JP2753035B2 - Liquid crystal display - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having improved display viewing angle characteristics.

2. Description of the Related Art Conventionally, liquid crystal display devices have been widely used in numerical segment type display devices such as watches and calculators, taking advantage of the features of thinness, light weight, and low power consumption. In recent years, a matrix type display method has been adopted in order to display even more information. A matrix-type liquid crystal display device selectively drives a plurality of display pixels for display, thereby enabling office automation (office automation) such as a personal computer, a word processing machine (word processor), and a copying machine.
Automation) Used as a display terminal for devices.
Further, in response to higher density, larger area, and diversification of display information, many technologies have been developed in connection with a color display system such as a color liquid crystal display device to which color information is added.

Hitherto, the following methods (1) to (4) have been mainly proposed as display methods of the color liquid crystal display device.

(1) A guest-host effect type liquid crystal cell in which a dye having a different transmission color is mixed into a liquid crystal depending on the direction of the dye molecule, and a two-color display is performed by causing the alignment of the dye molecule to follow a change in the alignment direction of the liquid crystal molecule. (2) a method of performing color display by combining a twisted nematic liquid crystal cell and a color polarizer, and (3) a color display using a change in the birefringence of liquid crystal according to an applied electric field. Electric field controlled birefringence interference (Electrical
(4) A method in which a liquid crystal cell provided with a color filter layer of red, green, blue, etc., performs color display using the liquid crystal layer as an optical shutter.

Among the above methods (1) to (4), the method (4) particularly has a high contrast by using a substrate on which an active element such as a thin film transistor is formed as a switching means for selecting a display pixel in a liquid crystal display device. It has the feature that a matrix type full-color display can be performed, and is a display system that has received the most attention at present.

In the method (4), a twisted nematic liquid crystal display system in which a nematic liquid crystal is twisted by 90 ° is generally employed. Further, this method is roughly classified into two types depending on the arrangement of a pair of polarizing plates.
That is, the polarization directions of a pair of polarizing plates are arranged in parallel with each other, and a normally black mode in which black is displayed in a state where no voltage is applied to the liquid crystal layer (off state), and a polarization direction perpendicular to each other. This is a normally white system in which white is displayed in the off state by arranging. In particular, the normally white method is effective in display characteristics such as display contrast, color reproducibility, and viewing angle dependence of display.

FIG. 7 is an exploded sectional view showing a liquid crystal display cell 17 of a conventional twisted nematic liquid crystal display device.
Here, the same reference numerals are used for the members corresponding to the embodiments described later. In the liquid crystal display cell 17, light-transmissive electrodes 5 and 6 made of tin-doped indium oxide (Indium Tin Oxide; hereinafter, abbreviated as “ITO”) are formed on the opposing surfaces of the pair of glass substrates 3 and 4 by pattern formation. The surface is covered with alignment films 7 and 8. These glass substrates
3, 4 are pasted together via a sealing resin not shown,
The liquid crystal layer 13 is sealed to form a liquid crystal display cell 17.

Rubbing treatment is performed on the surfaces of the alignment films 7 and 8 in advance,
The nematic liquid crystal of the liquid crystal layer 13 sealed by this is formed on a glass substrate as schematically shown in FIG.
A 90 ° twist orientation between 3 and 4. Therefore, for example, a driving circuit (not shown) is connected to the electrodes 5 and 6 formed opposite to each other in a matrix shape, and a predetermined voltage is selectively applied to a pixel at a portion where the electrodes 5 and 6 intersect to form a liquid crystal layer. Thirteen orientation states can be changed. Glass substrates 3, 4
The polarizers whose polarization directions are orthogonal to each other
15, 16 are provided.

For example, when no voltage is applied between the electrodes 5 and 6, the light source light incident in the direction of the arrow 19 is selectively transmitted by the polarizing plate 15 only in the direction of the arrow 20 in the polarization direction. The linearly polarized light in the direction of the arrow 20 is incident on the polarizing plate 16 from the glass substrate 4 in a state where the polarization direction is applied by 90 ° by the liquid crystal layer 13 having a 90 ° twist orientation. As described above, the polarization direction of the polarizing plate 16 is orthogonal to the polarization direction 20 of the polarizing plate 15, that is, the direction perpendicular to the paper surface indicated by the arrow 21, so that light passes through the polarizing plate 16.

On the other hand, when a predetermined voltage is applied between the electrodes 5 and 6, the liquid crystal layer 13 does not show the above-mentioned twisted orientation. Therefore, the light incident on the liquid crystal layer 13 is also not given its polarization direction. As a result, the polarization direction of the light incident on the polarizing plate 16 from the glass substrate 4 is orthogonal to the polarization direction indicated by the arrow 21 of the polarizing plate 16, and the light is blocked and not transmitted.

FIG. 8 is a diagram for explaining the following experimental data and a parameter θ of the experimental data in the embodiment described later. In general, the liquid crystal display cell 17 has a specific direction 22 at which the display contrast is maximized. Liquid crystal display cell
Consider a plane 24 formed by a direction 22 having a maximum display contrast and a normal 23 on a glass substrate 17. The angle formed between the line of sight 25 and the normal 23 on this plane 24 is hereinafter referred to as “viewing 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. is there. In the graph of FIG. 9, the measurement line 11 is the viewing angle θ.
= 0 °, the TV characteristic is shown, and the measurement line l2 has a viewing angle θ>
The TV characteristics for an arbitrary viewing angle θ in the range of 0 ° are schematically shown. As is clear from FIG. 9, the TV of the measurement line l2
In the characteristics, the light transmittance once becomes almost 0% when the applied voltage is around 2.5V, but the light transmittance rise phenomenon that the applied voltage rises again in the range of 3.0 to 4.0V (at this time, The maximum value of the light transmittance is hereinafter referred to as “T ^θ peak”).

FIG. 10 shows the viewing angle θ and the light transmittance T ^θ pe of the liquid crystal display cell 17.
It is a graph which shows the relationship with ak. Generally, when the viewing angle θ = 0 °, T ^θ peak does not appear, but when the viewing angle θ> 0 °, increasing the viewing angle θ increases the T ^θ peak value with a positive correlation. Therefore, at a viewing angle θ> 0 ° at which this phenomenon occurs, the gradation at the time of display of the liquid crystal display cell 17 is inverted due to the presence of the light transmittance T ^θ peak. Particularly, in a color display such as a color liquid crystal display device which gradation display is required, causing the gradation inversion occurs without a predetermined color is displayed for T ^theta peak value is not zero. Therefore, in order to realize a liquid crystal display device having good viewing angle characteristics,
It is necessary to eliminate the light transmittance T ^theta peak.

Applicant of the present invention, as a means to eliminate the light transmittance T ^theta peak described above effectively, filed on setting numerical conditions such as described below (the Japanese Patent Application No. Sho 63-72805) has already done .

Birefringence exhibiting a refractive index anisotropy of the liquid crystal Δn (= n _e -n _o,
n _e: refractive index of the liquid crystal molecular axis direction, n _o: the liquid crystal molecular axis direction and the refractive index in the vertical direction) in the range of retardation value [Delta] n · d of the formula which is the product of the liquid crystal layer thickness d of the liquid crystal cell Set to.

0.3 μm ≦ Δn · d ≦ 0.6 μm (1) The ratio K ₃₃ / of the bending elastic constant K _{33 of the} liquid crystal to the spreading elastic constant K ₁₁
Set K ₁₁ to a value of about 1.0 or less, and the bending elastic constant K of the liquid crystal.
₃₃ and twisting to the ratio K ₃₃ / K ₂₂ of about 2.0 or more values of the elastic constant K _22.

FIG. 11 shows the relationship between K ₃₃ / K ₁₁ and K ₃₃ / K ₂₂ when the composition ratio of the liquid crystal material used in the twisted nematic type liquid crystal display cell was variously changed, based on the measured values, Is a graph indicated by a symbol. As Table cracking in the graph of FIG. 11, it is a fact was roughly known from the prior art but, generally, positive correlation between the K ₃₃ / K ₁₁ and K ₃₃ / K ₂₂ It turns out that there is. Therefore, as described above, it is difficult to set the value of K ₃₃ / K ₁₁ to 1.0 or less and the value of K ₃₃ / K ₂₂ to 2.0 or more from the positive correlation shown in FIG. Yes, and therefore the T ^θ peak value cannot be reduced sufficiently. Further, in order to cope with an increase in the area of the liquid crystal display device (for example, a display of 5 inches or more), the light transmittance T is considered in view of human visual characteristics statistically.
It is desired that ^θ peak is about 3.0% or less.

The object of the present invention is to solve the above technical problems,
It is possible to provide a liquid crystal display device having a viewing angle characteristic in which high-quality display is possible for a wide range of viewing angles, and in particular, such as a color liquid crystal display device that requires gradation display, without gradation inversion. is there.

Means for Solving the Problems The present invention provides an active device including an active element including a liquid crystal layer in which a twisted nematic liquid crystal is aligned between a pair of translucent substrates on which translucent electrodes are respectively formed. A matrix type liquid crystal element for display, an optical compensation element arranged in a stacking direction of the display liquid crystal element, means for applying an electric field to a liquid crystal layer of the display liquid crystal element, the display liquid crystal element and the optical element. And a pair of polarizing members disposed in the stacking direction of the optical compensation element, wherein the retardation value Δn1 · d1 of the display liquid crystal element is 0.3 μm <Δn1 · d1.
<0.6 μm, and the retardation value Δn2 · Δd2 of the optical compensation element is 0.12 μm <Δn2 · d2 <0.3 μm
And abnormal light contained in the transmitted light of the display liquid crystal element is mutually canceled based on the optical birefringence of the display liquid crystal element and the optical compensation element. A liquid crystal display device characterized by the following.

Operation In the present invention, a display liquid crystal element and an optical compensation element are stacked and provided, and a pair of polarizing members are arranged in the stacking direction of these elements.

The liquid crystal layer and the optical compensation element of the above two elements have optical birefringence due to the difference between the refractive index in the liquid crystal molecular axis direction and the refractive index in the direction perpendicular to the molecular axis direction. Therefore, when the linearly polarized light transmitted through the polarizing member transmits the display liquid crystal element or the optical compensation element, it generates normal light and extraordinary light due to the birefringence, and corresponds to the phase difference therebetween. Elliptically polarized light.

Here, since the display liquid crystal element and the optical compensation element are provided in a stacked manner, the elliptically polarized light from one element is transmitted by compensating the phase difference based on the birefringence of the other element. Abnormal light contained in the light is mutually eliminated. As a result, the linearly polarized light transmitted through one polarizing member is linearly polarized even if it is transmitted through the stacked display liquid crystal element and optical compensation element, and is blocked or transmitted by the other polarizing member.

Thus, the light transmittance T ^theta peak that described in the prior art, it was resolved over a visible viewing angle substantially the entire liquid crystal display device, to prevent the gradation is reversed when displayed Can be. Further, in particular, if the present invention is applied to a color liquid crystal display device that performs a gradation display, it is possible to suppress gradation inversion such that a predetermined color display is not performed, 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 according to an embodiment of the present invention. The liquid crystal display device 18 includes a liquid crystal cell 1 for display, a liquid crystal cell 2 for optical compensation, and a pair of polarizing plates 15 and 16.
It is comprised including.

The display liquid crystal cell 1 includes a pair of translucent substrates, glass substrates 3 and 4, and a transparent electrode 5 made of ITO on each of opposing surfaces.
Patterns 6 are formed, and alignment films 7 and 8 made of, for example, a polyimide-based organic thin film are formed on the surface thereof. When the liquid crystal layer 13 is formed by enclosing a liquid crystal material to be described later between the glass substrates 3 and 4, the alignment films 7 and 8 are rubbed beforehand so that the liquid crystal molecules are twisted by 90 °. Perform processing. The display liquid crystal cell 1 is an active matrix type liquid crystal display device that performs display driving using an active element that is a switching means for selecting a display pixel, and is simplified in the description of the embodiments.

The optical compensation liquid crystal cell 2 has transparent electrodes 11 and 12 made of ITO formed on the entire surfaces of a pair of glass substrates 9 and 10 facing each other. The alignment films 29 and 30 made of a thin film are formed.
Rubbing treatment is also applied to the alignment films 29 and 30 in advance,
The liquid crystal molecules of the interposed liquid crystal layer 14 are in a so-called homogeneous alignment parallel to each other.

The display and optical compensation liquid crystal cells 1 and 2 including the above-described members are bonded together via a sealing resin (not shown), and the liquid crystal layers 13 and 14 are sealed therein. The liquid crystal cells 2 for target compensation are respectively formed. These display and optical compensation liquid crystal cells 1 and 2
The glass substrates 3 and 10 are abutted and bonded to each other, and a pair of polarizing plates 15 and 16 are superimposed on opposite sides of the glass substrates 4 and 9. Here, the polarization directions of the polarizing plates 15 and 16 are set in directions orthogonal to each other, for example, as indicated by arrows 20 and 21 in order to realize the above-described normally white display system.

Further, a driving circuit 27 is connected to the electrodes 5 and 6 of the display liquid crystal cell 1.
Is connected, and a drive circuit 28 is connected to the electrodes 11 and 12 of the optical compensation liquid crystal cell 2. A control circuit 26 is connected to the driving circuits 27 and 28, and the driving circuit 27 applies a predetermined voltage to the liquid crystal layer 13 of the liquid crystal cell 1 for display to perform display driving. The voltage applied to the liquid crystal layer 14 of the compensating liquid crystal cell 2 is adjusted to adjust the angle between the major axes of the liquid crystal molecules constituting the liquid crystal layer 14 and the glass substrates 9 and 10. Thereby, based on the optical birefringence of both the liquid crystal layers 13 and 14 of the display and optical compensation liquid crystal cells 1 and 2, the extraordinary light included in the transmitted light is canceled mutually as described later. I do.

As the liquid crystal material of the liquid crystal layers 13 and 14, for example, a nematic liquid crystal material having a positive dielectric anisotropy, for example, one or more kinds of cyclohexane-based compounds is used, but is not limited thereto. First
As schematically shown in the figure, the liquid crystal layer 13 has an alignment film 7,
No voltage is applied between electrodes 5 and 6 between 8 (off state)
As a result, the liquid crystal molecules are twisted at 90 °. Also the liquid crystal layer 14
In the case, the liquid crystal molecules are homogeneously aligned without applying a voltage between the electrodes 11 and 12 between the alignment films 29 and 30. Thus, the liquid crystal display device 18 can perform a normally white display in which white is displayed in an off state where no voltage is applied between the electrodes 5 and 6.

Next, FIG. 2 shows the light transmittance-applied voltage characteristic of the liquid crystal display device 18 having the above configuration, and FIG. 3 shows the same characteristic of the conventional liquid crystal display cell 17 as a comparative example. The characteristic curves l4, l5; l6, l7 shown in FIGS. 2 and 3 are measurement results under the following conditions.

Liquid crystal layers 13 and 14 of liquid crystal cells 1 and 2 for display and optical compensation
Are adjusted, and the wavelength λ of the incident light is 550 nm.
The liquid crystal layer 13 was set so that the refractive index anisotropy Δn1 = 0.10 and the liquid crystal layer 14 had the refractive index anisotropy Δn2 = 0.06. Further, the layer thickness d of the liquid crystal layer 13 of the liquid crystal cells 1 and 2 for display and optical compensation.
1 = 5.0 μm and the thickness d2 of the liquid crystal layer 14 were set to 2.0 μm.

Therefore, the display and optical compensation liquid crystal cells 1 and 2
When the pretilt angles of the liquid crystal layers 13 and 14 are approximated to be substantially 0 °, Δn1 · d1 = 0.50
μm, Δn2 · d2 = 0.12 μm.

The electrodes 11 and 12 of the liquid crystal cell 2 for optical compensation are applied with a threshold voltage from the drive circuit 28 so that the optical axis of the liquid crystal cell 2 for optical compensation is substantially perpendicular to the glass substrates 9 and 10. Also apply a sufficiently high voltage.

When the linearly polarized light transmitted through the polarizing plate 15 is transmitted through the liquid crystal layer 13 in which the twisted orientation is released by applying a threshold voltage during display driving, normal light and extraordinary light are generated due to the birefringence of the liquid crystal. Occur. The transmitted light may be elliptically polarized light in accordance with the phase difference. 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 are used. Light transmitted through 1 and 2 is again converted into linearly polarized light.

As a result, the linearly polarized light in the direction of the arrow 20 transmitted through the polarizing plate 15 remains linearly polarized even after transmitting through the liquid crystal cells 1 and 2 for display and optical compensation. Therefore, the polarizer 16
When the liquid crystal display 18 is viewed from the lower side in FIG. 1, liquid crystal display without gradation inversion is performed.

Further, when the viewing angle θ when the liquid crystal display device 18 is viewed from the lower side in FIG. 1 becomes larger than a certain degree, total reflection occurs on the surface of the polarizing plate 16 or the like, and the display contents of the liquid crystal display device 18 cannot be visually recognized. On the other hand, in the conventional example, when the liquid crystal display cell 17 is used, any viewing angle θ other than 0 °
Then, the light transmittance T ^θ peak appears. However, in practice, the critical angle θc
(For example, about 50 °), the light transmittance T ^θ
It can be said that it is sufficient to eliminate the occurrence of peaks.

In FIG. 2, a characteristic curve 14 is a light transmittance-applied voltage characteristic when the viewing angle θ = 0 °, and a characteristic curve 15 is a characteristic when the viewing angle θ = 45 °, for example. In the comparative example shown in FIG. 3, the characteristic curve 16 is the light transmittance-applied voltage characteristic when the viewing angle θ = 0 °, and the characteristic curve 17 is the viewing angle θ =
This is the characteristic for 45 ゜.

As is clear from a comparison between FIG. 2 (Example) and FIG. 3 (Comparative Example), the light transmittance-applied voltage characteristic curves l4 and l6 at the viewing angle θ = 0 ° show almost the same tendency. In particular, when the applied voltage is 4.0 V or more, both the light transmittances are almost 0.
% Are blocked.

On the other hand, comparing the characteristic curves l5 and l7 in the case where the viewing angle θ = 45 °, in the embodiment of FIG. 2, while the applied voltage is 3.0 V or more and the light transmittance is almost 0%, In the characteristic curve 17 of the comparative example shown in the figure, the light transmittance is temporarily cut off to almost 0% when the applied voltage is around 2.5 V, but the applied voltage is 3.
A lifting phenomenon in which the light transmittance increases again between 0 and 4.0 V has occurred.

Therefore, according to the present invention, it is possible to eliminate the light transmittance T ^θ peak in the case where the viewing angle θ> 0 °, and to improve the display state such as grayscale inversion in monochrome display or color display to improve the display of the liquid crystal display device. The quality is improved.

Such an effect is not achieved only when the viewing angle θ is between the critical angle θc and 0 °, but as described above, the viewing angle θ
As long as> 0 °, it can be realized for any viewing angle θ. The critical angle θc merely indicates a practical range in consideration of total reflection and the like.

Next, the light transmittance ^T θ peak ≒ 0 each retardation value to eliminate gray scale inversion as% .DELTA.n1 · d1, the relationship between .DELTA.n2 · d2, be described on the basis of the experimental results below.

4 shows a dependence on the retardation value .DELTA.n2 · d2 of the optical transmittance T ^theta peak in case of fixing the retardation value .DELTA.n1 · d1 at a constant value. That is, the figure shows the retardation value Δn1 · d1 of the display liquid crystal cell 1 = 0.5.
μm, the viewing angle θ when the retardation value Δn2 · d2 of the optical compensation liquid crystal cell 2 is variously changed.
= 45 ° light transmittance T ^{θ = 45 °} peak. From the measurement curve 18 in the same figure, there is a range of Δn2 · d2 where the light transmittance Tθ ^{= 45 °} peak is 3% or less, which is a practical reference level,
It can be seen that there is a further T ^{theta = 45 °} peak ≒ 0 and becomes minimum T ^{theta = 45 °} peak optimum retardation value with respect to values .DELTA.n2 · d2. In particular, under the conditions shown in FIG. 4, the optimum value is Δn2 · d2 = 0.12 μm.

FIG. 5 shows the relationship between the retardation values Δn1 · d1 and the optimum values of the retardation values Δn2 · d2.
As shown by the measurement curve 19 in the figure, there is a positive correlation between the retardation values Δn1 · d1, Δn2 · d2.

Although FIGS. 4 and 5 show the case where the viewing angle θ = 45 °, if the light transmittance T ^θ peak ≒ 0% at the viewing angle θ = 45 °, the viewing angle θ is 0 ° ≦ θ. It has been confirmed that similar results can be obtained in the range of ≤45 °.

By using the FIG. 5 described above, any retardation values for the display liquid crystal cell 1 with .DELTA.n1 · d1, the light transmittance ^T θ peak ≒ 0 optical compensation liquid crystal cell to be provided in order to 2, a design value of the retardation value Δn2 · d2 can be determined. However, it is difficult to manufacture each of the retardation values Δn1 · d1, Δn2 · d2 as designed values from the viewpoint of mass productivity of the liquid crystal cells 1 and 2.

That is, the liquid crystal cells 1 and 2 for display and optical compensation are:
The retardation values Δn1 · d1 and Δn2 · d2 are manufactured with variations centered on the design values. Therefore,
Strictly defining the standard value of each retardation causes 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, the liquid crystal layer of the optical compensation liquid crystal cell 2 is provided.
By adjusting the voltage applied to 14, the light transmittance T ^θ peak ≒
Can be 0%, therefore the respective retardation values .DELTA.n1 · d1, regardless of variations in the manufacturing stage of .DELTA.n2 · d2, it is possible to suppress the grayscale inversion display due to the light transmittance T ^theta peak it can.

That is, the retardation value R related to the elliptically polarized state of the light transmitted through the optical compensation liquid crystal cell 2 is defined by the following equation in consideration of the tilt angle α formed by the liquid crystal molecules with respect to the substrate.

R = Δn2 · d2cos ² α (2) The tilt angle α in the second equation changes according to the voltage applied to the liquid crystal layer 14, and therefore, the retardation value R of the optical compensation liquid crystal cell 2 also increases. It changes according to the second equation.

FIG. 6 is a graph showing the light transmittance T ^θ peak with respect to the voltage V applied to the liquid crystal layer 14. The result shown in the figure is a graph in which the optical compensation liquid crystal cell 2 is set to Δn2 · d2 = 0.15 μm, and Δn1 · d1 of the display liquid crystal cell 1 is used as a parameter, and the parameter Δn1 · d1 = 0.4 , 0.5,0.
Curves l10, l11, l measured for each value of 6 μm
12 is shown.

As is clear from the measurement results shown in FIG.
Even if the parameter Δn1 · d1 changes with respect to a constant value of d2 = 0.15 μm, the voltage applied to the optical compensation liquid crystal cell 2 is set to a value sufficiently higher than the threshold voltage _Vth , for example, the voltage _Vp.
= V _p1 , V _p2 , V _p3, etc., it is possible to make the light transmittance T ^θ peak ≒ 0%.

Therefore, according to the correlation shown in FIG. 5, for each of the predetermined retardation values Δn1 · d1, Δn2 · d2, each manufactured liquid crystal cell for display and optical compensation is provided.
Variations in the retardation values of the liquid crystal cells 1 and 2 are caused when the liquid crystal display device 18 shown in FIG. 2
By the voltage applied to the liquid crystal layer 14 is set to the applied voltage V _p to be 0% light transmission T ^theta peak ≒ in example viewing angle theta = 45 °, and to eliminate the lift of the light transmittance T ^theta peak be able to.

Incidentally, a practical viewing angle range to 0% light transmission T ^theta peak ≒ at (-45 ° ≦ theta ≦ 45 °), the display and optical compensation retardation value of the liquid crystal cells 1 and 2 Δn1
It is preferable that d1, Δn2, d2 be set in the range of the following equation.

0.3 μm <Δn1 · d1 <0.6 μm (3) 0.12 μm ≦ Δn2 · d2 <0.3 μm (4) When retardation Δn2 · d2 = 0.12 μm, as described with reference to FIG. In the practical viewing angle range, the light transmittance T ^θ peak ≒ 0% is an optimum value, and the excellent effect was similarly achieved when Δn 2 · d 2 = 0.15 μm as described above.

As described above, according to the present invention, the light transmittance T ^θ peak when the viewing angle θ> 0 ° is set to Δn1, d1, Δn2, d2, etc. generated in the manufacturing process of the display and optical compensation liquid crystal cells 1, 2. Can be eliminated in accordance with the variation in the values of, and undesirable display states such as grayscale inversion in monochrome display and color display are improved, and the display quality of the liquid crystal display device is improved.

In the above embodiments, the display system is a normally white mode, and so as to eliminate the light transmittance T ^theta peak only by the voltage V _p applied to the optical compensation liquid crystal cell 2. However, the present invention is not limited to these, and in a normally black display mode, the light transmittance T ^θ can be adjusted by mutually adjusting the voltages applied to the display and optical compensation liquid crystal cells 1 and 2. It is also possible to implement the present invention so as to eliminate the peak.

The present invention relates to a thin film transistor and a metal insulator (MIM).
The present invention is applied to an active matrix liquid crystal display device that performs display driving using an active element such as a metal element or a diode.

According to the present invention, a liquid crystal display device is configured by stacking a display liquid crystal element and an optical compensation element.
The viewing angle dependence of the display in the liquid crystal display is improved, and the grayscale inversion in monochrome display and the grayscale inversion in color display are eliminated. Therefore, the display quality of the liquid crystal display device is significantly improved.

[Brief description of the drawings]

FIG. 1 is an exploded sectional view showing a configuration of a liquid crystal display device 18 according to one embodiment of the present invention, FIG. 2 is a graph showing light transmittance-applied voltage characteristics of the liquid crystal display device 18, and FIG. conventional light transmittance of the liquid crystal display cell 17 as - a graph showing the applied-voltage characteristic, Figure 4 is a graph showing the relationship between the light transmittance T ^theta peak and .DELTA.n2 · d2, Fig. 5 light transmittance T ^theta peak ≒ .DELTA.n1 · d1 in the case of 0%, a graph showing the relationship between .DELTA.n2 · d2, FIG. 6 is a graph showing the relationship between the applied voltage V with respect to the light transmittance T ^theta peak and the liquid crystal layer 14, FIG. 7 is a conventional 8 is an exploded cross-sectional view showing the structure of the liquid crystal display cell 17, FIG. 8 is a diagram defining a viewing angle θ, FIG. 9 is a graph showing light transmittance-applied voltage characteristics of the conventional liquid crystal display cell 17, and FIG. FIG. 11 is a graph showing the relationship between the light transmittance of the display cell 17 and the viewing angle, and FIG. 11 shows the elastic constant ratios K ₃₃ / K ₁₁ and K ₃₃ / K.
₂₂ is a graph showing ₂₂ correlations. 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,
30 …… Alignment film, 13,14 …… Liquid crystal layer, 15,16 …… Polarizer, 18
... a liquid crystal display device, 26 ... a control circuit, 27, 28 ... a drive circuit, d1 ... a layer thickness of the liquid crystal layer 13, d2 ... a layer thickness of the liquid crystal layer 14, Δ
n1: birefringence of liquid crystal layer 13, Δn2: birefringence of liquid crystal layer 14, θ: viewing angle

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-244019 (JP, A) JP-A-62-150329 (JP, A) JP-A-2-111918 (JP, A) JP-A-2-2 43515 (JP, A)

Claims (1)

(57) [Claims] 1. An active matrix type liquid crystal display device having an active element comprising a liquid crystal layer in which a twisted nematic liquid crystal is oriented between a pair of light transmitting substrates each having a light transmitting electrode formed thereon. An optical compensation element arranged in a stacking direction of the display liquid crystal element; a unit for applying an electric field to a liquid crystal layer of the display liquid crystal element; and a stack of the display liquid crystal element and the optical compensation element. And a pair of polarizing members arranged in the directions, wherein a retardation value Δn1 · d1 of the display liquid crystal element is 0.3 μm <Δn1 · d1 <0.6 μm, and a retardation value of the optical compensation element. Value Δn2 ・ Δd2
0.12 μm <Δn2 · d2 <0.3 μm, and the extraordinary light included in the transmitted light of the display liquid crystal element is changed based on the optical birefringence of the display liquid crystal element and the optical compensation element. A liquid crystal display device characterized by mutually canceling each other.