JP2006018116A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of being widely applied to a computer, a word processor, a monitor of an on-vehicle navigation device, a TV and the like and having high response speed, excellent display quality and low power consumption. <P>SOLUTION: In the liquid crystal display device having a liquid crystal layer wherein a liquid crystal material having negative dielectric anisotropy is interposed between two substrates opposed to each other and the long axis direction of liquid crystal molecules which constitute the liquid crystal material is aligned in a direction nearly vertical to a principal surface of at least one substrate when voltage lower than a threshold voltage is applied and aligned in a direction nearly parallel thereto when voltage not lower than the threshold voltage is applied, when refractive index anisotropy of the liquid crystal material and thickness of the liquid crystal layer are defined as Δn and d (nm), respectively, retardation Δn×d satisfies formula (1): 240 nm<Δn×d<420 nm and at least one of a splay elastic constant K11 and a bend elastic constant K33 of the liquid crystal material satisfies formula (2); K11≤15 or K33≤15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a liquid crystal display device. More specifically, the present invention relates to a liquid crystal display device that can be widely applied to computers, word processors, in-vehicle navigation monitors, televisions, and the like.

In recent years, liquid crystal display devices have attracted attention as displays capable of realizing light weight, thinness, and low power consumption, and an active matrix driving method is generally used as a driving method. As a display method of a conventional active matrix liquid crystal display device, a TN method using a TN (Twisted Nematic) liquid crystal has been the mainstream. However, in the TN method, alignment is performed even when a voltage is not applied. Liquid crystal molecules are aligned in the normal direction of the liquid crystal display panel with a certain degree of azimuth, and azimuth angle dependence occurs in the alignment state of the liquid crystal molecules when a voltage is applied. There was room.

On the other hand, as a method that can improve the viewing angle characteristics, an electric field generated by a structure such as a protrusion provided on at least one substrate side of the liquid crystal display panel with vertically aligned liquid crystal molecules when no voltage is applied. An MVA (Multi-domain Vertical Alignment) type liquid crystal display device in which the orientation is controlled by the strain of the liquid crystal and the orientation of the liquid crystal molecules is divided in a plurality of directions has attracted attention (for example, see Patent Document 1).

Here, a conventional MVA liquid crystal display device will be described with reference to FIG. FIG. 5A is a schematic cross-sectional view schematically showing a main part of a conventional MVA type liquid crystal display device in a state where no voltage is applied, and FIG. 5B is a voltage application of the conventional MVA type liquid crystal display device. It is a cross-sectional schematic diagram which shows schematically the principal part in a state.
In the MVA type liquid crystal display device shown in FIG. 5A, a pixel electrode made of an ITO (Indium Tin Oxide) transparent electrode is provided on a TFT (Thin Film Transistor) substrate 31 (liquid crystal 39 side). 32, a protrusion 33 made of an insulator that locally regulates the alignment of the liquid crystal molecules 40 is provided, and a vertical alignment film 34 is provided so as to cover them. On the other hand, on a CF (Color Filter; color filter) substrate 35 facing the TFT substrate 31 (on the liquid crystal 39 side), an insulator that locally regulates the orientation of the liquid crystal molecules 40 together with a common electrode 36 made of an ITO transparent electrode. The protrusion 37 made of is provided at a position where it does not overlap with the protrusion 33 provided on the TFT substrate 31 side (as viewed in the direction perpendicular to the substrate surface), and a vertical alignment film 38 is provided so as to cover them. A liquid crystal 39 having negative dielectric anisotropy (Δε <0) is injected between the TFT substrate 31 and the CF substrate 35. In this case, the liquid crystal molecules 40 in the vicinity of the protrusions 33 and 37 exhibit an alignment state depending on the shape of the protrusions 33 and 37, and the normal direction of the vertical alignment films 34 and 38 covering the surfaces of the protrusions 33 and 37. It is inclined and aligned so as to be aligned with each other. On the other hand, the liquid crystal molecules 40 located away from the protrusions 33 and 37 are vertically aligned with respect to the substrates 31 and 35 under the restriction of the vertical alignment films 34 and 38.

In the MVA type liquid crystal display device having such a configuration, the polarizer 41 provided on the TFT substrate 31 side and the polarizer 42 provided on the CF substrate 35 side are arranged in a crossed nicols state so that “black” is applied in a state where no voltage is applied. ”Is displayed. Then, by applying a voltage, the tilted orientation of the liquid crystal molecules 40 in the vicinity of the protrusions 33 and 37 that have been tilted in advance propagates, and the orientation of the entire liquid crystal molecules 40 tilts by the tilt angle θp according to the applied voltage, An intermediate state (halftone) display can be obtained from the transmissive state.

As described above, in the MVA liquid crystal display device, since the protrusions 33 and 37 are provided and a part of the liquid crystal molecules 40 is tilted in advance, the response speed is faster than that of other conventional liquid crystal display devices such as the TN method. In addition, since the liquid crystal molecules 40 are aligned and divided in a plurality of directions, a wide viewing angle of 160 ° in the vertical and horizontal directions (an angle that can be displayed with a contrast ratio of 10 or more) can be realized. It is to be noted that the same effect can be obtained by providing notches, that is, slits in the pixel electrode 32 or the common electrode 36 instead of the protrusions 33 and 37.
However, in recent years, in liquid crystal display devices, demand for not only monitors for mainly still images such as personal computers but also monitors for moving images is increasing, and responsiveness that does not cause afterimages and display blurring is required. Accordingly, there is a demand for further improvement in response speed in the MVA type liquid crystal display device.

Accordingly, it has been proposed to reduce the cell thickness as a measure for improving the response speed of the MVA liquid crystal display device. However, when the cell thickness is reduced, a liquid crystal having a high refractive index anisotropy Δn is required to prevent a decrease in the light transmittance of the cell, and the viscosity of the liquid crystal increases as the refractive index anisotropy Δn increases. Because of this tendency, the response speed becomes slow, and the effect of reducing the cell thickness is offset. Therefore, it is difficult to obtain a sufficient response speed improvement effect.

In addition, IPS (In-Plane Switching) that drives liquid crystal molecules in a panel screen (in a direction parallel to the panel surface) by applying an electric field in a lateral direction (parallel to the panel surface). In the liquid crystal display device, the halftone response speed is increased. However, in the IPS liquid crystal display device, there is a limit to reducing the width between the electrodes from the viewpoint of the aperture ratio, so there is room for improvement in that the drive voltage increases.
In addition, in the liquid crystal display device, various devices are generally made to reduce the power consumption, but in order to reduce the power consumption of the liquid crystal display panel, it is necessary to drive the liquid crystal molecules at a low voltage. is there. For this purpose, it is necessary to increase the dielectric anisotropy | Δε | of the liquid crystal material. However, it is known that increasing the dielectric anisotropy | Δε | decreases the reliability. In contrast, moving image monitors, particularly televisions, require high reliability over a long period of time. Therefore, low power consumption of a liquid crystal display panel by controlling the dielectric anisotropy | Δε | It was a difficult situation.
Japanese Patent Laid-Open No. 11-242225 (first page 162, FIG. 1)

The present invention has been made in view of the above-described present situation, and an object of the present invention is to provide a liquid crystal display device that has a high response speed and excellent display quality and low power consumption.

The present inventors have made various studies on improving the response speed and reducing the power consumption of a vertical alignment (VA) type liquid crystal display device. As a result, characteristics of the liquid crystal material of the liquid crystal layer, particularly the elastic constant K11 of the spray and the elastic constant of the bend. We focused on K33. The retardation Δn · d of the liquid crystal layer satisfies 240 nm <Δn · d <420 nm, and at least one of the spray elastic constant K11 (pN) and the bend elastic constant K33 (pN) of the liquid crystal material is K11 ≦ 15. Alternatively, it has been found that by satisfying K33 ≦ 15, the response speed of the liquid crystal can be increased and the power consumption of the liquid crystal display panel can be reduced, and the above problem can be solved brilliantly. Has reached

That is, according to the present invention, a liquid crystal material having negative dielectric anisotropy is sandwiched between two substrates facing each other, and the major axis direction of the liquid crystal molecules constituting the liquid crystal material is the main of at least one substrate. A liquid crystal display device having a liquid crystal layer that is oriented in a substantially vertical direction with respect to a plane and less than a threshold voltage, and that is oriented in a substantially parallel direction with a threshold voltage or higher. Where Δn is the thickness of the liquid crystal layer and d (nm) is the retardation Δn · d is the following formula:
240 nm <Δn · d <420 nm (1)
And at least one of the spray elastic constant K11 (pN) and the bend elastic constant K33 (pN) of the liquid crystal material is the following formula:
K11 ≦ 15 or K33 ≦ 15 (2)
A liquid crystal display device satisfying the above requirements.
The present invention is described in detail below.

In the liquid crystal display device of the present invention, a liquid crystal material having negative dielectric anisotropy is sandwiched between two substrates facing each other, and the major axis direction of liquid crystal molecules constituting the liquid crystal material is at least one substrate The liquid crystal layer is aligned in a substantially vertical direction below the threshold voltage with respect to the main surface, and aligned in a substantially parallel direction above the threshold voltage. The liquid crystal material is not particularly limited as long as it has a negative dielectric anisotropy, but a nematic liquid crystal material is preferable. In the present invention, the liquid crystal material sandwiched between the substrates may be composed of one type of liquid crystal material or a mixture of a plurality of types of liquid crystal materials. In addition, about the characteristic of the liquid crystal material pinched | interposed between board | substrates, when comprised with 1 type of liquid crystal material, it is a property of the said 1 type of liquid crystal material, and when comprised with 2 or more types of liquid crystal materials, it is a board | substrate. This is a characteristic when the two or more liquid crystal materials are mixed in a ratio contained in the liquid crystal material sandwiched therebetween.

In the present invention, the threshold voltage means a voltage value that generates an electric field that causes an optical change in the liquid crystal layer and a display state in the liquid crystal display device. For example, when the light transmittance in the bright state is set to 100%, it means a voltage value that gives a light transmittance of 10%. The substantially vertical direction is preferably a direction substantially perpendicular to the main surface of the substrate. However, the vertical direction is vertical as long as it can function effectively as a vertical alignment (VA) liquid crystal display device. A direction having an angle with respect to the direction is also included. The substantially parallel direction is preferably a direction substantially parallel to the main surface of the substrate, but it is parallel as long as it can function effectively as a vertical alignment (VA) type liquid crystal display device. A direction having an angle with respect to the direction is also included.
In the present invention, when the voltage applied between two substrates facing each other is less than the threshold voltage, the major axis direction (alignment direction) of the liquid crystal molecules is mainly provided on the liquid crystal layer side on the substrate. It is controlled by the vertical alignment film and the like, and is aligned in a substantially vertical alignment with respect to the main surface of the substrate. When the threshold voltage is exceeded, the major axis direction (alignment direction) of the liquid crystal molecules is mainly applied by voltage application. It is controlled by the generated electric field and is oriented in a direction substantially parallel to the main surface of the substrate.
Note that the liquid crystal display device of the present invention is not particularly limited as long as such components are formed as essential components, and may or may not include other components. .

When the refractive index anisotropy of the liquid crystal material is Δn and the thickness of the liquid crystal layer is d (nm), the retardation Δn · d is expressed by the following formula:
240 nm <Δn · d <420 nm (1)
Meet. The optimum value of retardation Δn · d in the optical design of the liquid crystal layer is λ / 2 condition (275 nm) in the birefringence mode, and 400 nm in the mode using optical rotation. In the present invention, the retardation Δn · d is more than 240 nm and less than 420 nm, so that the optimum design value in the birefringence mode and the mode using optical rotation is included, and the manufacturing margin and the condition of the liquid crystal layer are included. Even when adjustment with other components is taken into consideration, a good display can be obtained. The more preferable range of retardation Δn · d is 260 to 280 nm or 390 to 410 nm.
The preferable lower limit of the refractive index anisotropy Δn of the liquid crystal material is 0.07, and the preferable upper limit is 0.13. The refractive index anisotropy Δn is a value measured at 25 ° C. with light having a design wavelength of 550 nm. The preferable lower limit of the thickness d of the liquid crystal layer is 2000 nm, and the preferable upper limit is 5500 nm. Note that the thickness d of the liquid crystal layer is also referred to as a cell gap.

In the liquid crystal layer, at least one of a splay (expansion) elastic constant K11 (pN) and a bend (bending) elastic constant K33 (pN) of the liquid crystal material has the following formula:
K11 ≦ 15 or K33 ≦ 15 (2)
Meet. That is, in the present invention, either (1) satisfying only K11 ≦ 15, (2) satisfying only K33 ≦ 15, or (3) satisfying both K11 ≦ 15 and K33 ≦ 15. Also good. As the spray elastic constant K11 and the bend elastic constant K33, values measured at 25 ° C. are used. When the elastic constant K11 of the spray is 15 pN or less, the liquid crystal can be driven at a low voltage, and the power consumption of the liquid crystal display panel can be reduced. When the bend elastic constant K33 is 15 pN or less, the liquid crystal can be driven at a low voltage, and the power consumption of the liquid crystal display panel can be reduced. As will be described later, when K33 is reduced, the response speed τoff when the applied voltage is off increases.

The effects of the present invention will be described in more detail with reference to FIGS.
FIG. 2 shows voltage-light transmittance (V-T) characteristics of the MVA liquid crystal display device of the present invention when measured by changing the elastic constant K33 of the bend while keeping the elastic constant K11 of the liquid crystal material spray constant. It is a figure which shows an example. In FIG. 2, the voltage-light transmittance characteristics are standardized by setting the light transmittance when 10 V is applied to 1.0, and the dielectric anisotropy Δε of the liquid crystal material used for the measurement is −3. 0, the splay elastic constant K11 is constant at 15 pN.
As can be seen from FIG. 2, when the bend elastic constant K33 is decreased, the VT characteristic shifts to the low voltage side.

FIG. 3 shows the voltage-light transmittance (VT) characteristics of the MVA type liquid crystal display device of the present invention when measured by changing the elastic constant K11 of the spray while keeping the elastic constant K33 of the bend of the liquid crystal material constant. It is a figure which shows an example. In FIG. 3, the voltage-light transmittance characteristics are normalized by setting the light transmittance when 10 V is applied to 1.0, and the dielectric anisotropy Δε of the liquid crystal material used for the measurement is −3. 0, the bend elastic constant K33 is fixed at 15 pN.
As shown in FIG. 3, it can be seen that when the splay elastic constant K11 is reduced, the VT characteristic shifts to the low voltage side.

Note that a liquid crystal material having a practically usable transition temperature, that is, a liquid crystal material that maintains a nematic phase at −20 to 80 ° C., K11 <10 or K33 <10 with respect to the elastic constant K11 of the spray and the elastic constant K33 of the bend. It is generally known that no one has the following characteristics. Therefore, the liquid crystal material preferably satisfies K11> 10, and preferably satisfies K33> 10. Furthermore, when applied to a liquid crystal display panel, the liquid crystal material is exposed to a vacuum state at the time of injection. Therefore, if the volatility is too high, the liquid crystal material is volatilized under a vacuum. Therefore, the liquid crystal material preferably satisfies K11> 11, and more preferably satisfies K33> 11.

Below, the preferable form of the liquid crystal display device of this invention is demonstrated in detail.
The liquid crystal material preferably has an elastic constant ratio K33 / K11 satisfying K33 / K11 <1.15. Thereby, since the difference in response speed between a gradation with a slow response speed and a fast gradation can be reduced, it can be suitably used for displaying a moving image such as a television. Specifically, it is possible to increase the difference in response speed between a gray scale with a slow response speed and a fast gray scale, which was about 10 times the conventional speed, by about 5 times. When the response speed is 80 msec at a slow gradation at room temperature and 8 msec at a fast gradation, the response speed of a gradation with a slow response speed can be set to 40 msec by using the liquid crystal material of the present invention. it can.
In addition, by reducing the elastic constant ratio K33 / K11, that is, by increasing the bend elastic constant K33 and by decreasing the splay elastic constant K11, the effect of reducing the power consumption of the liquid crystal display panel, the gradation It is also possible to obtain an effect of facilitating gradation by reducing the change in transmittance per gradation in display.

The point that the response speed of the liquid crystal is increased by the present invention will be described in more detail with reference to FIG.
FIG. 4A shows the response time-light transmittance characteristics of the MVA type liquid crystal display device of the present invention when measured by changing the elastic constant K11 of the spray while keeping the elastic constant K33 of the bend of the liquid crystal material constant. It is a figure which shows an example, FIG.4 (b) is an enlarged view which expands and shows immediately after the applied voltage OFF of (a) (50-65 msec). In FIG. 4, the voltage-light transmittance characteristic is normalized by setting the light transmittance when 10 V is applied to 1.0, and the dielectric anisotropy Δε of the liquid crystal material used for the measurement is −3. 0, the bend elastic constant K33 is fixed at 15 pN. Moreover, in the measurement which concerns on FIG. 4, the voltage is applied between 0-50 msec, and it can confirm response time from the change of the light transmittance with respect to it.
4 (a) and 4 (b), it can be seen that when K33 / K11 is reduced (K33 is reduced), the response speed τoff when the applied voltage is off increases.

In the liquid crystal display device of the present invention, it is preferable that at least one of the substrates has protrusions, and the liquid crystal molecules constituting the liquid crystal layer fall in two or more directions at a threshold voltage or higher. Thereby, since the liquid crystal molecules in the vicinity of the protrusions are tilted in advance, the response speed in the halftone display of the liquid crystal display device can be increased and a wide viewing angle can be obtained. That is, the liquid crystal display device of the present invention is a multi-domain vertical alignment (MVA) type liquid crystal display device, and includes a protrusion as a means for causing liquid crystal molecules to fall in two or more directions, and the protrusion causes the liquid crystal to exceed the threshold voltage. It is preferable that the molecules are oriented and divided in two or more directions. Photosensitive resin etc. are mentioned as a material of protrusion. Examples of the shape of the protrusion include a substantially conical shape and a belt shape, and it is preferable that the protrusion is provided periodically. Examples of the location where the protrusion is formed include an electrode. The size such as the height of the protrusion is not particularly limited.

In the liquid crystal display device of the present invention, at least one substrate has slits (electrode non-formed portions between the small electrodes) formed by a plurality of substantially rectangular small electrodes that are electrically connected to each other. The liquid crystal molecules constituting the liquid crystal layer preferably fall in two or more directions at a threshold voltage or higher. As a result, the liquid crystal molecules in the vicinity of the slits are easily tilted and aligned due to the distortion of the electric field when a voltage is applied, so that the response speed in the halftone display of the liquid crystal display device can be increased and a wide viewing angle can be obtained. That is, the liquid crystal display device of the present invention is a multi-domain vertical alignment (MVA) type liquid crystal display device, and a plurality of substantially rectangular shapes that are electrically connected to each other as means for tilting liquid crystal molecules in two or more directions. It is preferable that a slit formed by a small electrode having a shape is provided, and the liquid crystal molecules are aligned and divided in two or more directions at a threshold voltage or higher by the slit. The substantially rectangular shape is preferably a shape that is evaluated to be substantially rectangular, but within a range that can effectively function as a multi-domain vertical alignment (MVA) liquid crystal display device. If there is, it also includes similar shapes. A rectangular shape etc. are mentioned as a shape of a slit. Examples of the slit forming method include photolithography.
As a more preferable form of the liquid crystal display device of the present invention, the two substrates facing each other have a protrusion or a slit formed by a plurality of substantially rectangular small electrodes electrically connected to each other. Is mentioned.

Next, each component other than the liquid crystal layer constituting the liquid crystal display device of the present invention will be described.
Although it does not specifically limit as a material of a board | substrate, Glass is preferable. Usually, an active element, a signal wiring, a color filter, a vertical alignment film, a polarizer, and the like are appropriately provided on the substrate. Examples of the vertical alignment film include a polyimide film having a film surface subjected to a vertical alignment process (rubbing process). In the present invention, it is preferable that at least one of the electrodes provided on the opposing surfaces of the two substrates is composed of a transparent electrode.

According to the liquid crystal display device of the present invention, since at least one of the elastic constant K11 of the liquid crystal material and the elastic constant K33 of the bend is 15 pN or less, the response speed of the liquid crystal is increased and the liquid crystal display panel is reduced in consumption. Power can be realized, and since the retardation of the liquid crystal layer satisfies 240 nm <Δn · d <420 nm, good display can be obtained in the birefringence mode or the mode using optical rotation.

Examples of the transmissive active matrix liquid crystal display device of the present invention will be described below, and the present invention will be described in more detail. However, the present invention is not limited to these examples.

Example 1
FIG. 1 is a schematic cross-sectional view schematically showing a main part of an MVA liquid crystal display device of Example 1 which is an embodiment of the present invention.
As shown in FIG. 1, a pixel electrode 11 made of ITO is provided on a glass substrate 1 (liquid crystal layer side) serving as a TFT substrate, and on the glass substrate 2 serving as a CF substrate facing the TFT substrate (liquid crystal layer side). ) Was provided with a common electrode 12 made of ITO. The pixel electrode 11 was provided with the slit portion 5 having a width W3 of 10 μm and a depth of 100 nm, and then the vertical alignment film 3 was provided so as to cover the pixel electrode 11. On the other hand, the protrusions 6 made of a photosensitive resin (resist) or the like having a width W1 of 10 μm and a height of 1.3 to 1.6 μm are formed on the common electrode 12 with a mutual interval W2 of 25 μm or less, for example, 25 μm. Thus, the vertical alignment film 4 was provided on the entire surface after being provided so as not to projectly overlap the slit portion 5 (as viewed from the direction perpendicular to the substrate surface). Next, spacers 13 made of resin beads having a diameter of 4.5 μm were arranged by a coating method, and a TFT substrate and a CF substrate were bonded together using a thermosetting sealing material, whereby an empty cell having a cell thickness of d was produced. . In addition, when the cell thickness d was measured with a cell thickness measuring apparatus (manufactured by Oak Manufacturing Co., Ltd.), it was d≈D (4.5 μm). Next, after the liquid crystal material A having a negative dielectric anisotropy and the characteristics shown in Table 1 below is injected into this empty cell and sealed, the polarizers 9 and 10 are respectively placed in a crossed Nicols state. The MVA-type liquid crystal display device was manufactured by pasting together.
In Table 1, the splay elastic constant K11 and the bend elastic constant K33 are values measured at 25 ° C. The refractive index anisotropy Δn is a value measured at 25 ° C. with light having a design wavelength of 550 nm. The NI point represents the phase transition temperature (° C.) of each liquid crystal material (nematic liquid crystal material) from the nematic phase to the isotropic liquid phase. γ1 represents the viscosity (mPa · sec) of each liquid crystal material at 25 ° C.

In the MVA type liquid crystal display device configured as described above, the liquid crystal molecules 8 located away from the protrusions 6 restrict the vertical alignment films 3 and 4 as in the conventional MVA type liquid crystal display device shown in FIG. Then, the liquid crystal molecules 8 in the vicinity of the protrusions 6 are aligned perpendicularly to the substrates 1 and 2, and the liquid crystal molecules 8 in the vicinity of the protrusions 6 exhibit an alignment state depending on the shape of the protrusions 6. Thus, the tilted orientation is aligned with the normal direction of 4.

(Examples 2 to 4)
An MVA type liquid crystal display device was produced in the same manner as in Example 1 except that liquid crystal materials B to D having the characteristics shown in Table 1 below were used instead of the liquid crystal material A as the liquid crystal material.
(Comparative Example 1)
An MVA type liquid crystal display device was produced in the same manner as in Example 1 except that the liquid crystal material E having the characteristics shown in Table 1 below was used instead of the liquid crystal material A as the liquid crystal material.

(Evaluation test)
With respect to the MVA type liquid crystal display devices obtained in Examples 1 to 4 and Comparative Example 1, Vth and response speed τoff were measured to evaluate the moving image performance. The results are shown in Table 1.
Note that Vth represents an applied voltage indicating a light transmittance of 10% when the light transmittance when 10 V is applied is 100%. The response speed τoff is a time-light transmittance characteristic change from the time of 10 V application to 0 V (no voltage applied) when the light transmittance at 10 V application and 0 V is normalized to 100 and 0, respectively. The time from when the voltage application of 10 V is stopped to when the light transmittance reaches 10% is shown. In the evaluation of the moving image performance, “X” indicates that the ratio of the response speed between the gradation with a slow response speed and the fast gradation is large, and “◯” indicates that the response speed is small. Specifically, it was × when it was 10 times, and ◯ when it was 5 times. If the moving image performance is ◯, for example, when the subjective evaluation of the moving image quality is performed, the result of the influence evaluation of the response speed to the image quality based on the criteria shown in Table 2 below satisfies 4.5 or more.

As shown in Table 1, when the liquid crystal materials A and B having the same dielectric anisotropy Δε and the splay elastic constant K11 are compared, the liquid crystal material A having a smaller bend elastic constant K33 has a Vth of 0 than the liquid crystal material B. .14V lower. Further, when the liquid crystal materials C and D having the same dielectric anisotropy Δε and the bend elastic constant K33 are substantially equal, the liquid crystal material D having a larger splay elastic constant K11 has a VT characteristic curve than the liquid crystal material C. The response time τoff was 1.5 msec faster than the liquid crystal material C. Furthermore, in the liquid crystal display devices of the present invention of Examples 1 to 4 using the liquid crystal materials A to D (K33 / K11 <1.15), the moving image performance in the module drive satisfies the standard. In the liquid crystal display device of Comparative Example 1 using the material E (K33 / K11 = 1.18), Vth was as high as 2.9 V, the response speed was slow, and the moving image performance was not sufficient.

It is a cross-sectional schematic diagram which shows schematically the principal part of the MVA type | mold liquid crystal display device of Example 1 which is one Embodiment of this invention. An example of the voltage-light transmittance (VT) characteristic when the MVA type liquid crystal display device of the present invention is measured by changing the elastic constant K33 of the bend while keeping the elastic constant K11 of the liquid crystal material spray constant is shown. FIG. An example of voltage-light transmittance (VT) characteristics when the MVA type liquid crystal display device of the present invention is measured by changing the elastic constant K11 of the spray while keeping the bend elastic constant K33 of the liquid crystal material constant is shown. FIG. (A) is an example of the response time-light transmittance characteristic when the MVA type liquid crystal display device of the present invention is measured by changing the elastic constant K11 of the spray while keeping the elastic constant K33 of the bend of the liquid crystal material constant. (B) is an enlarged view showing an enlarged view immediately after the applied voltage is turned off (after 50 to 65 msec) in (a). (A) is a schematic cross-sectional view schematically showing a main part of a conventional MVA type liquid crystal display device in a voltage non-application state, and (b) is a main part of a conventional MVA type liquid crystal display device in a voltage application state. It is a cross-sectional schematic diagram which shows schematically.

Explanation of symbols

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

Claims (4)

A liquid crystal material having negative dielectric anisotropy is sandwiched between two substrates facing each other, and a major axis direction of liquid crystal molecules constituting the liquid crystal material is a threshold voltage with respect to at least one main surface of the substrate. A liquid crystal display device having a liquid crystal layer that is oriented in a substantially vertical direction at less than or less than a threshold voltage and oriented in a substantially parallel direction,
When the refractive index anisotropy of the liquid crystal material is Δn and the thickness of the liquid crystal layer is d (nm), the retardation Δn · d is expressed by the following formula:
240 nm <Δn · d <420 nm (1)
The filling,
And at least one of the elastic constant K11 (pN) of the spray of the liquid crystal material and the elastic constant K33 (pN) of the bend is the following formula:
K11 ≦ 15 or K33 ≦ 15 (2)
The liquid crystal display device characterized by satisfy | filling. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal material has an elastic constant ratio K33 / K11 that satisfies K33 / K11 <1.15. 3. The liquid crystal display device according to claim 1, wherein at least one of the substrates has protrusions, and liquid crystal molecules constituting the liquid crystal layer fall in two or more directions at a threshold voltage or higher. . In the liquid crystal display device, at least one substrate has a slit formed by a plurality of substantially rectangular small electrodes that are electrically connected to each other, and the liquid crystal molecules constituting the liquid crystal layer have a threshold voltage of 2 or more. The liquid crystal display device according to any one of claims 1 to 3, wherein the liquid crystal display device falls over in more than a direction.

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