JP2001343652A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device having high speed responsiveness, high contrast and high brightness. SOLUTION: The liquid crystal display device is provided with a pair of substrates 1 and 1 having transparent electrodes 2 and 2 and vertical alignment layers 3 and 3 respectively, a liquid crystal layer 5 consisting of a liquid crystal interposed between both the substrates 1 and 1 and having negative dielectric anisotropy and a polarizing plate. The vertical alignment layers 3 and 3 control alignment of liquid crystal molecules so that the direction of major axes of the liquid crystal molecules is substantially vertical to the surfaces of the substrates 1 and 1 when voltage is not applied between both the substrates 1 and 1. The vertical alignment layers 3 and 3 are applied with alignment treatment so that the direction of the major axes of the liquid crystal molecules are substantially parallel to surfaces of the both substrates 1 and 1 and the liquid crystal molecules are aligned twistedly by nearly 90 deg. when the voltage is applied between both the substrates 1 and 1. When the thickness of the liquid crystal layer 5 and the refractive index anisotropy of the liquid crystal are defined as d and Δn, respectively, d is 2.5 μm or less and Δn.d is 0.375 μm or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical alignment type liquid crystal display device in which liquid crystal molecules have a twist angle of about 90 degrees.

[0002]

2. Description of the Related Art Recent liquid crystal displays (LCs)
D) has a remarkable development, and is becoming widespread from small displays for mobile devices to monitors for personal computers and liquid crystal televisions.

A liquid crystal display is a thin and low power consumption display, and is expected to replace a CRT (cathode ray tube) display.
Due to its operating principle, it has disadvantages such as: large viewing angle dependence (narrow viewing angle), low contrast ratio, and poor display of moving images, as compared to CRT displays.

Among them, the viewing angle dependency has been considerably improved by the development of a compensation film, an in-plane switching (IPS) mode, and the like. As for the contrast ratio, a liquid crystal display approaching a CRT display is being developed.

[0005] For displaying moving images, the response speed of the liquid crystal is greatly related. In the early stages of development, the nematic liquid crystal used in ordinary liquid crystal displays has a problem that the response time is as slow as several tens of milliseconds, so that when moving images are displayed, the image trails. As development progresses,
This problem is gradually improving due to improvements in the response speed of liquid crystals and advances in liquid crystal drive technology, but no liquid crystal display with a sufficient response speed has yet been announced.

On the other hand, in the era of full-scale multimedia, the necessity of a display capable of supporting high image quality and moving images, such as a display for digital broadcasting, is called out. In the field of large multimedia displays, liquid crystal displays, Research and development are being actively conducted mainly on plasma displays (PDPs). Liquid crystal displays used for multimedia displays are required to have both high-speed response and high contrast.

There are various liquid crystal display modes. Among them, a mode in which a high contrast is obtained in principle is a vertical alignment (VA) mode. FIG. 10 shows a switching state in the liquid crystal display element in the vertical alignment mode.

In this liquid crystal display, a pair of substrates 1
In the state where no electric field is applied (electric field is turned off), the major axis of the liquid crystal molecule 102 held between
As shown in FIG.
It becomes dark. On the other hand, in an electric field application state (electric field application on) in which a vertical electric field is applied to the substrates 101, 101, FIG.
0 (b), the major axis of the liquid crystal molecules 102 is
The substrate 101 101 falls down from a direction perpendicular to the substrate 101
And it becomes a bright state. In the vertical alignment mode, the liquid crystal molecules 102 having a negative dielectric anisotropy are used because the major axes of the liquid crystal molecules need to be aligned in a direction parallel to the substrates 101, 101 by an electric field perpendicular to the substrates 101, 101. There is a need.

The horizontal alignment mode is a display mode in which the liquid crystal molecules are aligned so that the major axis of the liquid crystal molecules is parallel to the substrate when no electric field is applied. Most are formulas. In such a method, liquid crystal molecules near the interface of the substrate remain almost parallel to the substrate even when a voltage is applied due to the influence of interface anchoring. For this reason, a residual phase difference occurs near the substrate interface, and the brightness in the dark state becomes higher than expected, and a sufficient contrast cannot be obtained.

In the vertical alignment mode, when no electric field is applied (initial state), the major axis of the liquid crystal molecules is almost perpendicular to the substrate, and therefore, there is no residual phase difference. Therefore, when the liquid crystal display element in the vertical alignment mode is placed under the orthogonal Nicols, an optically isotropic state can be obtained in a state of no electric field. Therefore,
In the vertical alignment mode, a clear black display is obtained,
Therefore, the contrast is very high, which is a feature not found in the horizontal alignment mode.

In the vertical alignment mode, a vertical alignment film that controls the major axis direction of liquid crystal molecules when no electric field is applied so as to be substantially perpendicular to the surface of the substrate is used. For example, in the case of the example of FIG.
A vertical alignment film is provided on inner surfaces of 01 and 101 (surfaces facing each other). However, in general, the vertical alignment film has no regulating force in the direction in which the liquid crystal molecules tilt when an electric field is applied. Therefore, as it is, disclination occurs when an electric field is applied, and the bright luminance is impaired.

For this reason, a method of rubbing the vertical alignment film, providing a projection in the substrate surface, or the like, is used to regulate the direction in which the liquid crystal molecules are inclined when an electric field is applied. FIG. 11 shows a switching state of the liquid crystal display element in the vertical alignment mode in which the tilt direction of the liquid crystal molecules is regulated by such a method.

This liquid crystal display device is different from the liquid crystal display shown in FIG. 10A in that a vertical alignment film (not shown) provided on the inner surface of the substrates 101 is used as shown in FIG.
The rubbing process is performed in the direction indicated by the arrow in FIG.

A liquid crystal display using such a vertical alignment mode in which the tilt direction of liquid crystal molecules is restricted has already been announced, and a high contrast ratio of 300: 1 or more has been obtained.

[0015]

As described above, the liquid crystal display using the vertical alignment mode has an advantage that a high contrast can be obtained. On the other hand, in the vertical alignment mode, as in the display mode using other nematic liquid crystals, a response speed sufficient to express moving images satisfactorily has not been obtained at present. Generally, in a liquid crystal display mode using a horizontal alignment such as a twisted nematic (TN) mode or a voltage controlled birefringence (ECB) mode, the response speed is expressed by the following equations (1) to (3). expressed.

[0016] ^{_{τ rise = ηd 2 / {ε}} 0 Δε (V 2 -V c 2)} ... (1) τ fall = ηd 2 / Kπ 2 ... (2) K = k 1 + (k 3 · 2k 2) / 4 (3) where τ _rise is the rise time (the time required for the relative light transmittance to rise from 0% to 90%), and τ _fall is the fall time (the relative light transmittance is 90% to 10%). %), Η is the viscosity parameter of the liquid crystal, d is the cell thickness (liquid crystal layer thickness), ε ₀ is the dielectric constant in vacuum, and Δε is the dielectric anisotropy (long axis of the liquid crystal molecules). V is the applied voltage, V _c is the value obtained by subtracting the permittivity in the direction orthogonal to the permittivity from the permittivity.
Represents a threshold voltage, k ₁ represents a splay elastic constant, k ₂ represents a twist (twist) elastic constant, and k ₃ represents a bend (bend) elastic constant.

The response speed of the liquid crystal which can cope with a moving image is a standard of 10 ms. However, in the current liquid crystal display, a slightly thicker cell thickness is adopted due to various restrictions.
Therefore, the response speed is several tens of ms, and there is no ability to display a moving image satisfactorily. One solution to the lack of response speed of the nematic liquid crystal is considered to be to reduce the cell thickness d, that is, to make the cell thinner. The equation for the response speed for the vertical alignment mode is unknown at this time, but from the result of the horizontal alignment mode, it is considered that the speed can be increased by thinning the cells.

On the other hand, as shown in FIG. 11A, when a process for regulating the tilt direction of liquid crystal molecules when an electric field is applied is performed by a method such as rubbing the vertical alignment film or providing a protrusion in the substrate surface. In addition, the alignment of the liquid crystal molecules 102 in a state where no voltage is applied is such that the major axis of the liquid crystal molecules 102 is inclined from a direction perpendicular to the substrates 101. This means that a residual phase difference occurs near the interface between the substrates 101. In the vertical alignment mode, the major axis of the liquid crystal molecules 102 cannot be made perpendicular to the substrates 101 due to electric field application. Therefore, this residual phase difference cannot be eliminated,
The contrast will be reduced.

As a method of alleviating the influence of the residual retardation, the orientation of the liquid crystal molecules is twisted (the orientation vector of the liquid crystal molecules near one substrate is different from the orientation vector of the liquid crystal molecules near the other substrate). Orientation state). As such a twist orientation, for example, FIG.
As shown in (a), there is a twist alignment in which the orientation direction of the liquid crystal molecules 102 is twisted by 90 ° between the upper and lower substrates 101. As a result, most of the residual phase difference at the substrate interface is canceled, and a clear black state is obtained in principle as compared with the horizontal alignment TN mode. Therefore, in such a display mode in which the liquid crystal molecules are in a vertical orientation and the twist angle of the liquid crystal molecules is approximately 90 °, that is, in a so-called twisted vertical alignment (TVA) mode, a high contrast can be obtained. is there. In addition,
In order to obtain such a twisted vertical alignment, for example, FIG.
The rubbing direction of the vertical alignment film may be changed between the upper and lower substrates 101 as shown in FIG.

As such a TVA mode liquid crystal display element, for example, Japanese Patent Application Laid-Open No. 8-43825 discloses a vertical alignment type TN mode liquid crystal display panel in order to obtain high contrast.

In a TVA mode liquid crystal display device,
Although there is a possibility that high-speed response and high contrast can be realized at the same time by thinning the cells, the mere reduction in the thickness of the cells greatly reduces the brightness.

In a liquid crystal mode such as a TN mode which is a horizontal alignment and a twist alignment, research is being conducted on conditions for obtaining sufficient luminance. In a liquid crystal mode such as a TN mode in which the liquid crystal is horizontally and twisted, in order to obtain a sufficient luminance, it is necessary to set Δn · 4d It is known that the relationship of ≫λ (4) needs to be satisfied. 4d in the equation (4) corresponds to the helical pitch of the liquid crystal in the TN type display mode. Equation (4) is called Morgan's condition. Generally, the refractive index anisotropy Δn of the liquid crystal
Is at most about 0.2, so it is necessary to set the cell thickness d to a value that satisfies Morgan's condition, for example, about 5 μm. For example, the response speed becomes slower than the case of about 2.5 μm. In the case of a thin cell thickness which does not satisfy Morgan's condition, the response speed can be increased, but the T-axis which is a horizontal orientation and a twisted orientation is used.
In a liquid crystal mode such as an N mode, generally, a sufficient luminance cannot be obtained, and only a dark display can be obtained. This is because in a relatively thick twist alignment cell that satisfies Morgan's condition regardless of the type of liquid crystal, only the optical rotation need be considered, and the effect of birefringence can be almost ignored, but the thin cell swing alignment In the case of cells, the effects of birefringence cannot be ignored,
This is because a general liquid crystal cannot satisfy Morgan's condition.

However, in a TVA mode liquid crystal display device having a thin cell thickness which does not satisfy the Morgan condition, no study has been made to achieve both a thin cell for high-speed response and luminance.

The vertical alignment type TN mode disclosed in Japanese Patent Application Laid-Open No. 8-43825 is an invention intended only to improve the contrast and the viewing angle characteristics. JP-A-8-438
No. 25 does not mention at all speeding-up by thinning the cells and prevention of a reduction in bright luminance accompanying the speeding-up.

Therefore, TVA having a high contrast
In order to achieve both high-speed response and high luminance in a liquid crystal display element of the mode, it is necessary to find a condition of refractive index anisotropy Δn that can realize high luminance with a thin cell thickness d that does not satisfy Morgan's condition. Conceivable.

Further, when the cell thickness does not satisfy the Morgan condition, the propagation of light in the liquid crystal is affected by the effect of birefringence and the effect of optical rotation due to torsional alignment. It cannot be done.

By the way, in the horizontal alignment liquid crystal display mode using a nematic liquid crystal, much research has been made on high-speed response by thinning the cell. Also, much research has been done on the vertical alignment mode.

For example, in Japanese Patent Application Laid-Open No. 5-150273, a birefringence index of a liquid crystal is set as a condition for obtaining a bright white display and a high contrast in a thin cell horizontal alignment TN mode liquid crystal display device. (Refractive index anisotropy) Δn
0.1 or more, the product Δn · d of the birefringence Δn of the liquid crystal and the thickness d of the liquid crystal layer is 0.4 μm or more, and the thickness d of the liquid crystal layer is 2 μm.
It is disclosed that the thickness is set to m or more and 4 μm or less.

In the above publication, Δn · d is set to 0.4 μm.
It is described that the brightness of white display can be improved by setting it to be larger than m. Further, the above-mentioned publication also describes that a bright and high-contrast display can be obtained by setting d to 4 μm or less.

However, what is described in Japanese Patent Application Laid-Open No. 5-150273 is the condition of the refractive index anisotropy and the cell thickness for the horizontally aligned TN mode, and the refractive index anisotropy for the vertically aligned TN mode. And conditions for the cell thickness are not described.

The liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 5-150273 is of a horizontal alignment mode, so that the obtained contrast ratio is at most 200: 1.
This is not a high value compared to the VA mode. In particular, when the cell thickness is 3 μm or less, the contrast ratio is not so good at about 100: 1. In order to actually obtain a certain level of contrast, the cell thickness needs to be 3 μm or more, and as a result, it is impossible to achieve a good response speed.

Therefore, high-speed response and high contrast cannot be achieved at the same time simply by making the horizontal alignment TN mode thinner.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a liquid crystal display device having both high-speed response, high contrast, and high luminance.

[0034]

Means for Solving the Problems The inventor of the present invention has made intensive efforts to solve the above-mentioned problems, and as a result, has obtained a liquid crystal display which has a sufficient high-speed response, a high contrast, and a high luminance, which are applicable to moving images. The conditions for the cell thickness d and the refractive index anisotropy Δn for obtaining the element were found.

That is, in order to solve the above problems, the liquid crystal display element of the present invention comprises a pair of substrates each having an electrode and an alignment control layer, a liquid crystal layer sandwiched between the two substrates, and a polarizing plate. In the liquid crystal display device, the liquid crystal layer is made of liquid crystal having a negative dielectric anisotropy, and the alignment control layers of both substrates are aligned with each other in a state where no electric field is applied between the two substrates. Is a vertical alignment film that controls the alignment of liquid crystal molecules so as to be substantially perpendicular to the surfaces of both substrates. In the vertical alignment film, the major axis of the liquid crystal molecules is adjusted when an electric field is applied between the two substrates. The liquid crystal molecules are oriented substantially parallel to the surfaces of both substrates, and the liquid crystal molecules are oriented so as to be twisted by about 90 °. The thickness of the liquid crystal layer is d, and the refractive index anisotropy of the liquid crystal is Δn. Then, d is 2.5 μm or less (condition (A)), and Δ · D (retardation of the liquid crystal layer) is characterized in that at least 0.375Myuemu (condition (B)).

According to the above configuration, an effect obtained by integrating the effects of the above conditions (A) and (B) and the effect of the vertical alignment TVA mode can be obtained. That is, according to the above configuration, first, a high-speed responsiveness capable of handling a moving image can be realized according to the condition (A). According to the above configuration,
By combining the condition (A) with the condition (B), high brightness can be realized in a thin twist alignment mode liquid crystal display element that does not satisfy the Morgan's condition.
Therefore, sufficient high-speed response and sufficient luminance for moving images can be achieved. Further, in the above configuration, since the mode is the vertical alignment mode, uniform high-speed response can be obtained at all gradations as compared with the mode using the horizontal alignment. In addition, in the above configuration, since the liquid crystal molecules are in the vertical alignment mode (TVA mode) in which the liquid crystal molecules are twisted by approximately 90 °, a higher contrast is obtained as compared with the vertical alignment mode in which the liquid crystal molecules are twisted by approximately 180 °. Can be

Therefore, according to the above configuration, it is possible to provide a liquid crystal display device having both high-speed response, high contrast and high luminance.

It is to be noted that the expression that the liquid crystal molecules are twisted by approximately 90 ° means that the liquid crystal molecules are twisted, and the twist angle of the liquid crystal molecules (the orientation vector of the liquid crystal molecules at the interface with one substrate and the other substrate). (The angle between the liquid crystal molecules and the alignment vector at the interface with the liquid crystal molecules) is approximately 90 °. Also,
“Approximately 90 °” indicates that there may be a slight deviation from 90 °, such as a design error, and is preferably 90 ° ± 1 °.
It is.

In the liquid crystal display device of the present invention, the angle (pretilt angle) between the long axis of the liquid crystal molecules and the normal to the substrate when no electric field is applied between the substrates is 15 ° or less (0 to 15 °). (Within the range of °).

According to the above configuration, since the residual phase difference is canceled, a sufficient dark luminance is obtained to obtain a sufficiently high contrast. Therefore, according to the above configuration, it is possible to provide a liquid crystal display device having higher contrast and higher dark luminance.

The liquid crystal is preferably a nematic liquid crystal having a negative dielectric anisotropy.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the liquid crystal display device (liquid crystal display cell) of the present embodiment comprises a pair of substrates 1.1 each having a transparent electrode 2.2 and a vertical alignment film 3.3, and both substrates 1.1 And a liquid crystal layer 5 interposed between the liquid crystal layers 1 and 1.

The substrate 1 is a flat plate made of a transparent material such as glass, and forms one cell by being bonded via a spacer 4. Also, the substrate 1.1
Is sealed with a sealing material 6.

The transparent electrodes 2 are formed on the inner surfaces of the substrates 1 and 1, respectively, and are patterned into appropriate shapes.
It is a transparent conductive film such as TO (indium tin oxide). The transparent electrodes 2 and 2 are adapted to form pixels in portions where the patterns of the transparent electrodes 2 and 2 overlap each other. When different potentials are applied from the outside, an electric field is formed in the pixel portions. Are switched in the form shown in FIG.

The vertical alignment films 3.3 are formed on both substrates 1.1.
An orientation control layer that controls the orientation of the liquid crystal molecules so that the major axis of the liquid crystal molecules is substantially perpendicular to the surfaces of the two substrates 1.1 (a state closer to perpendicular than parallel) when no electric field is applied between them. The substrate 1 is formed so as to cover the entire surface of the substrate 1 on the side where the transparent electrodes 2 are formed. The vertical alignment films 3 and 3 have been subjected to a rubbing process for determining the direction in which liquid crystal molecules are inclined when an electric field is applied. In this rubbing treatment, in a state where an electric field is applied between the two substrates 1.1, the major axis of the liquid crystal molecules becomes substantially parallel to the surfaces of the two substrates 1.1, and the liquid crystal molecules are aligned by approximately 90 °. That is, the angle (twist angle) between the orientation vector of the liquid crystal molecules near one substrate 1 and the orientation vector of the liquid crystal molecules near the other substrate 1 is approximately 90 °. .

The liquid crystal layer 5 is made of a liquid crystal having a negative dielectric anisotropy Δε, preferably a nematic liquid crystal having a negative dielectric anisotropy Δε. This is because, in the vertical alignment mode, the liquid crystal molecules are originally in a state of rising, so if a liquid crystal having a positive dielectric anisotropy Δε is used, the liquid crystal molecules rise when an electric field is applied, and the switching by the electric field is performed. It will be impossible.

Although not shown, two polarizing plates are arranged outside the cell. One of the polarizing plates is arranged outside the upper substrate 1 and the other is arranged outside the upper substrate 1. In addition, each polarizing plate is arranged such that the direction of its polarization axis coincides with the rubbing direction of the substrate 1 closer to the polarizing plate.

The liquid crystal display element of the present embodiment has the above-described configuration, and thus has a display mode in which the twist angle of liquid crystal molecules is about 90 °, that is, twisted vertical alignment (TVA; Twis).
tedVertical Alignment) mode.

The liquid crystal display device of the present embodiment is a liquid crystal display device of a twisted vertical alignment (TVA) mode.
Assuming that the thickness of the liquid crystal layer 5 is d and the refractive index anisotropy of the liquid crystal constituting the liquid crystal layer 5 is Δn, d is 2.5 μm or less (condition (A)), and Δn · d is 0.375 μm. The above is the condition (condition (B)).

The above condition (A) is a condition for the thickness d of the liquid crystal layer 5 for realizing a high-speed response capable of coping with a moving image. In the present invention, what is important is not the lower limit but the upper limit of d. The lower limit of d is not particularly limited as long as there is a technique for producing a liquid crystal having a sufficiently large Δn and a cell. On the other hand, if d exceeds the upper limit, a required response speed cannot be obtained, so that the upper limit of d must be set.

Here, considering the refractive index anisotropy Δn of the liquid crystal, in the numerical range of the thickness d of the liquid crystal layer 5 under the condition (A),
Since the Morgan condition is not satisfied, the light incident on the liquid crystal display element is simultaneously affected by the birefringence and the optical rotation due to the twist alignment.

There is a 4 × 4 matrix method as a method for examining the state of light propagation inside the liquid crystal. 4 × 4
The condition (B) is a condition under which sufficient brightness can be obtained when the bright brightness is calculated using the matrix method. here,
When d = 2.5 μm, the minimum value of Δn is 0.15, which is not an impossible value for a liquid crystal.

The simulation by the calculation of the 4 × 4 matrix is a well-known method, but it is a considerably complicated calculation, and it is not expected that the numerical range can be easily derived. The 4 × 4 matrix method is a well-known calculation method and will not be described here. Also, 4
The × 4 matrix method calculates how transmitted light changes depending on the alignment state of liquid crystal molecules. Therefore, in the 4 × 4 matrix method, although the calculation is considerably complicated depending on the display mode of the liquid crystal, the calculation is possible regardless of the display mode of the liquid crystal, and there is no essential difference in the calculation method depending on the display mode.

Further, d is more preferably 2 μm or less in consideration of the response speed including the halftone. Further, Δn · d is within the range of 0.375 μm or more and 0.625 or less, since high brightness (a transmittance of 90% or more with respect to the parallel Nicols ratio) is obtained and real Δn can be realized. More preferably, there is.

In the liquid crystal display device of the present embodiment, the angle (pretilt angle) between the long axis of the liquid crystal molecules and the normal line of the substrate 1.1 when no electric field is applied between the substrates 1.1. θp is preferably 15 ° or less (within a range of 0 to 15 °).

The pretilt angle θp is generated when an alignment process for determining the direction in which molecules are inclined, for example, a rubbing process for the vertical alignment films 3 is performed in order to prevent the occurrence of disclination. This causes a residual phase difference. The residual phase difference at the interface is a TV having a twist angle of 90 ° and a pretilt angle θp of 0 °.
If A, the pretilt angle θp is too large, but even if the twist angle is 90 °,
In the absence of an electric field, the entire liquid crystal display element has a phase difference. Therefore, the dark luminance increases. As a result of a detailed study, the present inventor has found that the pretilt angle θp is 15
It has been found that, when the angle is not more than °, the residual phase difference is canceled and a sufficient dark luminance is obtained, and as a result, a sufficiently high contrast is obtained.

The method of controlling the pretilt angle θp varies depending on the alignment processing method. For example, when a method of rubbing the vertical alignment films 3 is adopted as the alignment processing method, the vertical alignment film By appropriately setting the conditions of the rubbing process in 3.3, the pretilt angle θp can be controlled.

Next, a method for manufacturing the liquid crystal display element of the present embodiment will be described with reference to FIGS.

First, a conductive film is formed on each of the two substrates 1, 1, and then the transparent electrodes 2, 2 are patterned by an appropriate method into an appropriate shape.
To form Next, after a vertical alignment film 3.3 is formed on the entire surface of the substrate 1.1 on the side where the transparent electrodes 2.2 are formed, the vertical alignment film 3.3 is parallel to the surface of the substrate 1.1. A rubbing process for giving an alignment control force for aligning liquid crystal molecules in various directions is performed.

The transparent electrodes 2 and the vertical alignment films 3
As shown in FIG. 2, a cell is produced by bonding the two substrates 1 and 1 on which the substrates 3 are formed, with the vertical alignment films 3 and 3 inside through the spacers 4 as shown in FIG. At this time,
The substrates 1 are separated from each other by a rubbing direction of the vertical alignment film 3 on one substrate 1 (a direction parallel to the paper surface of FIG. 2).
The rubbing directions (perpendicular to the plane of FIG. 2) of the vertical alignment film 3 are substantially 90 ° with each other, that is, the rubbing directions are substantially perpendicular to each other. The spacer 4 used for bonding the substrates 1.1 has a distance d between the substrates 1.1 of 2.5.
The size was adjusted to be less than μm.

Next, a liquid crystal having Δn such that Δn · d becomes 0.375 μm or more and having a negative dielectric anisotropy Δε is injected into the cell, that is, between the two substrates 1.1. . Next, the liquid crystal layer 5 is formed by sealing the cell with the sealing material 6 so that the liquid crystal does not spill. Thus, a liquid crystal cell is manufactured. Finally, the produced liquid crystal cell is sandwiched between two polarizing plates arranged in orthogonal Nicols to complete a liquid crystal display cell.

According to the above method, the negative dielectric anisotropy Δε
Rubbing direction (alignment direction) of the vertical alignment film 3 on one substrate 1 and rubbing direction (alignment direction) of the vertical alignment film 3 on the other substrate 1 are used. ) Are bonded so as to be substantially orthogonal to each other, whereby a liquid crystal display element of a twisted vertical alignment mode which can provide high-speed response and high contrast can be manufactured.
Further, in a liquid crystal display element of a thin twisted vertical alignment mode which does not satisfy Morgan's conditions, a liquid crystal display element having sufficient luminance can be manufactured. Therefore, it is possible to manufacture a liquid crystal display element having both high-speed responsiveness, high contrast, and sufficient luminance that can support moving images.

In the present embodiment, the rubbing treatment is performed on the vertical alignment films 3 to determine the direction in which the liquid crystal tilts. However, in the liquid crystal display device of the present invention, even the direction in which the liquid crystal tilts is not determined. It only has to be determined. Therefore, the method of determining the tilt direction of the liquid crystal (alignment treatment method) is a method other than performing the rubbing treatment on the vertical alignment films 3, 3, for example, the inner surfaces of the substrates 1.1 (the surfaces facing each other). Alternatively, a method of controlling the tilt direction of the liquid crystal by forming protrusions, or a method of performing other alignment processing such as oblique deposition on the vertical alignment films 3 instead of the rubbing processing may be used.

In this embodiment, the transmission type liquid crystal display device having the transparent electrodes 2, 2 formed on the respective substrates 1, 1 has been described. However, the present invention is also applied to the reflection type liquid crystal display device. In the case of a reflective liquid crystal display device, one of the transparent electrodes 2 may be a reflective electrode having both the function of a reflective film and the function of an electrode.

[0066]

The present invention will be described below in detail with reference to comparative examples, analysis examples, and examples. The present invention is not limited to these examples.

[Comparative Example 1] Here, in the cell forming method described in the above-mentioned [Embodiment of the invention], as shown in FIG. 3, the rubbing direction of one substrate 1 and the other substrate 1 A cell was manufactured by the method of manufacturing a cell described in the section of the above-described [Embodiment of the invention] except that the rubbing direction was set to be antiparallel (a direction different by 180 °).
VAF1 was used as the vertical alignment film 3. The thickness (cell thickness) of the cell thus produced was measured using a commercially available cell thickness measuring device. Here, the cell thickness of the liquid crystal display cell is 1 μm, 2 μm by the above method.
m, and three types of cells of 3 μm were produced, respectively.

Next, a nematic liquid crystal having a negative dielectric anisotropy was injected into the above three types of cells. A nematic liquid crystal having a negative dielectric anisotropy is generally known. Here, MJ95955 manufactured by Merck, which is a typical nematic liquid crystal having a negative dielectric anisotropy, is used.

As basic physical properties of MJ95955, MJ9
5955 of the extraordinary refractive index n _e, normal refractive index n _o, a refractive index anisotropy _{Δn (= n e -n o)} , in the direction parallel to the orientation vector (director) of the liquid crystal molecules dielectric constant epsilon //, Table 1 shows the dielectric constant ε⊥ in the direction perpendicular to the orientation vector of the liquid crystal molecules and the dielectric anisotropy Δε (= ε // − ε⊥).

[0070]

[Table 1]

Next, the above three types of cells were sealed with the sealing material 6.
Then, three types of liquid crystal cells were manufactured by sealing the liquid crystal so as not to spill. Each of the three types of liquid crystal cells thus produced is sandwiched between two polarizing plates arranged in orthogonal Nicols, and a liquid crystal display element in a display mode in which the twist angle of liquid crystal molecules is approximately 180 °, that is, a so-called anti-parallel vertical Alignment (APVA; Anti-Parallel Vertical Alignment)
A mode liquid crystal display device (hereinafter abbreviated as APVA cell) was completed.

The three types of A thus produced having different thicknesses.
Response speed of PVA cell (cell thickness 1 μm, 2 μm, 3 μm), specifically, rise time τ _0-90 (time _{required for} relative light transmittance to change from 0% to 90%) and fall time τ _100-10 (the time required for the relative light transmittance to change from 100% to 10%). The measurement result of the rise time τ _0-90 is shown in FIG. 4, and the measurement result of the fall time τ _100-10 is shown in FIG.

According to FIGS. 4 and 5, the refractive index anisotropy Δ
APVA cell using MJ95955 where n is 0.07
The rise time τ_0-90And fall time τ
_{100- Ten}In order to make both of them less than 10 ms, the cell thickness must be 2.
It is understood that the thickness needs to be 5 μm or less.

Comparative Example 2 The pretilt angle θp generated in the liquid crystal display element can be measured by using a crystal rotation method. However, in this measurement method, the alignment state of the liquid crystal is determined by antiparallel rubbing (both substrates 1.1 and 1.1).
Are rubbed in directions different from each other by 180 °) to obtain an anti-parallel alignment state (a state in which the directions of the alignment vectors of the liquid crystal molecules in the vicinity of the two substrates 1.1 are different by 180 °) or an alignment state equivalent thereto, and It is necessary to make the thickness (the thickness of the liquid crystal layer) several tens μm. Therefore, it is necessary to manufacture a liquid crystal display element for measuring the pretilt angle θp separately from the liquid crystal display element manufactured in Comparative Example 1.

Therefore, in this example, apart from the liquid crystal display element manufactured in Comparative Example 1, a liquid crystal display element for measuring a pretilt angle was prepared by changing only the cell thickness of the liquid crystal display element of Comparative Example 1 to 50 μm. The pretilt angle θp of this liquid crystal display element was measured by a crystal rotation method. As a result, the pretilt angle θp generated by the rubbing of VAF1 was 15 °.

[Comparative Example 3] In order to evaluate the moving image display characteristics of the liquid crystal display device, it is necessary to evaluate the gradation rather than the response time such as the rise time τ _0-90 and the fall time τ _100-10. It is important to evaluate the response speed between them, that is, the response speed (time required for response) from one gradation state A to another gradation state B.

In evaluating the response speed between the gradations,
First, a voltage (applied voltage V) -absolute transmitted light intensity (absolute light transmittance) T ₀ curve (V-T ₀ curve) of the liquid crystal display element was measured, and each gradation state was determined from the obtained V-T ₀ curve. Determine the voltage to obtain. An example of a V-T ₀ curve of MJ95955 shown in FIG. Generally, the driving voltage of a liquid crystal display is 5
V, but in this case, the V-T ₀ curve is 5 V
Not saturated at However, considering the substantial applied voltage, it is appropriate to determine the voltage that gives each gradation with the absolute transmitted light intensity T ₀ (%) when 5 V is applied as a saturated state (brightest state). Therefore, the relative transmitted light intensity (relative light transmittance) T (%) is the absolute transmitted light intensity T when 5 V is applied.
₀ (%) was calculated as 100%.

Next, the voltage for giving each gradation state obtained in this manner is applied to the same APVA cell as in Comparative Example 1 except that the cell thickness is 2.5 μm. The voltage was changed to give a gradation state. And 3
At 0 ° C., the time required for the relative transmitted light intensity T (%) to change from one gradation state to another gradation state is measured,
This measured value was used as the response speed between gradations. Table 2 shows the obtained results.

[0079]

[Table 2]

The viewpoint of Table 2 is as follows. First,
The numbers from 0 to 100 in the leftmost column of Table 2 indicate the relative transmitted light intensity T (%) in the gradation state A in the initial state. The column on the right is the voltage (V) that gives the gradation. next,
The numbers from 0 to 100 in the top row of the table show the relative transmitted light intensity T (%) in the final gradation state B, and the lower row shows the voltage (V) that gives the gradation state. ). Therefore, in Table 2, for example, the relative transmitted light intensity T is 80%
The response time (response speed) from the gray scale state to the gray scale state where the relative transmitted light intensity T is 40% is shown at the intersection of the left column 80 and the upper column 40. , In this case, 4.0 ms. This APVA mode is
In the normally black mode, when the applied voltage is 0.0 V, the relative transmitted light intensity T is 0% in a black state, and when the applied voltage is 5.0 V, the relative transmitted light intensity T is 100% in a white state. .

From Table 2, it can be seen that, with a cell thickness of 2.5 μm, the response speed between all gradations is 10 ms or less, and sufficient high-speed response is maintained. Further, it can be seen that the uniformity of the response speed between arbitrary gradations is very high. .

[Comparative Example 4] [Embodiment of the Invention]
In the manufacturing method of the liquid crystal display element described in the section, the VAF 1 is used as the vertical alignment film 3 and the cell thickness is 2.5 μm.
m, and MJ95555 is prepared in the cell.
Was injected to produce a TVA mode liquid crystal display device for comparison. In other words, the angle between the rubbing direction of one substrate 1 and the rubbing direction of the other substrate 1 is 90 °.
A liquid crystal display device of a TVA mode for comparison (hereinafter abbreviated as a TVA cell) was obtained in the same manner as in Comparative Example 3 except for the following.

The response speed between halftones was measured at 30 ° C. using the obtained TVA cell for comparison. Table 2 shows the results.
Table 3 shows the same notation as in Table 3.

[0084]

[Table 3]

In this TVA mode as well, when the applied voltage is 0.0 V, the relative transmitted light intensity T becomes a black state of 0%, and when the applied voltage is 5.0 V, the relative transmitted light intensity T becomes 1
This is a normally black mode in which the white state is 00%.

When the results of the TVA cell of Comparative Example 4 shown in Table 3 are compared with the results of the APVA cell of Comparative Example 3 shown in Table 2, both the APVA cell and the TVA cell showed almost no response speed. You can see there is no difference.

The APVA cell of Comparative Example 3 (liquid crystal: M
J95955, cell thickness 2.5 μm) and the TVA of Comparative Example 4.
For each cell (liquid crystal: MJ95955, cell thickness 2.5 μm), dark luminance (%), light luminance (%), contrast ratio, response speed τ _0-90 (relative light transmittance from 0% to 90%) Time required to change) [ms], response speed τ _100-10 (time required for relative light transmittance to change from 100% to 10%) [ms], and response speed τ
_0-20 (time required for the relative light transmittance to change from 0% to 20%) [ms] was measured. Table 4 shows the results.

[0088]

[Table 4]

Here, the luminance (dark luminance and bright luminance) shown in Table 4 is a relative luminance when the luminance of the light source is 100%. At this time, assuming that the light transmittance of the polarizing plate is 60%, the ideal luminance of the liquid crystal display element placed under the crossed Nicols is 36%. Looking at Table 6, the APVA of Comparative Example 3 is shown.
The cell has 10 times higher dark luminance than the TVA cell of Comparative Example 4, which indicates that the cell is a major cause of the decrease in contrast.

The TVA cell of Comparative Example 4 has Δn =
0.07 and the cell thickness d is 2.5 μm.
n · d is less than 0.375 μm (Δn · d = 0.175)
It is. Therefore, sufficient bright brightness has not been obtained. Therefore, high contrast is not obtained despite low dark luminance and a clear dark state.

Comparative Example 5 Using a horizontally aligned TN type liquid crystal display element having a cell thickness of 1.5 μm, the response speed between halftones was measured at 30 ° C. The results are shown in Table 4 in the same notation as in Table 2. In this TN type liquid crystal display device, when the applied voltage is 0.0 V, the relative transmitted light intensity T is 0.
% White state, and when the applied voltage is 5.0 V, the relative transmitted light intensity T is 100% black state.

[0092]

[Table 5]

Comparative Example 6 Using a horizontally aligned TN liquid crystal display element (normally white mode) having a cell thickness of 3.0 μm, the response speed between halftones was measured at 30 ° C. The results are shown in Table 5 in the same notation as in Table 2. This TN type liquid crystal display element also has a white state where the relative transmitted light intensity T is 0% when the applied voltage is 0.0 V, and is 100% when the applied voltage is 5.0 V. This is a normally white mode in which a black state is set.

[0094]

[Table 6]

According to the results of Comparative Examples 5 and 6,
In the TN type liquid crystal display device, the response speed (switching speed) from the halftone state to the black state is very high, but the response speed (switching speed) between the other gray scales.
Is slower than the response speed from the halftone state to the black state by about 10 times or more, and the response speed between gradations is poor. In addition, there is a halftone in which the response speed from the white state is extremely slow (for example, a halftone state in which the relative transmitted light intensity T is 80%), and a response speed of 10 ms or less has not been obtained between all gradations.

When a birefringent medium such as a liquid crystal is arranged under orthogonal Nicols, the intensity of light transmitted through the medium changes depending on the magnitude and thickness of the refractive index anisotropy of the medium. . Furthermore, if the medium has optical rotation,
Optical rotation also affects transmitted light intensity. In the case of a liquid crystal, in the case of a thick shake alignment cell that satisfies the Morgan condition represented by the above formula (4), only the optical rotation need be considered, and the influence of the refractive index anisotropy can be almost ignored.

However, in the thin cell TVA mode liquid crystal display device as in the present invention, the above formula (4)
Cannot be satisfied, and the influence of the refractive index anisotropy cannot be ignored. For this reason, it is difficult to easily estimate the transmitted light intensity. Therefore, in the following analysis examples 1 to 3, conditions for obtaining sufficient bright luminance in a thinned TVA cell were analyzed using a 4 × 4 matrix method.

[Analysis Example 1] First, the APVA cell of Comparative Example 3 (APV having a cell thickness of 2.5 μm using MJ95955)
A4 mode liquid crystal display device) and the TVA cell of Comparative Example 4 (a 2.5 μm thick TVA mode liquid crystal display device using MJ95955) using a 4 × 4 matrix method to transmit transmitted light in the bright state. (Maximum brightness) was calculated. The transmitted light intensity at this time is a relative transmitted light intensity when the transmitted light intensity of the polarizing plate in the parallel Nicol arrangement is set to 100%, and does not consider the reflection of light at the interface between the substrates 1.1. FIG. 7 shows the obtained calculation results. Note that θ in FIG.
Is the angle between the major axis direction of the liquid crystal molecules near the interface between the substrates 1 and 1 and the polarization axis direction of the polarizing plate.

In the APVA cell of Comparative Example 3, the substrates 1.1
The maximum brightness is obtained when the angle between the major axis direction of the liquid crystal molecules near the interface and the polarization axis direction of the polarizing plate is 45 °. On the other hand, T of Comparative Example 4
In the VA cell, the maximum luminance is obtained when the angle between the major axis direction of the liquid crystal molecules near the interface between the substrates 1 and 1 and the polarization axis direction of the polarizing plate is 0 °.

In this case, Δn of MJ95955 is 0.0
7, which is not the condition that the transmitted light intensity is maximized even in the APVA cell, but under this condition, the transmitted light intensity of the APVA cell is about three times that of the TVA cell.

[Analysis Example 2] For a TVA mode liquid crystal display element, the transmitted light intensity (maximum luminance) in the bright state when Δn · d was changed was calculated by a 4 × 4 matrix method. At this time, the transmitted light intensity of the polarizing plate in the parallel Nicol arrangement in a state where the liquid crystal display element is not present is 10%.
This is the relative transmitted light intensity when 0% (the transmitted light intensity relative to the parallel Nicols ratio), and does not take into account the reflection of light at the substrate interface. In the vertical alignment mode, the substrate 1.1 in the bright state is not used.
Although the tilt angle of the liquid crystal molecules from the normal line becomes a problem, here, it is assumed that the liquid crystal molecules are sufficiently tilted, and the tilt angle in this bright state is calculated as 80 °. FIG. 8 shows the obtained calculation results.

According to this, 85% or more of the transmitted light intensity relative to parallel Nicols can be obtained only when Δn · d is 0.375 μm.
It can be seen that the time is not less than m.

Further, Δn · d is more preferably in a range of 0.375 μm or more and 0.625 μm or less, since a transmittance (transmitted light intensity) with a parallel Nicols ratio of 90% or more can be obtained. It turns out that it is a range. Δn
Even if d is 0.85 μm or more, a transmittance (transmitted light intensity) of 90% or more with respect to the parallel Nicols ratio can be obtained, but Δn becomes a tremendous value, which is not realistic.

[Analysis Example 3] The light transmittance in the dark state when Δn · d is 0.375 μm in the TVA mode liquid crystal display element was measured by using the 4 × 4 matrix method, and the pretilt angle θp was 0 to 20 °. The dependence of the contrast ratio on the pretilt angle θp was estimated from the calculation results. FIG. 9 shows the result.

According to this, the pretilt angle θp is 15
It can be seen that a high contrast ratio of 150: 1 or more can be obtained at less than or equal to °. When the pretilt angle θp is around 15 °, the contrast ratio is significantly increased by slightly reducing the pretilt angle θp. Therefore, 0 ° ≦ θ
By setting p ≦ 15 °, a sufficient contrast ratio can be obtained. Normally, the VA mode is the pretilt angle θp
If the angle is not a few degrees, the contrast is greatly reduced. Therefore, it is generally difficult to determine the tilt direction in the rubbing process in which a pretilt angle θp exceeding several degrees is obtained.
On the other hand, in the TVA mode liquid crystal display element, a relatively large pretilt angle θp obtained by the rubbing process is used.
However, it can be seen that high contrast can be obtained.

The pretilt angle θp can be controlled by the rubbing condition for determining the direction in which the liquid crystal is inclined, the shape of the projections formed on the substrate 1.1, and the like.

[Example 1] A nematic liquid crystal NLC1 having a negative dielectric anisotropy Δε and a refractive index anisotropy Δn of 0.15 was injected into a cell in place of MJ95955 as a liquid crystal. In the same manner as in Comparative Example 4, a TVA mode liquid crystal display device having a cell thickness of 2.5 μm according to the present invention was manufactured. In this case, Δn · d = 0.375 μm.

With respect to this liquid crystal display device, the response speed between gradations was measured at 30 ° C. Table 7 shows the obtained measurement results in the same notation as in Table 2. In addition, this liquid crystal display element also
In the normally black mode, when the applied voltage is 0.0 V, the relative transmitted light intensity T is 0% in a black state, and when the applied voltage is 5.0 V, the relative transmitted light intensity T is 100% in a white state. .

[0109]

[Table 7]

Further, in the same manner as in Table 4, the dark luminance (%), the bright luminance (%), the contrast ratio, and the response speed τ _0-100 (relative light transmittance of 0% to 10%) were obtained for this liquid crystal display device.
The time required to change from 0% to 0%) [ms], the response speed τ _100-0 (the time required for the relative light transmittance to change from 100% to 0%) [ms], and the response speed τ
_0-20 (time required for the relative light transmittance to change from 0% to 20%) [ms] was measured. Table 8 shows the results.

[0111]

[Table 8]

Here, the luminance (dark luminance and bright luminance) shown in Table 8 is a relative luminance when the luminance of the light source is 100%.

From Tables 7 and 8, d = 2.5 μm, Δ
By setting n · d = 0.375 μm, 10
In addition to achieving a high-speed response speed of ms or less, a high contrast ratio of 650: 1 is obtained, and it can be seen that both high-speed response and high contrast are achieved.

Comparative Example 7 A comparative cell thickness of 2 was obtained in the same manner as in Comparative Example 4, except that a liquid crystal having a refractive index anisotropy Δn of 0.1 was injected into the cell instead of MJ95955. A 0.5 μm TVA mode liquid crystal display device was produced. In this case, Δn · d = 0.25 μm.

With respect to the obtained TVA for comparison, the dark luminance (%), the light luminance (%), and the contrast ratio were measured. Table 9 shows the results. Here, the luminance (dark luminance and bright luminance) shown in Table 9 is a relative luminance when the luminance of the light source is 100%.

[0116]

[Table 9]

When comparing Example 1 with Comparative Example 4, Δn
Brightness is 16% in Comparative Example 4 where d = 0.25 μm
It can be seen that in Example 1 where Δn · d = 0.375 μm, the brightness was remarkably improved to 30%. This also results in a contrast ratio of 400: 1.
To 650: 1. Therefore, Δn
It is understood that d is preferably 0.375 μm or more.

[0118]

As described above, in the liquid crystal display device of the present invention, the liquid crystal layer is made of liquid crystal having a negative dielectric anisotropy, and the alignment control layers on both substrates are applied with an electric field between the two substrates. A vertical alignment film that controls the alignment of the liquid crystal molecules such that the major axis of the liquid crystal molecules is substantially perpendicular to the surfaces of both substrates in a state where they are not in
The vertical alignment film is oriented such that, when an electric field is applied between the two substrates, the major axes of the liquid crystal molecules are substantially parallel to the surfaces of the two substrates, and the liquid crystal molecules have an orientation twisted by approximately 90 °. When the thickness of the liquid crystal layer is d and the refractive index anisotropy of the liquid crystal is Δn, d is 2.5 μm or less and Δn · d is 0.375 μm or more. is there.

According to the above configuration, by setting the thickness d of the liquid crystal layer to 2.5 μm or less, it is possible to realize a high-speed responsiveness capable of coping with moving images, and to reduce Δn · d to 0.37
By setting the thickness to 5 μm or more, high brightness can be realized. Further, in the above configuration, since the mode is the vertical alignment mode, uniform high-speed response can be obtained at all gradations. Moreover,
Since the liquid crystal molecules are twisted by approximately 90 °, higher contrast is obtained as compared with the case where the liquid crystal molecules are twisted by approximately 180 °.

Therefore, the above configuration has an effect that a liquid crystal display element having both high-speed response, high contrast, and high luminance can be provided.

In the liquid crystal display device of the present invention, the angle (pretilt angle) between the long axis of the liquid crystal molecules and the normal of the substrate when no electric field is applied between the substrates is 15 ° or less (0 to 15). (Within the range of °).

According to the above configuration, since the residual phase difference is canceled, a sufficient dark luminance is obtained to obtain a sufficiently high contrast. Therefore, the above configuration has an effect that a liquid crystal display device having higher contrast and higher dark luminance can be provided.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating a manufacturing process of the liquid crystal display device according to the present invention.

FIG. 3 is a cross-sectional view showing a liquid crystal display device in an antiparallel vertical alignment mode.

FIG. 4 is a graph showing a cell thickness dependency of a rise time in a liquid crystal display device in an antiparallel vertical alignment mode.

FIG. 5 is a graph showing a cell thickness dependency of a fall time in a liquid crystal display device in an antiparallel vertical alignment mode.

FIG. 6 shows a voltage-in a vertical alignment mode liquid crystal display device.
It is a graph which shows a transmitted light intensity curve.

FIG. 7 shows an antiparallel vertical alignment mode liquid crystal display device (APV).
A cell) and a liquid crystal display element (T
VA cell), a liquid crystal with Δn = 0.07 (MJ95
955) is a diagram showing the maximum luminance obtained when using (955).

FIG. 8 is a diagram showing the birefringence dependence of the maximum luminance in a liquid crystal display device in a twisted vertical alignment mode having a cell thickness of 2.5 μm.

FIG. 9 is a graph showing the pretilt angle dependence of light transmittance and contrast ratio in a dark state in a liquid crystal display device in a twisted vertical alignment mode where Δn · d = 0.375 μm.

FIGS. 10A and 10B are schematic diagrams illustrating a switching state of a liquid crystal display element in a vertical alignment mode, where FIG. 10A is a non-electric field state (electric field application is off), and FIG.
Is shown.

11A and 11B are schematic diagrams illustrating a state of switching of a liquid crystal display element in a twisted vertical alignment mode, wherein FIG. 11A illustrates a non-electric field state (electric field is off), and FIG. .

[Explanation of symbols]

 Reference Signs List 1 substrate 2 transparent electrode (electrode) 3 vertical alignment film 5 liquid crystal layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Kanabe 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Nobuyuki Ito 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (for reference) 2H090 KA05 KA07 LA01 LA09 MA01 MA06 MA10 MB01 2H091 FA08X FA08Z GA02 GA07 GA08 HA07 HA09 KA02 KA05 LA17 LA18 LA30

Claims (2)

[Claims] 1. An electrode having an electrode and an orientation control layer, respectively.
In a liquid crystal display device comprising a pair of substrates, a liquid crystal layer sandwiched between both substrates, and a polarizing plate, the liquid crystal layer is made of liquid crystal having a negative dielectric anisotropy, and the alignment control layers of both substrates are A vertical alignment film that controls the alignment of liquid crystal molecules such that the major axis of the liquid crystal molecules is substantially perpendicular to the surfaces of both substrates in a state where no electric field is applied between the two substrates. In a state in which an electric field is applied between the two substrates, the liquid crystal molecules are aligned so that the major axes thereof are substantially parallel to the surfaces of the two substrates, and the liquid crystal molecules are twisted by approximately 90 °. The thickness of the liquid crystal layer is d, and the refractive index anisotropy of the liquid crystal is Δn.
Then, d is 2.5 μm or less and Δn · d
Is 0.375 μm or more. 2. The liquid crystal display element according to claim 1, wherein the angle between the long axis of the liquid crystal molecules and the normal to the substrate when no electric field is applied between the two substrates is 15 ° or less. .