JP2001281664A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve response speed in a halftone display of an MVA(multi- domain vertical alignment) mode liquid crystal display device, with respect to a liquid crystal display device. SOLUTION: In the liquid crystal display device, which holds a liquid crystal with a negative dielectric anisotropy between two substrates 1, 2 placed opposite to each other, of which at least the one out of electrodes 11, 12 arranged on mutually opposed surfaces of the both substrates 1, 2 is composed of a transparent electrode, of which the liquid crystalline molecules 8 align, so as to make the direction of their long axes be nearly vertical at least to the one principal plane of the substrate 1, 2 without application of voltage and of which the aligned direction of the long axes of the liquid crystalline molecules 8 falls down in a direction parallel to the principal planes of the substrates 1, 2, when a voltage is applied, the retardation Δn.d of the liquid crystal layer 7 is set so that 0.24 μm<Δn.d<0.42 μm, and the thickness d of the liquid crystal layer 7 is set to be 2.0 μm<d<=3.5 μm in the case of vertical alignment.

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, and more particularly to a liquid crystal display device in which vertical alignment of liquid crystal molecules is controlled by electric field distortion caused by a structure such as a projection provided on at least one substrate side, and is controlled in a plurality of directions. (Multi-domain Ver.) That performs orientation division of liquid crystal molecules
The present invention relates to a liquid crystal display device characterized in that the relationship between a cell gap d and a refractive index anisotropy Δn for improving a response speed in a liquid crystal display device is specified.

[0002]

2. Description of the Related Art In recent years, a liquid crystal panel using an active matrix has attracted attention as a display capable of realizing lightweight, thin, and low power consumption. However, as an active matrix type liquid crystal display device, a TN (Twisted N) is used.
eTN) The TN method using liquid crystal has been the mainstream.

However, in the TN mode, even when a voltage is applied, the liquid crystal molecules are oriented in the normal direction of the panel while maintaining the orientation orientation when no voltage is applied to some extent, and the orientation state of the liquid crystal molecules is dependent on the azimuth angle. Therefore, there is a problem that the viewing angle characteristics are narrow.

As a method of improving this, MVA (Multi) in which liquid crystal molecules which are vertically aligned are controlled by electric field distortion caused by a structure such as a projection provided on at least one substrate side to perform liquid crystal molecule alignment division in a plurality of directions. -Doma
Attention has been paid to an in Vertical Alignment type liquid crystal display device (if necessary, JP-A-11-242225).

Here, a conventional MVA liquid crystal display device will be described with reference to FIG. FIG. 18A is a schematic cross-sectional view of a main part of a conventional MVA type liquid crystal display device in a state where a voltage is not applied. A pixel electrode 32 made of an ITO transparent electrode is formed on a TFT substrate 31. In addition, a projection 33 made of an insulator for locally regulating the alignment of the liquid crystal molecules 40 is provided, and a vertical alignment film 34 is provided so as to cover these. On the other hand, the TFT substrate 3
On a CF (color filter) substrate 35 facing 1
A common electrode 36 made of an ITO transparent electrode is provided, and a protrusion 37 made of an insulator for locally regulating the alignment of the liquid crystal molecules 40 is provided at a position that does not projectively overlap the protrusion 33, and a vertical alignment film is formed so as to cover these. A liquid crystal 39 having a negative dielectric anisotropy (Δε <0) is injected between the opposed TFT substrate 31 and CF substrate 35.

In this case, the liquid crystal molecules 40 near the projections 33 and 37 show an alignment state depending on the shapes of the projections 33 and 37, and the liquid crystal molecules 40 of the vertical alignment films 34 and 38 covering the surfaces of the projections 33 and 37. The liquid crystal molecules 40 are inclined so as to be aligned in the normal direction. On the other hand, the liquid crystal molecules 40 at positions away from the protrusions 33 and 37 are vertically aligned.

In such a liquid crystal display device, the polarizer 41 provided on the TFT substrate 31 side and the polarizer 42 provided on the CF substrate 35 side are arranged in crossed Nicols,
When no voltage is applied, "black" is displayed.

FIG. 18 (b) is a view showing an arrangement state of the liquid crystal molecules 40 in a state where a voltage is applied, and the projections 33 and 37 which are already inclinedly aligned by applying a voltage. , The entire liquid crystal molecules 40 having negative dielectric anisotropy are tilted by the tilt angle θ _p according to the applied voltage, and the display in the transmission state or the halftone state is performed. Is obtained.

As described above, in the MVA type liquid crystal display device, since the projections 33 and 37 are provided in advance and a part of the liquid crystal molecules 40 are tilt-aligned, a higher response speed can be obtained as compared with the conventional liquid crystal display device. In addition, since the liquid crystal molecules 40 are divided and aligned in a plurality of directions, a wide viewing angle of 160 ° vertically, horizontally, and horizontally is realized when the contrast ratio is 10 or more. Note that, instead of the protrusion, the pixel electrode 32
Alternatively, a similar effect can be obtained even if a cutout portion, that is, a slit portion is provided in the common electrode 36.

The manufacturing conditions of the display panel in mass-produced products of such an MVA type liquid crystal display device are as follows.
4.0 μm, and the refractive index anisotropy Δn of the liquid crystal is Δn = 0.
It is suitable for a high-performance liquid crystal monitor because it has characteristics such as a very high contrast ratio from the front and excellent black-and-white responsiveness.

In recent years, as the demand for a monitor for moving images has increased from a monitor for still images such as a personal computer, a halftone (gray scale) that does not cause an afterimage or a display blur.
IPS (In-Plane), which drives liquid crystal molecules in a panel surface by applying a TN type liquid crystal display device or a lateral electric field, is required.
In the case of a switching type liquid crystal display device, an increase in the halftone response speed has been achieved. Therefore, an improvement in the response speed has been demanded also in the MVA type liquid crystal display device.

However, in the MVA type liquid crystal display device, it takes time for the structure for regulating the tilt direction, that is, for the tilt of the liquid crystal to propagate in the region without the protrusions 33 and 37, and the liquid crystal of the entire pixel responds. It takes time to do
Sufficient responsiveness is not always obtained. Particularly, when the halftone display is at a low gradation, there is a problem that the propagation of the liquid crystal alignment becomes slow due to a low voltage, and the response time becomes three times or more than usual. This situation will be described with reference to FIGS.

Referring to FIG. 19, FIG. 19 shows a liquid crystal D (MJ96213:
Rise time to white display when using Merck Japan Ltd. trade name), i.e., an illustration of the applied voltage dependence of the response speed T _on, full white display by applying a voltage of about 5V Is obtained, T _on ２０20 ms (ms)
Although the response speed is high, displaying a halftone requires a response speed of several tens of milliseconds or more, which causes afterimages and display blur on a monitor screen. When the applied voltage is 5
When the voltage exceeds V, the response speed increases. This is due to the deviation of the alignment of the liquid crystal molecules.

FIG. 20 is a diagram illustrating the rise time from white display to black display, that is, the dependence of the response speed T _{off on} the applied voltage.
With increasing applied voltage, but also it increases the response speed T _off, a T _off ~10ms about at an applied voltage of about 5V, not a problem since quite small compared to T _on.

A vertical alignment type such as this MVA type liquid crystal display device is an ECB (Electrically Controlled).
This is a mode utilizing the LLed effect (Leed Birefringence) effect. Generally, the response speed τ relating to the electro-optical characteristics is represented by τ _r , a rise time from black display to white display, τ _d , a rise time from white display to black display, d Is the cell thickness, ε ₀ is the relative permittivity, Δε is the dielectric anisotropy, η _i is the viscosity parameter, K ₃₃ is the elastic parameter (bend), V
If the applied voltage, respectively, τ _r = η _i d ² becomes ^{_{(ε 0 · | V 2 -K}} 33 π 2 | Δε) -1 τ d = η i d 2 (K 33 π 2) -1 It is known.

Therefore, also in the MVA type liquid crystal display device, in consideration of the above relational expression, in order to increase the response speed τ, the cell thickness d must be reduced and the liquid crystal viscosity (η
It was considered advantageous to reduce _i ).

[0017]

However, when the cell thickness d is reduced, a liquid crystal with a high Δn is required in order to prevent the transmittance of the liquid crystal cell from decreasing, and it is necessary to consider the viscosity and the like. is there. That is, in general, when the liquid crystal molecules extend in the lateral direction, the refractive index anisotropy Δn increases, and the molecular weight increases, so that the viscosity tends to increase (η∝Δn). There is a problem that the response speed τ increases from the above relational expression, and the effect of reducing the cell thickness d is offset. In addition, in order to meet the demand for extending the operating temperature range of the liquid crystal panel, a liquid crystal having a high viscosity is required, but this also increases the response speed τ.

Therefore, it is necessary to select a liquid crystal material having a large Δn and a small viscosity η as much as possible. Was not available.

Further, in the MVA type liquid crystal display device,
Since the orientation in the vicinity of the projections and slits is involved, there is also a problem that even if the applied voltage is simply increased, "alignment blur" occurs and an afterimage occurs.

Therefore, an object of the present invention is to improve the response speed in the halftone display of the MVA type liquid crystal display device.

[0021]

Here, means for solving the problems in the present invention will be described with reference to FIG.
FIG. 1 is a schematic sectional view of an essential part of an MVA type liquid crystal display device of the present invention. See FIG. 1 (1) The present invention sandwiches a liquid crystal having a negative dielectric anisotropy between two substrates 1 and 2 facing each other,
Electrodes 11, 1 provided on opposing surfaces of both substrates 1, 2.
2 is composed of a transparent electrode, and the liquid crystal molecules 8 are oriented such that the major axis direction is substantially perpendicular to the main surface of at least one of the substrates 1 and 2 in a state where no voltage is applied,
When a voltage is applied, the orientation of the major axis of the liquid crystal molecules 8 is
In the liquid crystal display device which falls in the direction parallel to the main surface of No. 2,
The retardation Δn · d of the liquid crystal layer 7 during vertical alignment is 0.24 μm <Δnd <0.42 μm, and the thickness d of the liquid crystal layer 7 is 2.0 μm <d ≦ 3.5 μm. Features.

As described above, the retardation Δn · d of the liquid crystal layer at the time of vertical alignment in the MVA liquid crystal display device is 0.24 μm <Δn · d <in view of the ECB effect in consideration of the current liquid crystal panel configuration and the materials used. It needs to be 0.42 μm. Incidentally, Δn = 0.0822 and d = 4.0 μm of the current typical MVA type display panel, and therefore Δn · d = 0.3288 μm, which is almost an intermediate value in the above range.

Further, the cell thickness d is, too a large viscosity dependence of the response speed T _on exceeding 3.5 [mu] m, whereas, the viscosity dependence of the response speed T _on the cell thickness d is reduced decreases, various Can be used. However, if the cell thickness d is too small, the production becomes difficult, and the Δn of the high Δn liquid crystal material that can be used from the viewpoint of storage stability and the like can be used.
Is about 0.1200, so the lower limit of the cell thickness d is 2.0 μm from the relationship with the lower limit of retardation Δn · d of 0.24 μm. That is, the present invention has experimentally confirmed that the contribution of the cell thickness d among the two factors of the cell thickness d and the viscosity η for improving the response speed is large.

Further, the present invention is characterized in that, in the above (1), the refractive index anisotropy Δn of the liquid crystal satisfies 0.0900 <Δn <0.1200. That is, the refractive index anisotropy Δn of the currently available liquid crystal material is in the range of about 0.0700 to 0.1600.
It is realistic to set it to 200 or less, and the cell thickness d
In order to suppress a decrease in transmittance due to a decrease in the value, it is necessary to make Δn (= 0.0822) larger than that of a currently used liquid crystal. Therefore, it is preferable that Δn> 0.0900.

(2) Further, according to the present invention, in the above (1), the liquid crystal molecules 8 fall in two or more directions, and the pair of substrates 1 and 2 are arranged in a crossed Nicols. It is characterized in that it is sandwiched between the children 9 and 10.

As described above, the configuration of the above (1) is changed to the liquid crystal molecule 8
By applying the present invention to a liquid crystal display device having two or more falling directions, that is, an MVA type liquid crystal display device,
The response speed in the halftone display of the VA liquid crystal display device can be increased. In particular, a pair of polarizers 9 and 10 by a cross nicol state, the rise time of the white display, i.e., it is possible to reduce the response speed T _on.

(3) According to the present invention, in the above (2), the means for causing the liquid crystal molecules 8 to fall down in two or more directions includes a projection 6 or an electrode 11 formed on at least one of the substrates 1 and 2. And the gap between the protrusions 6 or the slits 5 of the electrode 11 is 25 μm or less.

As described above, in order to constitute the MVA type liquid crystal display device, it is necessary to form the projection 6 or the slit portion 5 of the electrode 11 on at least one of the substrates 1 and 2. By setting the gap between the slit portions 5 to 25 μm or less, the effect of improving the response speed of halftone display by reducing the cell thickness d can be effectively exhibited. Note that the protrusion 6 or the electrode 11
When the gap between the slit portions 5 is 30 μm or more, the effect of improving the response speed of halftone display cannot be obtained.

Further, according to the present invention, in any one of the above (1) to (3), one of the substrates 1 and 2 is a color filter substrate, and the projections 6 or the slits 5 of the red, green and blue pixels are formed. The gap w is set for each pixel.

In general, the refractive index anisotropy Δn has wavelength dependence. As the wavelength becomes shorter, Δn becomes larger, and in a liquid crystal having a larger refractive index anisotropy Δn, in the case of blue (B) having a shorter wavelength,
In the transmittance (T) -applied voltage (V) characteristic, a maximum value appears at a relatively low voltage, and at an applied voltage of about 5.4 V for complete white display, the relative value is higher than that of green (G) and red (R). Since the target strength is reduced, the display may be yellowish and the chromaticity may be reduced. Therefore, the gap w is set to w _B
By setting the relation of <w _G <w _R , blue (B)
Chromaticity can be suppressed by compensating for the saturation and attenuation of the chromaticity.

Further, according to the present invention, in any one of the above (1) to (3), one of the substrates 1 and 2 is a color filter substrate 1 or 2 and has a cell thickness d in red, green and blue pixels.
Is set for each pixel.

By setting the cell thickness d to satisfy the relationship of d _B <d _G <d _R , saturation and attenuation of blue (B) can be eliminated, thereby suppressing a decrease in chromaticity. . In order to set the cell thickness d in a relationship of d _B <d _G <d _R , the thickness t of the color filter is set to t _B > t _G >
It may be set in the relationship of t _R.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, an MVA type liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIGS. In the drawings, illustration of active elements such as TFTs, color filters, and the like is omitted. Referring again to FIG. 1, FIG. 1 is a schematic cross-sectional view of an essential part of an MVA type liquid crystal display device according to an embodiment of the present invention. As shown in FIG. 1, a pixel electrode is formed on a glass substrate 1 serving as a TFT substrate. ITO to become
On the other hand, an electrode 12 made of ITO as a common electrode is provided on the substrate 2 made of glass as a CF substrate facing the TFT substrate.

In this case, the electrode 11 is provided with a slit portion 5 having a width w ₃ of, for example, 10 μm, and then a vertical alignment film 3 (JALS-684: trade name, manufactured by JSR) is provided so as to cover the electrode 11. on the other hand, a photosensitive resin is formed on the electrode 12 (e.g., a resist or the like), for example, the width w ₁ 10 [mu]
In m, height mutual spacing projections 6 of 1.3～1.6Myuemu, i.e., the gap w ₂ are 25 [mu] m or less, for example, 25 [mu] m
And a vertical alignment film 4 (JALS-68) is provided on the entire surface after being provided so as not to overlap with the slit portion 5 in a projected manner.
4: JSR product name).

Then, spacers 13 made of resin beads having a diameter D are scattered and bonded using a thermosetting sealing material to form empty cells having a cell thickness of d. The diameter D of the spacer 13 in this case is 3.0
Using μm, 3.5 μm, 4.0 μm, and 4.5 μm, four types of empty cells were produced.

Next, a liquid crystal having a negative dielectric anisotropy is injected into the empty cell, which is then sealed.
The MVA liquid crystal display device was constructed by laminating 1 and 12 in a crossed Nicols state. Note that the cell thickness d in this case was obtained by a cell thickness measuring device manufactured by Oak Manufacturing Co., and d ≒ D.

As the liquid crystal in this case, four types of liquid crystal A to liquid crystal D having the characteristics shown in Table 1 below were used, and the liquid crystal D was MJ9621313 (used in a conventional MVA type liquid crystal display device). (Merck Japan's trade name).

[Table 1]

In this case, the liquid crystal molecules 8 are vertically aligned with respect to the substrates 1 and 2 under the control of the vertical alignment films 3 and 4, as in the conventional example shown in FIG. The liquid crystal molecules 8 in the vicinity of the projections 6 exhibit an alignment state depending on the shape of the projections 6, and the liquid crystal molecules 8 are inclined so as to be aligned with the normal direction of the vertical alignment film 4 covering the surface of the projections 6. become.

FIG. 2 is a TV characteristic diagram of an MVA type liquid crystal display device having a cell thickness d of 4.5 μm, where Δn = 0.1, which is the largest Δn.
In the liquid crystal A of 003, a peak appears near 5 V, and above this, the transmittance tends to decrease gradually.

FIG. 3 is a TV characteristic diagram of an MVA liquid crystal display device having a cell thickness d of 3.0 μm. In general, the transmittance tends to increase as Δn increases. Although not appearing,
It is understood that the absolute value of the transmittance decreases as the cell thickness d decreases as compared with the case of FIG.

[0041] See Figure 4. Figure 4, the response speed T _on the cell thickness d is 4.5μm in MVA type liquid crystal display device - is an illustration of the viscosity dependence of transmittance change, the response the larger rotational viscosity gamma ₁ It is understood that the speed _Ton is slow. The change in transmittance in this case is 5.4.
The transmittance is normalized by setting the transmittance at V to 100%.

FIG. 5 is an explanatory diagram of the response speed T _on of the MVA type liquid crystal display device having a cell thickness d of 3.0 μm and the viscosity dependency of the transmittance change, and shows a halftone region where the transmittance change is small. in gamma ₁ is seen as the response speed T _on is slow trend fairly high, as the response speed T _on a large gamma ₁ is a large area of the transmittance change is increased, by the cell thickness d is smaller as a whole , viscosity dependence of the response speed T _on is no longer seen.

Therefore, from the comparison between FIG. 4 and FIG.
Response speed T of halftone in MVA type liquid crystal display device
It is understood that _{on (LV)} is more dependent on the cell thickness d than _{on the} liquid crystal viscosity (γ ₁ ). Therefore, when the cell thickness d is reduced, even if a liquid crystal with a large rotational viscosity γ ₁ is used, response speed T _{on (LV)} of the tone will be greatly improved, a large liquid crystal rotational viscosity gamma _1, as described above, generally, delta
Since n is also large, it is possible to compensate for a decrease in transmittance due to a decrease in cell thickness d.

The effect of improving the halftone response speed Ton _(LV) by reducing the cell thickness d is greater for liquid crystals having a higher viscosity. For example, when the rotational viscosity γ ₁ is 282 mPa · s (millipascal · second), In the liquid crystal A, the speed can be increased from about （(transmittance change 50%) to slightly more than １ ／ (transmittance change 25%), and the rotational viscosity γ ₁ is 72 mPa · s, which is the smallest liquid crystal C. About 4/5 (transmissivity change 50
%) To slightly more than half (a change in transmittance of 25%).

Therefore, the liquid crystal A of Δn = 0.003
The MVA liquid crystal display device having a cell thickness d = 3.0 μm using a liquid crystal display device has a halftone response speed compared to the MVA liquid crystal display device having a cell thickness d = 4.5 μm using a conventional liquid crystal D having Δn = 0.0822. _{Ton (LV)} can be made faster.

Note that when Δn = 0.0821, γ₁= 72m
The liquid crystal C of Pa · s has the highest response speed T _onIs good, but
There are still problems with commercialization in terms of longevity and storage stability.
For example, the temperature range that can be stored stably is the clear point N
As can be seen from the fact that I is NI = 50 ° C.,
If it is only about 0-60 ° C, the usage environment is limited.
It was confirmed that it was not suitable for mass production.

[0047] Figure 6 Referring to FIG. 6, the response speed T _off of the cell thickness d is 4.5μm in MVA type liquid crystal display device - is an illustration of the viscosity dependence of transmittance change, also in this case, rotational viscosity gamma ₁ It is understood that the response speed _Toff is slower as is larger. The transmittance change in this case is also normalized by setting the transmittance at 5.4 V to 100%.

[0048] Figure 7 Referring to FIG. 7, the response speed T _off of the cell thickness d is 3.0μm in MVA type liquid crystal display device - is an illustration of the viscosity dependence of transmittance change, also in this case, rotational viscosity gamma ₁ It is understood that the response speed _Toff is slower as is larger.

Therefore, from the comparison between FIG. 6 and FIG.
The response speed T _off in the MVA type liquid crystal display device—the change in the transmittance is due to the reduction in the cell thickness d, the response speed T off
It is understood that the viscosity dependence of _off becomes smaller. The response speed T _off is about ４ of the response speed T _on , so there is no problem. However, since the viscosity dependency is reduced, a liquid crystal having a high Δn is used from the viewpoint of the response speed T _off. It is understood that there is no particular problem.

FIG. 8 is an explanatory diagram of the dependence of the response speed T _{on (25%)} -rotational viscosity γ ₁ characteristic on the cell thickness d, and d = 3.5 μm and d not explained above. Also, the characteristics of the MVA type liquid crystal display device of = 4.0 μm are shown. As is clear from the figure, as the cell thickness d decreases, the transmittance increases from 0% to 25%.
% Response speed _{Ton (25%)} in low gradation display
Be understood that the rotational viscosity gamma _1-dependent decreases, decreasing the cell thickness d that is understood to be effective for improving the response speed T _on even in the low-halftone from this point.

FIG. 9 shows the response speed _{Ton (25%)} -rotational viscosity γ shown in FIG.
The cell thickness d dependence of _one characteristic is viewed from another viewpoint as the rotational viscosity γ ₁ dependence of the cell thickness d-response speed Ton _(25%) characteristic. As is apparent from the figure, the smaller the cell thickness d, the lower the rotational viscosity γ ₁ dependence of the response speed T _{on (25%)} in the low gradation display from 0% to 25% in transmittance. Is understood.

Judging comprehensively from the above, it is desirable that the cell thickness d be 3.5 μm or less. On the other hand, as the upper limit, the manufacturability is one factor, and the current realistic upper limit of Δn is considered to be about 0.12. Therefore, the upper limit is considered to be the optimum range of the retardation Δn · d in the current liquid crystal display device. 0.24 μm <Δ
Considering the lower limit of 0.24 μm for n · d <0.42 μm, the value is 2.0 μm (= 0.24 μm / 0.12).

Therefore, in order to improve the response speed of the MVA type liquid crystal display device, it is desirable that the cell thickness d is 2.0 μm <d ≦ 3.5 μm.

As described above, since the transmittance decreases as the cell thickness d decreases, Δn is larger than that of the conventional liquid crystal D (Δn = 0.0822) in order to compensate for the reduction in the transmittance. It is desirable to use liquid crystal, and from such a viewpoint, the refractive index anisotropy Δn is desirably in the range of 0.0900 <Δn <0.1200.

Next, with reference to FIGS. 10 to 17, a description will be given of a second embodiment of the present invention that the gap w ₂ between the projections or between the slit portion of features. The structure of the MVA-type liquid crystal display device in this case is similar to the MVA liquid crystal display device shown in substantially 1, provided that the gap w _2, w ₂ = 1
Three types of cells of 0 μm, 20 μm, and 30 μm were prepared. Note that a liquid crystal D is used as the liquid crystal.

FIG. 10 is an explanatory diagram of the dependence of the response speed T _on -transmissivity change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 3.0 μm, where w ₂ ≦ 20 μm or less. in, the response speed T _on is smaller with increasing transmittance change, w ₂
= 30 μm, the response speed _Ton deteriorates.

FIG. 11 is an explanatory diagram of the dependence of the response speed T _off -transmissivity change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 3.0 μm. Although the rate T _on degrades with increasing transmission change, change itself is small, and it is understood the gap w ₂ dependent also small.

FIG. 12 is an explanatory diagram showing the dependence of the response speed T _on -transmissivity change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 3.5 μm, where w ₂ ≦ 20 μm or less. in, the response speed T _on is smaller with increasing transmittance change, w ₂
In the case of = 30 μm, the response speed _Ton is greatly deteriorated when the transmittance change is 50% or more.

FIG. 13 is an explanatory diagram showing the dependence of the response speed T _off -transmittance change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 3.5 μm. speed T _{of f} deteriorates with increasing transmission change, but change itself is small,
It is also understood that the gap w ₂ dependence is small.

FIG. 14 is an explanatory view of the dependence of the response speed T _on -transmissivity change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 4.0 μm, where w ₂ ≦ 20 μm or less. in, the response speed T _on is smaller with increasing transmittance change, w ₂
In the case of = 30 μm, the response speed _Ton is greatly deteriorated when the change in transmittance is 75% or more.

FIG. 15 is an explanatory diagram showing the dependence of the response speed T _off -transmittance change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 4.0 μm. speed T _{of f} deteriorates with increasing transmission change, but change itself is small,
It is also understood that the gap w ₂ dependence is small.

FIG. 16 is an explanatory diagram of the dependence of the response speed T _on -transmissivity change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 4.5 μm, and w ₂ ≦ 20 μm or less. in, the response speed T _on is smaller with increasing transmittance change, w ₂
In the case of = 30 μm, the response speed _Ton is greatly deteriorated when the change in transmittance is 75% or more. However, the absolute value of the response speed T _on is made considerably larger than even d = 3.0 [mu] m liquid crystal display device of the cases.

FIG. 17 is an explanatory diagram showing the dependence of the response speed T _off -transmittance change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 4.5 μm. speed T _{of f} deteriorates with increasing transmission change, but change itself is small,
It is also understood that the gap w ₂ dependence is small. However, the absolute value of the response speed T _off is d =
It is about twice as large as that of a 3.0 μm liquid crystal display device.

If the above-described FIGS. 10 to 17 are comprehensively determined, the gap w _{2 between the} response speed _Ton and the response speed _Toff can be determined.
Dependence, since the dependent cell thickness d is increased is reduced, velocity response by a gap w ₂ from this point T _on and the response speed T _off, in particular, to improve the response speed T _on the cell thickness It is desirable that d be 3.5 μm or less.

[0065] In the display cells of d ≦ 3.5 [mu] m, in order to obtain the effect of improving the response speed T _on the gap w ₂ is a 30μm which could not be obtained with 20μm and effect obtained a gap w ₂ effective Considering this, it is understood that the thickness is desirably 25 μm or less. The response speed _Ton
In the transmittance change characteristic, the local minimum value does not depend on the liquid crystal material, but the nature of the electric field response in the MVA type liquid crystal display device, that is, the azimuth angle after the liquid crystal molecules are oriented in the polar angle direction. This is due to the essence that the whole orientation is completed by orienting in the direction.

Next, a description will be given of a third embodiment of the present invention which is characterized by the configuration of each pixel for suppressing the deterioration of chromaticity in color display. The basic technical concept is as described in the first embodiment.
The illustration is omitted because it is similar to the second embodiment or the second embodiment. That is, as described above, generally, the refractive index anisotropy Δn has wavelength dependence, and the shorter the wavelength, the larger Δn. Therefore, when a MVA type liquid crystal cell is manufactured using a liquid crystal having a large refractive index anisotropy Δn, in the case of blue (B) having a short wavelength, the transmittance (T) -applied voltage (V) characteristic is relatively low. , A maximum value appears, and 5V. At an applied voltage of about 4, the relative intensity is lower than that of green (G) and red (R), so that the display may be yellowish and the chromaticity may be reduced.

In this case, the interval between the projections or slits in each of the red, green, and blue pixels constituting one dot in the color display, that is, the gap w ₂ , is set to have a relationship of w _B <w _G <w _R. Thereby, saturation and attenuation of blue (B) can be compensated, and a decrease in chromaticity can be suppressed.

That is, when the gap w ₂ is narrow, the response speed is increased as is apparent from the second embodiment. Thus, a perfect white display is conventionally obtained at 5.4 V. When the white display is set to a voltage lower than 5.4 V, the blue (B) pixel does not reach the maximum value in the complete white display, so that the balance of BGR is not disturbed and the image is yellowish. No white display is obtained.

Alternatively, a cell in each pixel of red, green, and blue
The thickness d is set to the thickness t of the color filter. _B> T_G> T_RNoseki
By setting the_B<D_G<D_RIn the relationship
By setting, it is possible to suppress the decrease in chromaticity.
Wear.

That is, when the cell thickness d is small, the first
As is clear from the embodiment, since the response speed becomes faster, when the perfect white display is set to a voltage lower than 5.4 V, the maximum value is reached in the blue (B) pixel in the complete white display. Since there is no white balance, the B-G-R balance is not lost and a white display that does not have a yellow tint is obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations and conditions described in the embodiments, and various changes can be made. For example, in each of the above embodiments, in order to configure a multi-domain, a slit portion is provided on the TFT substrate side and CF is provided.
Although the projection is provided on the substrate side, conversely, a projection may be provided on the TFT substrate side, and a slit portion may be provided on the CF substrate side. The same effect can be obtained even if both are formed as projections or both are formed as slits.

[0072]

According to the present invention, it has been confirmed that when the cell thickness d is reduced, the viscosity dependency of the response speed T _on is reduced. Therefore, in order to improve the response speed T _on , the cell thickness d is improved. In the case where is small, there is no problem even if a liquid crystal having a large viscosity and a large refractive index anisotropy Δn is used. As a result, MV with high quality and wide viewing angle
It is possible to increase the speed of the A-type liquid crystal display device and greatly contribute to the practical use of a high-quality MVA type liquid crystal display device having no afterimage or display blur in halftone display.

[Brief description of the drawings]

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

FIG. 2 is a TV characteristic diagram of an MVA liquid crystal display device having a cell thickness d of 4.5 μm.

FIG. 3 is a TV characteristic diagram of an MVA liquid crystal display device having a cell thickness d of 3.0 μm.

FIG. 4 is an explanatory diagram of the response characteristic T _on of the MVA type liquid crystal display device having a cell thickness d of 4.5 μm and the viscosity dependence of the transmittance change.

FIG. 5 is an explanatory diagram of a response characteristic T _on of a MVA type liquid crystal display device having a cell thickness d of 3.0 μm and a viscosity dependency of a transmittance change.

FIG. 6 is an explanatory diagram of a response characteristic T _off of a MVA type liquid crystal display device having a cell thickness d of 4.5 μm-viscosity dependence of transmittance change.

FIG. 7 is an explanatory diagram of a response characteristic T _off of a MVA type liquid crystal display device having a cell thickness d of 3.0 μm-viscosity dependence of transmittance change.

[8] the response speed - is an illustration of a cell thickness d dependence of rotational viscosity gamma ₁ properties.

FIG. 9 is an explanatory diagram of the rotational viscosity dependence of the response speed-cell thickness d characteristic.

[10] response T _on the cell thickness d is 3.0μm in MVA type liquid crystal display device - is an explanatory view of the gap w ₂ dependence of the transmittance change characteristic.

FIG. 11 is an explanatory diagram of the dependence of the response characteristic T _off -transmittance change characteristic on the gap w ₂ of the MVA liquid crystal display device having a cell thickness d of 3.0 μm.

[12] response T _on the cell thickness d is 3.5μm in MVA type liquid crystal display device - is an explanatory view of the gap w ₂ dependence of the transmittance change characteristic.

FIG. 13 is an explanatory diagram showing the dependence of the response characteristic T _off -transmittance change characteristic on the gap w ₂ of the MVA liquid crystal display device having a cell thickness d of 3.5 μm.

[14] the cell thickness d is response T _on the MVA type liquid crystal display device of 4.0 .mu.m - is an explanatory view of the gap w ₂ dependence of the transmittance change characteristic.

FIG. 15 is an explanatory diagram of the dependence of the response characteristic T _off -transmittance change characteristic on the gap w ₂ of the MVA liquid crystal display device having a cell thickness d of 4.0 μm.

FIG. 16 is an explanatory diagram of the gap w ₂ dependence of the response characteristic T _on -transmittance change characteristic of the MVA type liquid crystal display device having a cell thickness d of 4.5 μm.

FIG. 17 is an explanatory diagram showing the dependence of the response characteristic T _off -transmittance change characteristic on the gap w ₂ of the MVA type liquid crystal display device having a cell thickness d of 4.5 μm.

FIG. 18 is an explanatory diagram of a conventional MVA liquid crystal display device.

FIG. 19 shows the response speed T _{on of a} conventional MVA liquid crystal display device.
FIG. 4 is an explanatory diagram of an applied voltage dependence of the present invention.

FIG. 20 shows a response speed T of a conventional MVA liquid crystal display device.
FIG. 4 is an explanatory diagram of an applied voltage dependency of _off .

[Explanation of symbols]

 Reference Signs List 1 substrate 2 substrate 3 vertical alignment film 4 vertical alignment film 5 slit portion 6 projection 7 liquid crystal layer 8 liquid crystal molecule 9 polarizer 10 polarizer 11 electrode 12 electrode 13 spacer 31 TFT substrate 32 pixel electrode 33 projection 34 vertical alignment film 35 CF substrate 36 common electrode 37 protrusion 38 vertical alignment film 39 liquid crystal 40 liquid crystal molecule 41 polarizer 42 polarizer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kimiaki Nakamura 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term in Fujitsu Limited (Reference) 2H090 KA04 KA05 KA07 LA09 LA15 MA01 2H091 FA07X FA07Z HA07 HA09 KA02 LA16 LA30 2H092 GA14 GA15 NA01 NA05 PA08 QA07 QA09

Claims (3)

[Claims] 1. A liquid crystal having a negative dielectric anisotropy is sandwiched between two substrates opposed to each other, and at least one of electrodes provided on opposed surfaces of both substrates is constituted by a transparent electrode. In a state where no voltage is applied, the major axis direction of the liquid crystal molecules is oriented so as to be substantially perpendicular to the main surface of the at least one substrate, and when a voltage is applied, the orientation of the major axis of the liquid crystal molecules is oriented in the substrate. In a liquid crystal display device that falls down in a direction parallel to the main surface, the retardation Δn · d of the liquid crystal layer during vertical alignment is 0.24 μm <Δn · d <0.42 μm, and the thickness d of the liquid crystal layer is 2. A liquid crystal display device, wherein 0 μm <d ≦ 3.5 μm. 2. The liquid crystal display device according to claim 1, wherein said liquid crystal molecules are inclined in two or more directions, and said pair of substrates is sandwiched between a pair of polarizers arranged in crossed Nicols. Liquid crystal display device. 3. A means for causing the liquid crystal molecules to fall in two or more directions is a projection or a slit of an electrode formed on at least one of the substrates, and a gap between the projection or the slit of the electrode. 3. The liquid crystal display device according to claim 2, wherein the gap is 25 μm or less.