JPH02275416A - liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve the visual angle dependency of a liquid crystal display and to improve its display quality by laminating a display liquid crystal element and a liquid crystal element for optical compensation, applying a predetermined electric field to the liquid crystal layer and adjusting the angles of the long axes of liquid crystal molecules to a substrate, and eliminating extraordinary light. CONSTITUTION:The display liquid crystal element 1 and liquid crystal element 2 for optical compensation are laminated and a couple of polarizing members 15 and 16 are arranged on the mutually opposite sides in the laminating direction of both the liquid crystal elements. Further, both the liquid crystal elements 1 and 2 are provided with means for applying electric fields to the liquid crystal layers 13 and 14 respectively, and the angles of the long axes of liquid crystal molecules to the substrate are varied according to the electric fields applied to the liquid crystal layers to adjust the ellipticity of the elliptic polarized light beam transmitted through both the liquid crystal elements 1 and 2 and the extents of changes of the elliptic long-axis directions mutually. Consequently, a display of high quality can be made at a wide visual angle and the liquid crystal display device which has visual angle characteristics free from gradation inversion is obtained as a color liquid crystal display device which needs to make, specially, a gradational display.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device with improved viewing angle characteristics.

2. Description of the Related Art Conventionally, liquid crystal display devices have been widely used in numerical segment display devices such as watches and calculators, taking advantage of their characteristics of being thin, lightweight, and low power consumption. In recent years, matrix display systems have been adopted to display even more information. What is a matrix type liquid crystal display device? !
By selectively driving a number of display pixels, office automation such as personal computers, word processors, copying machines, etc.
ce＾utow＠Lion) It is used as a display terminal for devices. Furthermore, in response to the increasing density, larger area, and diversification of display information, numerous technological developments have been made in connection with color display systems, such as color liquid crystal display devices that add color information.

Up to now, the following methods (1) to (4) have been mainly proposed as display methods for color liquid crystal display devices.

(1) A guest phos that displays two colors by mixing dyes whose transmitted color differs depending on the direction of the dye molecules in the liquid crystal and causing the alignment of the dye molecules to follow changes in the alignment direction of the liquid crystal molecules.
- A method using an effect-type liquid crystal cell, <2) A method in which color display is performed by combining a twisted nematic liquid crystal cell and a color polarizing plate, <3) A method in which the birefringence of liquid crystal changes according to an applied electric field. Electric field controlled birefringence interference (Elect
Rally Controlled [liref
(4) In a liquid crystal cell provided with color filter layers for red, green, blue, etc., a method uses the liquid crystal layer as an optical shutter to display color.

Among the above methods (1) to (4), method (4) in particular uses a substrate on which active elements such as thin film transistors are formed as switching means for selecting display pixels in a liquid crystal display device, thereby achieving high contrast. It has the feature of being able to perform matrix-type full-color display, and is a display method that is currently attracting attention.

As for the method (4), a twisted nematic liquid crystal display method in which nematic liquid crystal is twisted and oriented by 90 degrees is generally being investigated. Furthermore, this method can be roughly divided into two types depending on how the pair of polarizing plates are arranged.

In other words, there is a normally black method in which the polarization directions of a pair of polarizing plates are arranged parallel to each other and a black color is displayed when no voltage is applied to the liquid crystal layer (off state), and a method in which the polarization directions of a pair of polarizing plates are arranged orthogonal to each other. This is a normally white (normally white) method that displays white in the off state. Generally, the normally white method is effective in terms of display characteristics such as display contrast, color reproducibility, and viewing angle dependence.

FIG. 7 is an exploded cross-sectional view showing a liquid crystal display cell 17 of a conventional twisted type liquid crystal display device.

Here, the same reference numerals are used for members corresponding to the embodiments described later.

The liquid crystal display cell 17 includes tin-doped indium oxide (Indium Oxide) on each opposing surface of a pair of glass substrates 3 and 4.
Tin Oxide (hereinafter abbreviated as rlTOj)
A translucent $15.6 film consisting of is patterned and its surface is coated with alignment films 7 and 8. These glass substrates 3 and 4 are pasted together with a sealing resin (not shown) interposed therebetween, and a liquid crystal layer 13 is sealed therein to form a liquid crystal display cell 17.

The surface of the alignment film 7.8 is subjected to a rubbing treatment in advance,
As a result, the liquid crystal in the liquid crystal layer 13 sealed therein is twisted by 90° between the glass substrates 3 and 4, as schematically shown in FIG. Therefore, for example, a drive circuit (not shown) is connected to the electrodes 5 and 6 formed facing each other in a matrix, and selectively applies a predetermined voltage to the pixels at the intersection of the electrodes 5 and 6 to form a liquid crystal layer. The orientation state of 13 can be changed. Further, on mutually opposite sides of the glass substrate 3.4, polarizing plates 15,16 whose polarization directions are orthogonal to each other are provided.

For example, when no voltage is applied between the $ poles 5 and 6, the light source light incident in the direction of arrow 19 is polarized [15], and only that polarization direction in the direction of arrow 20 is selectively transmitted. This linearly polarized light in the direction of arrow 20 enters the polarizing plate 16 from the glass substrate 4 with its polarization direction rotated by 90 degrees by the liquid crystal layer 13 twisted at 90 degrees.

As described above, the polarizing direction of the polarizing plate 16 is perpendicular to the polarizing direction 20 of the polarizing plate 15, that is, the direction perpendicular to the plane of the paper shown by the arrow 21, so that light is transmitted through the polarizing plate 16.

On the other hand, when a predetermined voltage is applied to '&', the liquid crystal layer 13 no longer exhibits the above-mentioned twisted orientation.

However, the polarization direction of the light incident on the liquid crystal layer 13 is not rotated by the glass substrate [4].
The polarization direction of the light incident on the polarizing plate 16 from the polarizing plate 16
is perpendicular to the polarization direction shown by the arrow 21, and the light is blocked and not transmitted.

Problems to be Solved by the Invention FIG. 8 is a diagram for explaining the experimental data shown below and the parameter θ of the experimental data in the examples described later. Generally, the liquid crystal display cell 17 has a specific direction 22 in which the display contrast is maximum. Consider a plane 24 formed by a direction 22 with the maximum display contrast and a normal line 23 on the glass substrate of the liquid crystal display cell 17. The angle formed by the line of sight 25 and the normal line 23 on this plane 24 will hereinafter be referred to as "visual angle θ."

FIG. 9 is a graph based on data obtained by measuring the viewing angle dependence of the light transmittance-applied voltage characteristic (hereinafter abbreviated as "TV characteristic") in the liquid crystal display cell 17 having the configuration shown in FIG. be. In the graph of FIG. 9, the measurement line 11 shows the T-■ characteristic of thirst at the viewing angle θ==-O″, and the measurement line 12
generally shows the TV characteristics for any viewing angle θ in the range of viewing angle θ>0°.As is clear from FIG. 9, in the TV characteristics of the measurement line 12, the applied voltage is 2.5V. The light transmittance was once around 0% in the vicinity, but when the applied voltage was 3.0 to 4. A phenomenon in which the light transmittance rises again in the range of Ov (the maximum value of the light transmittance at this time is hereinafter referred to as 'T'peak) occurs.

FIG. 10 shows the viewing angle θ and light transmittance T' of the liquid crystal display cell 17.
It is a graph showing the relationship with peak. In general, the viewing angle θ
= 0°, T'peak does not appear, but when viewing angle θ>0°, increasing viewing angle θ increases the T'peak value with a positive correlation. For this reason, at a viewing angle θ>0° where this phenomenon occurs, the gradation during display on the liquid crystal display cell 17 is reversed due to the existence of this light transmittance T'pe@k.
In particular, in a color display such as a color liquid crystal display device that requires gradation display, the T'peak value is not 0, which causes a predetermined color to not be displayed, causing gradation inversion. Therefore, in order to realize a liquid crystal display device with good viewing angle characteristics, it is necessary to eliminate this light transmittance T'peak.

The applicant of the present invention has determined that the above-mentioned light transmittance T', peak
As a means to effectively eliminate the
05) has already been performed.

Birefringence Δn (=n, −
rl. , n, : refractive index in the liquid crystal molecule axis direction, n, : refractive index in the direction perpendicular to the liquid crystal molecule axis direction) and the liquid crystal layer thickness d of the liquid crystal cell
Set d to the retardation value, which is the product of the following formula.

0.3um≦ΔrI-d≦0.6um・
...(1) The ratio of the bending elastic constant K)3 of the liquid crystal to the spreading elastic constant +++ is set to a value of about 1.0 or less, and the bending elastic constant of the liquid crystal is 33 and the torsional elastic constant The ratio K sy/K 22 with y □ should be set to a value of about 2.0 or more.

FIG. 11 shows the relationship between K33/K++ and K3)/Ktz when the composition ratio of the liquid crystal material used in the twisted type liquid crystal display cell is varied, based on measured values. This is a graph shown with an "x" symbol. As shown in the graph of Figure 11, this is a fact that has been known for a long time, but in general, K
It can be seen that there is a positive correlation between ss/K+1 and Kss/K22. Therefore, as mentioned above, the value of K 33 / K + 1 is set to 1.0 or less, and K
It is difficult to set the value of 2□ to 2.0 or more for ss/ due to the positive correlation shown in Figure 11, and therefore it is also difficult to sufficiently reduce the T'peak value. In addition, in order to cope with the increase in the area of liquid crystal display devices (for example, displays of 5 inches or more), the optical transmittance T"pe@k should be set to 3.0 by statistically considering the visual characteristics of entering the kindergarten. % or less.

An object of the present invention is to solve the above-mentioned technical problems and to enable high-quality display over a wide range of viewing angles, particularly in color liquid crystal display devices that require gradation display.
It is an object of the present invention to provide a liquid crystal display device having viewing angle characteristics in which gradation inversion does not occur.

Means for Solving the Problems The present invention provides a display liquid crystal element configured by interposing a liquid crystal layer between a pair of transparent substrates each having a transparent electrode formed thereon, and a stack of the display liquid crystal elements. a pair of light-transmitting groups disposed on one side of the direction, each having a light-transmitting electrode formed thereon; a liquid crystal element for optical compensation configured with a liquid crystal layer interposed therebetween; and a liquid crystal element of the display liquid crystal element; means for applying an electric field to the layer; means for applying an electric field to the liquid crystal layer of the optical compensation liquid crystal element; and a pair of display and optical compensation liquid crystal elements disposed on mutually opposite sides in the stacking direction. a polarizing member, and applying a predetermined electric field to the liquid crystal layer of at least one of the display and optical compensation liquid crystal elements to adjust the angle that the long axis of the liquid crystal molecules makes with the substrate. , a liquid crystal display device characterized in that the abnormal light contained in the transmitted light of each of the liquid crystal elements is mutually canceled out based on the optical birefringence of the liquid crystal layers.

In the present invention, a liquid crystal element for display and a liquid crystal element for optical compensation are provided in a stacked manner, and a pair of polarizing members are arranged on mutually opposite sides in the stacking direction of both liquid crystal elements.

The liquid crystal layers of both of the liquid crystal elements described above have optical birefringence due to the difference between the refractive index in the direction of the liquid crystal molecular axis and the refractive index in the direction perpendicular to the molecular axis direction. Therefore, when linearly polarized light that has passed through a polarizing member passes through a liquid crystal element for display or optical compensation, normal light and extraordinary light are generated due to the birefringence of the liquid crystal layer, and due to the phase difference between them, normal light and extraordinary light are generated. There are cases where the corresponding elliptical polarization occurs.

Here, by providing both liquid crystal elements for display and optical compensation in a stacked manner, elliptically polarized light from one liquid crystal element is absorbed by the other liquid crystal element based on its birefringence.
The phase difference is compensated to mutually eliminate abnormal light contained in the transmitted light. As a result, the linearly polarized light transmitted through one polarizing member remains linearly polarized light even when transmitted through both the stacked display and optical compensation liquid crystal elements, and is blocked or transmitted by the other polarizing member.

Furthermore, in the present invention, the display and optical compensation liquid crystal elements are each provided with means for applying an electric field to the liquid crystal layer, and the long axes of the liquid crystal molecules are aligned relative to the substrate in accordance with the electric field applied to the liquid crystal layer. The angle formed by the ellipsoids changes, and the degree of change in the ellipticity and the major axis direction of the elliptically polarized light transmitted through the liquid crystal element for display and optical compensation can be mutually adjusted.

As a result, the light transmittance T
At least one of the display and optical compensation liquid crystal elements adjusts the electric field applied to one of the liquid crystal layers so as to eliminate 'peak over the entire visible viewing angle of the liquid crystal display device. It is possible to prevent a situation in which the gradation is inverted during the process. Particularly, if the present invention is applied to a color liquid crystal display device that performs IIl tone display, it is possible to suppress gradation y4 inversion where a predetermined color display is not achieved, and the display quality of the liquid crystal display device is improved.

Embodiment FIG. 1 is an exploded sectional view of a liquid crystal display device 18 which is an embodiment of the present invention. The liquid crystal display device 18 includes a display liquid crystal cell 1, an optical compensation liquid crystal cell 2, and a pair of polarizing plates 15.
．． 16.

The display liquid crystal cell 1 has a pattern of transparent electrodes 5 and 6 made of ITO formed on each opposing surface of a pair of glass substrates 3 and 4, which are a pair of transparent substrates. An alignment film 7.8 made of an organic thin film is formed. The alignment films 7 and 8 include a glass substrate 3,
When the liquid crystal layer 13 is formed by sealing a liquid crystal material, which will be described later, between the two layers, the surface thereof is subjected to a rubbing treatment in advance so that the liquid crystal molecules are twisted at 90 degrees.

The optical compensation liquid crystal cell 2 includes a pair of glass substrates 9.10.
A translucent electrode 11 made of ITO is provided on each opposing surface of the electrode 11.
12 is formed on the entire surface, and alignment films 29 and 30 made of, for example, polyimide-based organic thin films are further formed on the surface thereof. The alignment films 29 and 30 are also subjected to a rubbing treatment in advance, so that the liquid crystal molecules of the interposed liquid crystal layer 14 are arranged in a so-called homogeneous alignment parallel to each other.

The liquid crystal cell 1.2 for display and optical compensation, which includes each of the above-mentioned members, is pasted together via a sealing resin (not shown), and a liquid crystal layer 13.14 is sealed in the liquid crystal cell 1.2 for display and optical compensation. Each optical compensation liquid crystal cell 2 is created. These liquid crystal cells for display and optical compensation 1.
2, the glass substrates 3 and 10 are attached to each other in contact with each other, and a pair of polarizing plates 1516 are stacked on opposite sides of the glass substrates 4 and 9. In order to realize the above-mentioned normally white display method, the polarizing plates 15 and 16 are set in directions perpendicular to each other, as shown by arrows 20 and 21, for example.

Furthermore, a drive circuit 27 is connected to the electrode 4f15.6 of the liquid crystal cell 1 for display, and the electrode 11 of the liquid crystal cell 2 for optical compensation is connected to the drive circuit 27.
．． A drive circuit 28 is connected to 12.

A control circuit 26 is connected to these drive circuits 27 and '28, and the drive circuit 27 is connected to the liquid crystal layer 13 of the display liquid crystal cell 1.
The drive circuit 28 performs display driving by applying a predetermined voltage to the liquid crystal layer 14 of the optical compensation liquid crystal cell 2.
The angle that the long axis of the liquid crystal molecules constituting the liquid crystal layer 14 forms with respect to the glass substrate 9.10 is adjusted by adjusting the voltage applied to the glass substrate 9.10. Based on the optical birefringence of both the liquid crystal layers 13 and 14 of the display and optical compensation liquid crystal cells 1.2, the extraordinary light contained in the transmitted light is determined as described below. be mutually resolved.

As the liquid crystal material for the liquid crystal layer 13, 14, for example, a nematic liquid crystal material having positive dielectric constant anisotropy, such as one or more types of cyclohexane-based compounds, is used, but the material is not limited thereto. 1st V! As schematically shown in i, the liquid crystal molecules of the liquid crystal layer 13 are twisted at 90° and aligned between the alignment films 7 and 8 when no voltage is applied to the electrodes 5 and 6 (off state vA). do. Further, the liquid crystal layer 14 is arranged between the electrodes 11 and 29 between the alignment films 29 and 30.
．． When no voltage is applied between 12 and 12, the liquid crystal molecules are homogeneously aligned. Thereby, the liquid crystal display device 18 can perform a normally white display in which white is displayed in an off state in which no voltage is applied between the electrodes 5 and 6.

Next, the light transmittance-applied voltage characteristics of the liquid crystal display device 18 having the above-described configuration are shown in the second section, and the same characteristics of the liquid crystal display cell 17 from the previous generation are shown in the second section as a comparative example in FIG.
Characteristic curves 14.15:16. shown in FIG.
17 shows the measurement results under the conditions described below.

Liquid crystal layer 13 of display and optical compensation liquid crystal cell 1.2
．． By adjusting each of the 14 composition ratios, the wavelength of the incident light ^-
At 55 Orr m, the refractive index anisotropy of the liquid crystal layer 13 Δn1=
0.10, refractive index anisotropy Δr+2 of liquid crystal layer 14 = 0.0
It was set to be 6.

Further, the layer thickness cil of the liquid crystal layer 13 of the display and optical compensation liquid crystal cell 1.2 is 5.0 μm, and the layer thickness d of the liquid crystal layer 14 is
2=2.0 μm.

Therefore, the display and optical compensation liquid crystal cell 1.2
The retardation values are approximately C, Mk, Δn when the pretilt angle of the liquid crystal layer 13°14 is approximately Oo.
1 ・d 1=0.50um, Δrt 2 ・d2=0
．． It is set to 12 μm.

Further, the electrodes 11 and 12 of the liquid crystal cell 2 for optical compensation include
A voltage sufficiently higher than the threshold voltage is applied from the drive circuit 28 so that the optical axis of the optical compensation liquid crystal cell 2 is substantially perpendicular to the glass substrate 9.10.

When the linearly polarized light that has passed through the polarizing plate 15 passes through the liquid crystal layer 13, which has been twisted and unoriented by applying a threshold voltage during display driving, normal light and extraordinary light are separated due to the birefringence of the liquid crystal. Occur. Corresponding to these phase differences, there are four types of transmitted light that become elliptically polarized light.

Here, the optical compensation liquid crystal cell 2 configured based on the above conditions and to which a predetermined voltage sufficiently higher than the threshold voltage is applied eliminates the phase difference, and these display and optical compensation liquid crystal cells 1. The light passing through 2 is made linearly polarized again.

As a result, the linearly polarized light in the direction of arrow P20 transmitted through the polarizing plate 15 is transmitted to each liquid crystal cell 1 for display and optical compensation.
Therefore, the linearly polarized light in the direction perpendicular to the direction of the reference mark 21 enters the polarizing plate 16, is blocked by the polarized light [15, and is transmitted to the liquid crystal display device 18.
When viewed from the bottom side of FIG. 1, a liquid crystal display without #-key inversion is performed.

Further, when the viewing angle θ when viewing the liquid crystal display device 18 from the lower side in FIG. 1 becomes larger than a certain degree, total reflection occurs on the surface of the polarizing plate 16, etc., and the display contents of the liquid crystal display device 18 become invisible. On the other hand, in the conventional example, when the liquid crystal display cell 17 is used, the light transmittance T'peak appears at any viewing angle θ other than 0°.However, in reality, due to the occurrence of total reflection, etc. It can be said that it is sufficient to eliminate the occurrence of the light transmittance T'peak near the critical angle θC (for example, about 50'').

In FIG. 2, a characteristic curve 14 is a light transmittance-applied voltage characteristic when the viewing angle is θ-0°, and a characteristic curve 15 is, for example, the simultaneity of four beams at a viewing angle of θ-45°. Further, in the comparative example shown in FIG. 3, the characteristic curve 16 is the thirst light transmittance-applied voltage characteristic at the viewing angle θ-゛, and the characteristic curve 17
is the simultaneity when the viewing angle is θ-45°.

As is clear from comparing Figure 2 (Example) and Figure 3 (Comparative Example), the light transmittance-applied voltage characteristic curves 14 and 16 at the viewing angle θ = 0° have almost the same tendency. shows,
In particular, when the applied voltage is 4.0 square meters or more, the light transmittance is cut off to almost 0%.

On the other hand, when comparing the characteristic curve 15°I7 when the viewing angle is θ-45°, the applied voltage is 3.0° in the embodiment shown in FIG.
■The light transmittance is almost 0% in the above cases, whereas in the characteristic curve 17 of the comparative example shown in Fig. 3, the applied voltage is 2.5%.
Although the light transmittance is once cut off to approximately 0% near v, a lifting phenomenon occurs in which the light transmittance increases again when the applied voltage is between 3.0 and 4.0 .

Therefore, according to the present invention, it is possible to eliminate the light transmittance T'peak in the case of viewing angle θ and 0゛, and display conditions such as monochrome display and color display are improved, and the display of the liquid crystal display device is improved. Improves quality.

Such an effect occurs when the visual angle θ is the critical angle θC and O.

This is not achieved only by leaping between the two angles, but can be achieved for any viewing angle θ as long as the viewing angle θ]−0° as described above. The critical angle θC merely indicates a practical range when total reflection and the like are taken into consideration.

Next, each retardation value ΔrotodiΔr is set to eliminate the tone inversion by setting the light transmittance T'peak''=tO%.
The relationship between t 2 and dl will be explained below based on experimental results.

Figure 4 shows the dependence of the light transmittance T'peak on the retardation value Δn2·dl when the retardation value Δr1·dl is fixed at a constant value. Retardation value Δ of cell 1
Light transmittance T' in the direction of viewing angle θ = 45° when the retardation value Δr凰2·dl of the liquid crystal 7 for optical compensation was variously changed for n1·dl = 0.5 μm
From the measurement curve 18 in the same figure showing the peak, the light transmittance Tp0° peak is 3%, which is the practical standard level.
There exists a range of Δn2・dl that is as follows, and furthermore, T ”
It can be seen that there is an optimal tardition value ΔrI2·dl for the peak value, which is the minimum T for which the peak value is 0. In particular, under the conditions shown in FIG. 4, the optimum value is Δr+2·d2= It is 0.12 μm.

FIG. 5 shows the relationship between the optimum value of the retardation value Δn1·dl and the retardation value Δn1·dl, as shown in the measurement curve 19 of the figure. l・dl.

There is a positive correlation between 6 mouths 2·dl.

Above is the 411th! Although FIG. 5 shows the case where the viewing angle θ=45°, if the light transmittance T'peak”i at the viewing angle θ=45° is 0%, the viewing angle θ is 0.
It has been confirmed that similar results can be obtained in the range of ゛≦θ≦45°.

If the above-mentioned No. 521 is used, the optical compensation liquid crystal cell 2 to be provided in order to set the light transmittance T'peakζ0 to the display liquid crystal cell 1 having an arbitrary litter radiation value Δrr l·dl can be obtained. Retardation value Δn2・d
2 design values can be determined. However, from the viewpoint of mass production of liquid crystal cells 1 and 2, each retardation value Δn
It is difficult to manufacture Δr 1.dl and Δr 2.d2 according to their designed values.

In other words, the display and optical compensation liquid crystal cell 1゜2 is
Each retardation value Δr11·dl.

Manufactured with variations in Δn 2 ·d2 around the design value. Therefore, strictly determining the standard value of each retardation results in a decrease in the yield of manufactured products.

On the other hand, according to the liquid crystal display device 18 shown in FIG. 1 provided by the present inventors, by adjusting the voltage applied to the liquid crystal layer 14 of the optical compensation liquid crystal cell 2, the light transmittance T'
peak ”v can be 0%, so each of the retardation values Δn1·(amount 1, Δrl 2·
Light transmittance T'p regardless of variations in the manufacturing stage of d2
Display gradation inversion caused by e@k can be suppressed.

That is, the terdisicon value R, which is related to the elliptically polarized state of light transmitted through the optically compensating liquid crystal cell 2, is defined by the following equation, taking into account the tilt angle α that the liquid crystal molecules form with respect to the substrate.

R=Δn2−d2cos”a...
-(2) The tilt angle α in the second equation above changes depending on the voltage applied to the liquid crystal layer 14, and therefore the retardation value R of the optical compensation liquid crystal cell 2 also changes according to the second equation. .

FIG. 6 is a graph showing the light transmittance T'peak with respect to the voltage applied to the liquid crystal layer 14. The results shown in the figure show that the optical compensation liquid crystal cell 2 is Δn2·d2=0.
Δr+ 1・d of display liquid crystal cell 1
The curve 110.l is shown as a parameter, and the curves 110. Z 11. Z
12 are shown.

As is clear from the measurement results shown in Figure 6, Δn2
・Parameter Δn for a constant value of d2 = 0.15 μm
Even if 1·dl changes, the voltage applied to the optical compensation liquid crystal cell 2 is kept within a value range sufficiently higher than the threshold voltage Vah, for example, voltage V p =V p +V p 2 , V
By adjusting p to 3, etc., the light transmittance T'pe
It is possible to set the ak piece to θ%.

Therefore, each retardation value Δn l·dl is predetermined based on the correlation shown in FIG.

With respect to Δr12・d2, the variation in the polarization value of each of the manufactured display and optical compensation liquid crystal cells 1.2 is calculated as shown in the first figure when actually using both of these liquid crystal cells 1.2. When configuring the liquid crystal display device 18 and performing display driving, the voltage applied to the liquid crystal layer 14 of the optically compensating liquid crystal cell 2 is set to a light transmittance T' at a viewing angle of θ-45°, for example.
By setting the applied voltage to 0%, the rise in the light transmittance T'peak can be eliminated.

In addition, the light transmittance T' peak! in a practical viewing angle range (-45°≦θ≦45°). =tO%, it is preferable to set the ratio dion values Δrx 1·di and Δn 2·d2 of the liquid crystal cell 1.2 for display and optical compensation within the range of the following formula.

0.3μm<Δn1−d1<0. 6μm
-(3)0.05um-2Δn2
-d2<0.3μm ・=<4> Thus, according to the present invention, the light transmittance T'peak at the viewing angle θ:, -o' is set to 1.2 for the liquid crystal cell for display and optical compensation. Δn1・d 1 , Δr generated in the manufacturing process of
It is possible to resolve variations in values such as t2 and d2, improve undesirable display conditions such as white dots and gradation inversion in color displays, and improve the display quality of liquid crystal display devices. improves.

In the actual aiPi4 described above, the display method is a normally white method, and the voltages applied to the optical compensation liquid crystal cell 2,
The light transmittance T'peak is resolved only by this. However, the present invention is not limited to these, and can also be applied to a normally black display system by mutually adjusting the voltages applied to the display and optical compensation liquid crystal cells 1.2 to achieve the light transmittance T'. It is also possible to implement the present invention so as to eliminate the peak.

Furthermore, although the present invention has been described with respect to a twisted nematic type liquid crystal display device, the present invention can be practiced in connection with other types of liquid crystal display devices, such as a super twisted nematic type liquid crystal display device in which the twisted orientation of the liquid crystal is 90° or more. can.

Furthermore, the present invention provides thin film transistors and M I M (M
It goes without saying that the present invention can be suitably applied to an active matrix type liquid crystal display device that performs display drive using active elements such as metal insulator elements, diodes, and the like.

Effects of the Invention According to the present invention, a liquid crystal display device is constructed by laminating a liquid crystal element for display and a liquid crystal element for optical compensation, so that the viewing angle dependence of the display in the liquid crystal display is improved, and the black and white display is improved. This eliminates the gradation inversion during color display and the gradation inversion in color display. Therefore, the display quality of the liquid crystal display device is significantly improved.

Further, according to the present invention, since a means for applying an electric field to each liquid crystal layer of the display and optical compensation liquid crystal elements is provided, characteristics such as optical birefringence of each of the liquid crystal elements that occur during the manufacturing process can be controlled. It becomes possible to improve the viewing angle dependence of display in response to variations in design values such as liquid crystal layer thickness and liquid crystal layer thickness, and the productivity of liquid crystal display devices is significantly improved.

[Brief explanation of drawings]

FIG. 1 is an exploded cross-sectional view showing the structure of a liquid crystal display device 18 which is an embodiment of the present invention, FIG. 2 is a graph showing the light transmittance-applied voltage characteristics of the liquid crystal display device 18, and FIG. 3 is a comparative example. 4 is a graph showing the light transmittance-applied voltage characteristics of the conventional liquid crystal display cell 17, and FIG. 4 shows the light transmittance T'peak and Δn2・
A graph showing the relationship between d2 and FIG. 5 is the light transmittance T'pea
FIG. 6 is a graph showing the relationship between Δn1·dl and Δn2·d2 when kζ0%. FIG. 6 is a graph showing the relationship between light transmittance T'peak and voltage V applied to the liquid crystal layer 14.
The figure is an exploded cross-sectional view showing the configuration of a conventional liquid crystal display cell 17.
FIG. 8 is a diagram defining the viewing angle θ, FIG. 9 is a graph showing the light transmittance-applied voltage characteristics of the conventional liquid crystal display cell 17, and FIG.
FIG. 0 is a graph showing the relationship between light transmittance and viewing angle of the liquid crystal display cell 17, and FIG. 11 is a graph showing the elastic constant ratio K. / to 11 and K 35
It is a graph showing the correlation of /K12. DESCRIPTION OF SYMBOLS 1... Liquid crystal cell for display, 2... Liquid crystal cell for optical compensation, 3, 4, 9.10... Glass substrate, 5.6, 11
．． 12... Electrode, 7, 8, 29, 3rd region... Alignment film,
13.14...Liquid crystal layer, 15.16...Polarizing plate, 1
8...Liquid crystal display device, 26...Control circuit, 27.28
...Drive circuit, dl...Layer thickness of liquid crystal layer 13, d2.
...Thickness of the liquid crystal layer 14, Δn1...Birefringence of the liquid crystal layer 13, Δn2...Birefringence of the liquid crystal layer 14, θ...Viewing angle agent Patent attorney Kei Nishikyo Figure 1 ■Electricity applied to pressure (V) ■ρ1 Egg applied to melon (V) Vp Figure 6 Figure Figure Figure Figure Figure 8 Figure Figure #Tl7711It Pressure (V) Figure 10

Claims (1)

[Scope of Claims] A display liquid crystal element configured by interposing a liquid crystal layer between a pair of light-transmitting substrates each having a light-transparent electrode formed thereon; an optical compensation liquid crystal element configured by interposing a liquid crystal layer between a pair of transparent substrates arranged and each having a transparent electrode formed thereon; and applying an electric field to the liquid crystal layer of the display liquid crystal element. means for applying an electric field to the liquid crystal layer of the liquid crystal element for optical compensation; and a pair of polarizing members disposed on mutually opposite sides in the stacking direction of the liquid crystal elements for display and for optical compensation. , by applying a predetermined electric field to the liquid crystal layer of at least one of the display and optical compensation liquid crystal elements, and adjusting the angle that the long axis of the liquid crystal molecules forms with the substrate, A liquid crystal display device characterized in that extraordinary light contained in transmitted light is mutually canceled out based on the optical birefringence of the liquid crystal layers.