate 1.
Is the intersection angle between the absorption axis direction 11 of the optical anisotropic body 3 and the emission side optical axis 13 of the optically anisotropic body 3, and β is the angle between the optical axis (S axis) 12 of the phase difference plate 2 and the emission side optical axis 13 of the optically anisotropic body 3. The intersection angle, γ is the liquid crystal panel 10
Is the intersection angle between the liquid crystal molecule alignment direction 16 on the incident side substrate 4b and the absorption axis direction 17 of the back side polarizing plate 8.

In FIGS. 5 and 6, those indicating the same angle or the same axis as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. δ is the intersection angle between the liquid crystal molecule orientation direction 16 on the incident side substrate 4b of the STN liquid crystal panel 10 and the optical axis 12 of the phase difference plate 2, and ε is the absorption axis of the optical axis 12 of the phase difference plate 2 and the back side polarizing plate 8. The angle of intersection with the direction 17. Τ is the intersection angle between the optical axis 12 of the phase difference plate 2 and the liquid crystal molecule orientation direction 15 on the emission side substrate 4a of the STN liquid crystal panel 10, and ξ
Are the absorption axis direction 11 of the front polarizing plate 1 and the optical axis 1 of the retardation plate 2
2, υ is the intersection angle between the liquid crystal molecule orientation direction 16 on the incident side substrate 4b of the STN liquid crystal panel 10 and the incidence side optical axis 14 of the optical anisotropic body 3, and ν is the incidence side of the optical anisotropic body 3. This is the intersection angle between the optical axis 14 and the absorption axis direction 17 of the rear polarizing plate 8.

In the liquid crystal display device having the above structure, a better black and white level can be obtained by optimizing the retardation value of each of the liquid crystal panel, the optically anisotropic member and the retardation plate and the arrangement of the respective axis angles. And the contrast ratio can be improved.

For example, in the liquid crystal display device having the structure shown in FIG. 3, a case where the STN liquid crystal layer 7 is a levorotatory retardation film having a retardation of 840 nm and the retardation film 2 is a uniaxially stretched polymer film having a retardation film of 565 nm is used. Think. Λ = 450 nm (blue) and λ = 5 as light having a typical wavelength among the light immediately before being incident on the front side polarizing plate 1.
FIG. 7 shows the azimuth angles of the emission ellipses of the respective lights of 50 nm (green) and λ = 650 nm (red). From this figure, the above ST
With respect to the N liquid crystal layer 7 and the phase difference plate 2, an optically anisotropic body 3 having a retardation of 500 nm and a twist angle of 90 degrees is used. It can be seen that a better black level can be obtained by adjusting the absorption axis angle of the polarizing plate 1.

(Embodiment 1) In this embodiment, the optically anisotropic body 3 shown in FIG. 1 is levorotatory and has a retardation of 900 nm.
Is used as a retardation plate 2 for retardation 450n
m, a uniaxially stretched polycarbonate film having a left-rotation and a retardation of 900 nm was used as the STN liquid crystal layer 7. Φ = 240 degrees, ψ = 90 degrees, θ = 0
Degrees, β = 90 degrees and γ = 40 degrees.

In the liquid crystal display device of the present embodiment, λ = 450 nm (blue), λ = 550 nm (green), and λ = 450 nm (blue) as light having a typical wavelength (λ) immediately before entering the front side polarizing plate 1.
FIG. 8 shows the emission ellipse of each light of = 650 nm (red). In addition, as a comparative example, the conventional STN-
In the LCD, the front-side retardation plate 2 and the back-side retardation plate 9
FIG. 18 shows an emission ellipse of each light when a uniaxially stretched polycarbonate film having a retardation of 430 nm is used and a STN liquid crystal layer 7 having a retardation of 900 nm is used. FIGS. 8 and 18 show that the liquid crystal display device of the present example has better ellipticity and azimuth as compared with the conventional STN-LCD.

The liquid crystal display of this embodiment is
The luminance and the CIE chromaticity coordinates when the absorption axis 11 of the front side polarizing plate 1 was actually adjusted to the azimuth of the emission ellipse were measured. As a result, Y = 0.425, x = 0.2696, y = 0.28.
As a result, a good black tone was obtained.

FIG. 9 shows that λ = 550 for the polycarbonate used as the uniaxially stretched polymer film.
In addition to the chromatic dispersion change rate of the retardation value normalized by the retardation value at nm, the chromatic dispersion change rate of the retardation value immediately before the liquid crystal display device of this embodiment enters the retardation plate 2 is shown. Show. In FIG. 9, the chromatic dispersion change rate curves of the two substantially coincide with each other. Therefore, in the liquid crystal display device of this embodiment, optical compensation can be realized over all wavelengths in the visible region.

Embodiment 2 In this embodiment, the optically anisotropic body 3 shown in FIG. 1 is dextrorotatory and has a retardation of 400 nm.
Is used as retardation plate 2 for retardation 460n
m uniaxially stretched polyvinyl alcohol film
A liquid crystal layer 7 having a left-handed rotation and a retardation of 900 nm was used. Φ = 240 degrees, ψ = 90 degrees, θ =
90 degrees, β = 90 degrees, and γ = 40 degrees.

FIG. 10 shows the light emission ellipse of the liquid crystal display of this embodiment immediately before the light enters the front polarizing plate 1.
As a comparative example, the conventional STN shown in FIG.
FIG. 19 shows an emission ellipse of each light when an uniaxially stretched polyvinyl alcohol film having a retardation of 430 nm is used as the front-side retardation plate 2 and the back-side retardation plate 9 and the STN liquid crystal layer 7 has a retardation of 900 nm. Shown in From these figures, it can be seen that the liquid crystal display device of the present embodiment has better ellipticity and azimuth than the conventional STN-LCD.

The liquid crystal display of this embodiment is
The luminance and CIE chromaticity coordinates when the absorption axis 11 of the front-side polarizing plate 1 was actually adjusted to the azimuth of the emission ellipse were measured. As a result, Y = 1.2439, x = 0.2865, and y = 0.3.
It was 191 and a good black tone was obtained. The complete black state is represented by Y = 0, x = 0.3101, y = 0.3162.
(C light source).

Further, FIG. 9 shows that, for the polyvinyl alcohol used as the uniaxially stretched polymer film, λ = 5
The chromatic dispersion change rate of the retardation value normalized by the retardation value at 50 nm is shown, and the chromatic dispersion change rate of the retardation value immediately before the liquid crystal display device of the present embodiment is incident on the retardation plate 2 is shown. Show. In this figure, both the chromatic dispersion change rate curves are substantially coincident.
Therefore, in the liquid crystal display device of this embodiment, optical compensation can be realized over all wavelengths in the visible region.

Embodiment 3 In this embodiment, the optically anisotropic body 3 shown in FIG. 2 is dextrorotatory and has a retardation of 500 nm.
Is used as retardation plate 2 for retardation 565n
A uniaxially stretched polycarbonate film having a left-handedness and a retardation of 840 nm was used as the STN liquid crystal layer 7. In FIG. 5, φ = 240 degrees and ψ = 90 degrees.
Degrees, θ = 90 degrees, δ = 90 degrees, and ε = 30 degrees.

The liquid crystal display device of the present embodiment is turned off.
The relationship between the spectral transmittance and the wavelength when a voltage is applied is shown by a solid line A in FIG. As a comparative example, in the conventional STN-LCD shown in FIG. 17B, a uniaxially stretched polycarbonate film having a retardation of 430 nm as the front retardation plate 2 and the back retardation plate 9, and a retardation of 900 nm as the STN liquid crystal layer 7. A broken line B shows the case where the above-mentioned is used. From FIG. 11, it can be seen that the liquid crystal display device of the present embodiment has a lower transmittance in all visible wavelengths than the conventional STN-LCD, and thus provides a good display. As a result of measuring the luminance and the CIE chromaticity coordinates at this time, Y = 1.7170, x = 0.755, y = 0.
It was 2266, and a good black tone with low luminance was obtained.

Embodiment 4 In this embodiment, the optically anisotropic body 3 shown in FIG. 3 is dextrorotatory and has a retardation of 700 nm.
Is used as the phase difference plate 2 for the retardation 430n
A uniaxially stretched polycarbonate film having a left-handedness and a retardation of 815 nm was used as the STN liquid crystal layer 7. In FIG. 5, φ = 240 degrees and ψ = 90 degrees.
Degrees, θ = 90 degrees, δ = 90 degrees, and ε = 30 degrees.

The relationship between the spectral transmittance and the wavelength when the ON voltage is applied in the liquid crystal display device of this embodiment is shown by a solid line A in FIG. As a comparative example, in the conventional STN-LCD shown in FIG. 17B, a uniaxially stretched polycarbonate film having a retardation of 430 nm as the front retardation plate 2 and the back retardation plate 9, and a retardation of 900 nm as the STN liquid crystal layer 7. The broken line B indicates the spectral transmittance in the case of using the above. FIG. 12 shows that the liquid crystal display device of this embodiment is 400 to 6 times smaller than the conventional STN-LCD.
It can be seen that the transmittance at a wavelength of 00 nm is high, and a good display is obtained. As a result of measuring the luminance and the CIE chromaticity coordinates at this time, Y = 24.9535 and x = 0.
2530, y = 0.2456, and a good white tone was obtained. In the first to fourth embodiments, the description has been made using the optically anisotropic body having a 90-degree twist structure. However, the present invention is not limited to this, and the twist angle is 90 degrees or less, for example, 60 degrees. Degrees, 70 degrees, 80 degrees, etc.
Similar effects can be obtained even when a twist angle of 90 degrees or more, for example, 130 degrees is used.

(Embodiment 5) In the present embodiment, the optically anisotropic body 3 shown in FIG.
m, a λ / 4 plate made of polycarbonate was used as the retardation plate 2, and a STN liquid crystal layer 7 having a left-rotation and a retardation of 660 nm was used. In FIG. 6, φ = 240 degrees, ψ = 64 degrees, τ = 45 degrees, ξ = 20 degrees.
Degrees, υ = 90 degrees, and ν = 10 degrees.

FIG. 13 shows the relationship between the spectral transmittance and the wavelength when the OFF voltage is applied in the liquid crystal display device of this embodiment by a solid line A. As a comparative example, in the conventional STN-LCD shown in FIG. 17B, a uniaxially stretched polycarbonate film having a retardation of 430 nm is used as the front retardation plate 2 and the back retardation plate 9, and a retardation of 900 nm is used as the STN liquid crystal layer 7. The broken line B indicates the spectral transmittance in the case of using the above. From FIG. 13, it can be seen that the liquid crystal display device of the present example has a lower transmittance in the visible region wavelength than the conventional STN-LCD, so that good display can be obtained. As a result of measuring the luminance and the CIE chromaticity coordinates at this time, Y = 0.8052, x = 0.346, y
= 0.2660, and a good black tone with low luminance was obtained.

Embodiment 6 In this embodiment, the optically anisotropic member 3 shown in FIG.
m, a λ / 4 plate made of polycarbonate was used as the retardation plate 2, and a STN liquid crystal layer 7 having a left-rotation and a retardation of 660 nm was used. In FIG. 6, φ = 240 degrees, ψ = 84 degrees, τ = 45 degrees, ξ = 90 degrees.
Degrees, υ = 90 degrees, and ν = 105 degrees.

FIG. 14 shows the relationship between the spectral transmittance and the wavelength when the OFF voltage is applied in the liquid crystal display device of this embodiment by a solid line A. As a comparative example, in the conventional STN-LCD shown in FIG. 17B, a uniaxially stretched polycarbonate film having a retardation of 430 nm is used as the front retardation plate 2 and the back retardation plate 9, and a retardation of 900 nm is used as the STN liquid crystal layer 7. The broken line B indicates the spectral transmittance in the case of using the above. From FIG. 14, it can be seen that the liquid crystal display device of the present example has a lower transmittance in the visible region wavelength than that of the conventional STN-LCD, so that good display can be obtained. As a result of measuring the luminance and the CIE chromaticity coordinates at this time, Y = 0.6648, x = 0.2539, y
= 0.2950, and a good black tone with low luminance was obtained.

Embodiment 7 In this embodiment, the optically anisotropic body 3 shown in FIG. 3 is dextrorotatory and has a retardation of 280 n.
m, a λ / 4 plate made of polycarbonate was used as the retardation plate 2, and a STN liquid crystal layer 7 having a left-rotation and a retardation of 660 nm was used. In FIG. 6, φ = 240 degrees, 度 = 124 degrees, τ = 45 degrees, ξ = 14 degrees.
0 degree, υ = 90 degrees, and ν = 170 degrees.

FIG. 15 shows the relationship between the spectral transmittance and the wavelength when the OFF voltage is applied in the liquid crystal display device of this embodiment by a solid line A.
Indicated by As a comparative example, in the conventional STN-LCD shown in FIG. 17B, a uniaxially stretched polycarbonate film having a retardation of 430 nm is used as the front retardation plate 2 and the back retardation plate 9, and a retardation of 900 nm is used as the STN liquid crystal layer 7. The broken line B indicates the spectral transmittance in the case of using the above. From FIG. 15, it can be seen that the liquid crystal display device of the present example has a lower transmittance in the visible region wavelength than that of the conventional STN-LCD, so that good display can be obtained. As a result of measuring the luminance and CIE chromaticity coordinates at this time, Y = 0.6770, x = 0.3274, y =
0.2929, and a good black tone with low luminance was obtained.

Embodiment 8 In this embodiment, the optically anisotropic member 3 shown in FIG. 3 is dextrorotatory and has a retardation of 280 n.
m, a λ / 4 plate made of polyvinyl alcohol was used as the retardation plate 2, and a STN liquid crystal layer 7 having a left-rotation and a retardation of 660 nm was used. In FIG. 6, φ = 240 degrees, ψ = 84 degrees, τ = 45 degrees, ξ = 2
0 degree, υ = 90 degrees, and ν = 15 degrees.

FIG. 16 shows the relationship between the spectral transmittance and the wavelength when the OFF voltage is applied in the liquid crystal display device of this embodiment by a solid line A.
Indicated by As a comparative example, in the conventional STN-LCD shown in FIG. 17B, a uniaxially stretched polycarbonate film having a retardation of 430 nm is used as the front retardation plate 2 and the back retardation plate 9, and a retardation of 900 nm is used as the STN liquid crystal layer 7. The broken line B indicates the spectral transmittance in the case of using the above. From FIG. 16, it can be seen that the liquid crystal display device of the present example has a lower transmittance in the visible region wavelength than the conventional STN-LCD, so that good display can be obtained. As a result of measuring the luminance and the CIE chromaticity coordinates at this time, Y = 0.8678, x = 0.2965, y =
0.2899, and a good black tone with low luminance was obtained.

As can be seen from the above description, the optically anisotropic body having the above-mentioned twisted structure is a conventional two-layer type ST.
The role of the liquid crystal polymer film is greatly different from that of the liquid crystalline polymer film aimed at replacing the optical compensation cell of the N-LCD, and when used in combination with a retardation plate made of a uniaxially stretched polymer film, light is emitted from the STN liquid crystal. The optical rotation caused by passing through the panel is eliminated, and the phase difference is compensated. Therefore,
By using the optically anisotropic body having the above-mentioned twist structure, a good black-and-white color tone can be obtained. Also, while the conventional liquid crystal polymer film had to have a twist angle in the reverse twist direction that is the same as the twist angle of the STN liquid crystal panel to be combined, the liquid crystal display device according to the present invention has an optical difference. It can be used in any of the left-handed and right-handed torsional directions, depending on the phase difference plate to be laminated and combined with a twist angle of around 90 degrees as a rectangular parallelepiped. The liquid crystal display device having high performance can be provided.

An optically anisotropic body having a twisted structure is, for example,
It can be formed by sandwiching a low molecular nematic liquid crystal to which a chiral dopant is added, between a translucent substrate having been subjected to an alignment treatment. Alternatively, a polymer liquid crystal in which a chiral nematic molecule is attached to a side chain of a polymer chain such as acrylate may be formed as a layer on a translucent substrate that has been subjected to an alignment treatment.

[0053]

As is apparent from the above description, according to the present invention, the STN liquid crystal is obtained by using an optically anisotropic body having a twisted structure and a retardation plate comprising a uniaxially stretched polymer film. The optical rotation caused by transmission through the panel can be eliminated, and the phase difference between the liquid crystal panel and the phase difference plate can be compensated. Therefore, it is possible to perform optical compensation over all wavelengths in the visible region, and to achieve complete achromatic display. Therefore, the liquid crystal display device, which is thinner and lighter than the two-layer type STN-LCD, can improve the black and white level and the contrast ratio.

Further, by using an optically anisotropic body having a twisted structure, the wavelength dispersion of retardation can be controlled, so that a retardation plate composed of different types of polymer films can be used freely. . Therefore, a liquid crystal display device which can greatly contribute to improvement in display quality, large size, high resolution, and colorization, and which is excellent in mass productivity and reliability can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display device according to the present invention.

FIG. 2 is a schematic sectional view of a liquid crystal display device according to the present invention.

FIG. 3 is a schematic sectional view of a liquid crystal display device according to the present invention.

FIG. 4 is a diagram showing a relationship between axes of respective components in the liquid crystal display device of FIG. 1;

FIG. 5 is a diagram showing a relationship between axes of respective constituent members in the liquid crystal display device shown in FIGS. 2 and 3.

6 is a diagram showing a relationship between axes of constituent materials in the liquid crystal display device of FIG.

FIG. 7 is a diagram showing an azimuth of a final emission ellipse when an OFF voltage is applied to the liquid crystal display device of FIG. 3;

FIG. 8 shows the liquid crystal display device of Example 1 where λ = 450 nm, 550 nm, and 650 immediately before the light enters the front polarizing plate.
It is a figure which shows the emission ellipse of each wavelength of nm.

FIG. 9 is a diagram showing the chromatic dispersion change rate of the retardation value normalized by the retardation value when λ = 550 nm in the liquid crystal display devices of Examples 1 and 2.

10 is λ = 450 nm, 550 nm, 65 immediately before entering the front side polarizing plate in the liquid crystal display device of Example 2. FIG.
It is a figure which shows the emission ellipse of each wavelength of 0 nm.

FIG. 11 is a diagram showing the spectral transmittance of the finally emitted light when an OFF voltage is applied to the liquid crystal display device of Example 3 and a conventional liquid crystal display device.

FIG. 12 is a diagram showing the spectral transmittance of the finally emitted light when an ON voltage is applied to the liquid crystal display device of Example 4 and a conventional liquid crystal display device.

FIG. 13 is a diagram showing the spectral transmittance of the finally emitted light when an OFF voltage is applied to the liquid crystal display device of Example 5 and the conventional liquid crystal display device.

FIG. 14 is a diagram showing the spectral transmittance of the finally emitted light when an OFF voltage is applied to the liquid crystal display device of Example 6 and the conventional liquid crystal display device.

FIG. 15 is a diagram showing the spectral transmittance of the finally emitted light when an OFF voltage is applied to the liquid crystal display device of Example 7 and the conventional liquid crystal display device.

FIG. 16 is a diagram showing the spectral transmittance of the finally emitted light when an OFF voltage is applied to the liquid crystal display device of Example 8 and the conventional liquid crystal display device.

FIG. 17 is a schematic sectional view of a conventional liquid crystal display device.

FIG. 18 shows the liquid crystal display device shown in FIG. 17B, in which λ = 450 nm, 550 nm,
It is a figure which shows the emission ellipse of each wavelength of 650 nm.

FIG. 19 shows the liquid crystal display device of FIG. 17B in which λ = 450 nm, 550 nm,
It is a figure which shows the emission ellipse of each wavelength of 650 nm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front-side polarizing plate 2 Retardation plate consisting of a uniaxially stretched polymer film 3 Optically anisotropic body having a twisted structure 4a, 4b Transparent substrate of STN liquid crystal panel 5 Transparent electrode 6 Alignment film 7 STN liquid crystal layer 8 Back side polarizing plate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/133 500 G02F 1/1335 510 G02F 1/13363

Claims (1)

(57) [Claims] 1. A liquid crystal panel comprising a pair of substrates, a super-twisted nematic liquid crystal sealed between the pair of substrates and having a twisted structure having a twist angle of 180 degrees or more, and sandwiches the liquid crystal panel. And a twist structure having a twist angle of 60 degrees or more and 130 degrees or less, and disposed between one of the pair of polarizers and the liquid crystal panel. A liquid crystal display comprising an optically anisotropic body, and a retardation plate comprising a uniaxially stretched polymer film and disposed between the other one of the pair of polarizing plates and the liquid crystal panel. A liquid crystal display device, wherein the retardation plate is a λ / 4 plate.