JP2001343653A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a liquid crystal display device in which alignment disorder does not have an influence on display and display quality is hardly decreased even when alignment directions of liquid crystal molecules are controlled so as to be different from one another in pixels. SOLUTION: In the liquid crystal display device 1, circularly polarized light passed through a λ/4 plate 23a is made incident to a liquid crystal layer 21 exhibiting radial tilt alignment in which the alignment direction changes continuously when voltage is applied. As a result, the liquid crystal molecules can contribute to the display as far as the alignment direction and the visual angle of the liquid crystal molecules are not coincident with each other not only about an in-plane component but also about a substrate normal component even if the alignment state of the liquid crystal molecules is disordered. Thus as a result of using the liquid crystal layer in which the alignment directions of the liquid crystal molecules are controlled so as to be different from one another in the pixel for securing a wide visual field angle, the liquid crystal display device 1 having high display quality without roughness can be realized, even though not only the edge region of a pixel electrode but also the boundary region of domains exist.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which the alignment directions of liquid crystal molecules are controlled so as to be different from each other in a pixel, for example, such as radial tilt alignment and multi-domain alignment. The present invention relates to a liquid crystal display device capable of improving the display quality by suppressing roughness caused by the above.

[0002]

2. Description of the Related Art For example, a liquid crystal display device used as a display screen of a notebook personal computer or a word processor has a narrower viewing angle than a display device such as a CRT due to the optical anisotropy of liquid crystal. When viewed, the display quality tends to deteriorate. Therefore, for example, see
JP-A-258605 and JP-A-11-109391 propose a so-called multi-domain system in which a plurality of regions are formed in the alignment direction of liquid crystal.

As an example of a multi-domain liquid crystal display device, a multi-domain configuration of a vertical alignment mode liquid crystal display device using a vertical alignment film and a liquid crystal having negative dielectric anisotropy will be described. In the added state, the liquid crystal molecules are vertically aligned. When linearly polarized light enters the liquid crystal layer in this state from the polarizing plate, the liquid crystal layer has almost no birefringence anisotropy, so that linearly polarized light is emitted while maintaining the polarization state, and is opposite to the liquid crystal layer. Absorbed by the polarizing plate disposed in As a result, the liquid crystal display device can perform black display.

[0004] Conversely, when a voltage is applied, FIG.
As shown in FIG. 8, the liquid crystal layer 121c of the liquid crystal display device 101
In this case, the liquid crystal molecules M tilt according to the applied voltage. In addition,
FIG. 3 shows a case of radial tilt alignment in which the alignment direction of the liquid crystal molecules M changes continuously. Even in the same pixel, the alignment direction of the liquid crystal molecules M is centered on the central axis A of the radial tilt. In addition, one area A101 and the other area A102 are different from each other. In this state, the polarizing plate 122a
When linearly polarized light enters the liquid crystal layer 121c from the liquid crystal layer 121c, the liquid crystal layer 121c can impart a phase difference to the transmitted light and change the polarization state of the transmitted light. Therefore, the liquid crystal cell 12
The outgoing light from 1 generally changes to elliptically polarized light.

When the elliptically polarized light is incident on the polarizing plate 122b disposed on the exit side of the liquid crystal cell 121, the amount of light corresponding to the phase difference given by the liquid crystal layer 121c is transmitted, unlike when no voltage is applied. I do. Therefore, by controlling the voltage applied to the liquid crystal layer 121c and adjusting the alignment direction of the liquid crystal molecules M, the amount of light emitted from the liquid crystal display device 101 can be changed.
A gradation display is enabled.

Here, in the liquid crystal display device 101, 1
Even in a pixel, the alignment directions of the liquid crystal molecules M are different from each other. Therefore, when viewed obliquely, even if the amount of emitted light passing through a certain liquid crystal molecule M is reduced, the alignment direction with the liquid crystal molecule M does not change. Some of the other liquid crystal molecules M differing from each other increase the amount of emitted light. As a result, regions where the liquid crystal molecules M having different alignment directions are present mutually optically compensate each other, so that the display quality when viewed obliquely can be improved and the viewing angle can be increased.

[0007]

However, as in the liquid crystal display device 101 having the above-described structure, if the alignment directions in the pixels are separately controlled, alignment disturbances are likely to occur.
Therefore, for example, alignment disturbance occurs due to a small factor such as an external electric field from a source signal line or a gate signal line, which is not a problem in a single alignment direction. Here, if the location where the alignment disturbance occurs is darkened due to the alignment disturbance, the alignment disturbance is different for each location and for each pixel, so that roughness is observed in the display, which causes a problem of deteriorating the display quality.

In the case where the alignment directions are controlled so as to be different from each other as compared with the case of the single alignment, there are directions in which the light is always extinguished under two polarizing plates as shown in FIG. Therefore, the brightness of the entire pixel is reduced as compared with the case where the predetermined transmittance is maintained in all the portions. As a result, the light use efficiency (effective aperture ratio) of the liquid crystal display device also decreases.

Here, the resolution and the number of gradations of the liquid crystal display device are improving year by year, and a liquid crystal display device capable of displaying more gradations even if the area of one pixel is reduced is required. I have. However, when the effective aperture ratio is reduced due to the above-mentioned orientation disorder, the luminance at the time of white display is reduced, and it is difficult to improve the number of gradations. Although the luminance can be improved by enlarging the pixel area, it is difficult to improve the resolution.

The present invention has been made in view of the above-mentioned problems, and has as its object to solve the problem even when the alignment directions of liquid crystal molecules are controlled to be different from each other in a pixel.
An object of the present invention is to realize a liquid crystal display device in which alignment disturbance does not affect display and display quality is not easily deteriorated.

[0011]

In order to solve the above-mentioned problems, a liquid crystal display device according to the present invention has a first substrate provided with a pixel electrode corresponding to a pixel and a second substrate provided with a counter electrode. And a liquid crystal layer provided between the two substrates, wherein the voltage between the pixel electrode and the counter electrode is at least a predetermined value and the orientation directions of the liquid crystal molecules are controlled to be different from each other in the pixel. And an analyzer disposed on the emission side of the liquid crystal layer, a circularly polarizing unit for setting incident light to the liquid crystal layer to a substantially circularly polarized state, and a surface provided between the liquid crystal layer and the analyzer. It is characterized in that the retardation in the inward direction includes a first retardation layer set to approximately one quarter of the wavelength of the transmitted light.

Further, another liquid crystal display device according to the present invention comprises:
In order to solve the above problem, a first substrate provided with a pixel electrode corresponding to a pixel, a second substrate provided with a counter electrode, and a second substrate provided between the two substrates, wherein the pixel electrode and the counter electrode A liquid crystal layer exhibiting a radially inclined alignment in which the alignment direction of liquid crystal molecules continuously changes when at least a predetermined voltage is applied, an analyzer disposed on an output side of the liquid crystal layer, and the liquid crystal layer. A circularly polarizing means for setting incident light to the layer to a substantially circularly polarized state, and provided between the liquid crystal layer and the analyzer, wherein the retardation in the in-plane direction is substantially a quarter wavelength of the wavelength of the transmitted light. And a first retardation layer set to the following.

Still another object of the present invention is to provide a liquid crystal display device comprising: a liquid crystal layer having a multi-domain orientation; an analyzer disposed on an emission side of the liquid crystal layer; Circular polarization means for setting incident light to a substantially circular polarization state, and between the liquid crystal layer and the analyzer, the retardation in the in-plane direction is reduced to approximately a quarter of the wavelength of the transmitted light. And a set first retardation layer.

In the liquid crystal display device of each of the above structures, the incident side and the output side of the liquid crystal display device may be in opposite directions, as in a transmission type liquid crystal display device, or a reflection type liquid crystal display device. , The emission side and the incidence side may be the same.

In the liquid crystal display device of each of the above structures, substantially circularly polarized light is incident on the liquid crystal layer, and light emitted from the liquid crystal layer is given a phase difference of a quarter wavelength by the first phase difference layer. After that, it is incident on the analyzer.

If the liquid crystal molecules of the liquid crystal layer are oriented in the normal direction (vertical direction) of the substrate, the liquid crystal layer cannot give a phase difference to transmitted light. As a result, the transmitted light is emitted while maintaining substantially circular polarization. The output light is converted to linearly polarized light by the first retardation layer, and then input to the analyzer, where transmission is restricted. As a result, the liquid crystal display device can perform black display. On the other hand, when the voltage between the pixel electrode and the counter electrode is a predetermined voltage, such as the initial alignment state when a voltage is applied or when no voltage is applied, the alignment directions of the liquid crystal molecules are different from each other in the pixel. Controlled. In this state, the liquid crystal layer
Since a phase difference corresponding to the alignment state is given to the transmitted light, the circularly polarized light is converted to elliptically polarized light. Therefore, even if the light passes through the first retardation layer, it does not return to linearly polarized light, and a part of the light emitted from the first retardation layer is emitted from the analyzer. As a result, the amount of light emitted from the analyzer can be controlled in accordance with the applied voltage, and gray scale display can be performed.

Further, since the alignment directions of the liquid crystal molecules are different from each other in the pixel, the regions where the liquid crystal molecules having different alignment directions exist can optically compensate each other. As a result, the display quality when viewed obliquely can be improved, and the viewing angle can be increased.

Here, in the liquid crystal layer, the alignment directions of the liquid crystal molecules are controlled so as to be different from each other in the pixels in order to secure a wide viewing angle. Therefore, in the case of a conventional liquid crystal display device in which linearly polarized light is incident on the liquid crystal layer and light emitted from the liquid crystal layer is incident on the analyzer, the alignment of the liquid crystal molecules is disturbed, and the in-plane component of the alignment direction is reduced. If the absorption axis coincides with the absorption axis of the analyzer, the liquid crystal molecules cannot provide a phase difference to the transmitted light regardless of the component in the normal direction of the substrate. Here, the way in which the alignment state is disordered differs between pixels, and even within the same pixel, differs depending on the location, so that roughness occurs. Also,
Since the liquid crystal molecules whose in-plane components in the alignment direction coincide with the absorption axis of the analyzer cannot contribute to the improvement in brightness, the light use efficiency (effective aperture ratio) decreases. As a result, it is difficult to secure a contrast ratio, and it is difficult to increase the number of gradations.

On the other hand, in the liquid crystal display device according to the present invention, since substantially circularly polarized light is incident on the liquid crystal layer, there is no anisotropy in the alignment direction of the liquid crystal layer, and the alignment direction of liquid crystal molecules and transmitted light are eliminated. The liquid crystal molecules can give a phase difference to the transmitted light as long as the liquid crystal molecules do not coincide with both the in-plane component and the substrate normal direction. Therefore, in order to secure a wide viewing angle, the alignment directions of the liquid crystal molecules are controlled to be different from each other in the pixel. As long as they do not match, the brightness can be improved. As a result, high light use efficiency can be secured while maintaining a wide viewing angle, and an improvement in the contrast ratio and an increase in the number of gradations can be realized.

In addition to the above configuration, the circularly polarizing means sets light having a wavelength of 550 nm to a substantially circularly polarized state, and the first retardation layer has a retardation in the in-plane direction of 550 nm. It is preferable to set the value to approximately one-fourth.

In this configuration, the human visual sensitivity is the highest 5
For a wavelength of 50 nm, substantially circularly polarized light is incident, and it is possible to prevent a decrease in brightness and generation of roughness for light of the wavelength. As a result, it is possible to realize a liquid crystal display device in which a decrease in brightness and roughness are less visible than when substantially circularly polarized light is incident only at other wavelengths.

The circularly polarized light means only needs to be capable of entering circularly polarized light, but it is sufficient if substantially circularly polarized light can be incident to such an extent that the decrease in brightness and the occurrence of roughness are not noticeable. Also, the first
The retardation of the retardation layer may be exactly equal to a quarter wavelength of the transmitted light, but may be approximately a quarter wavelength so that the decrease in brightness and the occurrence of roughness are not noticeable.

Specifically, when the light having a wavelength of 550 nm is set as a reference, it is preferable that the in-plane retardation of the first retardation layer is set to be 95 nm or more and 175 nm or less.

In the above configuration, the retardation is 95n
Since the distance is set to m or more and 175 nm or less, even if the brightness is reduced, the overall reduction in brightness and the reduction in brightness in the alignment disorder region are suppressed to about 10%. As a result, compared to setting it in another range,
It is possible to realize a liquid crystal display device in which a decrease in brightness and roughness are hard to be visually recognized.

In addition to the above configuration, the circularly polarizing means is provided on the incident side of the liquid crystal layer, and transmits circularly polarized light in a predetermined rotating direction and reflects circularly polarized light rotating in the opposite direction. It is desirable to be a reflective layer.

In this configuration, of the light incident on the selective reflection layer, circularly polarized light having a predetermined turning direction is transmitted through the selective reflection layer. On the other hand, circularly polarized light that rotates in the opposite direction to the direction is
Since the light is reflected by the selective reflection layer, unlike the case where the light is absorbed by the polarizer, the light can be reused by being returned to a backlight light source, for example. As a result, light utilization efficiency can be improved despite substantially circularly polarized light being incident on the liquid crystal layer.

On the other hand, instead of using a selective reflection layer as the circularly polarizing means, the circularly polarizing means is disposed between a polarizer provided on the incident side of the liquid crystal layer and the polarizer and the liquid crystal layer, A second retardation layer in which retardation in the in-plane direction is set to approximately one quarter of the wavelength of the transmitted light may be provided. Even in this case, linearly polarized light emitted from the polarizer is converted into substantially circularly polarized light by the second retardation layer.
Substantially circularly polarized light can be incident on the liquid crystal layer. In addition, the incident side and the outgoing side of the liquid crystal display device may be the same side or the opposite side, but in the case of the same side, the analyzer and the polarizer, or the first and second phase difference Layers can be shared.

Further, in addition to the above configuration, the analyzer is disposed on one of the liquid crystal layers, the polarizer is disposed on the other, and the transmission axis of the analyzer and the first retardation layer are disposed. Make an angle of 45 degrees with the slow axis of the analyzer, and further, the analyzer, the polarizer and the second polarizer so that the transmission axis of the polarizer and the slow axis of the second retardation layer form an angle of 45 degrees. 1st and 2nd
It is desirable that a retardation layer is provided.

In this configuration, the transmission axis of the analyzer and the first
Since the slow axis of the retardation layer forms an angle of 45 degrees with the slow axis of the polarizer and the slow axis of the second retardation layer forms an angle of 45 degrees, the linear axis is efficiently and linearly formed. Polarized light and circularly polarized light can be mutually converted.

Further, in the case of the structure having the first and second retardation layers, the analyzer is arranged on one of the liquid crystal layers,
The polarizer is disposed on the other side, the first and second retardation layers are disposed such that their slow axes are orthogonal to each other, and the analyzer and the polarizer are disposed on respective transmission axes. Are desirably arranged so as to be orthogonal to each other.

In the above arrangement, the first and second retardation layers are arranged such that the slow axes are orthogonal to each other. Therefore, the wavelength dispersion of the refractive index anisotropy of both retardation layers is offset by each other. As a result, in the black display state, the transmitted light in a wider wavelength range is absorbed by the analyzer. Thereby, a better black display can be realized.

Further, in any of the configurations, the inclination from the normal line direction of the first substrate to the viewing angle is included in the phase difference provided between the analyzer and the polarizer and provided by the liquid crystal layer. It is desirable to have a viewing angle compensation layer in which the refractive index anisotropy is set so as to cancel the phase difference that fluctuates according to the angle.

In this configuration, the inclination angle of the viewing angle
The phase difference provided by the liquid crystal layer is canceled by the viewing angle compensation layer.
Therefore, the dependence of the viewing angle can be suppressed, and a liquid crystal display device having a good contrast ratio in a wider viewing angle range can be realized.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An embodiment of the present invention will be described below with reference to FIGS. For example, as a liquid crystal layer in which the orientation direction is not constant, when no voltage is applied, the orientation is perpendicular to the substrate,
When a voltage is applied, for example, a liquid crystal layer exhibiting a radially inclined alignment in which the alignment direction changes continuously, the liquid crystal panel 2 of the liquid crystal display device 1 according to the present embodiment, as shown in FIG.
A liquid crystal cell 21 including a TFT (Thin Film Transistor) substrate 21a, a counter substrate 21b, and the liquid crystal layer 21c sandwiched between the substrates 21a and 21b, polarizing plates 22a and 22b disposed on both sides of the liquid crystal cell 21, TFT substrate 2
A λ / 4 plate (second retardation layer) 23a disposed between the polarizing plate 22a on the 1a side and the liquid crystal cell 21;
A λ / 4 plate 23b (first retardation layer) is provided between the 1b-side polarizing plate 22b and the liquid crystal layer 21c. The two substrates 21a and 21b correspond to the first and second substrates described in the claims. The polarizing plate 22a corresponds to a polarizer, and the polarizing plate 22b corresponds to an analyzer.

The liquid crystal cell 21 is a vertical alignment (VA) type liquid crystal cell in which pixel electrodes 31 (described later) formed of ITO (Indium Tin Oxide) or the like and thin film transistors (not shown) are arranged in a matrix. TFT substrate 21a and counter substrate 21b having a counter electrode
After applying a vertical alignment film (not shown) to both substrates 21a
21b, and both substrates 21a and 21b
The liquid crystal layer 21c having a negative dielectric anisotropy is sealed in the gap between the layers. Thus, when no voltage is applied, the liquid crystal molecules M of the liquid crystal layer 21c are oriented substantially vertically as shown in FIG. 1, and when a voltage is applied, the liquid crystal molecules are inclined and horizontally oriented as shown in FIG. it can.

Further, the liquid crystal cell 21c according to the present embodiment
In FIG. 3, as shown in FIG. 3, a resin 32a having a circular hole 32 is provided on each pixel electrode 31 provided on the TFT substrate 21a. The wall surface H of the hole 32 is shown in FIG.
As shown in FIG. 7, the liquid crystal molecules M are inclined and near the wall surface H, the liquid crystal molecules M are oriented so as to be perpendicular to the surface of the wall surface H.
In addition, when a voltage is applied, the electric field near the wall H tilts in a direction parallel to the surface of the wall H. As a result, when the liquid crystal molecules M are tilted when a voltage is applied, the liquid crystal molecules M are easily tilted radially around the center of the hole 32 in the in-plane direction, as indicated by arrows in FIG. Each liquid crystal molecule M of the layer 21c can be radially tilt-aligned. Further, when the applied voltage further increases, the inclination angle with respect to the normal direction of the substrate increases, and each liquid crystal molecule M is oriented substantially parallel to the display screen and radially in the plane. The hole 32
Can be formed by applying a photosensitive resin on the TFT substrate 21a and processing it by a photolithography process.

Further, for example, when the pixel pitch is increased, the provision of the holes 32 one by one in the pixel electrode 31 weakens the alignment regulating force in the central region of the hole 32 and makes the alignment unstable. There is a fear. Therefore, when the alignment regulating force in the central region is insufficient, it is preferable to provide a plurality of holes 32 on each pixel electrode 31 as shown in FIG. In the drawing, reference numeral 33 denotes a source wiring, and reference numeral 34 denotes a gate wiring.

On the other hand, the λ / 4 plate 23a · 2 shown in FIG.
3b is formed of a material having birefringence anisotropy, such as a uniaxially stretched polymer film, and has a thickness (substrate) such that the optical path difference between the ordinary ray and the extraordinary ray becomes a quarter wavelength of the incident light. Length in the normal direction) is set. Thus, linearly polarized light having a polarization direction of 45 degrees with respect to the slow axis can be converted to circularly polarized light. Further, when circularly polarized light is incident, 45 ° with respect to the slow axis of the λ / 4 plate 23a (23b).
It can be converted to linearly polarized light having a polarization direction of a degree. Note that, when the liquid crystal layer 21c is formed and a chiral agent is added and the liquid crystal layer 21c is axially symmetrically aligned, a twist angle occurs in the liquid crystal layer 21c. Therefore, in this case, it is desirable to shift the optical path difference of the λ / 4 plate 23a (23b) from a quarter wavelength in consideration of the twist angle of the liquid crystal layer 21c.

In the liquid crystal panel 2 according to the present embodiment, the transmission axis PAa (PA) of the polarizing plate 22a (22b) is used.
b) and the slow axis SL of the λ / 4 plate 23a (23b)
a (SLb) is set in the direction as shown in FIG. Specifically, the slow axis SLa of the λ / 4 plate 23a is disposed so as to form an angle of 45 degrees with the transmission axis PAa of the polarizing plate 22a. Further, the slow axis SLb of the λ / 4 plate 23b is arranged so as to form 45 degrees with the transmission axis PAb of the polarizing plate 22b in the same direction as when the angles of the slow axis SLa and the transmission axis PAa are set. ing. Note that FIG. 6 illustrates an example in which the angle becomes 45 degrees clockwise when viewed from the counter substrate 21b side along the substrate normal direction. Also, FIG. 3 shows a state in which no voltage is applied, and the liquid crystal molecules M
Are oriented substantially vertically.

Further, the liquid crystal display device 1 according to the present embodiment
As shown in FIG. 1, a backlight 3 serving as a light source of the liquid crystal display device 1 is provided on one of both surfaces of the liquid crystal panel 2.
Is arranged. In the example of FIG. 1, the TFT substrate 21
The figure shows a case where the backlight 3 is arranged on the side a.

In the above configuration, while no voltage is applied between the pixel electrode 31 and the counter electrode (not shown), the liquid crystal molecules M of the liquid crystal layer 21 c are in the vicinity of the wall surface H of the hole 32 as shown in FIG. Except for a small number of molecules, it is in a vertical alignment state. In this state (when no voltage is applied), light incident on the liquid crystal panel 2 from the backlight 3 passes through the polarizing plate 22a, and has a polarization direction of 45 degrees with respect to the slow axis SLa of the λ / 4 plate 23a. Becomes Further, the linearly polarized light is
By passing through 3a, it is converted into circularly polarized light.

Here, the liquid crystal molecules M do not give a phase difference to light incident in a direction parallel to the alignment direction. Therefore, the liquid crystal layer 21c cannot give a phase difference to the light vertically incident on the liquid crystal layer 21c from the backlight 3, and has almost no birefringence.

As a result, the circularly polarized light emitted from the λ / 4 plate 23a passes through the liquid crystal layer 21c while maintaining the polarization state, and enters the λ / 4 plate 23b. Circularly polarized light is λ / 4 plate 2
After passing through 3b, the circularly polarized light is converted into linearly polarized light having a polarization direction of 45 degrees with respect to the slow axis SLb of the λ / 4 plate 23b, that is, a direction orthogonal to the transmission axis PAb of the polarizing plate 22b. You. Therefore, the linearly polarized light is absorbed by the polarizing plate 22b, and the liquid crystal display device 1 can perform black display without applying a voltage.

On the other hand, when a voltage is applied between the pixel electrode 31 and the counter electrode, the liquid crystal molecules M of the liquid crystal layer 21c are radially tilt-aligned as shown in FIGS. Even in this state, the polarization state is changed from the backlight 3 to the liquid crystal cell 21 in the same manner as when no voltage is applied, and circularly polarized light enters the liquid crystal layer 21c.

However, when a voltage is applied, the alignment direction of the liquid crystal molecules M changes, and the liquid crystal molecules M are tilted radially. Here, the liquid crystal molecules M do not give a phase difference to light incident in a direction parallel to the alignment direction, but when the alignment direction and the incident direction are different, a phase difference according to the angle of the two is given. Can be given to transmitted light.

As a result, in the case of light that is perpendicularly incident on the liquid crystal cell 21, except for a small area where the liquid crystal molecules M are oriented in the normal direction of the substrate, such as the central area of the hole 32, for example.
The liquid crystal layer 21c can impart a phase difference to the transmitted light,
The polarization state of transmitted light can be changed. Therefore, the light emitted from the liquid crystal cell 21 generally changes to elliptically polarized light.
This elliptically polarized light does not become linearly polarized light even when passing through the λ / 4 plate 23b, unlike when no voltage is applied. Therefore,
Polarizing plate 22b from liquid crystal cell 21 via λ / 4 plate 23b
A part of the light supplied to the polarizing plate 22b can pass through the polarizing plate 22b. Here, the amount of polarized light transmitted through the polarizing plate 22b depends on the magnitude of the phase difference provided by the liquid crystal layer 21c. Therefore, by controlling the voltage applied to the liquid crystal layer 21c and adjusting the alignment direction of the liquid crystal molecules M, the amount of light emitted from the liquid crystal display device 1 can be changed, and gradation display can be performed.

In the above configuration, the liquid crystal layer 21c is radially tilt-aligned. Therefore, even if the liquid crystal panel 2 is viewed from a direction in which the in-plane components are different from each other (in-plane azimuth), the entire liquid crystal molecules M related to the display of a certain pixel have substantially the same phase difference to the transmitted light. As a result, a wider viewing angle can be secured as compared with the case where all the liquid crystal molecules M related to the display of a certain pixel are inclined and aligned in a single specific direction.

Here, the liquid crystal display device 101 shown in FIG.
In order to secure a wide viewing angle as shown in FIG.
Even if the liquid crystal layer 12 has a configuration in which c is radially inclined, the liquid crystal layer 12
In the case of a configuration in which linearly polarized light is incident on 1c, there is a liquid crystal molecule group whose in-plane component in the alignment direction is inclined and aligned in a direction coinciding with the direction of linearly polarized light. Here, these liquid crystal molecules cannot give a phase difference to the transmitted light regardless of the normal direction component of the alignment direction, so that the light transmitted through the liquid crystal molecules is emitted in the same manner as in the vertical alignment. Side polarizing plate 122
Absorbed by b.

As a result, centering on the center position of the hole 32,
The transmittance in the region along the direction of the linearly polarized light and in the region along the direction perpendicular to the direction of the linearly polarized light decreases. Further, for example, as shown in FIG. 19, in the edge region of the pixel electrode 31, the alignment of the liquid crystal molecules M is disturbed under the influence of an external electric field or the like, and the disturbance of the alignment differs depending on the location. Would.

On the other hand, in the configuration of the present embodiment, since circularly polarized light is incident on the liquid crystal cell 21, despite the fact that a wide viewing angle is secured by radially inclined alignment,
Liquid crystal molecules M that cannot give a phase difference to transmitted light are:
When viewed from the front, only the liquid crystal molecules M are aligned perpendicular to the substrate surface. When viewed obliquely, only the liquid crystal molecules M are oriented in the same direction as the viewing angle direction. As a result, the number of liquid crystal molecules that cannot contribute is reduced,
If the viewing angle is not the same in both the in-plane component and the normal direction component, a phase difference can be provided. Therefore, as shown in FIG. 8, the region where the shadow is displayed is only the center position of the hole 32 and the intermediate position between the adjacent holes 32, and the shadow region is also located in the edge region of the pixel electrode 31. The area where is displayed can be greatly reduced. Furthermore, the number of liquid crystal molecules M capable of giving a phase difference to transmitted light is increased regardless of whether or not a shadow is visually recognized. As a result, FIG.
As shown in (1), the transmission intensity T1 of the liquid crystal display device 1 according to the present embodiment is higher than the transmission intensity T101 of the conventional liquid crystal display device 101 into which linearly polarized light is incident, and the light use efficiency (effective aperture ratio) and Brightness can be improved. In FIG. 9, the voltage [V] applied to the liquid crystal layer of each of the liquid crystal display devices 1 and 101 is plotted on the horizontal axis, with respect to the theoretical maximum transmittance (50% of the air transmittance) of the liquid crystal display device. The ratio of each transmittance (transmission intensity) is shown.

In the above description, the retardation of the λ / 4 plates 23a and 23b is set so that the incident light becomes circularly polarized light. However, even if the light is not completely circularly polarized, the brightness is significantly reduced. If it is a deviation that does not cause roughness,
Elliptically polarized light of substantially circular polarization may be used. Specifically, for example, in the configuration of FIG. 1, while changing the retardation of the λ / 4 plates 23a and 23b, the wavelength (550n) having the highest visibility is changed.
FIG. 10 shows the transmittance (m) measured (simulated) in FIG. Here, if the change rate of the brightness is within 10%, that is, if the transmittance is 0.9 or more, the decrease in the brightness is hardly recognized by the observer, and the roughness is hardly recognized. Therefore, the λ / 4 plate 23a
The retardation of 23b is optimal if it is 135 nm with respect to light near 550 nm, and if it is in the range of 95 nm or more and within 175 nm, the same effect can be obtained even if it is not perfectly circularly polarized. . In addition, when the value is out of the above range, the brightness is sharply reduced, and roughness caused by the poorly-aligned region is easily observed.

The λ / 4 plates 23a and 23b
If, at the wavelength with the highest visibility, circularly polarized light or elliptically polarized light close to circularly polarized light and linearly polarized light can be converted into each other, that is, if the wavelength satisfies the substantially λ / 4 condition in the above numerical range, Although it is effective for improving brightness and preventing roughness, especially when performing display that emphasizes color tone,
It is preferable that circularly polarized light or elliptically polarized light close to circularly polarized light and linearly polarized light can be mutually converted over the entire visible light band.
However, it is generally difficult to completely eliminate chromatic dispersion in the single-layer λ / 4 plates 23a and 23b. For example, λ /
As the four plates 23a and 23b, the wavelength (5
50 nm), when a λ / 4 plate made to satisfy the λ / 4 condition is used, the wavelength of the light is 550 nm.
Deviates from the λ / 4 condition. As a result, even if the applied voltage is set to a value at which light of 550 nm is blocked in order to realize black display, visible light deviated from 550 nm may pass through the polarizing plate 22b and cause a coloring phenomenon. .

Therefore, when it is required to suppress the coloring phenomenon such as in the case of color display, as shown in FIG. 11, the transmission axis PAa of the polarizing plate 22a and the transmission axis PAb of the polarizing plate 22b are made orthogonal to each other. And λ / 4 plate 23a
Is desirably orthogonal to the slow axis SLa of the λ / 4 plate 23b. The angle between the transmission axis PAa and the slow axis SLa, and the angle between the transmission axis PAb and the slow axis S
The angle with Lb is set to 45 degrees in the same direction as in FIG.

In the liquid crystal display device 1a according to the modification,
Since the slow axis SLa of the λ / 4 plate 23a and the slow axis SLb of the λ / 4 plate 23b are orthogonal to each other, the λ / 4 plate 23a
And 23b cancel each other out of the wavelength dispersion of the refractive index anisotropy. As a result, in the black display state, the transmitted light in a wider wavelength range can be absorbed by the polarizing plate 22b, and a good black display without coloring can be realized.

The λ / 4 plates 23a and 23b may be formed of λ / 4 plates made of different materials from each other. However, at least the same material, preferably a λ / 4 plate manufactured by the same manufacturing method is used.
Using a / 4 plate can realize a liquid crystal display device without coloring at a lower cost than using a broadband λ / 4 plate.

By the way, in the above description, when displaying black,
The case where light is perpendicularly incident on the liquid crystal layer 21c has been described. However, in particular, in the transmission type liquid crystal display device 1, although vertically incident light most contributes to display, the liquid crystal layer 21 c
Light incident from an oblique direction (a direction inclined from the normal direction of the display surface of the liquid crystal display device 1) also contributes to the display. Here, the oblique incident light is given a phase difference even by the liquid crystal layer 21c in the vertical alignment state. Therefore, when the display surface of the liquid crystal display device 1 is viewed obliquely, there is a risk that light leakage occurs and the display contrast ratio is reduced despite the vertical alignment state which should be a black display state. is there.

Therefore, when the improvement of the contrast ratio in the oblique direction is required, as in the liquid crystal display device 1b shown in FIG. 12, the refractive index anisotropy is set so as to cancel the phase difference with respect to the oblique incident light. It is desirable to further provide a viewing angle compensating plate (viewing angle compensating layer) 24 made of a retardation plate obtained. In FIG. 12, as an example, the TFT substrate 21a
Is shown on the outer side (the side farthest from the liquid crystal layer 21c), a viewing angle compensating plate 24 made of a single retardation plate is illustrated, but the present invention is not limited to this. The viewing angle compensating plate 24 may be formed as follows. Further, the position at which the viewing angle compensating plate 24 is provided is not limited to the outside of the TFT substrate 21a, but may be outside the counter substrate 21b, or may be provided outside both substrates 21a and 21b.

In any case, the viewing angle compensating plate 24
Is set so as to cancel the phase difference with respect to the obliquely incident light, the light leakage in the oblique direction can be suppressed, and the contrast ratio can be improved. Thereby, a liquid crystal display device having a good contrast ratio in all viewing angle ranges can be realized.

In the above description, the hole 32
A radial tilt orientation has been realized, but is not limited to this. For example, as in a liquid crystal display device 1c shown in FIG.
Instead of the hole 32, a substantially hemispherical projection 3 is formed on the pixel electrode 31.
Even if 5 is provided, a radially inclined orientation can be realized. Also in this case, the liquid crystal molecules M near the protrusion 35 are aligned perpendicular to the surface of the protrusion 35 and when a voltage is applied, the liquid crystal molecules M
Is inclined in a direction parallel to the surface of the protrusion 35. Accordingly, the liquid crystal molecules M are easily inclined radially around the protrusion 35 in the in-plane direction, as indicated by arrows in the drawing, similarly to the configuration of FIG. 3, and each liquid crystal molecule M of the liquid crystal layer 21c is It can be radially inclined. Each projection 35
Can be formed by applying a photosensitive resin and processing it in a photolithography process.

In the above description, when the voltage is applied, the liquid crystal layer 2
1c is tilted so that each liquid crystal molecule M
Have been described by way of example in which the orientation directions are radially changed continuously, but the present invention is not limited to this. As shown in FIGS. 14 to 16, the liquid crystal layer is divided into a plurality of domains, and the use of a liquid crystal layer having a configuration (multi-domain alignment) in which the alignment directions when applying a voltage are different from each other is also effective.

For example, in the liquid crystal display device 1d shown in FIG. 14, a quadrangular pyramid-shaped projection 35a is formed on the pixel electrode 31 instead of the hemispherical projection 35 shown in FIG. Also in this configuration, in the vicinity of the protrusion 35a, the liquid crystal molecules M are aligned so as to be perpendicular to each slope. In addition, when a voltage is applied, the electric field at the protrusion 35a is inclined in a direction parallel to the slope of the protrusion 35a. As a result, when a voltage is applied, the in-plane component of the orientation angle of the liquid crystal molecules M becomes the in-plane component in the normal direction of the closest slope (direction P1, P2, P3 or P3).
4). Therefore, the pixel region is divided into four domains D1 to D4 having different orientation directions when inclined. As a result, when the liquid crystal display device 1d is viewed from a certain domain side, even if the transmittance of the domain is reduced, the transmittance of the remaining domain is not reduced, and a decrease in the overall transmittance can be suppressed. This makes it difficult for the brightness of the liquid crystal display device 1d to depend on the in-plane azimuth of the viewing angle.

Here, in the four-division multi-domain alignment, the in-plane component in the alignment direction is limited. Therefore, unlike the case of the above-mentioned radially inclined orientation, even when linearly polarized light is incident, the transmitted light is set by setting the angle between the directions P1 to P4 and the direction of the linearly polarized light to be 45 degrees. The number of liquid crystal molecules that cannot give a phase difference can be reduced.

However, even with such a setting,
B12, B23, B34 or B between the domains
In the outer edge region of the pixel electrode 41 or the pixel electrode 31, the alignment state of the liquid crystal molecules M is easily disturbed. There is a possibility that the number of liquid crystal molecules that cannot give a phase difference to light increases.

More specifically, in the boundary region, the liquid crystal molecules M are oriented so as to be supported by the liquid crystal molecules M existing in both domains, so that the orientation of the liquid crystal molecules M is not fixed.
In an unstable state. As a result, if the balance between the alignment regulating forces from the domains on both sides is lost due to a slight trigger, the alignment state of the boundary region changes (inclines).
Here, the balance changes not only due to a slight variation in the alignment regulating force in the manufacturing process, but also due to a lateral electric field due to a voltage applied to the gate signal line or the source signal line, a temporal deterioration, or the like. Therefore, the change of the alignment state is different not only for each part in the boundary region but also for each picture element. As a result, when the linearly polarized light is incident, there is a possibility that the light is visually recognized as a roughness.

In the edge region, the alignment state changes continuously, and the influence of an external electric field such as an electric field from a source signal line or a gate signal line is smaller than that in the central portion of the pixel electrode 31. Easy to receive. Further, when the orientation is controlled by the wall structure, three-dimensional distortion is likely to occur. As described above, since the edge region is easily affected by the surroundings, the alignment regulating force is likely to be non-uniform, and the alignment state of the liquid crystal molecules is likely to change (tilt). This change in orientation state
Not only does it differ from part to part in the boundary area, but also from pixel to pixel. As a result, when linearly polarized light is incident on the liquid crystal layer having the multi-domain configuration, there is a possibility that the disorder of the alignment state may be visually recognized as a roughness.

On the other hand, in the present embodiment, circularly polarized light is incident on the liquid crystal cell of the multi-domain orientation by the λ / 4 plate 23a. As a result, even if the alignment state of the liquid crystal molecules M is disturbed, as in the case of the radially tilted alignment, unless the alignment direction and the viewing angle of the liquid crystal molecules M match not only the in-plane component but also the substrate normal component, the liquid crystal molecule M is not affected. The molecule M can contribute to the display. Thereby, as a result of using the liquid crystal layer of the multi-domain alignment to secure a wide viewing angle, the display is free from roughness, not only in the presence of the edge region of the pixel electrode 31 but also the boundary region of the domain. A high-quality liquid crystal display device can be realized.

In the liquid crystal display device 1d shown in FIG. 14, the projection 35a is provided to realize multi-domain alignment. For example, as shown in the liquid crystal display device 1e shown in FIG.
The pixel electrode 31 is provided with stripe-shaped protrusions 36 whose shape in the normal direction is mountain-shaped and whose in-plane shape is bent substantially at right angles to the zigzag, and the same shape of protrusions on the counter electrode of the counter substrate 21b. 37 may be provided. The distance between the two convex portions 36 and 37 in the in-plane direction is
And the normal of the slope of the convex portion 37 is aligned. The projections 36 and 37 can be formed by applying a photosensitive resin on the pixel electrode 31 and the counter electrode and processing the same in a photolithography process, like the projections 35 and 35a.

In the above-described structure, of the convex portions 36, in the line portions L1 (L2) other than the corner portions C, the regions D1 and D2 near the line portions are formed.
The liquid crystal molecules M of (D3 · D4) are aligned along both slopes of the mountain shape. The two line portions L1 and L2 are orthogonal to each other. As a result, each pixel can be divided into a plurality of domains D1 and D2 (D3 and D4) having different alignment directions.

Even in this configuration, the boundary regions B13 and B24 of the domain exist so as to connect the corners C. Further, domain boundary regions B12 and B34 exist along the line portions L1 and L2. Therefore, when linearly polarized light is incident on the liquid crystal cell, the line portion L1 ·
Even if the direction of L2 is inclined 45 degrees with respect to the linearly polarized light,
The disorder of the orientation direction state in the boundary regions B13, B24, B12, and B34 may be visually recognized as roughness. Note that the boundary areas B13 and B24 connecting the corners C
Is to arrange the corner portion C so as to overlap with a light-shielded region, for example, an auxiliary capacitance wire made of metal formed on the TFT substrate 21a or a light-shielding film provided on the opposite substrate 21b as a color filter substrate. Can be hidden, but the boundary areas B12 and B34 along the line portions L1 and L2.
Cannot be hidden unless an extra light-shielding film is provided.

A method for realizing multi-domain orientation is as follows.
Instead of using the projection, the pixel electrode 31 or the counter electrode may be provided with a slit to perform orientation division. For example, FIG.
6 is disclosed in Japanese Patent Application Laid-Open No. 11-1093.
Similarly to the liquid crystal cell described in JP-A-91, a Y-shaped slit is formed on the counter electrode of the counter substrate 21b in the vertical direction (in the plane, in a direction parallel to any side of the substantially square pixel electrode 31). An alignment control window 38 connected symmetrically is provided.

In this configuration, in the area of the surface of the counter substrate 21b immediately below the alignment control window 38, an electric field enough to incline the liquid crystal molecules M is not applied, and the liquid crystal molecules M are vertically aligned. On the other hand, in the region around the orientation control window 38 on the surface of the counter substrate 21b, an electric field is generated that spreads away from the orientation control window 38 as approaching the counter substrate 21b. As a result, the long axis of the liquid crystal molecules M is tilted in a direction perpendicular to the electric field, and the in-plane component of the alignment direction of the liquid crystal molecules M is substantially perpendicular to each side of the alignment control window 38 as shown by the arrow in the figure. become. Thereby, a plurality of domains D1 to D4 are included in one pixel.
Can be formed. Although not shown in the figure for convenience of explanation, in actuality, a TFT in which the gate electrode is connected to the gate signal line 34, the source electrode is connected to the source signal line 33, and the drain is connected to the pixel electrode 31. An element is provided.

However, even in this case, the alignment direction of the liquid crystal molecules M is likely to be disturbed in the boundary region of each domain (the region immediately below the alignment control window 38), and there is a possibility that the disclination line DL may be visually recognized. is there. As described in the above publication, when the distance between adjacent pixel electrodes 31 is Wp, the distance between the pixel electrode 31 and the counter electrode is d, and the slit width of the alignment control window 38 is Ws, Wp> d / 2; And / or if Ws> d / 2, the appearance of the disclination line DL can be made uniform. However, since the boundary region is still present, it is impossible to completely reduce the alignment abnormality. difficult.

In any case, in a multi-domain liquid crystal cell, a plurality of domains are provided in one pixel in order to enlarge the viewing angle, so that a boundary region is formed in a pixel (in a display region). Exists. Therefore, when linearly polarized light is incident, a disclination line DL is generated in the alignment control window 38 along the direction of the absorption axis (crossed Nicols) of the polarizing plates 22a (22b) due to the disorder of the alignment state in the boundary region. Since the state of the disclination line DL differs for each location and each pixel, there is a possibility that the roughness may be visually recognized.

On the other hand, in the present embodiment, circularly polarized light is incident on the liquid crystal cell of multi-domain alignment. Thereby, as a result of using a multi-domain oriented liquid crystal cell to secure a wide viewing angle, not only the edge region of the pixel electrode 31 but also the domain boundary region exist,
In the orientation control window 38, the disclination line is hardly observed. Therefore, it is possible to realize the liquid crystal display device 1 with no roughness and high display quality.

In the present embodiment, as an example of the liquid crystal cell, the liquid crystal cell has a negative dielectric anisotropy, is initially aligned perpendicular to the substrate surface, and when a voltage is applied, the liquid crystal in the pixel is turned on. Although the description has been made by taking as an example the case where the liquid crystal layer in which the molecule M is inclined in a plurality of directions is used, a liquid crystal having a positive dielectric anisotropy and being horizontally aligned with the substrate surface and in a plurality of directions at the time of initial alignment. Layers may be used.

In any case, when a certain voltage is applied, a liquid crystal layer whose orientation is controlled such that the in-plane components of the orientation of each liquid crystal molecule M are different from each other in one pixel is used. With the conventional liquid crystal display device, substantially the same effects as in the present embodiment can be obtained.

Further, even in a liquid crystal layer in which the alignment direction of the liquid crystal molecules M is controlled so that the alignment direction of the liquid crystal molecules M in the pixel is a single direction, for example, the source signal The orientation direction may be disturbed by an oblique electric field from a bus line such as a line or a gate signal line. Therefore, a certain effect can be obtained in a liquid crystal display device using a liquid crystal layer in which the in-plane components in the alignment direction of each liquid crystal molecule M are different from each other in one pixel in a state where a certain voltage is applied.

However, the alignment direction is controlled so that the in-plane components of the alignment direction of each liquid crystal molecule M are different from each other within one pixel in a state where a certain voltage is applied, such as multi-domain alignment or radial tilt alignment. In the case of a liquid crystal layer, the alignment state is more likely to be disturbed and the display quality is more likely to be lower than in a liquid crystal layer in which the alignment direction is controlled to be a single direction. Therefore, when the circularly polarized light is incident on the liquid crystal layer, the display quality can be further improved.

Further, the liquid crystal cell of the vertical alignment system is TN
Compared to a (Twisted Nematic) type liquid crystal cell, the display contrast is higher and the black-and-white level response speed is faster. Furthermore, the in-plane azimuth dependence of the viewing angle can be suppressed by combining the radial tilt alignment or the multi-domain alignment. Therefore, liquid crystal that satisfies all of contrast, response speed, viewing angle, in-plane azimuth dependence of viewing angle, and display quality by injecting circularly polarized light into a multi-domain or radially tilted liquid crystal cell in a vertical alignment method. A display device can be realized. In particular, in the case of the radially inclined orientation, roughness is more easily recognized when combined with linearly polarized light than in the case of multi-domain orientation, but the orientation in the plane is less dependent. Therefore, as in the present embodiment, a liquid crystal display device with little in-plane azimuth dependence can be realized without impairing display quality by injecting circularly polarized light and suppressing roughness.

[Second Embodiment] In the first embodiment, a polarizing plate 22a is provided between the backlight 3 and the liquid crystal cell 21 as a circularly polarizing means for entering the circularly polarized light into the liquid crystal cell 21. And the case where the λ / 4 plate 23a is provided has been described. However, the polarizing plate 22a has a transmission axis P
In order to absorb vibration components other than Aa, the amount of light emitted from the polarizing plate 22a is limited to about 40% to 60% of the amount of incident light.

On the other hand, in the liquid crystal display device 1g according to the present embodiment, as shown in FIG.
A selective reflection layer 25 is provided as a circularly polarized light means instead of 23a. The selective reflection layer 25 transmits circularly polarized light that rotates in a certain direction among the incident light,
Circular polarized light turning in the opposite direction is characterized by being reflected, and can be formed of, for example, a cholesteric liquid crystal film or the like.
The cholesteric liquid crystal film has a helical structure.For example, in the case of a cholesteric liquid crystal film having a left-handed helical structure, incident light is separated into left circularly polarized light and right circularly polarized light while passing through the helical structure. At the same time, left circularly polarized light is reflected and right circularly polarized light is transmitted. Conversely, in a cholesteric liquid crystal having a right-handed helical structure, right circularly polarized light is reflected and left circularly polarized light is transmitted. As a result, it is possible to extract the required circularly polarized light in the turning direction. Further, by using a film having a different helical pitch in the thickness direction, selective reflection can be performed in a wide band. The cholesteric liquid crystal film can be produced, for example, by irradiating a bifunctional cholesteric monomer and a monofunctional nematic monomer with ultraviolet rays and utilizing a speed difference of photocrosslinking. The selective reflection layer 25 is desired to have selective reflectivity over a wide wavelength range. However, if it is difficult, the selective reflection layer 25 should be adjusted to the emission spectrum of the backlight 3 so that the light from the backlight 3 can be selectively reflected. Then, a wavelength that can be selectively reflected may be set. For example,
When a three-wavelength tube is used for the backlight 3,
The selective reflection layer 25 only needs to have selective reflectivity at the three wavelengths.

In the liquid crystal display device 1g having the above configuration, the light emitted from the backlight 3 is transmitted through the selective reflection layer 25 to become a circularly polarized light in a desired rotation direction, and becomes a liquid crystal cell 21g.
Incident on On the other hand, the circularly polarized light turning in the opposite direction is reflected by the selective reflection layer 25 and returned to the backlight 3. Here, a part of the circularly polarized light returned to the backlight 3 has its polarization state broken inside the backlight 3 and is emitted from the backlight 3 to the selective reflection layer 25 again. Therefore,
In the liquid crystal display device 1g according to the present embodiment, a part of the light from the backlight 3 absorbed by the polarizing plate 22a of the liquid crystal display device 1 in FIG. 1 can be reused. As a result, the light use efficiency of the backlight 3 can be improved, and a brighter liquid crystal display device can be realized.

[0083]

As described above, the liquid crystal display device according to the present invention has a liquid crystal layer in which the alignment directions of the liquid crystal molecules are controlled to be different from each other in the pixel, and a detector disposed on the emission side of the liquid crystal layer. Photons, circular polarization means for setting incident light to the liquid crystal layer to a substantially circular polarization state, provided between the liquid crystal layer and the analyzer, and retardation in the in-plane direction is substantially equal to the wavelength of the transmitted light. And a first retardation layer set to a quarter wavelength.

As described above, another liquid crystal display device according to the present invention has a configuration in which a liquid crystal layer exhibiting a radially inclined alignment in which the alignment direction of liquid crystal molecules changes continuously is provided instead of the liquid crystal layer. It is.

[0085] Still another liquid crystal display device according to the present invention comprises:
As described above, a configuration in which a liquid crystal layer of multi-domain orientation is provided instead of the liquid crystal layer.

In the liquid crystal display device of each of the above structures, since substantially circularly polarized light is incident on the liquid crystal layer, there is no anisotropy in the alignment direction of the liquid crystal layer, and the alignment direction of the liquid crystal molecules and the transmitted light become in-plane. Liquid crystal molecules can impart a phase difference to transmitted light as long as they do not match in both the component and the substrate normal direction. Therefore, in order to secure a wide viewing angle, the alignment directions of the liquid crystal molecules are controlled to be different from each other in the pixel. As long as they do not match, the brightness can be improved. As a result, there is an effect that high light use efficiency can be secured while maintaining a wide viewing angle, and an improvement in contrast ratio and an increase in the number of gradations can be realized.

As described above, in the liquid crystal display device according to the present invention, in addition to the above-mentioned configuration, the above-mentioned circularly polarizing means is 550 nm.
Is set to a substantially circular polarization state, and the first
The retardation layer has an in-plane retardation of 550n.
This is a configuration that is set to approximately 1/4 of m.

In this configuration, human luminosity factor 5 is the highest.
For a wavelength of 50 nm, substantially circularly polarized light is incident, and it is possible to prevent a decrease in brightness and generation of roughness for light of the wavelength. As a result, there is an effect that it is possible to realize a liquid crystal display device in which a decrease in brightness and roughness are less likely to be visually recognized as compared with a case where substantially circularly polarized light is incident only at other wavelengths.

As described above, in the liquid crystal display device according to the present invention, in addition to the above-described configuration, the in-plane retardation of the first retardation layer is set to be 95 nm or more and 175 nm or less. is there.

In the above configuration, the retardation is set to 95 nm or more and 175 nm or less with respect to light having a wavelength of 550 nm.
The overall decrease in brightness and the decrease in brightness in the region of misalignment are suppressed to about 10%. As a result, as compared with the case where the range is set to another range, there is an effect that a liquid crystal display device in which a decrease in brightness and roughness are less visible can be realized.

As described above, in the liquid crystal display device according to the present invention, in addition to the above configuration, the circularly polarizing means is provided on the incident side of the liquid crystal layer, and transmits circularly polarized light in a predetermined rotation direction while transmitting the circularly polarized light. , A selective reflection layer that reflects circularly polarized light turning in the opposite direction.

In this configuration, the circularly polarized light turning in the direction opposite to the predetermined direction is reflected by the selective reflection layer.
Unlike the case where it is absorbed by the polarizer, it can be reused. As a result, there is an effect that the light use efficiency can be improved although substantially circularly polarized light can be incident on the liquid crystal layer.

As described above, the liquid crystal display device according to the present invention, instead of the selective reflection layer, is arranged between the polarizer provided on the incident side of the liquid crystal layer and the polarizer and the liquid crystal layer, In this configuration, the retardation in the in-plane direction is provided with a second retardation layer whose wavelength is set to approximately one quarter of the wavelength of the transmitted light.

Also in this configuration, since the linearly polarized light emitted from the polarizer is converted into substantially circularly polarized light by the second retardation layer, substantially circularly polarized light can be incident on the liquid crystal layer. As a result, there is an effect that high light use efficiency can be secured while maintaining a wide viewing angle, and an improvement in contrast ratio and an increase in the number of gradations can be realized.

As described above, in the liquid crystal display device according to the present invention, in the above configuration, the analyzer is disposed on one of the liquid crystal layers, and the polarizer is disposed on the other. The transmission axis of the photon and the slow axis of the first retardation layer are 4
Make an angle of 5 degrees, and the transmission axis of the polarizer and the second
In this configuration, the slow axis of the retardation layer forms an angle of 45 degrees.

In this configuration, the transmission axis of the analyzer and the first
Since the slow axis of the retardation layer forms an angle of 45 degrees with the slow axis of the polarizer and the slow axis of the second retardation layer forms an angle of 45 degrees, the linear axis is efficiently and linearly formed. There is an effect that the polarized light and the circularly polarized light can be mutually converted.

As described above, in the liquid crystal display device according to the present invention, in the above configuration, the analyzer is disposed on one of the liquid crystal layers, the polarizer is disposed on the other, and The first and second retardation layers are arranged such that their slow axes are orthogonal to each other, and the analyzer and the polarizer are arranged so that their transmission axes are orthogonal to each other.

In this configuration, the slow axes of the first and second retardation layers are arranged so as to be orthogonal to each other. Therefore, the wavelength dispersion of the refractive index anisotropy of both retardation layers is offset by each other. As a result, in the black display state, the transmitted light in a wider wavelength range is absorbed by the analyzer. As a result, there is an effect that a better black display can be realized.

As described above, the liquid crystal display device according to the present invention is provided between the analyzer and the polarizer in addition to the components described above. In this configuration, a viewing angle compensation layer having a refractive index anisotropy is set so as to cancel a phase difference that fluctuates according to an inclination angle from a normal direction of one substrate to a viewing angle.

In this configuration, depending on the inclination of the viewing angle,
The phase difference provided by the liquid crystal layer is canceled by the viewing angle compensation layer.
Therefore, there is an effect that the dependency of the viewing angle can be suppressed and a liquid crystal display device having a good contrast ratio in a wider viewing angle range can be realized.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a schematic diagram illustrating a main configuration of a liquid crystal display device when no voltage is applied.

FIG. 2 is a schematic diagram illustrating a configuration of a main part of the liquid crystal display device when a voltage is applied.

FIG. 3 is a perspective view showing a configuration example of a liquid crystal cell of the liquid crystal display device and showing a pixel electrode.

FIG. 4 is a cross-sectional view taken along line α-α of the vicinity of a pixel electrode of the liquid crystal cell.

FIG. 5 shows another configuration example of the liquid crystal cell.
FIG. 3 is a plan view showing a pixel electrode.

FIG. 6 illustrates the liquid crystal display device, and is an explanatory diagram showing a relationship between an alignment state of liquid crystal molecules when no voltage is applied, a slow axis of a λ / 4 plate, and a transmission axis of a polarizing plate. .

FIG. 7 illustrates the liquid crystal display device, and is an explanatory diagram illustrating a relationship between an alignment state of liquid crystal molecules when a voltage is applied, a slow axis of a λ / 4 plate, and a transmission axis of a polarizing plate.

FIG. 8 is an explanatory diagram showing a display example of the liquid crystal display device.

FIG. 9 is a graph showing the transmission intensity of the liquid crystal display device and the transmission intensity of a conventional liquid crystal display device.

FIG. 10 is a graph showing a relationship between retardation of a λ / 4 plate and transmittance.

FIG. 11 shows a modification of the liquid crystal display device, and is an explanatory diagram showing a relationship between a slow axis of a λ / 4 plate and a transmission axis of a polarizing plate.

FIG. 12 shows a modification of the liquid crystal display device, and is a schematic diagram showing a configuration of a main part of the liquid crystal display device.

FIG. 13 is a perspective view showing still another configuration example of the liquid crystal cell, and showing a pixel electrode.

FIG. 14 is a perspective view showing another configuration example of the liquid crystal cell and showing a pixel electrode.

FIG. 15 is a plan view showing another configuration example of the liquid crystal cell and showing the vicinity of a pixel electrode.

FIG. 16 is a plan view showing yet another configuration example of the liquid crystal cell and showing the vicinity of a pixel electrode.

FIG. 17 illustrates another embodiment of the present invention, and is a schematic diagram illustrating a configuration of a main part of a liquid crystal display device.

FIG. 18 illustrates a conventional example, and is a schematic diagram illustrating a configuration of a main part of a liquid crystal display device.

FIG. 19 is an explanatory diagram showing a display example of the liquid crystal display device.

[Explanation of symbols]

1.1a to 1g Liquid crystal display device 21a TFT substrate (first substrate) 21b Counter substrate (second substrate) 31 Pixel electrode 21c Liquid crystal layer 22a Polarizer (polarizer; circular polarizer) 22b Polarizer (analyzer) 23a λ / 4 plate (second retardation layer; circular polarizing means) 23b λ / 4 plate (first retardation layer) 24 viewing angle compensator (viewing angle compensating layer) 25 selective reflection layer (circular polarizing means)

Continued on the front page F term (reference) 2H049 BA02 BA05 BA06 BA07 BA42 BB03 BC22 2H090 HA11 HC05 HC12 KA04 LA06 LA08 LA09 MA01 MA13 2H091 FA08X FA08Z FA11X FA11Z FA12Z GA06 HA06 KA02 LA16 LA20 5G435 AA02 AA03 BB12H BB15 CC

Claims (10)

[Claims] A first electrode provided with a pixel electrode corresponding to the pixel;
A substrate, a second substrate provided with a counter electrode, provided between the two substrates, and when the voltage between the pixel electrode and the counter electrode is at least a predetermined value, the alignment direction of the liquid crystal molecules is changed. A liquid crystal layer that is controlled to be different from each other in the pixel; an analyzer disposed on an emission side of the liquid crystal layer; a circular polarization unit that sets light incident on the liquid crystal layer to a substantially circular polarization state; A liquid crystal comprising: a first retardation layer provided between the layer and the analyzer, wherein the retardation in the in-plane direction is set to approximately one quarter of the wavelength of the transmitted light. Display device. A first electrode provided with a pixel electrode corresponding to the pixel;
A substrate, a second substrate provided with a counter electrode, provided between the two substrates, and when the voltage between the pixel electrode and the counter electrode is at least a predetermined value, the alignment direction of the liquid crystal molecules is changed. A liquid crystal layer exhibiting a continuously changing radially tilted orientation, an analyzer arranged on an emission side of the liquid crystal layer, a circular polarization means for setting light incident on the liquid crystal layer to a substantially circular polarization state, and the liquid crystal A liquid crystal comprising: a first retardation layer provided between the layer and the analyzer, wherein the retardation in the in-plane direction is set to approximately one quarter of the wavelength of the transmitted light. Display device. A first electrode provided with a pixel electrode corresponding to the pixel;
A substrate, a second substrate provided with a counter electrode, provided between the two substrates, and when the voltage between the pixel electrode and the counter electrode is at least a predetermined value, the alignment direction of the liquid crystal molecules is changed. A liquid crystal layer that performs multi-domain alignment, an analyzer disposed on the emission side of the liquid crystal layer, a circular polarization unit that sets incident light to the liquid crystal layer to a substantially circular polarization state, and the liquid crystal layer and the analyzer. A liquid crystal display device comprising: a first retardation layer provided between the first retardation layer and the retardation in the in-plane direction being set to approximately one quarter wavelength of the wavelength of transmitted light. 4. The circularly polarizing means sets light having a wavelength of 550 nm in a substantially circularly polarized state, and the first retardation layer has an in-plane retardation.
4. The liquid crystal display device according to claim 1, wherein the wavelength is set to approximately one quarter of 550 nm. 5. The method according to claim 1, wherein the retardation is 95 nm or more.
The liquid crystal display device according to claim 4, wherein the thickness is set to 175 nm or less. 6. The circularly polarizing means is a selective reflection layer provided on the incident side of the liquid crystal layer and transmitting circularly polarized light having a predetermined rotating direction and reflecting circularly polarized light rotating in the opposite direction. The liquid crystal display device according to claim 1, 2, 3, 4, or 5. 7. The circularly polarizing means is disposed between the polarizer provided on the incident side of the liquid crystal layer and the polarizer and the liquid crystal layer, and the retardation in the in-plane direction is determined by the wavelength of the transmitted light. 6. The liquid crystal display device according to claim 1, further comprising a second retardation layer set to substantially a quarter wavelength. 8. The analyzer according to claim 1, wherein the analyzer is disposed on one of the liquid crystal layers, the polarizer is disposed on the other, and a transmission axis of the analyzer and a slow axis of the first retardation layer are aligned. The analyzer, the polarizer, and the first and second phase difference are formed at an angle of 45 degrees so that the transmission axis of the polarizer and the slow axis of the second phase difference layer form an angle of 45 degrees. The liquid crystal display device according to claim 7, wherein a layer is provided. 9. The analyzer according to claim 1, wherein the analyzer is disposed on one of the liquid crystal layers, the polarizer is disposed on the other, and the first and second retardation layers have respective slow axes which are opposite to each other. The analyzer and the polarizer are arranged so as to be orthogonal to each other, and the analyzer and the polarizer are arranged so that their transmission axes are orthogonal to each other.
The liquid crystal display device according to the above. 10. A phase difference provided between the analyzer and the polarizer, wherein the phase difference fluctuates according to an inclination angle from a normal direction of the first substrate to a viewing angle among phase differences provided by the liquid crystal layer. And a viewing angle compensation layer having a refractive index anisotropy set so as to cancel out.
The liquid crystal display device according to 3, 4, 5, 6, 7, 8, or 9.