JP2000081618A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a visual angle characteristic without sacrificing production efficiency and transmittance by impressing an approximately perpendicular electric field to a liquid crystal layer arranged between a pair of polarizing plates arranged in a orthogonal Nicols state. SOLUTION: Display of a normally black mode is executed by impressing the approximately perpendicular electric field to the liquid crystal layer 101 consisting of a nematic liquid crystal material which is arranged between a pair of the polarizing plates 108, 109 arranged in the orthogonal Nicols state and has positive dielectric anisotropy. The liquid crystal layer 101 has at least first and second domains 101a, 102b varying in the alignment of liquid crystal molecules from each other with each of display picture element regions and, therefore, the change in the display quality by the visual angle direction may be suppressed. In addition, the refractive index anisotropy of the liquid crystal molecules when the display device is observed from a front direction may be effectively compensated by using a pair of phase difference plates 102, 103 which have positive negative anisotropy and are arranged on both sides of the liquid crystal layer 101 as a phase compesation element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor display for a computer and a liquid crystal display device for displaying video images and the like, and more particularly to a liquid crystal display device having excellent viewing angle characteristics.

[0002]

2. Description of the Related Art In order to increase the viewing angle of a liquid crystal display device,
Various display modes have been proposed. As a typical example, IPS (In-P1aneSwitch) that moves liquid crystal molecules in parallel to the substrate surface by using a lateral electric field is used.
ng) mode, a liquid crystal display device in which liquid crystal molecules are oriented substantially perpendicular to the substrate surface when no voltage is applied and the tilt direction of the liquid crystal is divided when a voltage is applied (Japanese Patent Laid-Open No. 7-28068).
Japanese Patent Application Laid-Open No. HEI 10-108, in which liquid crystal molecules are aligned substantially horizontally on the substrate surface when no voltage is applied, and regions where the rising directions of the liquid crystal molecules are different when voltage is applied are formed. No. 3081) and a liquid crystal display device (JP-A-5-289097) that enlarges the viewing angle by using an optical compensation element in a normally black mode in which black display is performed when no voltage is applied.

[0003]

In the IPS mode,
Since it is necessary to provide a plurality of non-transparent electrodes in a display picture element, the number of openings is reduced and the transmittance (display luminance) of the display device is reduced.
There was a problem that it became low. JP-A-7-2806
No. 8 discloses a liquid crystal display device having a negative dielectric anisotropy (n-type liquid crystal) and a substrate which has been subjected to a vertical alignment process. There is a problem that the time required for injecting the liquid crystal material is more than twice as long as the case where the substrate (p-type liquid crystal) and the substrate subjected to the horizontal alignment treatment are used, and the manufacturing efficiency is reduced. JP-A-10-308
In the liquid crystal display device disclosed in Japanese Patent Laid-Open Publication No. 1 (1993) -1994, liquid crystal molecules are driven by transparent electrodes disposed above and below the substrate, so that the transmittance, which is a problem in the IPS mode, does not decrease, and the dielectric anisotropy is positive. Since the liquid crystal material and the substrate subjected to the horizontal alignment treatment are used, there is no problem that the manufacturing efficiency is reduced, which is a problem in JP-A-7-28068, but the viewing angle characteristics are reduced.
There is a problem that it is inferior to the liquid crystal display device disclosed in Japanese Patent No. 8068. The liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 10-3081 has a problem that the gradation characteristics in the vertical direction of the display surface are asymmetric.

As shown in FIG. 48, a liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 5-289097 has a driving liquid crystal panel 4 and a birefringence for optically compensating for birefringence anisotropy in the plane direction. An anisotropic compensation panel 3 is optically continuously laminated, and the viewing angle dependent compensation panel 2
And a pair of polarizers 1 and 5 are connected to the panel 2,
Sandwiching 3, 4 and their absorption axes (1.1, 5.1)
Are arranged so as to be orthogonal to each other. The birefringence anisotropy compensating panel 3 has its optical axis (3.1 or 3.2) (rubbing direction) parallel to the substrate surface of the driving liquid crystal panel 4,
And the optical axis (4.1 or 4.2) of the driving liquid crystal panel 4.
(Rubbing direction). The viewing angle dependent compensation panel 2 is arranged so that its optical axis (2.1) (rubbing direction) is perpendicular to the substrate surface of the driving liquid crystal panel 4. I have. In the above-mentioned prior art, although the viewing angle dependent compensating panel 2 is superimposed, the effect of improving the viewing angle to some extent can be obtained, but the contrast is reduced when the viewing angle is lowered, and sufficient viewing angle characteristics are obtained. Did not. In addition, in the driving liquid crystal panel disclosed in the related art, it is difficult to stably obtain uniform alignment and transmittance in a display surface when a voltage is applied.

The present invention has been made to solve the above-mentioned problems of the prior art, and has as its object to provide a liquid crystal display device having excellent viewing angle characteristics without sacrificing manufacturing efficiency and transmittance. And

[0006]

According to the liquid crystal display device of the present invention, at least one of the first and second substrates is sandwiched between the first and second substrates, and has a positive dielectric anisotropy. A liquid crystal layer made of a nematic liquid crystal material having: and first and second electrodes provided on the first and second substrates, respectively, for applying an electric field substantially perpendicular to the first and second substrates to the liquid crystal layer;
The liquid crystal layer includes first and second polarizers provided outside each of the first and second substrates and arranged in a crossed Nicols state, and a phase difference compensating element. To
The phase difference compensating element has at least first and second domains in which alignment of liquid crystal molecules is different from each other, and the liquid crystal is aligned substantially parallel to the surfaces of the first and second substrates when no voltage is applied. Compensate for the refractive index anisotropy of the molecule, thereby achieving the above objective.

[0007] Both the first and second substrates are transparent substrates, and the phase difference compensating element comprises a first phase difference compensating element provided between the first substrate and the first polarizing plate; The second
It may be configured to have a second phase difference compensating element provided between the substrate and the second polarizing plate.

The first and second phase difference compensating elements have a positive refractive index anisotropy, the slow axes of the first and second phase difference compensating elements are substantially parallel to each other, and no voltage is applied. The liquid crystal layer may be configured so as to be substantially perpendicular to the slow axis of the liquid crystal layer in the added state.

A third phase difference compensating element is further provided between the first phase difference compensating element and the first polarizing plate, and the third phase difference compensating element has a positive refractive index anisotropy. The slow axis of the third phase difference compensating element may be substantially orthogonal to the first and second substrates.

A fourth phase difference compensating element is further provided between the second phase difference compensating element and the second polarizing plate, and the fourth phase difference compensating element has a positive refractive index anisotropy. The slow axis of the fourth phase difference compensating element may be substantially orthogonal to the first and second substrates.

A fifth phase difference compensating element provided between the first phase difference compensating element and the third phase difference compensating element, and a second phase difference compensating element and a fourth phase difference compensating element. A sixth phase difference compensating element provided between the first and second phase difference compensating elements, wherein the fifth and sixth phase difference compensating elements have a positive refractive index anisotropy; The axis may be substantially orthogonal to the polarization axis of the first polarizing plate, and the slow axis of the sixth phase difference compensating element may be substantially orthogonal to the polarization axis of the second polarizing plate.

[0012] The direction in which the directors of the liquid crystal molecules rise when no voltage is applied, which is located in the middle of the thickness direction of the liquid crystal layer in the first and second domains, is 1
The configuration may be such that the direction is different by 80 ° and the direction of the director is approximately 45 ° with respect to the polarization axes of the first and second polarizers.

[0013] The liquid crystal molecules in the first domain and the second domain may be aligned in parallel.

[0014] The liquid crystal molecules in the first domain and the second domain may be twist-aligned.

The pretilt angles of the liquid crystal molecules on the first substrate and the second substrate in the first and second domains may be different from each other.

The liquid crystal layer is provided for each of the display picture element regions.
It is good also as composition which has a plurality of the 1st domains and a plurality of the 2nd domains, and the number of the 1st domain and the 2nd domain is the same number. It is preferable that the sum of the areas of the first and second domains is equal to each other.

The operation will be described below.

In the liquid crystal display device of the present invention, a substantially vertical electric field is applied to a liquid crystal layer made of a nematic liquid crystal material having a positive dielectric anisotropy and disposed between a pair of polarizing plates disposed in a crossed Nicols state. Thus, a display in a normally black mode (black display when no voltage is applied) is performed. Since the liquid crystal layer has at least first and second domains in which the orientation of liquid crystal molecules is different from each other for each display picture element region,
A change in display quality depending on the viewing angle direction can be suppressed. The phase difference compensation element compensates for the refractive index anisotropy of liquid crystal molecules that are oriented almost parallel to the surface of the substrate in all observation directions including the front in the absence of a voltage, and displays black with little viewing angle dependence. To achieve. Further, as the phase difference compensating element, a pair of phase difference plates having a positive refractive index anisotropy and arranged on both sides of the liquid crystal layer are used, and their slow axes are parallel to the substrate surface and the liquid crystal layer has When arranged so as to be orthogonal to the slow axis, the refractive index anisotropy of the liquid crystal molecules when observed from the front can be effectively compensated.

Further, a retardation plate having a positive refractive index anisotropy is arranged so that its slow axis is substantially perpendicular to the substrate, so that the slow axis is aligned with the liquid crystal layer in the plane of the substrate. It is possible to compensate for a change in retardation when the observation direction (viewing angle direction) with the phase difference compensating element is tilted.

Further, a retardation plate having a positive refractive index anisotropy is arranged such that its slow axis is orthogonal to the polarizing axis of the polarizing plate (becomes 45 ° with the slow axis of the liquid crystal layer). Thereby, the rotation of the elliptically polarized light can be compensated. As a result, good black display is obtained in all observation directions including the front.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. First, referring to FIG.
The operation principle of the liquid crystal display device of the present invention will be described.

FIG. 1 shows a liquid crystal display device 100 according to the present invention.
It is the figure which represented typically. FIG. 1 illustrates a transmissive liquid crystal display device.

The liquid crystal display device 100 includes a liquid crystal layer 101,
A pair of electrodes 100a and 100b for applying a voltage to the liquid crystal layer 101, and a pair of retardation plates disposed on both sides of the liquid crystal layer 101 (of course, having a suitable refractive index anisotropy such as a retardation compensation film and a liquid crystal cell). Anything can be used.)
102 and 103, and further, retardation plates 102 and 10
3 and retarders 104 and 1 provided outside each of
05 and the phase difference plates 110 and 111, and a pair of polarizing plates 10 sandwiching these components and arranged in a crossed Nicols state.
8 and 109. Note that the phase difference plates 104 and 105 and the phase difference plates 110 and 111 may be omitted, or one or an arbitrary combination of them may be provided. The ellipses in FIG. 1 schematically represent liquid crystal molecules, and the arrows are axes having the maximum refractive index (that is, slow axes) of the refractive index ellipsoids (all having positive uniaxial characteristics) of each retardation plate. The arrows in the polarizing plates 108 and 109 indicate the polarizing axes (transmission axes) of the polarizing plates.

The liquid crystal layer 101 shown in FIG. 1 shows the orientation of the liquid crystal molecules in one display picture element region when no voltage is applied. As a liquid crystal material, a nematic liquid crystal material having a positive dielectric anisotropy (abbreviated as Np liquid crystal material) is used. The liquid crystal molecules are
They are oriented substantially parallel to the surfaces of a pair of substrates (not shown).
The liquid crystal layer 10 of a pair of substrates is sandwiched so as to sandwich the liquid crystal layer 101.
By applying a voltage to the electrodes 100a and 100b formed on one side, an electric field in a direction substantially perpendicular to the surface of the substrate is applied to the liquid crystal layer.

As shown in FIG. 1, the liquid crystal layer 101 has first alignment states different from each other in each display picture element region.
It has a domain 101a and a second domain 101b. In the example of FIG. 1, the directors of the liquid crystal molecules in the first domain 101a and the directors of the liquid crystal molecules in the second domain 101b are oriented in azimuth directions different from each other by 180 °. When a voltage is applied between the electrodes 100a and 100b, the liquid crystal molecules in the first domain 101a rise clockwise,
The orientation of the liquid crystal molecules in the second domain 101b is controlled so as to rise in the counterclockwise direction, that is, in the directions opposite to each other. Such director alignment of liquid crystal molecules can be realized using a known alignment control technique using an alignment film. By forming a plurality of first domains and second domains in which the director orientations differ by 180 ° in one display pixel region, the viewing angle characteristics can be made more uniform.

As described above, the brightness change of the image obtained by observing the halftone display image of the liquid crystal display device 100 having the display pixels divided in the orientation direction from the normal direction of the display surface to the first domain 101a side. And the luminance change of the image observed while tilted toward the second domain 101b is symmetric. Preferably, the area of the first domain 101a and the second domain 10
It is preferable that the area of 1b is substantially the same. It is not always necessary to make the area of each domain the same for each display picture element region, and the first domain 101a
And the sum of the areas of the second domains 101b may be equal to each other. The configuration of the orientation division is not limited to the above example.

As shown in FIG. 1, the first domain 101
a of the liquid crystal molecules in a and the second domain 101b
The azimuthal directions of the liquid crystal molecules are aligned in directions different from each other by 180 °.
It is parallel to the direction represented by the arrow 609 in the middle. Therefore,
Regarding the refractive index of the liquid crystal molecules with respect to the light perpendicularly incident on the display surface, the refractive index for the polarized light having the polarization direction in the direction 609 is the largest, and the refractive index for the direction 608 orthogonal to the direction 609 is the smallest. In the present specification, the direction 609
Is the slow axis direction of the liquid crystal layer in the state where no voltage is applied.
More generally, the direction of the slow axis of the liquid crystal layer in the state where no voltage is applied is defined as the azimuthal direction in which the liquid crystal molecules near the center in the thickness direction of the liquid crystal layer rise by voltage. This definition can be applied not only to a liquid crystal layer in which liquid crystal molecules are aligned parallel to the substrate surface (including antiparallel), but also to a liquid crystal layer in which liquid crystal molecules are twisted.

Each of the retardation plates 102 and 103 typically has a positive uniaxial refractive index anisotropy, and its slow axis (in the direction of the arrow in FIG. 1) indicates the direction of the liquid crystal when no voltage is applied. Layer 101
Are arranged so as to be orthogonal to the slow axis. Therefore, light leakage due to the refractive index anisotropy of the liquid crystal molecules in a state where no voltage is applied is suppressed, and as a result, a black display (normally black characteristic) is obtained.

Each of the retardation plates 104 and 105 typically has a positive uniaxial refractive index anisotropy, and its slow axis (in the direction of the arrow in FIG. 1) is perpendicular to the substrate surface. (That is, perpendicular to the slow axes of the liquid crystal layer 101 and the retardation plates 102 and 103), and compensates for a change in transmittance due to a change in viewing angle. In particular, at the time of black display, light leakage (floating black) due to a change in viewing angle is suppressed. Therefore, the phase difference plate 1
By providing the elements 04 and 105, a display with further excellent viewing angle characteristics can be provided. However, the phase compensators 104 and 105 may be omitted, or only one of them may be used.

Each of the retardation plates 110 and 111 typically has a positive uniaxial refractive index anisotropy, and its slow axis (in the direction of the arrow in FIG. 1) coincides with the polarization axis of the polarizing plate. The liquid crystal layer 101, the phase difference plates 102 and 103
At 45 ° with the slow axis of the elliptically polarized light, and compensates for the rotation of the polarization axis of the elliptically polarized light. Therefore, the phase difference plate 11
By providing 10 and 111, a display with further excellent viewing angle characteristics can be provided. However, the phase compensators 110 and 111 may be omitted, or only one of them may be used.

The retardation plate need not necessarily have uniaxial refractive index anisotropy, but may have positive biaxial refractive index anisotropy. An example in which a retardation plate having positive biaxial refractive index anisotropy is used will be described in a later embodiment.

Hereinafter, the components of the present invention will be described in more detail.

(Nematic Liquid Crystal Material Having Positive Dielectric Anisotropy: Np Liquid Crystal Material) In the present invention, as in the case of a TN mode liquid crystal display device which is widely used at present, a substrate subjected to a horizontal alignment treatment and an Np liquid crystal material are used. Is used. Therefore, the time required for injecting the liquid crystal material can be reduced to about に or less as compared with the case where the substrate subjected to the vertical alignment treatment and the Nn liquid crystal material are used as in the liquid crystal display device of JP-A-7-28068.
Generally, the Np liquid crystal material has a lower viscosity than the Nn liquid crystal material, and the horizontal alignment processing substrate surface has higher wettability to the liquid crystal material than the vertical alignment processing substrate surface. The factors have a synergistic effect, and as a result, the liquid crystal material can be injected at a high speed. Injection time of liquid crystal material accounts for a large percentage of the time required for each process of manufacturing a liquid crystal display device, and greatly reducing the time leads to a significant improvement in manufacturing efficiency of the liquid crystal display device. .

(Vertical Electric Field) In the present invention, an electric field perpendicular to the liquid crystal layer (perpendicular to the substrate) is generated by a pair of electrodes (at least one of which is necessarily a transparent electrode) arranged so as to sandwich the liquid crystal layer. Is applied to drive the liquid crystal molecules. That is, since the same aperture ratio as that of the conventional TN mode liquid crystal display device can be obtained, it is not necessary to form an opaque electrode in the display picture element region unlike the IPS mode. A liquid crystal display having a high pixel aperture ratio is obtained.

(Orientation Division) At present, T is widely used.
In a liquid crystal display device that changes the transmittance by moving liquid crystal molecules in the thickness direction of the liquid crystal layer, including the N mode,
There is a problem that viewing angle dependence of display luminance is large (viewing angle characteristics are inferior). This problem will be described with reference to FIGS. 2A, 2B, and 2C. 2A and 2B schematically show a liquid crystal display device having a liquid crystal layer 203 twisted. In these figures, a pair of electrodes 201 and 20 are disposed between a pair of polarizing plates 206 and 207 arranged in a crossed Nicols state.
2 sandwiches the liquid crystal layer 203. The long axis of the liquid crystal molecules located near the center in the thickness direction of the liquid crystal layer 203 is drawn so as to be positioned in the plane of the drawing (looking longest). 2A shows a state where no voltage is applied, and FIG. 2B shows a state where a voltage is applied.

As shown in FIG. 2A, when no voltage is applied, the liquid crystal molecules 203a near the center in the thickness direction are oriented substantially parallel to the substrate surface. Even if this state is observed from the viewing angle directions 204 and 205, no difference is recognized. On the other hand, as shown in FIG. 2B, in a state where a voltage for displaying a halftone is applied, a state to be observed is different depending on a viewing angle direction. This is because the liquid crystal molecules have a positive uniaxial refractive index anisotropy (cigar-shaped refractive index ellipsoid). When a voltage is applied, the liquid crystal molecules 203b rise in the direction determined by the pretilt (counterclockwise in this example). When the liquid crystal molecules 203b are observed from the 204 direction (coincident with the long axis direction of the liquid crystal molecules 203b), the anisotropy of the refractive index of the cigar-shaped liquid crystal molecules 203b disappears (the liquid crystal molecules 203b look circular). On the other hand, when the liquid crystal molecules 203b are observed from the 205 direction, the refractive index anisotropy becomes maximum.

Therefore, when the liquid crystal molecules 203b in the liquid crystal cell are viewed from the direction of the arrow 204, most of the liquid crystal molecules look circular, that is, the refractive index anisotropy of the liquid crystal layer is small. Therefore, the linearly polarized light transmitted through the polarizing plate 206 reaches the polarizing plate 207 without any change in the polarization state in the liquid crystal layer 203, and is blocked by the polarizing plate 207 having a polarizing axis orthogonal to the polarizing axis of the polarizing plate 206. Therefore, the transmittance decreases. On the other hand, the liquid crystal molecules 203 in the liquid crystal cell
When viewing b, most of the liquid crystal molecules look like rods. That is,
The liquid crystal layer 203 has the maximum refractive index anisotropy. Therefore, the polarization state of the polarized light that has passed through the polarizing plate 206 is changed by the liquid crystal layer 203, and the amount of light transmitted through the polarizing plate 207 is maximized.

As a result, as shown in FIG. 2C, the display when the viewing angle is changed in the rising direction of the liquid crystal molecules (the direction of arrow 204 in FIG. 2B) and in the opposite direction (in the direction of arrow 205 in FIG. 2B). The change in luminance varies greatly.
The liquid crystal display device is set so that the upward direction (12 o'clock direction) is 205 direction and the downward direction (6 o'clock direction) is 204 direction. Note that each curve in FIG. 2 shows the transmittance for different applied voltages. The applied voltage increases in order from the one with the highest front transmittance (normally white).

That is, in the conventional TN mode, when the viewing angle is changed along the alignment direction of the liquid crystal molecules, the luminance significantly changes. As understood from the above description, such asymmetry of the gradation characteristic is not limited to the TN mode.
This is common to display modes in which liquid crystal molecules move in the cell thickness direction of a liquid crystal cell, and in which alignment division is not performed.

By performing orientation division for each pixel region,
Improves the asymmetry of the gradation characteristics with respect to the viewing angle direction,
A symmetrical gradation characteristic (viewing angle characteristic) is obtained. This will be described with reference to FIGS. 3A and 3B
As shown in (1), for example, one pixel region is divided into two regions A and B (first domain and second domain) in which the rising directions of liquid crystal molecules by voltage differ by 180 °. In the state where no voltage is applied, as shown in FIG. 3A, the liquid crystal molecules in any region are oriented almost parallel to the substrate surface (the pretilt angle is ignored for simplicity). When a voltage for halftone display is applied, as shown in FIG.
Of the liquid crystal molecules 303a of the region B are counterclockwise.
03b rises clockwise (the rising direction is determined by the pretilt direction). As described above, the gradation characteristics of the regions A and B depend on the viewing angle directions 304 and 305, respectively, as shown in FIGS. 3C and 3D. Since the region A and the region B exist in one pixel region, the gradation characteristics of the whole one pixel region are obtained by averaging the gradation characteristics of FIGS. 3C and 3D in consideration of the area ratio of each region. It will be. Therefore, by setting the area SA of the area A and the area B of the area B to 1: 1,
As shown in FIG. 3E, symmetrical gradation characteristics are obtained in both directions of arrow 304 and arrow 305.

Next, the ratio between SA and SB and the gradation characteristics will be described in order to estimate the range in which the effect of the orientation division can be obtained. FIG. 4A shows the viewing angle dependency of a voltage application state in which the transmittance at the front is 50% among the gradation characteristics shown in FIG. 3E.
As a measure of vertical symmetry, arrow 30 in FIGS. 3A and 3B
The relationship between the ratio TA / TB of the transmittances TA and TB at a viewing angle of 50 ° in the directions of 4 (upper) and 305 (lower) and the ratio SA / (SA + SB) of the areas SA and SB of the regions A and B is shown. As shown in FIG. 4B. FIG. 4B shows that the upper and lower gradation characteristics are substantially symmetric (TA / TB = about 1) when the ratio of SA is around 0.5.

Note that the alignment division is not limited to two divisions, and that the liquid crystal molecules rise in the opposite direction when a voltage is applied over the entire display surface.
It is sufficient that the sum of the areas of the two regions is substantially the same. In consideration of display uniformity, it is preferable that the unit of the alignment division is smaller, and it is preferable to perform the alignment division into two or more for each picture element region. Further, as shown in FIGS. 4C and 4D, a plurality of regions A and a plurality of regions B may be provided for each picture element region, and the two regions A and B may be alternately arranged. By forming a plurality of regions A and regions B for each pixel region and reducing the unit of orientation division, the viewing angle characteristics can be made more uniform. The reason is shown in FIG.
As shown in E, the light (arrow 402) transmitted only through the regions A and B when observing the liquid crystal display device from an oblique direction.
This is because the ratio of the light (arrow 401) transmitted across the AB2 region to A, 402B) increases.

(Normal Black Mode and Improvement of Contrast Ratio) In a normally black mode in which a black display state is obtained when no voltage is applied, the viewing angle characteristics are improved by using a phase difference compensating element. The viewing angle characteristic is an apparent change of a display image generated when the display image is observed from a direction (oblique direction) shifted from a direction perpendicular to the display surface of the liquid crystal display device, and is a viewing angle characteristic (display that changes depending on the viewing angle). The characteristics include a gradation change, a contrast ratio change, a color change, and the like. The gradation change can be improved by the orientation division as described above. Hereinafter, the improvement of the viewing angle dependency of the contrast ratio by the combination of the normally black mode and the phase difference compensating element will be described.

The contrast ratio (CR) is defined as a value obtained by dividing the maximum transmittance (transmittance during white display) by the minimum transmittance (transmittance during black display). In a normal liquid crystal display device, the change in transmittance due to observation in an oblique direction is larger in the black display state than in the white display state. Therefore, in order to improve the viewing angle characteristics of the contrast ratio, it is sufficient to improve the transmittance change (floating black) due to oblique observation during black display.

This will be described with reference to FIGS. 5A to 5F. In order to realize the normally black mode, the refractive index anisotropy of the horizontally aligned liquid crystal layer when no voltage is applied may be compensated (can be canceled). This compensation is performed by the phase difference plates 102 and 103 in FIG. In FIG. 5A, the phase difference plates 502 and 503 play the same role as the phase difference plates 102 and 103. The liquid crystal layer of the present invention is substantially horizontally aligned when no voltage is applied as shown in FIG. 5A. When the liquid crystal layer is viewed from the front of the liquid crystal display device, the refractive index in the direction of the arrow 508 (orientation direction) in FIG. 5B is the largest, and the refractive index in the direction perpendicular thereto is the smallest. In the present invention, for example, the value obtained by multiplying the difference between the maximum refractive index and the minimum refractive index by the thickness of the liquid crystal layer, that is, the retardation value of the liquid crystal layer is set to about 250 nm (50 nm to 500 nm). Therefore, if the retardation plates 502 and 503 are not used, the liquid crystal layer 5 sandwiched between the polarizing plates 504 and 505
It goes without saying that 01 transmits light due to the birefringence effect. Therefore, in order to realize the characteristics of normally black, a retardation plate 502 having a positive uniaxial refractive index anisotropy,
503 is used. Specifically, the phase difference plates 502 and 50
The retardation value of 3 is approximately １ ／ of the retardation value of the liquid crystal layer, that is, approximately 125 nm, and its slow axis is aligned with arrows 509 and 510 (perpendicular to 508). At this time, the retardation values of 502 and 503 are 125
It is not limited to nm.

It suffices that the sum of the retardation values of 502 and 503 substantially coincides with the retardation value of the liquid crystal layer, and as a result, when no voltage is applied, black display is observed in the front view.

Further, the wavelength dependence of the retardation value of the liquid crystal layer and the total wavelength dependence of the retardation values of the retardation plates 502 and 503 are also appropriately adjusted (for example, matched), so that the result when no voltage is applied is obtained. It is preferable that a good black display is obtained in observation from the front. Thereby, the birefringence effect in the liquid crystal layer can be compensated for by the birefringence effect of the retardation plate, so that normally black characteristics can be obtained.

Next, the difference between the normally black type and the normally white type with respect to the phase difference compensation method for improving black floating will be described. As shown in FIG. 5A, in the case of a liquid crystal display device that performs black display when no voltage is applied, the liquid crystal layers in the region A and the region B have substantially the same orientation. On the other hand, in the normally white type shown in FIG. 5D, that is, in the case where black display is performed when a voltage is applied, the orientations of the region A and the region B are different. This affects the angle dependence of the retardation value in the black display state.

FIG. 5C shows the change in the retardation value in each of the A and B regions when observed in the directions of arrows 520 and 521 in FIG. 5A, and the change in the retardation value in the case where it is changed in the directions of arrows 522 and 523. Shown in 5G.
For comparison, A, when observed from the directions of arrows 520 and 521 in the normally white type shown in FIG.
FIG. 5F shows the change in the retardation value of the area B in an arrow 52.
FIG. 5H shows a change in the retardation value when the observation is performed while tilting in the directions of 2 and 523.

Referring to FIGS. 5C and 5G, arrows 520,
The angle dependency of the retardation value in the area A is not affected by the angle in any of the directions 521, 522 and 523.
Of it matches. In addition, 520, 521, 52
The change of the retardation value with respect to the angle change in any of the directions 2 and 523 is almost the same. In particular, in any region, even when the angle changes in any direction, the extreme points of the retardation values (points protruding downward in the figure) match (0 de in the figure).
g). And each is also consistent. That is, according to the present invention, in the normally black state, the phase difference compensation can be performed by the same phase difference compensating element in both the area A and the area B. Further, since the pole is 0 deg, two main axes of the refractive index of the phase compensation element can be set in a plane parallel to the liquid crystal panel surface, and the other main axis can be set parallel to the normal line of the liquid crystal panel surface. And it may be uniaxial. this is,
This is because the alignment of the liquid crystal layer in the black display in the region A and the region B is substantially the same. Further, comparing FIG. 5C and FIG. 5G, the angle changes in any direction of the arrows 520, 521, 522 and 523 show almost the same change. This is because the liquid crystal molecules of the liquid crystal layer 501 are horizontally aligned, and the slow axis of the liquid crystal layer and the slow axes of the retarders 502 and 503 are in the same plane and are orthogonal to each other. are doing. As described above, in the present invention, in the regions A and B, one of the principal axes of the refractive index is parallel to the normal to the retardation plate surface, and the other two principal axes are in a plane parallel to the retardation plate surface. It can be seen that black floating can be improved by phase difference compensation by a certain phase difference compensating element.

On the other hand, according to FIG. 5F, arrows 520, 521
The change in the retardation value with respect to the change in the angle in the direction is significantly different between the region A and the region B. As an example, the retardation value of the area A takes the minimum value when the angle is inclined in the direction of the arrow 520, whereas the retardation value of the area B takes the minimum value when the angle is inclined in the direction of the arrow 521. As described above, in order to improve the floating of black in the liquid crystal display device of FIG. 5A, different phase difference compensating elements corresponding to the regions A and B are required. Regions A and B are regions into which one picture element is divided, and since the area of each is very small, it is actually difficult to compensate for a phase difference for improving black floating.

(Phase plate having a slow axis in the normal direction of the display surface) The retardation of the liquid crystal layer 101 and the phase plates 102 and 103 due to oblique observation by the phase plates 104 and 105 of FIG. To compensate for floating black. That is, the purpose is to compensate for the retardation angle dependence in FIGS. 5C and 5G and to make the retardation value constant (substantially zero) regardless of the angle. If the specific method is raised, a liquid crystal cell having a positive uniaxial refractive index and refractive index anisotropy as shown in FIG. 1 and a retardation plate are used, and the slow axis of the liquid crystal cell surface during black display is changed. In the case of a liquid crystal display device included in a plane parallel to the liquid crystal cell, a retardation plate having a positive uniaxial refractive index anisotropy is used, and its slow axis is parallel to the normal to the liquid crystal cell surface. Just place them.

This will be briefly described with reference to FIG. 6 while paying attention to the angle change of the refractive index anisotropy of the liquid crystal molecules and the phase difference plate. In FIG. The refractive index ellipsoid of the liquid crystal layer 101 in FIG. 1 is 601 and the refractive index ellipsoids of the retardation plates 102 and 103 are 602 and 603. Each of the refractive index ellipsoids has positive uniaxiality, and its optical axis is in a plane parallel to the liquid crystal cell surface.

The refractive index ellipsoid 706 (slow axis 70
4, a change in the refractive index when a circle 705) orthogonal to the slow axis is viewed from an oblique direction will be described with reference to FIGS. First, consider a case where the liquid crystal display device is viewed from the front. The refractive index anisotropy that contributes to the birefringence of the liquid crystal layer or the retardation plate is biaxially 702 and 70 that are in a plane whose normal line is the traveling direction of the incident linearly polarized light and form 45 ° with the polarization axis 701 of the linearly polarized light.
3 is the refractive index difference in the direction parallel to 3. Therefore, the refractive index anisotropy that contributes to the transmittance in the front direction is na1 and nb in FIG. 7A.
It is the difference na1-nb1 of one.

The refractive index anisotropy contributing to the transmittance when the viewing angle is inclined in the major axis direction of the refractive index ellipsoid of the liquid crystal molecules or the phase difference plate is represented by the difference na2 between na2 and nb2 in FIG. 7B.
nb2. In this case, as shown in FIG. 7B, the refractive index na
2 is smaller than na1 shown in FIG. 7A. On the other hand, nb1 and nb2 are equal (nb1 = nb2). That is, when the viewing angle is inclined along the major axis of the refractive index ellipsoid, the refractive index anisotropy is in a direction of decreasing.

As shown in FIG. 7C, when the viewing angle is changed along the minor axis of the refractive index ellipsoid, the refractive index anisotropy contributing to the transmittance is the difference na3-nb3 between na3 and nb3. That is, when the viewing angle is changed along the minor axis direction of the refractive index ellipsoid, the refractive index anisotropy does not change.

Finally, consider the case where the main axis of the refractive index ellipsoid coincides with the normal to the display surface of the display device. When viewed from the front, the refractive index contributing to the transmittance is the difference na4-nb4 between na4 and nb4 shown in FIG. 7D. That is, when a retardation plate having a refractive index ellipsoid of na4 = nb4 is used, the transmittance in the front direction does not change at all. When the viewing angle is changed in an oblique direction, the difference between na5 and nb5 shown in FIG. 7E is na5-nb5. That is, in such a refractive index ellipsoid, the refractive index anisotropy increases as the viewing angle is inclined from the front direction. That is, there is an effect of compensating for the change in the refractive index shown in FIG. 7B.

Based on the discussion of a single refractive index ellipsoid described in FIG. 7, FIG. 6 shows an embodiment of the present invention.
The following summarizes the phase difference compensating effect of the refractive index ellipsoid group of FIG. In the refractive index ellipsoid group representing the liquid crystal layer and the retardation plate when no voltage is applied according to the embodiment of the present invention shown in FIG. 6, when the linearly polarized light (polarization direction 607) is incident, two azimuth directions are used. Table 1 summarizes changes and increases / decreases in refractive index anisotropy that affect the transmittance when the viewing angle is changed in the azimuthal directions indicated by 608 and 609.

[0059]

[Table 1]

From the above table, it can be seen that oblique viewing angle changes can be compensated for by a retardation plate having a refractive index ellipsoid having the maximum refractive index in the normal direction of the liquid crystal display device surface. Further, the refractive index that contributes to the transmittance is a refractive index in a direction forming 45 ° with the polarization axis of the incident linearly polarized light. Therefore, it can be easily understood that the refractive index in this direction should be smaller than the refractive index in the normal direction of the surface of the liquid crystal display device.

(Phase plate having a slow axis in the direction of 45 ° with respect to the slow axis of the liquid crystal layer) The phase plates 110 and 111 shown in FIG. 1 have elliptically polarized light (including linearly polarized light) incident thereon. ) To rotate the main shaft.

In order to improve the contrast ratio, it is necessary to suppress an increase in transmittance (floating of black) when viewed from an oblique direction in a black display state. That is, polarized light incident on the polarizing plate 109 from any angle is
, Ie, elliptically polarized light having an ellipticity of zero and a principal axis orthogonal to the 109 polarization axis. A change in retardation of the liquid crystal layer 101 due to a change in viewing angle is compensated by the above-described retardation plates 104 and 105. Compensation for this change in retardation mainly corresponds to suppressing an increase in ellipticity of elliptically polarized light (to zero). Furthermore, in order to obtain good contrast, it is necessary to compensate for rotation of the principal axis of elliptically polarized light due to a change in viewing angle. The retarders 110 and 111 compensate for the rotation of the principal axis of the elliptically polarized light.

FIG. 8 shows the transmittance in the black display state when the viewing angle is set to 60 ° in the azimuthal direction (direction of arrow 609) parallel to the long axis of the liquid crystal molecules, and the phase difference plate 110.
And 111 with the retardation values. FIG.
As is clear from FIG. 7, it is understood that good black display can be obtained by appropriately setting the retardation values of the phase difference plates 110 and 111 and adjusting the rotation angle of the principal axis of the elliptically polarized light. Only one of the phase difference plates 110 and 111 may be used.

[0064]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, parameters that are commonly used in the description of the following embodiments and characterize the configurations of a liquid crystal layer, a polarizing plate, and a retardation plate are defined as follows.

The definition of each parameter, especially the value of the angle, is based on the XYZ orthogonal coordinate system appropriately set on the liquid crystal panel. As shown in FIGS. 9A to 9C, the reference coordinate system only needs to have the XY plane parallel to the liquid crystal panel surface, and the directions of the X axis and the Y axis are not limited at all.
(B) to (c)). However, in one liquid crystal display device, a common axis is used for all of the liquid crystal layer, the polarizing plate, and the retardation plate. In the following description, X_REF, Y_REF, Z_RE
F.

The parameters that characterize the alignment state of the liquid crystal molecules in the liquid crystal layer will be described with reference to FIG. FIG.
(A) is a perspective view of a liquid crystal cell. In the following description, domains in a uniform alignment state will be described for simplicity. In a configuration in which a picture element region is orientation-divided into a plurality of domains, parameters characterizing the liquid crystal layer in each domain include a retardation value of the liquid crystal layer, a twist angle of the liquid crystal layer, and a liquid crystal molecule (located in the middle of the thickness direction of the liquid crystal layer). Liquid crystal molecule) (slow axis of the liquid crystal layer).

FIG. 10B is a sectional view of the liquid crystal layer. The retardation value of the liquid crystal layer is determined by the substrates 5101 and 5102.
And the distance between the substrate 5101 (eg, a substrate on which a color filter is formed) and the substrate 5102 (eg, a substrate on which a TFT array is formed) (the liquid crystal layer 5103). Thickness = cell gap) d
With the product d · △ n.

FIG. 10C is a plan view when the liquid crystal cell is observed from the observer side. The straight line 5104 is a straight line parallel to the long axis of the liquid crystal molecules adjacent to the light source side substrate 5102, and the straight line 5105 is a straight line parallel to the long axis of the liquid crystal molecules adjacent to the observer side substrate 5101. For simplicity, a case where the twist angle of the liquid crystal molecules is 90 ° or less will be described.
In this case, the twist angle of the liquid crystal layer is expressed by the straight line 5104 and the straight line 5
This is a rotation angle when the rotation is performed until 104 coincides with the straight line 5105, and the rotation counterclockwise is defined as positive. This angle is shown as θtwist in the figure.

The orientation direction of the liquid crystal layer is defined as follows.
A straight line bisecting θtwist shown in FIG. This straight line 5106 coincides with the direction in which the liquid crystal molecules located in the middle of the thickness direction of the liquid crystal layer rise due to the electric field, and is called the orientation direction or slow axis of the liquid crystal layer.
When a voltage (halftone voltage) giving an intermediate transmittance is applied to the liquid crystal layer, the liquid crystal molecules in the liquid crystal layer whose major axis is parallel to the straight line 5106 are considered. FIG. 10D shows a cross-sectional view of the liquid crystal cell parallel to the straight line 5106. The rising direction of the liquid crystal molecules is indicated by an arrow, and the arrow parallel to the straight line 5106 is indicated by 5107. The orientation direction of the liquid crystal layer is an angle β with respect to the reference axis X_REF when the counterclockwise direction is defined as positive.
And

The parameter of the polarizing plate is a polarization axis (transmission axis).
Direction (angle). A method of defining the direction of the polarization axis will be described (not shown). The direction of the polarization axis is the reference axis X_RE.
The angle was defined as an angle with F, and the counterclockwise direction was defined as positive. Of course, a polarizing plate represented by any polarization axis direction α,
The directions of the polarization axes of the polarizing plates represented by α + 180 ° and α−180 ° are all equivalent.

The parameters of the phase difference plate are defined.
The parameters of the retardation plate are the in-plane retardation value (in a plane parallel to the display surface), the thickness direction retardation value (the direction perpendicular to the liquid crystal display surface), and the angle of the a-axis (X_REF and a
Angle of the shaft).

FIG. 11 shows a refractive index ellipsoid of the phase difference plate.
The three main axes of the refractive index ellipsoid of the retardation plate used in this embodiment are a, b, and c. The main axes a, b and c form an orthogonal coordinate system. The main axes a and b are in a plane parallel to the phase plate surface, that is, in a plane parallel to the display surface. At this time, the spindle a,
The values of the refractive index along b and c are defined as na, nb and nc, respectively. Further, the thickness of the phase difference plate is d.

The in-plane retardation of the retardation plate is d
-It is defined as (na-nb).

The retardation in the thickness direction is d · (n
a-nc).

The angle of the a-axis is determined based on the reference axis X_REF and a
It is defined as the angle γ formed by the axis. The sign of the angle is positive in the counterclockwise direction.

(Production of Liquid Crystal Cell / Orientation Division) A method of producing a liquid crystal cell used in this embodiment, particularly a method of orientation division will be described. The liquid crystal display device of the present invention can be manufactured by appropriately combining known manufacturing methods.

The liquid crystal cell is manufactured on a normal TFT (thin film transistor) substrate under substantially the same conditions as those for manufacturing a current TN liquid crystal cell. However, in this embodiment, the rubbing direction (angle) is different from the conventional TN type liquid crystal cell. Further, in order to form a two-divided alignment, the pretilt angle is controlled by irradiating the alignment film with UV light.

FIG. 12A is a schematic view of the liquid crystal cell in this embodiment as viewed from the observer side substrate. Arrow 12 in the figure
02 is the rubbing direction on the color filter substrate side;
03 is the rubbing direction on the TFT substrate side.

The alignment state of the liquid crystal molecules after the liquid crystal is injected into the substrate rubbed in the rubbing direction and subjected to the realignment processing will be described. X- in FIG.
X 'cross section, that is, liquid crystal molecules 1 having a cross section parallel to the rubbing direction
It is considered that the orientation of 206 is schematically represented as shown in FIG. Liquid crystal molecules 1206 and observer side substrate 12
05 or the light source side substrate 1204, and the liquid crystal molecules in the intermediate layer of the liquid crystal cell are oriented substantially parallel to the substrate surface. If a voltage is applied to this liquid crystal layer, the liquid crystal molecules in the intermediate layer will become the arrows 1207 or 1
It can rotate (get up) in the direction of 208 with the same probability.

Therefore, in the present invention, rubbing was performed after irradiating one of the upper and lower substrates with UV light. FIG. 12 schematically shows the orientation of liquid crystal molecules in the XX ′ section in this state.
It is shown in (c). One picture element was divided into two areas A and B, and UV irradiation was performed.

In the region A, UV light is applied to the alignment film of the opposite substrate.
In the area B, U is applied only to the alignment film on the TFT substrate side.
Irradiate V light. As a result of evaluating the optical characteristics of the liquid crystal cell subjected to such processing, the liquid crystal molecules in the intermediate layer in the region A are in the direction of arrow 1207, and the liquid crystal molecules in the region B are in the direction of arrow 1208
It was confirmed that it turned in the direction of. That is, the alignment (pretilt) of the liquid crystal molecules located near the middle in the thickness direction of the liquid crystal layer could be controlled. Note that UV irradiation may be performed after the rubbing treatment. In addition, UV
Split orientation may be performed by means other than irradiation and rubbing.

Further, it is preferable to use light-shielding beads as the spacer beads.

This is because, in the present invention, normally black characteristics are obtained by compensating for the retardation of the liquid crystal layer with a retardation plate. That is, if the retardation value of the liquid crystal layer changes due to beads or the like, black display cannot be obtained in that portion, resulting in lower contrast. Therefore, it is necessary to take appropriate measures such as shielding such portions from light (using light-shielding beads) or not providing such portions (beadless).

(Embodiment 1) An embodiment of the present invention is shown in FIG. In FIG. 1, reference numeral 101 denotes a liquid crystal cell;
Reference numerals 3, 104, 105, 110, and 111 denote retarders.
08 and 109 represent polarizing plates.

The liquid crystal cell 101 is divided into two regions, A and B, for each picture element. The orientation parameters for each region are as follows.

[0086]

[Table 2]

The parameters of the polarizing plate are as follows.

[0088]

[Table 3]

The parameters of the phase difference plate are shown below.

[0090]

[Table 4]

FIG. 13 shows the relationship between the transmittance and the applied voltage of the liquid crystal display device of this embodiment. In FIG. 13, the transmittance at an applied voltage of 4 V is set to 100%. FIG. 13 shows that the liquid crystal display device of this example displays black at an applied voltage of 0 V, and the transmittance increases (white display) as the applied voltage increases.

14A to 14C show the dependence of the transmittance at each gradation on the viewing angle (polar angle: angle with respect to the normal to the display surface) in the eight gradation display state. FIG. 14A shows the viewing angle change in each direction parallel to the X_REF axis, and FIG.
_REF ± 45 ° viewing angle change in the azimuth direction parallel to the axis,
FIG. 14C shows the viewing angle change in the azimuth direction parallel to the Y_REF axis. From these figures, it can be seen that the gradation characteristics of the liquid crystal display device of this embodiment are substantially symmetric.

FIG. 15 shows a value obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V (contrast ratio).
FIG. The center of the circle is the normal direction of the display surface (viewing angle 0 °), and each concentric circle has a viewing angle of 20 ° from the inside,
40 °, 60 °, and 80 ° are shown, respectively. In addition, the horizontal axis of the drawing indicates the X_REF axis, and the vertical axis indicates Y_REF. The isocontrast curves show contrast ratios (CR) = 100, 50, and 20, respectively, from the inside. As is apparent from this figure, in the liquid crystal display device of this example, in all azimuth directions, a display with CR = 50 or more can be obtained in a range of a viewing angle of 60 ° or more, and has excellent viewing angle characteristics. I understand.

(Embodiment 2) FIG. 16 schematically shows the structure of a liquid crystal display device according to Embodiment 2 of the present invention. In FIG. 16, 6
101 is a liquid crystal cell, 6102, 6103, 6104,
Reference numeral 6105 denotes a retardation plate, and reference numerals 6106 and 6107 denote polarizing plates.

The liquid crystal cell 6101 is divided into two regions, A and B, for each pixel. The orientation parameters for each region are as follows.

[0096]

[Table 5]

The parameters of the polarizing plate are as follows.

[0098]

[Table 6]

The parameters of the phase difference plate are shown below.

[0100]

[Table 7]

The liquid crystal display of this embodiment also has extremely good viewing angle characteristics, as in the first embodiment.

(Embodiment 3) FIG. 17 schematically shows the structure of a liquid crystal display device according to Embodiment 3 of the present invention. In FIG. 17, 6
201 denotes a liquid crystal cell, 6202, 6203, 6204,
Reference numeral 6205 denotes a retardation plate, and reference numerals 6206 and 6207 denote polarizing plates.

The liquid crystal cell 6201 is divided into two regions, A and B, for each picture element. The orientation parameters for each region are as follows.

[0104]

[Table 8]

The parameters of the polarizing plate are as follows.

[0106]

[Table 9]

The parameters of the phase difference plate are shown below.

[0108]

[Table 10]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the first embodiment.

(Embodiment 4) FIG. 18 schematically shows the structure of a liquid crystal display device according to Embodiment 4 of the present invention. In FIG. 18, 6
Reference numeral 301 denotes a liquid crystal cell, 6302, 6303, and 6304 denote retardation plates, and 6305 and 6306 denote polarizing plates. The liquid crystal cell 6301 is divided into two regions, A and B, for each picture element. The orientation parameters for each region are as follows.

[0111]

[Table 11]

The parameters of the polarizing plate are as follows.

[0113]

[Table 12]

The parameters of the phase difference plate are shown below.

[0115]

[Table 13]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the first embodiment.

(Embodiment 5) FIG. 19 schematically shows the structure of a liquid crystal display device according to Embodiment 5 of the present invention. In FIG. 19, 6
Reference numeral 401 denotes a liquid crystal cell, 6402, 6403, 6404,
Reference numeral 6405 denotes a retardation plate, and reference numerals 6406 and 6407 denote polarizing plates.

The liquid crystal cell 6401 is orientation-divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0119]

[Table 14]

The parameters of the polarizing plate are as follows.

[0121]

[Table 15]

The parameters of the phase difference plate are shown below.

[0123]

[Table 16]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the first embodiment.

(Embodiment 6) FIG. 23 schematically shows the structure of a liquid crystal display device according to Embodiment 6 of the present invention. 23 in FIG.
Reference numeral 501 denotes a liquid crystal cell, reference numerals 6502, 6503, and 6504 denote retardation plates, and reference numerals 6505 and 6506 denote polarizing plates.

The orientation of the liquid crystal cell 6501 is divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0127]

[Table 17]

The parameters of the polarizing plate are as follows.

[0129]

[Table 18]

The parameters of the phase difference plate are shown below.

[0131]

[Table 19]

In Examples 1 to 6, the twist angle of the liquid crystal layer was 0 °, but the effect of the present invention is not limited to this. By providing an arbitrary twist angle in the liquid crystal layer,
The selection range of each parameter, the margin, and the like can be expanded. Especially, the twist angle is 0 ° or more and 90 ° or more.
In a smaller range, alignment division can be easily performed without mixing a chiral agent into the liquid crystal. An example in which the twist angle is 30 ° will be described below as an example.

(Embodiment 7) FIG. 1 schematically shows the structure of a liquid crystal display device according to Embodiment 7 of the present invention. In FIG.
Are liquid crystal cells, 102, 103, 104, 105, 11
Reference numerals 0 and 111 denote retardation plates, and 108 and 109 denote polarizing plates.

The liquid crystal cell 101 is orientation-divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0135]

[Table 20]

The parameters of the polarizing plate are as follows.

[0137]

[Table 21]

The phase difference plates 102, 103, 104, 10
The parameters of 5,110,111 are shown below.

[0139]

[Table 22]

FIG. 20 shows the relationship between the transmittance and the applied voltage of the liquid crystal display device of this embodiment. In FIG. 20, the transmittance at an applied voltage of 4 V is set to 100%. From FIG. 20, it can be seen that the liquid crystal display device of this example displays black at an applied voltage of 0 V, and the transmittance increases (white display) as the applied voltage increases.

21A to 21C show the viewing angle (polar angle: angle with respect to the normal to the display surface) dependency of the transmittance at each gradation in the eight gradation display state. 21A shows the viewing angle change in each direction parallel to the X_REF axis, and FIG.
_REF ± 45 ° viewing angle change in the azimuth direction parallel to the axis,
FIG. 21C shows the viewing angle change in the azimuth direction parallel to the Y_REF axis. From these figures, it can be seen that the gradation characteristics of the liquid crystal display device of this embodiment are substantially symmetric.

FIG. 22 shows a value obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V (contrast ratio).
FIG. The center of the circle is the normal direction of the display surface (viewing angle 0 °), and each concentric circle has a viewing angle of 20 ° from the inside,
40 °, 60 °, and 80 ° are shown, respectively. In addition, the horizontal axis of the drawing indicates the X_REF axis, and the vertical axis indicates Y_REF. The isocontrast curves show contrast ratios (CR) = 100, 50, and 20, respectively, from the inside. As is apparent from this figure, in the liquid crystal display device of this example, in all azimuthal directions, a display of CR = 10 or more can be obtained at a viewing angle of 60 ° or more, and has excellent viewing angle characteristics. I understand.

(Embodiment 8) FIG. 16 schematically shows the structure of a liquid crystal display device according to Embodiment 8 of the present invention. In FIG. 16, 6
101 is a liquid crystal cell, 6102, 6103, 6104,
Reference numeral 6105 denotes a retardation plate, and reference numerals 6106 and 6107 denote polarizing plates.

The orientation of the liquid crystal cell 6101 is divided into two regions, A and B, for each picture element. The orientation parameters for each region are as follows.

[0145]

[Table 23]

The parameters of the polarizing plate are as follows.

[0147]

[Table 24]

The parameters of the phase difference plate are shown below.

[0149]

[Table 25]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the seventh embodiment.

(Embodiment 9) FIG. 17 schematically shows the structure of a liquid crystal display device according to Embodiment 9 of the present invention. In FIG. 17, 6
201 denotes a liquid crystal cell, 6202, 6203, 6204,
Reference numeral 6205 denotes a retardation plate, and reference numerals 6206 and 6207 denote polarizing plates.

The orientation of the liquid crystal cell 6201 is divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0153]

[Table 26]

The parameters of the polarizing plate are as follows.

[0155]

[Table 27]

The parameters of the phase difference plate are shown below.

[0157]

[Table 28]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the seventh embodiment.

(Embodiment 10) FIG. 18 schematically shows the structure of a liquid crystal display device according to Embodiment 10 of the present invention. In FIG. 18, reference numeral 6301 denotes a liquid crystal cell, 6302, 6303, and 630.
Reference numeral 4 denotes a retardation plate, and reference numerals 6305 and 6306 denote polarizing plates.

The liquid crystal cell 6301 is orientation-divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0161]

[Table 29]

The parameters of the polarizing plate are as follows.

[0163]

[Table 30]

The parameters of the phase difference plate are shown below.

[0165]

[Table 31]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the seventh embodiment.

(Embodiment 11) FIG. 19 schematically shows the structure of a liquid crystal display device according to Embodiment 11 of the present invention. In FIG. 19, 6401 denotes a liquid crystal cell, 6402, 6403, and 640.
4,6405 represents a retardation plate, and 6406,6407 represent polarizing plates.

The liquid crystal cell 6401 is orientation-divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0169]

[Table 32]

The parameters of the polarizing plate are as follows.

[0171]

[Table 33]

The parameters of the phase difference plate are shown below.

[0173]

[Table 34]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the seventh embodiment.

(Embodiment 12) FIG. 23 schematically shows a structure of a liquid crystal display device according to Embodiment 12 of the present invention. In FIG. 23, reference numeral 6501 denotes a liquid crystal cell, 6502, 6503, 650.
Reference numeral 4 denotes a retardation plate, and reference numerals 6505 and 6506 denote polarizing plates.

The liquid crystal cell 6501 is orientation-divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0177]

[Table 35]

The parameters of the polarizing plate are as follows.

[0179]

[Table 36]

The parameters of the phase difference plate are shown below.

[0181]

[Table 37]

The liquid crystal display of this embodiment also has very good viewing angle characteristics, as in the seventh embodiment.

(Thirteenth Embodiment) In the third embodiment, the retardation plate 6
204, 6205, the liquid crystal layer 6 accompanying oblique observation
201, compensation for floating black at the time of black display due to a change in retardation of the phase difference plates 6202 and 6203. The polarizing plate used in the present invention may be provided with a protective film such as TAC on its surface. When a material having a refractive index anisotropy such as TAC is used as the protective material of the polarizing plate, the refractive index anisotropy of the TAC can be reduced even when an optical design for suppressing black floating during black display due to oblique observation is performed. It needs to be considered. In addition to the retardation change of the liquid crystal layer 6201 and the phase difference plates 6202 and 6203, the retardation value of the phase difference plates 6204 and 6205 is appropriately selected in consideration of the retardation change of the TAC, and the floating angle is compensated for. The characteristics can be further improved. In the following embodiments, TAC is regarded as an independent phase difference compensating element (phase difference plate).

This embodiment will be described with reference to FIG. In FIG. 24, reference numeral 2401 denotes a liquid crystal cell;
Reference numerals 2403, 2404, 2405 denote retardation plates, 2408,
Reference numeral 2409 denotes a polarizing plate. 2406,24
Reference numeral 07 denotes a TAC provided for protecting the polarizing plate. T
Since AC has refractive index anisotropy, TAC between the polarizing plate and the liquid crystal cell is shown as an independent retardation plate in FIG.

The liquid crystal cell 2401 is divided into two regions A and B for each picture element. The orientation parameters for each region are as follows.

[0186]

[Table 38]

The parameters of the polarizing plate are as follows.

[0188]

[Table 39]

The parameters of the phase difference plate are shown below.

[0190]

[Table 40]

FIG. 25 shows the relationship between the transmittance and the applied voltage of the liquid crystal display device of this embodiment. In FIG. 25, the transmittance at an applied voltage of 4 V is set to 100%. As shown in FIG. 25, the liquid crystal display device of this embodiment has a normally black electro-optical characteristic in which black is displayed at an applied voltage of 0 V, and the transmittance increases (white display) as the applied voltage increases.

FIGS. 26 to 29 show the dependence of the transmittance at each gradation on the viewing angle (polar angle: angle with respect to the normal to the display surface) in the eight gradation display state. FIG. 26 shows the change of the viewing angle in each direction parallel to the X_REF axis, and FIG.
28. Viewing angle change in azimuthal direction parallel to F + 45 ° axis, FIG.
FIG. 29 shows the viewing angle change in the azimuth direction parallel to the X_REF-45 ° axis, and FIG. 29 shows the viewing angle change in the azimuth direction parallel to the Y_REF axis. From these figures, it can be seen that the gradation characteristics of the liquid crystal display device of this embodiment are substantially symmetric.

FIG. 30 shows a value obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V (contrast ratio).
FIG. The center of the circle is the normal direction of the display surface (viewing angle 0 °), and each concentric circle has a viewing angle of 20 ° from the inside,
40 °, 60 °, and 80 ° are shown, respectively. In addition, the horizontal axis of the drawing indicates the X_REF axis, and the vertical axis indicates Y_REF. The isocontrast curve shows a contrast ratio (CR) = 50 from the inside. As is clear from this figure, the liquid crystal display device of the present embodiment has
It can be seen that a display of CR = 50 or more is obtained in a range of a viewing angle of 60 ° or more, and has excellent viewing angle characteristics.

Example 13 was carried out under the conditions shown in Tables 38 to 40, but the effect of the present invention is not limited to these conditions. In other words, the liquid crystal layer has a liquid crystal layer that is substantially horizontally aligned in a state where no voltage is applied, and exhibits at least two types of alignment states when a voltage is applied, and the liquid crystal layer exhibits a refractive index anisotropy that a liquid crystal layer exhibits when no voltage is applied in all directions. What is necessary is just to have a phase difference compensating element designed so as to substantially compensate over the whole.

For example, even when the retardation value of the liquid crystal layer is changed in the liquid crystal display device having the configuration shown in FIG. 24, it is possible to find an optimum retardation plate for each. The results are shown in FIGS. The horizontal axis R in FIG.
LC is the retardation value of the liquid crystal layer (see Table 38), and the vertical axis R1 is the phase difference compensating elements 2402 and 240 shown in FIG.
3 is the retardation value d · (na−nb) (= R1), and the curve in the figure indicates the optimum value of R1 corresponding to the retardation value of the liquid crystal layer.

In FIG. 32, the horizontal axis is R1 and the vertical axis R2a is the retardation value d.multidot.d of the retardation plate numbers 2404 and 2405.
(Na-nb), and the curve in the figure shows the optimum value of R2a corresponding to R1.

In FIG. 33, the horizontal axis is R2a, and the vertical axis is -R2b.
Is the retardation value −d · (na−nc) of the retardation plate numbers 2404 and 2405, and the curve in the figure shows the optimal value of R2b corresponding to R2a.

The liquid crystal display devices constituted by the respective retardation values shown in FIGS. 31 to 33 exhibit good viewing angle characteristics. That is, the effects of the present invention are not limited to the respective retardation setting values described in the respective embodiments of the present invention, and a good visual field can be obtained by appropriately setting the retardation values of the liquid crystal layer and the phase difference compensating element. An angular characteristic can be obtained. Further, the retardation value of the liquid crystal layer is approximately 240 nm.
The effect of the present invention can be sufficiently obtained in the range of ３２０320 nm.

Furthermore, the effect of the present invention is not limited to the conditions shown in FIGS. The curves shown in FIGS. 31 and 32 show the relationship between the retardation change of the liquid crystal cell and Table 4.
0, the polarizing plate protective material TAC, 2406 and 24
This is a value optimized based on the retardation value of 07, and if the material and the retardation value change, the curves shown in FIGS. 31 and 32 change accordingly. Also, the curve shown in FIG. 31 is the twist angle and orientation direction shown in Table 38 and the phase difference plate 2402 shown in Table 40,
This curve is established when the set value of the na axis is 2403, and when these values change, the curve in FIG. 30 also changes.
Further, FIG. 31 shows that the liquid crystal cell 2401 may exhibit black display when no voltage is applied. In general, when a Poincare sphere or the like is used, setting of a phase difference compensating element that produces such an effect, various liquid crystal alignment ( Countless with respect to the twist angle and the orientation direction). Even in this case, for example, by using the phase difference compensating elements 2402 and 2403 or a phase difference compensating element instead of the phase difference compensating elements, black floating can be suppressed in oblique observation without applying a voltage, and good viewing angle characteristics can be obtained. It is specifically shown that black floating is suppressed in each of the above embodiments. The innumerable number of combinations of the arrangement of the liquid crystal cell, the phase difference compensating element, and the polarizing plate that can obtain the normally black characteristic will be described briefly in Example 14.

(Examples 13-A to 13-D and Comparative Example 1)
3-E to 13-H) In Example 13, the phase difference compensating elements 24 having the same refractive index anisotropy above and below the liquid crystal cell 2401
02 and 2403, 2404 and 2405, and 2406 and 2
407 is arranged. In the present embodiment, the effect when the phase difference compensating elements arranged above and below these cells are arranged on one side is confirmed. However, TAC for protecting the polarizing plate, that is, retardation plates 2406 and 2407 are always arranged above and below the liquid crystal cell.

The arrangement (with or without) of each phase difference compensating element in the embodiment described below is summarized in the following table.

[0202]

[Table 41]

(Embodiment 13-A) The structure of the liquid crystal display device in Embodiment 13-A will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensating element 2405 has been removed.

First, the parameters of the liquid crystal cell are shown in Table 42.

[0205]

[Table 42]

Next, Table 43 shows parameters of the polarizer.

[0207]

[Table 43]

Finally, Table 44 shows the parameters of the phase difference compensating element.

[0209]

[Table 44]

FIG. 34 shows an iso-contrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device of Example 13-A.

(Embodiment 13-B) The structure of the liquid crystal display device in Embodiment 13-B will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensating element 2404 has been removed.

First, Table 45 shows the parameters of the liquid crystal cell.

[0213]

[Table 45]

Next, Table 46 shows the parameters of the polarizer.

[0215]

[Table 46]

Finally, Table 47 shows the parameters of the phase difference compensating element.

[0219]

[Table 47]

FIG. 35 shows an iso-contrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device of Example 13-B.

(Example 13-C) The structure of the liquid crystal display device in Example 13-C will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensating element 2402 has been removed.

First, the parameters of the liquid crystal cell are shown in Table 48.

[0221]

[Table 48]

Next, Table 49 shows the parameters of the polarizer.

[0223]

[Table 49]

Finally, Table 50 shows the parameters of the phase difference compensating element.

[0225]

[Table 50]

FIG. 36 shows an iso-contrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device of Example 13-C.

(Example 13-D) The structure of the liquid crystal display device in Example 13-D will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensating element 2403 has been removed.

First, the parameters of the liquid crystal cell are shown in Table 51.

[0229]

[Table 51]

Next, Table 52 shows the parameters of the polarizer.

[0231]

[Table 52]

Finally, Table 53 shows parameters of the phase difference compensating element.

[0233]

[Table 53]

FIG. 37 shows an iso-contrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device in Example 13-D.

(Comparative Example 13-E) The configuration of the liquid crystal display device in Comparative Example 13-E will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensating elements 2402 and 2405 have been removed.

First, the parameters of the liquid crystal cell are shown in Table 54.

[0237]

[Table 54]

Next, Table 55 shows parameters of the polarizer.

[0239]

[Table 55]

Finally, Table 56 shows the parameters of the phase difference compensating element.

[0241]

[Table 56]

FIG. 38 shows an iso-contrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device of Comparative Example 13-E.

(Comparative Example 13-F) The configuration of the liquid crystal display device in Comparative Example 13-F will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensating elements 2402 and 2404 have been removed.

First, the parameters of the liquid crystal cell are shown in Table 57.

[0245]

[Table 57]

Next, Table 58 shows the parameters of the polarizer.

[0247]

[Table 58]

Finally, Table 59 shows the parameters of the phase difference compensating element.

[0249]

[Table 59]

FIG. 39 shows an iso-contrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device of Comparative Example 13-F.

(Comparative Example 13-G) The configuration of the liquid crystal display device in Comparative Example 13-G will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensating elements 2403 and 2405 have been removed.

First, Table 60 shows the parameters of the liquid crystal cell.

[0253]

[Table 60]

Next, the parameters of the polarizer are shown in Table 61.

[0255]

[Table 61]

Finally, Table 62 shows the parameters of the phase difference compensating element.

[0257]

[Table 62]

FIG. 40 shows an iso-contrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device of Comparative Example 13-G.

(Comparative Example 13-H) The structure of the liquid crystal display device in Comparative Example 13-H will be described below. The basic configuration of the liquid crystal display device is as shown in FIG. However, as shown in Table 41, the phase difference compensation elements 2403 and 2403
404 has been removed.

First, the parameters of the liquid crystal cell are shown in Table 63.

[0261]

[Table 63]

Next, the parameters of the polarizer are shown in Table 64.

[0263]

[Table 64]

Finally, Table 65 shows the parameters of the phase difference compensating element.

[0265]

[Table 65]

FIG. 41 shows an isocontrast contour curve obtained by dividing the transmittance at an applied voltage of 4 V by the transmittance at an applied voltage of 0 V in the liquid crystal display device of Comparative Example 13-H.

Compared with the thirteenth embodiment, the phase difference compensating element 240
2 or 2403 and the phase difference compensating element 2404
Or isocontrast contour curves of Comparative Examples 13-E, 13-F, 13-G and 13-H in which one of 2405 or 2405 was simultaneously removed (FIGS. 38, 39, 40 and 4).
In 1), X-REF ± 45 deg axis direction, X-REF
When the viewing angle is 50 deg or more including the Y-REF axis direction, the contrast is 20 or less, and the viewing angle characteristics are inferior.

Compared with the thirteenth embodiment, the phase difference compensating element 240
The equal contour contour curves (see FIGS. 36 and 37) of Examples 13-C and 13-D in which only one of 2 and 2403 was removed are shown in Comparative Examples 13-E, 13-F and 13-E.
The characteristics in the X-REF and Y-REF axis directions are superior to the iso-contrast contour curves of 13-G and 13-H.

Compared with the thirteenth embodiment, the phase difference compensating element 240
The iso-contrast contour curves of Examples 13-A and 13-B (see FIGS. 34 and 35) from which only one of 4 and 2405 was removed are shown in Comparative Examples 13-E, 13-F, and 13-E.
The characteristics in the X-REF ± 45 deg axis direction are superior to the iso-contrast contour curves of 13-G and 13-H.

If one of the combinations of the phase difference compensating elements 2402 and 2403 or the combination of the phase difference compensating elements 2404 and 2405 is arranged above and below the liquid crystal cell, good viewing angle characteristics can be obtained. Is obtained.

Desirably, as shown in Embodiment 13, better viewing angle characteristics are obtained when the same number of phase difference compensating elements are arranged substantially symmetrically on the light source side and the observer side with the liquid crystal cell interposed therebetween. More preferably, the retardation value of the phase difference compensating element equidistant from the intermediate layer of the liquid crystal cell may be the same value on the light source side and the observer side. In the thirteenth embodiment,
Phase difference compensating elements 2402 and 2403 and 2404 and 24
Example 13-A to Example 13 are combinations of phase difference compensating elements having the same retardation value.
In −D, the phase difference compensating elements 2402, 2403 and 240
Any of the phase difference compensating elements was removed from the combination of Nos. 4 and 2405, that is, the retardation value was zero. From this, the phase difference compensating elements 2402 and 2403
It can be inferred that good viewing angle characteristics can be obtained even when any of the phase difference compensating elements is not removed from the combination of 2404 and 2405 and the combination is not the same.

Further, comparing the ninth embodiment with the thirteenth embodiment, the light source side polarizer (6206,
2408) and the observer-side polarizer (6207, 24).
09) that the transmission axes are orthogonal to each other,
The point that the na axes of 04, 6205, 2404, and 2405 are substantially orthogonal to the transmission axes of the phase difference compensating elements closest to them. At this time, the angle of the light source side polarizer is not limited at all. That is, it is not limited to 45 deg shown in the embodiment,
-45 deg may be any other angle. However, it should be noted that when the voltage is approximately 0 deg or 90 deg, sufficient transmittance cannot be obtained when a voltage is applied (when white is displayed). If these common points are satisfied, the effects of the present invention can be obtained for a liquid crystal cell having a twist angle of 0 deg. In order to obtain a better effect, the phase difference compensating elements 6202 and 6203 and 2402 and 2
The na axes of 403 are parallel, and the na axes are orthogonal to the rubbing axes of the liquid crystal cells 6201 and 2401.

(Embodiment 14) In Embodiment 9 shown above,
In order to obtain a good black display in the front direction of the liquid crystal display device with respect to the liquid crystal cell having a twist angle of 30 °, na of the retardation plate adjacent to the liquid crystal cell in the state without twist shown in Example 13 etc. The axis was changed. Specifically, when the twist angle is zero, the na axes of the phase difference compensating elements above and below the liquid crystal cell are parallel, but when the twist angle is 30 °, an appropriate pinch angle (18.8 ° in Example 9) is obtained. And This embodiment shows that a good black display in the front direction can be obtained in a liquid crystal cell having a twist angle other than 0 ° as in the ninth embodiment by other methods. Finally, using the Poincare sphere concept, it is briefly shown that there are countless combinations of phase difference compensating elements capable of obtaining a black display in the front direction when no voltage is applied.

The structure of the liquid crystal cell of Embodiment 14 is the same as that of FIG. However, the parameters of the polarizer, the liquid crystal cell and the phase difference compensating element are different. Liquid crystal cell 2 in Example 14
Table 66 shows the parameters of 401.

[0275]

[Table 66]

Next, Table 67 shows parameters of the polarizing plate in Example 14.

[0277]

[Table 67]

Finally, Table 68 shows the parameters of the phase difference compensating element in the fourteenth embodiment.

[0279]

[Table 68]

FIG. 42 shows the applied voltage-transmittance characteristics in the front direction of the liquid crystal display device of this embodiment. As shown in FIG. 42, in the liquid crystal display device of this example, the transmittance is approximately 0% at an applied voltage of about 0 V, and the transmittance increases with an increase in the applied voltage in a region where the applied voltage is approximately 1.5 V or more. It can be seen that the electro-optical characteristics of the normally black increases. In addition, since the transmittance near the applied voltage of 0 V is approximately 0%, it can be seen that good contrast characteristics are obtained.

Next, FIG. 43 shows an isocontrast curve with respect to a change in viewing angle in the liquid crystal display device of this embodiment. The equal contrast contour curve in FIG. 43 is a value obtained by dividing the transmittance at the applied voltage of 4 V by the transmittance at the applied voltage of 0 V. FIG.
From this, it can be seen that the liquid crystal display device of this embodiment exhibits good electro-optical characteristics as in the other embodiments 13 and 9 and the like.

Next, it will be exemplified that there are countless combinations of settings of the liquid crystal cell, the polarizing plate, and the phase difference compensating element for obtaining black display in the front direction.

First, the point where a black display is obtained by observing the liquid product display device from the front in the fourteenth embodiment will be outlined using the Poincare sphere in FIG.

Point A Point indicating the polarization state of the light transmitted through the polarizer 2408 and the phase difference compensation element 2406 Point B Point indicating the polarization state of the light transmitted through the phase difference compensation element 2404 Point C transmitted through the phase difference compensation element 2402 Point D indicating the polarization state of the transmitted light Point D indicating the polarization state of the light transmitted through the liquid crystal cell 2401 Point E indicating the polarization state of the light transmitted through the phase difference compensating element 2403 Point F indicating the phase difference compensating elements 2405 and 2407 Point G indicating the polarization state of the transmitted light Point G Point indicating the polarization state of the transmitted light by the polarizer 2409 Axis 1 Rotation axis in the Poincare sphere corresponding to the birefringence effect by the phase difference compensation element 2406 Axis m Phase difference compensation element Rotational axis on Poincare sphere corresponding to birefringence action by 2404 and 2405 Axis n Rotation on Poincare sphere corresponding to birefringence action by phase difference compensating element 2402 Axis Axis o1 Rotation axis in Poincare sphere corresponding to the birefringence effect by liquid crystal molecules adjacent to phase difference compensating element 2402 in liquid crystal cell Axis o2 Birefringence action by liquid crystal molecules adjacent to phase difference compensating element 2403 in liquid crystal cell The axis of rotation of the Poincare sphere corresponding to the axis p The axis of rotation of the Poincare sphere corresponding to the birefringence effect of the phase difference compensating element 2407 FIG. 44 is a diagram of the Poincare sphere viewed from the pole. Therefore, the center point S in FIG. 44 is circularly polarized light, and on the outer circumference circle (on the equator).
Points indicate linearly polarized light, and points outside the center point S and inside the outer periphery indicate elliptically polarized light. Numerals attached to the outer periphery of the figure are angles formed by the polarization axis of the corresponding linearly polarized light and the X-REF axis.

With reference to FIG. 44, a description will be given of a change in the polarization state from the light source of light having a wavelength of 550 nm to the observer in the liquid crystal display device shown in Embodiment 14.

The linearly polarized light transmitted through the polarizing plate 2408 shown in FIG. 24 is point A on the equator. Phase difference compensating element 240
6 is perpendicular to the transmission axis of the polarizing plate 2408, the linearly polarized light at the point A is rotated around the axis l by the phase difference compensating element 2406. As a result, point A does not move.

Next, since the na axis of the phase difference compensating element 2404 is -45 deg, the point A on the equator rotates around the axis m. Further, d · (na−
Since the value of nb) is 92 nm, the rotation angle is 60 nm.
°. As a result, point A on the equator moves to point B.

Next, since the na axis of the phase difference compensating element 2402 is 0 °, the point B rotates around the axis n. Also,
The value of d · (na−nb) of the phase difference compensating element 2402 is 7
Since it is 5 nm, the rotation angle is 49 °. As a result, point B moves to point C.

Next, the main axis of the refractive index anisotropy of the liquid crystal cell 2401 is from 105 ° to the viewer side from the light source side.
Since it rotates continuously to 75 °, it rotates around an axis that continuously changes from o1 to o2. In addition, since the retardation value of the liquid crystal cell 2401 is 260 nm, the rotation angle around the axis is 170 °. As a result, point C follows the trajectory roughly as shown
A hemispherical point D different from the hemisphere with the point is reached.

Next, since the na axis of the phase difference compensating element 2403 is 0 °, it rotates around the axis n. Also, the retardation value d · (na−n) of the phase difference compensating element 2403
Since b) is 75 nm, the rotation angle is 49 °. As a result, point D reaches point E.

Next, since the na axis of the phase difference compensating element 2405 is 45 deg, the point E rotates around the axis m.
In addition, since the value of d · (na−nb) of the phase difference compensating element 2405 is 92 nm, the rotation angle is 60 °. As a result, the point E moves to the point F substantially on the equator.

Next, since the na axis of the phase difference compensating element 2407 is perpendicular to the transmission axis of the polarizer 2409, the point D rotates around the axis p. As a result, the point F does not move.

Finally, the transmission axis G of the polarizing plate 2409 is
Since it is located at the diagonal of the point, the phase difference compensating element 2407
The polarized light transmitted through is blocked by the polarizer 2409.
As a result, the liquid crystal display device of the present example exhibits the electro-optical characteristics of normally black, which has a transmittance of approximately 0% at an applied voltage of 0 V.

Next, the case of the ninth embodiment in which the twist angle of the liquid crystal cell is 30 ° can be verified in the same manner as in the fourteenth embodiment. FIG. 45 shows the locus of the change in the polarization state in the ninth embodiment.

Point A Point indicating the polarization state of the light transmitted through the polarizer 6206 and the phase difference compensating element 6204 Point B indicating the polarization state of the light transmitted through the phase difference compensating element 6202 Point C transmitted through the liquid crystal cell 6201 Point D indicating the polarization state of light Point D indicating the polarization state of the light transmitted through the phase difference compensating elements 6203 and 6205 Point E indicating the polarization state of the light transmitted by the polarizer 6207 Polarizer 620 shown in 17
6, the linearly polarized light transmitted through the phase difference compensating element 6 is at the point A.
204 does not move point A, phase difference compensating element 6202 moves the polarization at point A to point B, liquid crystal cell 6201 moves the polarization at point B to point C, and phase difference compensating element 6203
Move the point polarization to point D. The phase difference compensating element 6205 does not move at the point D. Point D is the same point as point A, which is at the diagonal of the polarization state E of the linearly polarized light transmitted by the observer-side polarizer 6207, and the polarized light transmitted through the phase difference compensating element 6205 is converted by the polarizer 6207. Will be shut off. As a result, the liquid crystal display device of Example 9 also shows the electro-optical characteristics of normally black in which the transmittance at an applied voltage of 0 V is approximately 0%.

Finally, when the twist angle of the liquid crystal cell is 0 °, for example, the thirteenth embodiment is examined in the same manner as the fourteenth embodiment. 46A and 46B show the trajectory of the change in the polarization state in the thirteenth embodiment.

Point A Polarizer 2408, phase difference compensating element 2
Point B indicating the polarization state of light transmitted through 406 and 2404 Point B Point indicating the polarization state of light transmitted through phase difference compensating element 2402 Point C indicating the polarization state of light transmitted through liquid crystal cell 2401 Point D Phase difference compensation Elements 2403, 2405 and 2407
Point E indicating the polarization state of light transmitted through the point E showing the polarization state of light transmitted by the polarizer 2409 Although detailed description is omitted, the polarizer 240 shown in FIG.
The linearly polarized light transmitted through 8 is at point A. Phase difference compensating element 2
406 and 2404 do not move the point A. The phase difference compensating element 2402 moves the polarized light at point A to point B,
Numeral 1 moves the polarized light at point B to point C on a hemisphere different from point B. The phase difference compensating element 2403 moves the polarization at the point C to a point D on the equator. Phase difference compensating elements 2405 and 2407
Does not move point D. Point D is substantially the same as point A, which is at the diagonal of the polarization state E of the linearly polarized light transmitted by the polarizer 2409 on the observer side.
07 is blocked by the polarizer 2409. As a result, the liquid crystal display device of Example 13 also has an applied voltage of 0
It shows electro-optical characteristics of normally black having a transmittance of V of about 0%.

As described above, in order to obtain the normally black characteristic in which a black display is obtained when no voltage is applied, the polarization state of light transmitted through the polarizing plate on the light source side must be checked by the observer. The parameters of the liquid crystal cell and the phase difference compensating element may be appropriately set so as to move to the diagonal of the polarization state of the light transmitted by the polarizing plate, that is, the polarization state of the light absorbed by the polarizing plate on the observer side. Such settings can be found innumerably using the concept of the Poincare sphere. This is because, as shown in FIG. 47, the number of trajectories that move the polarization state A transmitted from the light source-side polarizing plate to the polarization state Z absorbed by the observer-side polarizing plate on the Poincare sphere can be infinite.

However, from the viewpoint of obtaining good viewing angle characteristics, it is preferable that the same number of the phase difference compensating elements be disposed substantially symmetrically on the light source side and the observer side in the comparative example. It is on the street.

[0300]

As described above, according to the present invention, a normally black mode liquid crystal display device in which a change in display quality depending on the viewing angle direction is extremely small is provided. The liquid crystal display device of the present invention does not sacrifice the manufacturing efficiency and transmittance unlike the conventional wide viewing angle liquid crystal display device. INDUSTRIAL APPLICABILITY The liquid crystal display device of the present invention is suitably used for a display device requiring a wide viewing angle, such as a monitor display for a computer and a liquid crystal display device for displaying video images and the like.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing one embodiment of a liquid crystal display device of the present invention.

FIG. 2A is a cross-sectional view schematically showing the alignment of liquid crystal molecules when no voltage is applied.

FIG. 2B is a schematic diagram schematically showing the orientation of liquid crystal molecules when a voltage is applied.

FIG. 2C is a graph showing a change in the transmittance of the area A when the viewing angle is changed in the cross section of the areas A and B, using the transmittance of the front as a parameter.

FIG. 3A is an alignment-divided liquid crystal region A in a black display state.
3A and 3B are cross-sectional views schematically showing alignment states of liquid crystal molecules in B.

FIG. 3B is a cross-sectional view schematically illustrating an alignment state of liquid crystal molecules in liquid crystal regions A and B that have undergone alignment division in a halftone display state.

FIG. 3C is a graph showing a change in transmittance with respect to a change in viewing angle in a region A, using the transmittance of the front as a parameter.

FIG. 3D is a graph showing a change in transmittance with respect to a change in viewing angle in a region B, using the transmittance of the front as a parameter.

FIG. 3E is a graph showing a change in overall transmittance with respect to a change in viewing angle between regions A and B, using the transmittance of the front as a parameter.

FIG. 4A is a diagram for explaining the pixel division ratio (area ratio of areas A and B) and the symmetry of gradation, and is a diagram for explaining the definition of the transmittance used for evaluating the symmetry.

FIG. 4B is a diagram for explaining the pixel division ratio (area ratio of regions A and B) and the symmetry of gradation, and is a diagram showing the area ratio of regions A and B and the symmetry of gradation.

FIG. 4C is a diagram schematically showing a modification of the orientation division of one display picture element region according to the present invention.

FIG. 4D is a diagram schematically showing another modified example of the orientation division of one display picture element region according to the present invention.

FIG. 4E: By reducing the unit of orientation division,
It is a schematic diagram for demonstrating the reason that a viewing angle characteristic can be made more uniform.

FIG. 5A is a schematic cross-sectional view of a liquid crystal molecule alignment at the time of black display in a normally black liquid crystal display device.

FIG. 5B is a diagram showing a relative relationship among an absorption axis of a polarizing plate, an alignment axis of liquid crystal molecules, and a slow axis of a retardation plate for obtaining a normally black characteristic in a horizontal alignment cell.

FIG. 5C is a graph showing a change in retardation value when a viewing angle is changed along a direction of alignment of liquid crystal molecules in a black display state in a normally black display device.

FIG. 5D is a schematic cross-sectional view of a liquid crystal molecule orientation during black display in a normally white liquid crystal display device.

FIG. 5E is a diagram showing a relative relationship between an absorption axis of a polarizing plate and an alignment axis of liquid crystal molecules for obtaining a normally white characteristic in a horizontal alignment cell.

FIG. 5F is a graph showing a change in retardation value when the viewing angle is changed along the alignment direction of liquid crystal molecules in a normally white liquid crystal display device in a black display state.

FIG. 5G is a graph showing a change in a retardation value when a viewing angle is changed along a direction perpendicular to the alignment direction of liquid crystal molecules in a normally black display device in a black display state.

FIG. 5H is a graph showing a change in retardation value when a viewing angle is changed in a normally white liquid crystal display device in a black display state along a direction orthogonal to the alignment direction of liquid crystal molecules.

FIG. 6 is a diagram illustrating improvement in viewing angle characteristics of contrast in the present invention. FIG. 3 shows a liquid crystal layer, a refractive index ellipsoid of a retardation plate group, and a polarization axis of incident linearly polarized light in one embodiment of the present invention.

FIG. 7A is a diagram showing a refractive index ellipsoid having a positive uniaxial refractive index anisotropy.

FIG. 7B is a diagram illustrating transmitted light when linearly polarized light having an angle of 45 ° with the slow axis from the normal direction of the plane is incident.

FIG. 7C is a diagram illustrating a refractive index ellipsoid having a positive uniaxial refractive index anisotropy, in which the slow axis and the slow axis are inclined from the direction inclined along the slow axis to the normal to the plane including the slow axis. Angle of 45
FIG. 4 is a diagram for explaining transmitted light when linearly polarized light at an angle of ° is incident.

FIG. 7D is a diagram illustrating transmitted light when linearly polarized light is incident on a refractive index ellipsoid having a positive uniaxial refractive index anisotropy from the direction of its slow axis.

FIG. 7E is a diagram illustrating transmitted light when linearly polarized light is incident on a refractive index ellipsoid having a positive uniaxial refractive index anisotropy from a direction inclined from its slow phase.

FIG. 8 is a graph showing a relationship between retardation of a 45 ° retardation plate and transmittance in a black display state.

FIG. 9 is a diagram illustrating a definition of a main axis direction for describing the configuration of the embodiment.

FIG. 10 is a schematic diagram for explaining a configuration of an example.

FIG. 11 is a diagram schematically showing a refractive index ellipsoid of a retardation plate used in an example.

FIG. 12 is a schematic diagram illustrating a liquid crystal cell in the liquid crystal display device of the present invention. (A) is a diagram showing a rubbing direction, and (b) is a schematic diagram showing an alignment state of liquid crystal molecules in a cell thickness direction by the rubbing process of (a). (C)
FIG. 3A is a schematic diagram illustrating an alignment state of liquid crystal molecules in a cell thickness direction when the rubbing treatment of FIG.

FIG. 13 is a graph showing the relationship between the transmittance and the applied voltage of the liquid crystal display device of the example according to the present invention.

FIG. 14A is a graph showing the viewing angle dependence of the transmittance at each gradation in each of the eight gradation display states of the liquid crystal display device according to the embodiment of the present invention (each direction in the direction parallel to the X_REF axis).

FIG. 14B is a graph showing the viewing angle dependence of the transmittance at each gradation in the eight gradation display state of the liquid crystal display device according to the embodiment of the present invention (in each direction in the direction parallel to the axis of X_REF ± 45 °).

FIG. 14C is a graph showing the viewing angle dependence of the transmittance at each gray scale (each direction in the direction parallel to the Y_REF axis) in the eight gray scale display state of the liquid crystal display device according to the embodiment of the present invention.

FIG. 15 is an isocontrast diagram of a liquid crystal display device according to an embodiment of the present invention.

FIG. 16 is a diagram schematically showing a configuration of one embodiment of the present invention.

FIG. 17 is a diagram schematically showing the configuration of another embodiment of the present invention.

FIG. 18 is a diagram schematically showing the configuration of another embodiment of the present invention.

FIG. 19 is a diagram schematically showing the configuration of another embodiment of the present invention.

FIG. 20 is a graph showing the relationship between the transmittance and the applied voltage of the liquid crystal display device of the example according to the present invention.

FIG. 21A is a graph showing the viewing angle dependence of the transmittance at each gradation in the eight gradation display state of the liquid crystal display device according to the embodiment of the present invention (in each direction in the direction parallel to the X_REF axis).

FIG. 21B is a graph showing the viewing angle dependence of the transmittance at each gradation in each of eight gradation display states of the liquid crystal display device according to the embodiment of the present invention (each direction in the direction parallel to the axis of X_REF ± 45 °).

FIG. 21C is a graph showing the viewing angle dependence of the transmittance at each gradation in each of eight gradation display states of the liquid crystal display device according to the embodiment of the present invention (in each direction in the direction parallel to the Y_REF axis).

FIG. 22 shows an isocontrast diagram of the liquid crystal display device according to the embodiment of the present invention.

FIG. 23 is a diagram schematically showing a configuration of another embodiment of the present invention.

FIG. 24 is a diagram illustrating a configuration of a liquid crystal display device in Example 13, Examples 13-A to 13-D, and Comparative Examples 13-E to 13-H and 14.

FIG. 25 is a diagram showing a transmittance-applied voltage characteristic observed from the front direction in the liquid crystal display device of Example 13.

FIG. 26 is a diagram illustrating a change in transmittance of each gradation with respect to a change in viewing angle in the X_REF axis direction in eight gradation display in the liquid crystal display device of Example 13.

FIG. 27 is a diagram illustrating a change in transmittance of each gradation with respect to visualization in the X_REF + 45 deg axis direction in 8-gradation display in the liquid crystal display device of Example 13.

FIG. 28 is a diagram illustrating a change in transmittance of each gradation with respect to a change in viewing angle in the X_REF-45 deg axis direction in eight gradation display in the liquid crystal display device of Example 13.

FIG. 29 is a diagram illustrating a change in transmittance of each gradation with respect to a change in viewing angle in the Y_REF axis direction in eight gradation display in the liquid crystal display device of Example 13;

FIG. 30 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Example 13.

FIG. 31 shows a phase difference compensating element 240 for the retardation value d · Δn (RLC) of the liquid crystal cell in the thirteenth embodiment.
Retardation value d · (na−nb) of 2 and 2403
It is a figure showing the optimal value of (R1).

FIG. 32 shows a phase difference compensating element 2402 in the thirteenth embodiment.
And the retardation value d · (na−nb) of 2403
Phase difference compensating elements 2404 and 2405 for (R1)
FIG. 5 is a diagram showing an optimum value of a retardation value d · (na−nb) (R2a) of FIG.

FIG. 33 shows a phase difference compensating element 2404 in the thirteenth embodiment.
And the retardation value d · (na−nb) of 2405
Phase difference compensating elements 2404 and 240 for (R2a)
5 retardation value −d · (na−nc) (− R2
It is a figure showing the optimal value of b).

FIG. 34 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Example 13-A.

FIG. 35 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Example 13-B.

FIG. 36 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Example 13-C.

FIG. 37 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Example 13-D.

FIG. 38 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Comparative Example 13-E.

FIG. 39 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Comparative Example 13-F.

FIG. 40 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Comparative Example 13-G.

FIG. 41 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Comparative Example 13-H.

FIG. 42 is a diagram showing transmittance-applied voltage characteristics observed from the front direction in the liquid crystal display device of Example 14.

FIG. 43 is a diagram showing an equal contrast contour curve in the liquid crystal display device of Example 14.

FIG. 44 is a diagram illustrating a change in the polarization state of light transmitted in parallel to the normal to the liquid crystal cell surface when the applied voltage is 0 V in the liquid crystal display device of Example 14. .

FIG. 45 is a diagram illustrating a change in the polarization state of light transmitted in parallel to the normal to the liquid crystal cell surface when the applied voltage is 0 V in the liquid crystal display device of Example 9;

FIGS. 46 (a) and (b) show, in the liquid crystal display device of Example 13, when the applied voltage is 0 V in the liquid crystal display device.
FIG. 7 is a diagram illustrating a change in the polarization state of light transmitted in parallel to the normal to the liquid crystal cell surface.

FIG. 47 illustrates that there are innumerable parameters of a liquid crystal cell, a phase difference compensator, and a polarizer that can obtain a normally black electro-optical characteristic using a liquid crystal cell that is substantially horizontally aligned when no voltage is applied. FIG.

FIG. 48 is a schematic view of a liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 5-289097.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 100 Liquid crystal display device 100a, 100b Electrode 101 Orientation bipartite liquid-crystal layer 101a, 100b Orientation-divided area | region 102, 103, 104, 105, 110, 111 Phase difference plate 108, 109 Polarizing plate 1201 Rubbing direction of opposing substrate 1202 TFT substrate Rubbing direction 1204 TFT substrate 1205 opposing substrate 1206 liquid crystal molecules 1207 arrow indicating the direction in which liquid crystal molecules rise when voltage is applied 1208 arrow indicating the direction in which liquid crystal molecules rise when voltage is applied

Claims (12)

[Claims] A first liquid crystal layer sandwiched between at least one of the first and second substrates, and a liquid crystal layer made of a nematic liquid crystal material having a positive dielectric anisotropy; First and second electrodes provided on the first and second substrates, respectively, for applying an electric field substantially perpendicular to the first and second substrates to the liquid crystal layer, outside the first and second substrates, respectively; And first and second polarizers arranged in a crossed Nicols state, and a phase difference compensating element, wherein the liquid crystal layer has first and second polarities different from each other for each display picture element region. Having at least a second domain, the phase difference compensating element compensates for the refractive index anisotropy of the liquid crystal molecules which are oriented substantially parallel to the surfaces of the first and second substrates in a state where no voltage is applied. , Liquid crystal display device. 2. The first and second substrates are both transparent substrates, and the phase difference compensating element is a first phase difference compensating element provided between the first substrate and the first polarizing plate. The liquid crystal display device according to claim 1, comprising: a second phase difference compensating element provided between the second substrate and the second polarizing plate. 3. The first and second phase difference compensating elements have positive refractive index anisotropy, and the slow axes of the first and second phase difference compensating elements are substantially parallel to each other, and 3. The liquid crystal display device according to claim 2, wherein the liquid crystal layer is substantially perpendicular to a slow axis of the liquid crystal layer in a state where no voltage is applied. 4. A device further comprising a third phase difference compensating element between the first phase difference compensating element and the first polarizing plate, wherein the third phase difference compensating element has a positive refractive index anisotropy. The liquid crystal display device according to claim 3, wherein a slow axis of the third phase difference compensating element is substantially orthogonal to the first and second substrates. 5. A fourth phase difference compensating element between the second phase difference compensating element and the second polarizing plate, wherein the fourth phase difference compensating element has a positive refractive index anisotropy. 5. The liquid crystal display device according to claim 4, wherein a slow axis of the fourth phase difference compensating element is substantially orthogonal to the first and second substrates. 6. A fifth phase difference compensating element provided between the first phase difference compensating element and the third phase difference compensating element,
The device further includes a sixth phase difference compensating element provided between the second phase difference compensating element and the fourth phase difference compensating element, wherein the fifth and sixth phase difference compensating elements have a positive refractive index. Anisotropic, the slow axis of the fifth phase difference compensating element is substantially orthogonal to the polarizing axis of the first polarizing plate, and the slow axis of the sixth phase difference compensating element is the slow axis of the second polarizing plate. The liquid crystal display device according to claim 1, which is substantially orthogonal to a polarization axis. 7. The direction in which directors of the liquid crystal molecules, which are located in the middle of the thickness direction of the liquid crystal layer in the first and second domains when no voltage is applied, are different from each other by 180 °, and The direction of the director is substantially 45 ° with respect to the polarization axes of the first and second polarizers,
The liquid crystal display device according to claim 1. 8. The liquid crystal display device according to claim 1, wherein the liquid crystal molecules in the first domain and the second domain are aligned in parallel. 9. The liquid crystal display according to claim 1, wherein the liquid crystal molecules in the first domain and the second domain are twist-aligned. 10. The liquid crystal display device according to claim 8, wherein pretilt angles of the liquid crystal molecules on the first substrate and the second substrate in the first and second domains are different from each other. 11. The liquid crystal layer has a plurality of the first domains and a plurality of the second domains for each of the display picture element regions, and the number of the first domains and the number of the second domains are the same. The liquid crystal display device according to any one of claims 1 to 10. 12. The liquid crystal display device according to claim 1, wherein the sum of the areas of the first and second domains is equal to each other.