JPH0659258A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a bright liquid crystal display device little in coloring and small in color difference between a display part and a periphery by optimizing spectrum spread in the birefringence ratio of a phase difference film. CONSTITUTION:In the liquid crystal display device providing with a super twisted liquid crystal cell 3 and the phase difference film 2, when the value nu(identicalDELTAn (450nm)/DELTAn (590nm)) of the spectrum spread of DELTAn of the phase difference film 2 is specified as y, the nu value of a liquid crystal is specified as x, the liquid crystal 3 and the phase difference film 2 are selected so that they are satisfied with the relation of x+0.08>y>(4/3)x-0.36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art Conventional twisted nematic (TN)
The liquid crystal display (LCD) using the mode is bright white /
Since it can display black, it is widely used in watches, calculators, measuring instruments, telephones, home appliances, and the like. However, T
The N-LCD has an essential problem that the contrast deteriorates when the display capacity increases because the threshold characteristic of the electro-optical characteristic is not steep.

As a countermeasure against this, the twist angle of the liquid crystal is set to TN.
A super twisted nematic (STN) mode, which is larger than the mode, has been proposed, and high contrast can be obtained even with a large display capacity. However, since this STN-LCD utilizes the birefringence effect of liquid crystal, coloring of display such as yellow / black or blue / white is unavoidable, which is not preferable from the viewpoint of ergonomic recognition.

As a countermeasure against this, a means for compensating for STN mode coloring using a retardation film has been devised, and
Mode, FSTN mode, etc. FTN-L
In recent years, CDs have been widely adopted in personal information devices such as notebook computers.

[0005]

However, the conventional F
The liquid crystal display device using the TN mode is not always sufficient in terms of display performance such as color difference when no voltage is applied and when a non-selection voltage is applied, brightness, and coloring.

The present invention is intended to solve such a problem. An object of the present invention is to optimize the wavelength dispersion of Δn of a retardation film so that it is bright, and when no voltage is applied and when a non-selection voltage is applied. An object of the present invention is to provide a liquid crystal display device having a small time difference and little coloring.

[0007]

A liquid crystal display device of the present invention includes a liquid crystal cell having a twisted liquid crystal sandwiched between two substrates facing each other, and at least one retardation film. In a liquid crystal display device provided with a pair of polarizing plates arranged so as to sandwich it, when the wavelength dispersion value ν of the birefringence Δn of the retardation film is y and the ν value of the liquid crystal is x, these Is x + 0.08>y> (4/3)
It is characterized in that the relational expression of x−0.36 is satisfied.

In addition, one of the liquid crystal display devices is characterized in that a reflector is provided.

[0009]

The optical characteristics of a normal liquid crystal display device utilizing birefringence are determined by the optical path length difference Δn × d / λ between ordinary light and extraordinary light. Since the wavelength λ of light is included in this equation, the liquid crystal display element has different characteristics depending on the color of light, and the display is colored or the contrast is lowered. On the other hand, the value of Δn also changes depending on the wavelength of light.
Is the Δn value for light of wavelength 450 nm and wavelength 590n
Using the Δn value for m light, ν≡Δn (450 nm) /
It is defined as Δn (590 nm).

[0010] Now, FTN for compensation with one film
Consider the mode. When Δn × d of the liquid crystal is 0.79 μm, the ν value of the liquid crystal and the ν value of the film are changed from 1.00 to 1.18 while keeping the maximum transmittance, and the color difference (ΔE≡
(A ^{* 2} + b ^{* 2} ) ^0.5 ) was investigated, and the results shown in FIGS. 5, 6 and 7 were obtained. FIG. 5 shows the color difference between when no voltage is applied and a white point, FIG. 6 is the color difference between when a non-selection voltage is applied and a white point, and FIG. 7 is the color difference when no voltage is applied and a non-selection voltage is applied. These numbers are C
It is represented by the IE1976L ^* A ^* B ^* color system. The numbers in the figure are color differences.

From these isochromaticity curves, the portions with little coloring are distributed around the point where the ν value of the film is 0.04 larger than the ν value of the liquid crystal when no voltage is applied, and when no voltage is applied, It can be seen that is distributed mainly around the ν value of the film and the ν value of the liquid crystal. Further, it can be seen that the less colored portions are wide when the mutual dispersion is small, but become narrower as the dispersion becomes larger. In addition, the color difference between when no voltage is applied and when a non-selection voltage is applied is widely distributed, with the ν value of the film being 0.02 larger than the ν value of the liquid crystal.

Further, the color difference was similarly examined when Δn × d of the liquid crystal was 0.85 μm and 0.73 μm, and FIG.
9, FIG. 10, FIG. 11, FIG. 12, and FIG. 13 were obtained. 8,
FIGS. 10 and 10 show the case of Δn × d = 0.85 μm, and FIGS. 11, 12 and 13 show the case of Δn × d = 0.73 μm. Further, FIGS. 8 and 11 are color differences from a white point when no voltage is applied, FIGS. 9 and 12 are color differences from a white point when a non-selected voltage is applied, and FIGS. 10 and 13 are non-selected when no voltage is applied. This is the color difference during voltage application. These are also CIE1976L ^* A ^* B ^*
It is represented by a color system. The numbers in these figures are also color differences.

From FIG. 9 and FIG. 12, the portions that are less colored when a non-selection voltage is applied are distributed mainly around the fact that the ν value of the film and the ν value of the liquid crystal are almost the same regardless of Δn × d of the liquid crystal. I understand. Further, from FIGS. 10 and 13, the color difference between when no voltage is applied and when a non-selective voltage is applied does not depend on Δn × d, but is widely distributed around the point where the ν value of the film is 0.02 larger than the ν value of the liquid crystal. ing. On the other hand, on the other hand, it can be seen from FIGS. 8 and 11 that the center of the less colored portion when no voltage is applied varies depending on Δn × d of the liquid crystal, and Δn ×
When d is 0.85 μm, the ν value of the film is 0.06 larger than the ν value of the liquid crystal, and when Δn × d is 0.73 μm, the ν value of the film is 0.03 larger than the ν value of the liquid crystal. It is at the center. The degree of coloring is smaller when Δn × d is larger, but the change in color difference due to the difference in dispersion is Δ
The smaller n × d is, the smaller it is. From now on, in order to reduce coloring, it is desired that Δn × d be large.

Therefore, in order to maintain high transmittance, little coloring, and to reduce the color difference between when no voltage is applied and when a non-selective voltage is applied, the wavelength dispersion of the birefringence Δn of the retardation film is determined. When the value ν is y and the ν value of the liquid crystal is x, these are x + 0.08>y> (4/3) x−0.3.
A liquid crystal and a retardation film that satisfy the relational expression 6 may be adopted. More preferably, the liquid crystal and the retardation film should be adopted so as to satisfy the relational expression of y = x + 0.02.

[0015]

【Example】

(Embodiment 1) FIG. 1 is a sectional view of a liquid crystal display device according to Embodiment 1 of the present invention. In the figure, 1 is an upper polarizing plate, 2 is an upper retardation film, 3 is a liquid crystal cell, 4 is a lower polarizing plate, 5
Is a reflector. Further, 6 is an upper substrate of the liquid crystal cell, 7 is a lower substrate, 8 is a transparent electrode, and 9 is a liquid crystal.

The liquid crystal cell has a liquid crystal ZLI-3 manufactured by Merck.
Using 125 (Δn = 0.0516, ν = 1.015), twist alignment was performed in a cell having a cell gap d of 15.8 μm. Polypropylene (ν
= 1.025, Δnd = 541 nm) was used. It has a ν value that is 0.01 greater than liquid crystals.

FIG. 2 is a relational diagram of each axis of the liquid crystal display device in the first embodiment. Here, the angle 2 formed by the absorption axis direction 11 of the upper polarizing plate and the stretching direction 12 of the upper retardation film 2
1 is 40 degrees to the right, 12 is an angle 22 with the rubbing direction 13 of the upper substrate, 77 is left to be 77 degrees, and 13 is the rubbing direction 14 of the lower substrate.
The twist angle 23 of the liquid crystal determined by
To the right of the angle 24 made by the absorption axis direction 15 of the lower polarizing plate.
I took it.

The characteristics of this embodiment are x = 0.3049, y = 0.3268 and reflectance (hereinafter R) = 30.0% when no voltage is applied. When a non-selection voltage is applied, x = 0.
2982, y = 0.3268, R = 27.6%. The color is C
According to the IE1931XYZ color system. A bright display is obtained in which there is little color difference between when no voltage is applied and when a non-selection voltage is applied and there is little coloring.

(Embodiment 2) The structure and axial relationship of the liquid crystal display device of Embodiment 2 are the same as those of Embodiment 1. However, in the liquid crystal cell, liquid crystal ZLI-2977 (Δn = 0.
1319, ν = 1.121,) and the cell gap d
Was twist-oriented to a cell having a thickness of 6.0 μm. Polyester naphthalate (ν = 1.1
6, Δnd = 529 nm) was used. It has a ν value that is 0.039 larger than that of liquid crystal.

The characteristics of this embodiment are as follows: x = 0.2988, y = 0.3288, R = 29.1 when no voltage is applied.
%. X = 0.2916, y = when non-selection voltage is applied
0.3246, R = 26.7%. Color is CIE1931X
According to YZ color system. A bright display is obtained in which there is little color difference between when no voltage is applied and when a non-selection voltage is applied and there is little coloring.

(Embodiment 3) The structure and axial relationship of the liquid crystal display device of Embodiment 3 are the same as those of Embodiment 1. However, in the liquid crystal cell, liquid crystal ZLI-3125 (Δn = 0.
0516, ν = 1.015) was used to twist-align the cells with a cell gap d of 16.8 μm. Polyvinyl alcohol (ν = 1.00, △
nd = 586 nm) was used. This is 0.01 from liquid crystal
Has a large ν value.

The characteristics of this embodiment are as follows: x = 0.3188, y = 0.3232, R = 30.4 when no voltage is applied.
%. When non-selection voltage is applied, x = 0.3132, y =
0.3193, R = 28.8%. Color is CIE1931X
According to YZ color system. A bright display is obtained in which there is little color difference between when no voltage is applied and when a non-selection voltage is applied and there is little coloring.

(Embodiment 4) The structure and axial relationship of the liquid crystal display device of Embodiment 4 are the same as those of Embodiment 1. However, in the liquid crystal cell, liquid crystal ZLI-2977 (Δn = 0.
1319, ν = 1.121,) and the cell gap d
Was twist-aligned in a cell of 6.4 μm. Polysulfone (ν = 1.16, Δnd =
529 nm) was used. It has a ν value that is 0.039 larger than that of liquid crystal.

The characteristics of this embodiment are as follows: x = 0.3251, y = 0.3461, R = 30.1 when no voltage is applied.
%. When non-selection voltage is applied, x = 0.3132, y =
0.3349, R = 28.3%. Color is CIE1931X
According to YZ color system. A bright display is obtained in which there is little color difference between when no voltage is applied and when a non-selection voltage is applied and there is little coloring.

(Fifth Embodiment) FIG. 3 is a sectional view of a liquid crystal display device according to a fifth embodiment of the present invention. In the figure, 1 is an upper polarizing plate, 2 is an upper retardation film, 3 is a liquid crystal cell, 4 is a lower polarizing plate, and 5 is a reflecting plate. Further, 6 is an upper substrate of the liquid crystal cell, 7 is a lower substrate, 8 is a transparent electrode, and 9 is a liquid crystal.

The liquid crystal cell has a liquid crystal ZLI-2 manufactured by Merck.
977 (Δn = 0.319, ν = 1.121) was used to perform twist orientation in a cell having a cell gap d of 6.0 μm. Polyester naphthalate (ν = 1.16, Δnd = 529 nm) was used for the upper retardation film.
It has a ν value that is 0.039 larger than that of liquid crystal.

FIG. 4 is a relational diagram of each axis of the liquid crystal display device in the fifth embodiment. Here, the angle 2 formed by the absorption axis direction 11 of the upper polarizing plate and the stretching direction 12 of the upper retardation film 2
1 is 55 degrees to the right, 12 is an angle of 22 with the upper substrate rubbing direction 13 is 100 degrees to the left, and 13 is the lower substrate rubbing direction 1
Liquid crystal twist angle 23 determined by 4 is 240 degrees to the left, 1
The angle 25 formed by 4 with the lower phase difference plate 16 was left 50 degrees, and the angle 26 formed by the lower phase difference plate 16 with the absorption axis direction 15 of the lower polarizing plate was right 55 degrees.

The characteristics of this embodiment are as follows: x = 0.3138, y = 0.3220, R = 29.8 when no voltage is applied.
%. When non-selection voltage is applied, x = 0.3179, y =
0.3236, R = 31.6%. Color is CIE1931X
According to YZ color system. A bright display is obtained in which there is little color difference between when no voltage is applied and when a non-selection voltage is applied and there is little coloring.

Comparative Example 1 The structure and axial relationship of the liquid crystal display device of Comparative Example 1 are the same as those of Example 1. However, in the liquid crystal cell, liquid crystal ZLI-2977 (Δn = 0.
1319, ν = 1.121), and twist-oriented to a cell having a cell gap d of 6.0 μm. Polycarbonate (ν = 1.09, Δnd =
536 nm) was used. It has a ν value that is 0.031 less than liquid crystal. This is outside the scope of the present invention.

The characteristics of this embodiment are as follows: x = 0.3054, y = 0.395, R = 29.2 when no voltage is applied.
%. When non-selection voltage is applied, x = 0.2948, y =
0.3137, R = 27.1%. Color is CIE1931X
According to YZ color system. Although there is little coloring and a bright display is obtained, the difference in color between when a selection voltage is applied and when no voltage is applied is large, which is not satisfactory as compared with the liquid crystal display device of the present invention.

Comparative Example 2 The structure and axial relationship of the liquid crystal display device of Comparative Example 2 are the same as in Example 1. However, in the liquid crystal cell, liquid crystal ZLI-2977 (Δn = 0.
1319, ν = 1.121), and twist-oriented to a cell having a cell gap d of 6.0 μm. Polycarbonate (ν = 1.09, Δnd =
566 nm) was used. It has a ν value that is 0.031 less than liquid crystal. This is outside the scope of the present invention.

The characteristics of this embodiment are as follows: x = 0.3012, y = 0.3214, R = 28.1 when no voltage is applied.
%. When non-selection voltage is applied, x = 0.2931, y =
0.3117, R = 23.6%. Color is CIE1931X
According to YZ color system. This is one in which the thickness of the film is adjusted so that the color difference between the time when the selection voltage is applied and the time when the voltage is not applied in Comparative Example 1 is reduced. Is not satisfactory.

[0033]

As described above, according to the present invention, by optimizing the wavelength dispersion of Δn of the retardation film, there is little color change between the time when no voltage is applied and the time when non-selection voltage is applied, and the coloring at that time is suppressed. It is possible to provide a bright liquid crystal display device which has a small number of pixels.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display device according to Examples 1 to 4 of the present invention and a comparative example.

FIG. 2 is a relationship diagram of each axis of the liquid crystal display devices in Examples 1 to 4 of the present invention and a comparative example.

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

FIG. 4 is a relationship diagram of axes of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 5 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color characteristics when no voltage is applied, when Δn × d = 0.79 μm.

FIG. 6 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color characteristics when a non-selection voltage is applied when Δn × d = 0.79 μm.

FIG. 7 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color difference when no voltage is applied and when a non-selection voltage is applied when Δn × d = 0.79 μm.

FIG. 8 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color characteristics when no voltage is applied, when Δn × d = 0.85 μm.

FIG. 9 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color characteristics when a non-selection voltage is applied when Δn × d = 0.85 μm.

FIG. 10 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color difference when no voltage is applied and when a non-selection voltage is applied when Δn × d = 0.85 μm.

FIG. 11 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color characteristics when no voltage is applied, when Δn × d = 0.73 μm.

FIG. 12 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color characteristics when a non-selection voltage is applied when Δn × d = 0.73 μm.

FIG. 13 is a diagram showing the influence of the ν value of the liquid crystal and the ν value of the film on the color difference when no voltage is applied and when a non-selection voltage is applied when Δn × d = 0.73 μm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper polarizing plate 2 Upper retardation film 3 Liquid crystal cell 4 Lower polarizing plate 5 Reflector 6 Upper substrate of liquid crystal cell 7 Lower substrate of liquid crystal cell 8 Transparent electrode 9 Liquid crystal 10 Lower retardation plate 11 Upper polarizing plate 1 Absorption axis direction of the upper retardation film 2 13 rubbing direction of the upper substrate 6 of the liquid crystal cell 14 rubbing direction of the lower substrate 7 of the liquid crystal cell 15 absorption axis direction of the lower polarizing plate 4 16 lower retardation plate Stretching axis direction of 10 21 11 angle with 12 22 12 angle with 13 23 twist angle of liquid crystal 9 24 14 angle with 15 25 14 angle with 16 26 16 angle with 15

Claims (2)

[Claims] 1. A liquid crystal cell having a twisted liquid crystal sandwiched between two substrates facing each other, at least one retardation film, and 1 disposed so as to sandwich these.
In a liquid crystal display device provided with a pair of polarizing plates, when the wavelength dispersion value ν of the birefringence Δn of the retardation film is y and the ν value of the liquid crystal is x, these are x + 0.08>y>
A liquid crystal display device characterized by satisfying a relational expression of (4/3) x-0.36. 2. The liquid crystal display device according to claim 1, wherein one of the liquid crystal display devices is provided with a reflection plate.